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CHAPTER 29
THERMAL PROPERTIES OF FOODS
Commodity Refrigeration Load Data; Enthalpy, Specific Heat, and Thermal Diffusivity; Thermal Conductivity
HIS chapter provides data and information for thermal process
T
(heating, cooling, freezing, and thawing) calculations for foods
and food substances. The material was selected and prepared for
general usefulness to engineers and others interested in applying
these processes to foods in industry, teaching, and research. Since
the data selected were considered the best available, discussion of
errors, accuracy, and methods for obtaining the data is minimal.
References are given, where possible, for those interested in
obtaining more detail. Another criterion for data selection was need
or potential usefulness. Since comprehensiveness was also sought
within this limitation, the amount of data presented in each area
reflects the amount of data available.
Variability in composition and structure seems to be the major
characteristic of food substances to keep in mind in considering their
thermal properties. For example, foods are generally nonhomogeneous, varying in composition and structure both within and
between products or samples of products. In addition, their chemical
and physical (and hence thermal) properties will probably change
with time, temperature, and other ambient conditions. If the food is a
living commodity, such as a stored fruit or vegetable, it will generate
heat, use atmospheric oxygen, and give off carbon dioxide, water
vapor, and other gases, all of which affect its ambient surroundings,
quality, and storage life.
As a specific example, consider conductivity of meat. the
composition and structure (fat, lean, bone, moisture, muscle and bone
size and shape, fiber direction, etc.) will vary between animals with
species, age, feeding, slaughter, and post slaughter conditions, and
within a given animal with the particular muscle or muscle part
considered. Above freezing, temperature change may cause changes
in the conductivity due to changes in the fat; below freezing, the
conductivity changes rapidly until the water is substantially frozen.
After thawing and refreezing, or a period of above-freezing storage,
the conductivity may be different, due to water loss and other
changes. Some changes may not be significant, but others are. Care
must be taken in measuring and predicting, and in the use of thermal
conductivity and other thermal properties.
This chapter uses SI units except where other metric units seemed
preferable. Some of the most frequently needed conversion factors
are given with tables and figures. For more detailed information see
Chapter 35.
COMMODITY REFRIGERATION LOAD DATA
Design of systems for cooling, freezing, or storing foods requires
reliable values for thermal properties of various products. Food
properties described in this section are specific heat, latent heat of
fusion, and heat of respiration. Related properties are freezing point
and water content. These data are given in Tables I to 3.
Water Content. Although not directly a thermal property, water
content significantly influences all thermal properties.
The preparation of this chapter is assigned to TC 11.9, Thermal Properties of Foods.
In fact, values of specific heat and latent heat of fusion (Table
1) are based on the amount of water in the food.
Values for percent water content (Table I) should be considered
the average for the commodity. With fruits and vegetables, water
content varies with stage of development or maturity when
harvested, cultivar, growing conditions, and amount of moisture
lost after harvest. Values normally apply to fully mature products
shortly after harvest. For fresh meat, water content values are for
time of slaughter or after the usual aging period. In cured or
processed products, water content depends on the particular
process or product.
Some foods are hygroscopic, gaining moisture during storage,
but most lose water that cannot be recovered. Values for specific
heat and latent heat of fusion in Table 1 apply only for the
corresponding water content given.
Freezing Point. Freezing point values in Table 1 are based on
experiments where the product was cooled slowly until freezing
occurred. Sensitive temperature indicators, such as thermocouples,
were inserted into the product, and a sudden temperature rise
caused by ice formation indicated the beginning of freezing. For
fruits and vegetables, the highest temperature at which specimens
froze is given (Table 1), for they can be seriously damaged by
freezing. For other foods, average freezing temperature is shown,
largely because initial freezing temperatures are unavailable.
Freezing points of foods vary with composition. All apples in a
given lot, for example, do not freeze at the same temperature.
As a food product is frozen, ice crystals form, concentrating the
remaining unfrozen portion and lowering the freezing temperature.
Foods packed in high syrup concentrations, or high in sugar
content, such as dried fruits, may never be completely frozen,
even at frozen food storage temperatures. Also, foods normally
low in moisture, such as dried beans and peas, do not freeze at
these temperatures.
Specific Heat. Siebel's formulas used to calculate listed specific
heat values for above and below freezing, are:
cp=0.008 a+0.20 (above freezing)
(1)
cp=0.003 a+0.20 (below freezing)
(2)
where cp is specific heat in Btu per pound per degree Fahrenheit,
or calories per gram per degree Celsius; a is percent water content;
and 0.20 is an arbitrary base, assumed to represent the specific
heat of the solid constituents. To convert calories to joules,
multiply by 4.1868.2
Specific heat is a function of temperature. Siebel's formulas are
based on the specific heat of water and ice at O°C of 1.0 and 0.5
cal/(g) (QC), respectively. Specific heat values in Table 1 are for
O°C. In nonfrozen foods, specific heat becomes slightly lower as
temperatures rise from 0 to 20°C. In frozen foods, there is a large
change in specific heat as temperatures decrease. For example,
frozen beef at -40°C has a specific heat of 0.49, as compared with
0.35 at -79°C. 3 As mentioned previously, variability in
composition is a major characteristic
Publica tion of standards in th e fie lds of heat ing, refr igerating, air -cond ition ing and ventilating engineer ing from (ASHRAE:
29.1
American Society o f Hea ting , Refrigerating and Air - Cond itioning
Engineers, I nc.
Reprinted from ASHRAE handbook Chapter 29
doc081113brev00_11-13-08-thermal_properties_of_foods.doc
(1)
(2)
CHAPTER 29
29.2
1977 Fundamentals Handbook
of food substances; this is true for those constituents, particularly
water content, that affect specific heat.
In calculating specific heat of frozen foods, all the water is assumed
to be frozen to ice; the specific heat involved is that of ice. This
assumption is not entirely correct. As indicated, freezing of most
foods is a gradual process, occurring over a wide temperature range.
Specific heat values are subject to error, since freezing may be
incomplete, the specimen may not be ice but a mixture of frozen and
unfrozen constituents.)
Latent Heat of Fusion. Latent heat of fusion is useful in
determining the amount of refrigeration required to freeze a product.
As with specific heat, the values listed are subject to error because
they do not take into account the chemical composition other than its
water content. They are simply the product of the heat of fusion of
water (79.71 cal/g) and the water content expressed in decimal form.
Their use is limited to practical applications, being subject to some
discrepancy depending on product composition.
The following examples show that errors inherent in calculating
heat of fusion of foods are not significantly large:
of respiration energy is in the form of heat, which must be contended
with in cooling and storing these living products.
As in all chemical reactions, temperature plays a leading role in the
rate of respiration. A 10°C rise in temperature generally causes
respiration rates to double or triple in the range of about 0 to 30°C.
Higher temperatures usually retard respiration.
Fruits, vegetables, flowers, bulbs, florists' greens, and nursery
stocks are storage commodities with significant heats of respiration.
Dry plant products, such as seeds and nuts have very low respiration
rates. Young, actively, growing tissues, like asparagus, broccoli,
spinach, and green beans have high rates, as do immature seeds such
as green peas and sweet corn. Fast developing fruits like strawberries,
raspberries, and blackberries, have much higher respiration rates than
fruits that are slow to develop, such as apples, pears, grapes, and citrus
fruits (Table 2).
Almost all commodities in Table 2 have a low and a high value for
heat of respiration at each temperature. When no range is given, the
value is an average for the specified temperature, and may be an
average of the respiration rates for many days.
Example 1: Assume a food of 75°10 moisture content, initially at
O°C to -20°C; latent heat of fusion of water, 79.71 cal/lg; specific
heat of ice, 0.50 cal/(g) (DC); specific heat of water, 1.01 cal/(g) (DC);
specific heat of non-aqueous 25OJo of the food (Eq. 2), 0.20 cal/(g) (DC).
Assume only 90OJo of the water present freezes, a good assumption for
many foods. 4 Now:
Most vegetables, other than root crops, have a high initial rate for
the first day or two after harvest. Within a few days, it quickly lowers
to what may be called the equilibrium rate. 5 Asparagus is a good
example. The first day, heat of respiration of 0ºC is 4900 kcal/(metric
ton) (day). Within 3 days, it is down to 2410, and in 16 days to 1 710
(Table 3). Great Lakes lettuce at 0° has a rate of 1040 kcal/(ton)(day)
the first day, which falls to 550 in 5 days. Artichokes at 0°C respire at
a rate of 2750 kcal/(ton)(day) the first day and by 16 days the heat
produced amounts to only 920 kcal/(ton)(day). Sweet corn in the husk
at 0ºC produces the first day 3140 kcal/(ton)(day) and in 4 days
decreases to 1880 kcal/(ton)(day). Onions are an exception. They
increase in respiration with time as the bulbs lose dormancy. The
same is true with garlic (Table 3).
Fruits present a somewhat different picture than most vegetables.
Those that do not ripen in storage, such citrus fruits and grapes, have
fairly constant respiration rates. Those that ripen in storage (i.e.,
apples, pears, peaches, plums, mangos, and avocados) increase in
respiration rate. If a fruit can be held at DOC, as most apples can,
respiration barely increases, since no ripening takes place. But if held
at higher temperatures (10 or 15°C), respiration increases and then
decreases (see apples, Table 3). Soft fruits, such as blueberries, figs,
and strawberries show a decrease in respiration at O°C with time. If
they become infected with decay organisms, however, respiration
increases.
(a) latent heat of freezing:
79.7IxO.75xO.9
(b) sensible heat to cool the
ice: (0. 75xO. 9xO.5)x20
(cY sensible heat to cool unfrozen
water: (0.75xO.lx1.01 )x20
(d) sensible heat to cool non-aqueous material:
(0.25xO.2)x20
Total
=53.8
cal/lg
6.8 call g
1.5 call
g
1.0 call
g
63.1
Calculated from the freezing of water only, O. 75x79.cal/g
71 =59.8 call g
for an error of [(63.1-59.8)/63.I1X 1 00=5.2 O%.
Example 2: Assume a food of 50OJo water content. Calculating as
above: (a) =35.9 cal/g; (b) =4.5 cal/g; (c) =1.0 calling; and (d)=2.0
calling; the total is 43.4 cal/g.
Using heat of fusion of water gives only 39.9 calling for an error of
8.1OJo. Note that in some foods with low water content, very little
water will be frozen at -200e This causes a large error if the "90170
freezing" assumption is adhered to.
For computing cooling or freezing loads of frozen products,
specific heat below freezing and latent heat of fusion are
interdependent, and should be used together. For many food products,
both freezing and temperature change of frozen material take place
simultaneously. This occurs over a temperature range, narrow for
foods with low solid matter content, wide for those with high solid
matter content. (See Enthalpy, Specific Heat, and Thermal
Diffusivity, below.)
In Table I, no latent heat of fusion values or specific heat values
below freezing are given for products so low in moisture that the
water in them does not freeze.
Heat of Respiration. All living food products respire. In
respiration, a sugar, usually glucose, combines with oxygen by a step
process involving enzymes. A simplified formula for the process is:
e6H 1206+602--6e02+6H20
+energy (heat and energy of A TP)
The end products are CO2, H 2' and energy in the form of heat as well
as of adenosine triphosphate (A TP), that the cell can use for growth
and development. In most stored plant products, little cell
development takes place, and the greater part
To use Table 2," select the lower value when estimating respiration
heat at the equilibrium state for storage; and the higher value if
calculating the heat load for the first day or two, as for precooling and
short distance transport. If the storage temperature is 0 or 5°C,
respiration increase in fruits, due to ripening, is slight. In fruits that
must be held at 10°C or higher, such as mangos, avocados, or
bananas, ripening occurs and the higher rates should be used.
Vegetables that lose dormancy in storage, like onions, garlic, and
cabbage, may increase in heat production after long storage.
Not all variations in respiration heat can be attributed to change in
rate with time. Broccoli with many flower heads respires faster than if
mostly stem tissue. Immature fruits and vegetables usually respire
faster than more mature specimens (see potatoes, Table 2). Usually,
the early, fast-growing cultivars of fruits and vegetables have higher
respiration rates than later, slower developing types.
To obtain the values in Tables 2 and 3, the heat of respiration was
assumed to be derived from glucose oxidation in the reaction given
earlier. One mole of glucose (180 g) is oxidized by 6 moles of
oxygen to produce 6 moles of CO2 (264 g). Glucose oxidation
produces 673 kcal and 1 g of CO2, therefore represents
(673/264)=2.549 kcal; I mg of CO2 represents 2.549 cal. Respiration
rate in mg CO2/(kg) (hr)x2.549x24=heat produced/kg in 24 hr. This
is equivalent to kcal/(metric ton) (24 hr).
To convert heat of respiration to Btu/(ton) (24 hr) from
kcal/(metric ton) (24 hr), multiply the latter by 3.60.
If substrates other than glucose are oxidized in the respiration
process, as they sometimes are, the heat produced amounts to less
when organic acids are the substrate, and considerably more when
fats are utilized.
C.
29.3
Thermal Properties of Foods
ENTHALPY, SPECIFI C HEA T AND
THERMAL DIFFUSIVITY
When enthalpy is tabulated as a function of temperature, a base
temperature must be identified. This base is the temperature at which
enthalpy is arbitrarily designated as zero. In this chapter, zero enthalpy
is taken at -40°C.
Frozen Foods
The data shown in Table 1 consist of latent heat, freezing point, and
specific heat above and below freezing. This table is used to perform
refrigeration load calculations by (1) using specific heat above
freezing to compute the sensible heat removed during cooling from
the starting temperature to freezing point; (2) using latent heat to
compute the heat removed during freezing; and (3) using specific heat
below freezing to compute the sensible heat removed during cooling
from the freezing point to the final frozen storage temperature. This
procedure assumes the latent heat of fusion is removed at constant
temperature (the freezing point).
Foods do not freeze at constant temperature, however. Beef begins
to freeze at about -1°C, but 25070 of the latent heat is still to be
removed at -4°C. 4 In haddock muscle, some water is bound to
proteins and does not freeze at -40°C. 58 In reviewing problems of
measuring specific heat and latent heat of foods, Ref. 59 points out
that fresh beef is not completely frozen at -62°C, and orange juice is
not completely frozen at -95°C.
Ref 60 explains the process of food freezing as follows.
When food begins to freeze, the concentration of food solids is
increased in the remaining unfrozen water, thereby establishing a
lower freezing point for additional change of phase. With additional
freezing, there is a gradual depression of the freezing point until all
freezable water is frozen. Measurement of heat removed during
freezing includes both latent and sensible heat. For this reason, the
generally accepted criterion of latent heat {change of phase at
constant temperature) cannot be rigorously applied to the process of
freezing foods.3 Neither the concept of specific heat nor thermal
diffusivity can be applied because there is, as yet, no way to separate
the specific heat component from latent heat in a food freezing
process.
Using Table 1 to compute refrigeration loads can lead to errors, but
the errors will always be conservative (i.e., the computed refrigeration
load will always be somewhat greater than that actually required). The
error diminishes for lower frozen storage temperatures. Conversely, if
the product is to be cooled only slightly below the initial freezing
temperature, using Table 1 can lead to significant errors because only
a small fraction of the latent heat is actually removed from the product. Results from Table 1 assume all latent heat is removed.
When the product is to be cooled only slightly below initial
freezing temperature, or where greater accuracy is desired for any
final frozen storage temperature, the physical quantity employed in
frozen food calculations is the total heat content, or enthalpy. 59.61-63
This approach has the additional advantage of yielding estimates of
percent water unfrozen.
Enthalpy of Meats, Fruits, Vegetables, and Eggs
Enthalpy of some frozen foods is in Table 4, as a function of
temperature from -40 to O°C. In the temperature range of Table 4,
water in the food is never completely frozen, and the percent (by
weight) of unfrozen water is also shown as a function of temperature.
To identify enthalpy, use:
(3)
where
Q = total heat
transferred, kilocalories. W = weight,
kilograms.
h = enthalpy, kilocalories per kilogram.
An example of the use of tabulated enthalpy values follows.
Example 3: A quantity of beef (150 kg) is to be frozen to a temperature of 20°C. Initial temperature of the beef is + IO°C, and moisture content is
74.5070. How much heat must be removed, and what is the total weight of
unfrozen water at -20°C? The heat removed in cooling from 10 to O°C is
calculated from temperatures and specific heat (cp)' From Table 4, specific heat
is 0.84 kcal/(kg)(OC), so from 10 to O°C: Q = [(150 kg) x (0.84
kcal)1/[(kg)(°C) x (10°C - O°C)1 = 1260 kcal.
'
From the tabulated values in Table 4: h2 at O°C = 73.0 kcal/kg; hi at -20°C
= 10.0 kcal/kg. Therefore, from O°C to -20°C: Q = W(h2 - hi) = (150 kg) x
(73.0 - 10.0) = 9450 kcal.
The total heat to be removed is: QlOtal = 1260 kcal + 9450 kcal =
10,710kcal.
The amount of unfrozen water at -20°C is taken directly from Table 4 as II
%. The total weight of unfrozen water is (150 kg) x (0.745) x (0.11) = 12.3 kg.
Using enthalpy values for beef of various water contents, Ref 4
includes a graph of enthalpy vs water content with connected data
points along lines of constant temperature so that enthalpy values can
be obtained for beef of any water content. Another graph4 shows
percent water frozen vs temperature in beef. These two graphs were
combined3 into one using the British Gravitational System of units; the
data have been converted to the metric system in Fig. 1.
. For a beef sample of known water content, a single vertical line in
Fig. I yields enthalpy and percent water unfrozen as a function of
temperature.
For temperatures below -40°C, the freezing process is nearly
complete for beef, and use of specific heat yields reliable results.
Table 564 gives specific heat of frozen beef for temperatures between 110 and -40°C.
Enthalpy and percent water unfrozen for fruit juices and vegetable
juices are given in Fig. 2. Working with twelve juices, Riedel 65
showed that enthalpy data were represented by Fig. 2 within
approximately 2070. Fig. 2 exhibits the same general trends as shown
in Fig. 1 for beef. However, Fig. 2 has a different range of water
content, and isotropic lines of percent water unfrozen are not shown
extrapolated to zero enthalpy as in Fig. 1.
The effect of soluble solids in the juice on the temperature range
over which latent heat is removed is apparent in Fig. 2. For example, a
vertical line at a water content of 95070 shows the heat to be removed
during freezing. For this high water content, freezing starts at a
temperature very close to 0ºC, and the main part of the freezing
process occurs over a narrow
29.4
CHAPTER 29
Table 1
Thermal and Related Properties
1977 Fundamentals Handbook
Table 1
of Food and Food Materials
Specific Heate
Highest
Food or Food
Material
Below
Latent
Water
Freezing
Above
Content,
'10 (wO)
Point
°Ch
Freezing
cal/(g)("C)
heal of
84
-1.2
0.87
0.45
67.0
80
93
89
67
II
88
90
85
92
88
92
88
94
87
74
96
-2.5
-0.6
-0.7
-0.6
0.84
0.94
0.91
0.74
0.29
0.90
0.92
0.88
0.94
0.90
0.94
D.90
0.95
0.90
0.79
0.97
0.44
0.48
0.47
0.40
63.8
74.1
70.9
53.4
0.46
0.47
0.46
0.48
0.46
0.48
0.46
0.48
0.46
0.42
D.49
70.1
71.7
67.8
73.3
70.1
73.3
70.1
74.9
69.3
59.0
76.5
0.48
0.48
0.38
0.46
0.43
0.46
0.47
0.46
0.49
0.47
0.47
0.47
0.46
D.45
0.44
0.42
74.1
74. 1
48.6
69.3
59.8
69.3
71.7
67.8
75.7
n.5
71.7
70.9
70.1
67.8
63.0
59.0
-0.8
-0.7
-0.9
-1.1
-1.1
-0.3
-0.5
-0.8
D.94
0.94
0.69
0.90
0.80
D.90
0.92
0.88
0.96
0.93
0.92
0.91
0.90
0.88
0.83
0.79
0.30
0.30
0.94
0.85
0.82
0.75
0.79
0.93
0.96
0.96
0.91
0.83
0.94
0.95
0.88
0.48
0.44
0.43
0.41
0.42
0.47
0.49
0.49
0.47
0.44
0.48
0.48
0.46
73.3
64.6
62.2
55.0
59.0
n.5
75.7
75.7
70.9
63.0
74.1
74.9
67.8
-0.6
-0.5
-0.2
-I.J
-0.3
D.94
0.95
0.92
0.94
0.94
0.48
0.48
0.47
0.48
0.48
74.1
74.9
71.7
73.3
74.1
fusion
Freezing
cal/(g)(OC) cal/gd
Vegetables
Artichokes,
Globe
Artichokes,
Jerusalem
Asparagus
Beans, Snap
Beans, Lima
Beans, Dried
Beets, Roots
Broccoli
Brussels Sprouts
Cabbage, Late
Carrots, Roots
Cauliflower
Celeriac
Celery
Collards
Corn, Sweet
Cucumbers
Eggplant
Endive (Escarole)
Garlic
Ginger, Rhizomes
Horseradish
Kale
Kohlrabi
Leeks
Lettuce
Mushrooms
Okra
Onions, Green
Onions, Dry
Parsley
Parsnips
Peas, Green
Peas, Dried
Peppers, Dried
Peppers, Sweet
Potatoes, Early
Potatoes, Main Crop
Potatoes, Sweet
Yams
Pumpkins
Radishes
Rhubarb
Rutabagas
Salsify
Spinach
Squash, Summer
Squash, Winter
Tomatoes,
Mature Green
Tomatoes, Ripe
Turnip Greens
Turnip
Watercress
93
93
61
87
75
87
90
85
95
91
90
89
88
85
79
74
12
12
92
81
78
69
74
91
95
95
89
79
93
94
85
93
94
90
92
93
-1.1
-0.6
-0.8
-0.9
-1.4
-0.8
-0.9
-0.5
-0.8
-0.6
-0.5
-0.8
-0.1
-0.8
-1.8
-0.5
-1.0
-0.7
-0.2
-0.9
-1.8
-0.9
-0.8
-1.1
-0.9
-0.6
-0.7
-0.6
-0.6
-1.3
(continued)
Highest
-
-
Water Freezing
Food or Food
Content,
Material
Grapefruit
Grapes, American
Grapes
Lemons
Limes
Mangos
Melons, Casaba
Melons, Crenshaw
Melons, Honeydew
Melons, Persian
Melons, Watermelon
Nectarines
Olives
Oranges
Peaches, Fresh
Peaches, Dried
Pears
Persimmons
Pineapples
Plums
Pomegranates
Prunes
Quinces
Raisins
Raspberries
Strawberries
Tangerines
'10 (wO)
89
82
82
89
86
81
93
93
93
93
93
82
75
87
89
25
83
78
85
86
82
28
85
18
81
90
87
Point
°Cb
-I.1
-1.6
-2.1
-1.4
-1.6
-0.9
-1.1
-1.1
-0.9
-0.8
-0.4
-0.9
-1.4
-0.8
-0.9
Specific Heat
Latent
Above
Below
heal of
Freezing
Freezing
fusion
cal/(g)("C) cal/gd
0.47
70.9
0.45
65.4
0.45
65.4
0.47
70.9
0.46
68.6
0.44
64.6
0.48
74.1
0.48
74.1
0.48
74.1
0.48
74.1
0.48
74.1
0.45
65.4
0.43
59.8
0.46
69.3
0.47
70.9
-0.6
-0.8
-1.1
cal/(g)(OC)
0.91
0.86
0.86
0.91
0.89
0.85
0.94
0.94
0.94
0.94
0.94
0.86
0.80
0.90
0.91
0.40
0.86
0.82
0.88
0.89
0.86
0.42
0.88
0.34
0.85
D.92
0.90
78
-2.2
0.82
0.43
62.2
Halibut
Herring, Kippered
Herring, Smoked
Menhaden
Salmon
Tuna
Filets or Steaks
75
70
64
62
64
70
-2.2
-2.2
-2.2
-2.2
-2.2
-2.2
0.80
0.76
0.71
0.70
0.71
0.76
0.43
0.41
0.39
0.39
0.39
0.41
59.8
55.8
51.0
49.4
51.0
55.8
Haddock-Cod Perch
Hake· Whiting
Pollock
Mackerel
80
82
79
57
-2.2
-2.2
-2.2
-2.2
0.84
0.86
0.83
0.66
0.44
0.45
0.44
0.37
63.8
65.4
63.0
45.4
80
83
79
-2.2
-2.2
-2.2
0.84
0.86
0.83
0.44
D.45
0.44
63.8
66.2
63.0
87
80
-2.2
-2.8
0.90
0.84
0.46
0.44
69.3
63.8
49
45
56
67
48
70
-1.7
-2.2
0.59
0.56
0.65
0.74
0.58
0.76
D.35
D.33
0.37
0.40
0.34
0.5 I
39.1
35.9
44.6
53.4
38.3
55.8
66
0.73
O.4D
52.6
19
57
42
37
30
8
49
56
38
0.35
0.66
0.54
0.50
0.44
0.26
D.59
0.65
0.50
D.26
0.37
0.33
0.31
0.29
15.1
45.4
33.5
29.5
23.9
0.35
0.37
0.31
39. J
44.6
30.3
Whole Fish
Haddock - Cod
Shell Fish
Scallop, Meat
Shrimp
Lobster, American
Oysters - Clams,
Meat and Liquor
Oyster in Shell
Beef
Carcass (60% Lean)
Carcass (54'10 Lean)
Sirloin, Retail Cui
Round, Retail Cut
Dried, Chipped
Liver
Veal, Carcass
(810J0 Lean)
-1.6
-2.2
-1.0
-D.8
-3.0
-2.D
-1.7
0.45
0.43
0.46
0.46
0.45
66.2
62.2
67.8
68.6
65.4
0.46
67.8
D.44
0.47
0.46
64.6
71.7
69.3
Fruits
Apples, Fresh
Apples, Dried
Apricots
Avocados
Bananas
Blackberries
Blueberries
Cantaloupes
Cherries, Sour
Cherries, Sweet
Cranberries
Currants
Dates, Cured
Figs, Fresh
Figs, Dried
Gooseberries
84
24
85
65
75
85
82
92
84
80
87
85
20
78
23
89
-1.1
-1.1
-0.3
-0.8
-D.8
- I .6
-} .2
- 1.7
-1.8
-0.9
- J.O
-15.7
-2.4
-1.1
0.87
0.39
0.88
o.80
0.80
0.88
0.86
0.94
0.87
0.84
0.90
0.88
0.36
0.82
0.38
0.91
0.45
67.0
0.46
0.40
0.43
0.46
0.45
0.48
0.45
0.44
0.46
D.46
0.43
67.8
51.8
59.8
67.8
65.4
73.3
67.0
63.8
69.3
67.8
62.2
0.47
70.9
Pork
Bacon
Ham, Light Cure
Ham, Country Cure
Carcass (47'10 Lean)
Bellies (330J0 Lean)
Backfat (IOOO% Fat)
Shoulder (67'10 Lean)
Ham (74"70 Lean)
Sausage, Links or Bulk
Sausage, Country
Style, Smoked
Sausage,
Frankfurters
Sausage,
Polish Style
-
-2.2
-1.7
50
-3.9
0.60
0.35
39.9
56
-1.7
0.65
0.37
44.6
54
-
0.63
D.36
43.0
29.5
Thermal Properties of Foods
Table 1
Food or Food
Material
Water
Content,
"10 (wt)"
(continued)
Highest
Freezing
Point
°Cb
Specific HeatC
Latent
Above
Below
heat of
Freezing
Freezing
fusion
cal/(gWC) cal/(g)(OC) call g
Lamb
Composite of Cuts
(67"10 Lean)
Leg (83 "10 Lean)
61
65
1.9
0.69
0.72
0.38
0.40
48.6
51.8
Dairy Products
Butter
Cheese, Camembert
Cheese, Cheddar
Cheese, Cottage
(Uncreamed)
Cheese, Cream
Cheese, Limburger
Cheese, Roquefort
Cheese, Swiss
Cheese,
Processed American
Cream,
Half and Half
Cream, Table
Cream, Whipping,
Heavy
Ice Cream (10"10 Fat)
Milk, Canned, Condensed, Sweetened
Milk, Evaporated,
Unsweetened
Milk, Dried (Whole)
Milk, Dried (Nonfat)
Milk, Fluid (3.7"10 Fat)
Milk, Fluid (Skim)
Whey, Dried
16
52
37
-12.9
7
9
1.2
-7.4
51
45
40
39
40
80
72
57
63
-16.3
-10.0
6.9
2.2
27
5.6
-15.0
74
-1.4
2
3
87
-0.6
91
5
0.33
0.62
0.50
0.25
0.36
0.31
12.8
41.4
29.5
0.83
0.61
0.56
0.52
0.51
0.44
0.35
0.33
0.32
0.32
63.0
40.7
35.9
31.9
31.1
0.5
2
0.84
0.78
0.3
9
0.54
0.42
31.9
0.66
0.70
0.37
0.39
45.4
50.2
0.4
2
0.79
0.22
0.22
0.90
0.93
0.24
0.2
8
0.4
2
21.5
0.46
0.47
69.3
72.5
74
88
51
51
50
-0.6
-0.6
-0.6
-3.9
-17.2
4
9
74
64
69
2.8
0.79
0.90
0.61
0.61
0.60
0.23
0.27
0.79
0.71
0.77
63.8
57.4
59.
0
17
33
10
0.7
7
0.42
0.46
0.35
0.35
0.35
0.42
0.39
0.41
59.0
70.1
40.7
40.7
39.9
59.0
51.0
55.0
1
0.21
0.22
0.28
0.34
0.4
1
56.
6
Candy
Milk Chocolate
Peanut Brittle
Fudge, Vanilla
Marshmallows
2
1
0
17
Nuts, Shelled Peanuts
(with Skins) Peanuts
(with
Skins, Roasted)
Pecans
Almonds Walnuts,
English Filberts
6
2
3
5
0.2
5
0.22
0.22
0.24
0.23
0.25
a
Water contents of fruits and vegetables are from Ref 6, except for Jerusalem artichokes. dried beans and
peas, yams, dried apples, figs, peaches, prunes and raisins; the Jatter are from Ref 7. Water contents of
meats, dairy and poultry products, miscellaneous candy and nuts are also from Ref 7; water contents of
eggs. (yolks, salted) are from Ref 8, while those of fish are from Ref 9 and 10.
b
Freezing points of fruits and vegetables are from Ref 11, and average freezing points of other food and
food materials are from Ref 8,9,10, and 12.
c
Specific heat was calculated from Siebel's formulas. I
d
O"C
S'C
Apples,
Y. Transparent
420
740
Latent heat of fusion was obtained by multiplying water content expressed in decimal form by 79.71, the
heat of fusion of water in caI/g.
1000C
15"C
2190
2O"C
3440
Apples, Delicious
210
310
Apples,
Golden Delicious
220
330
Apples, Jonathan
240
360
Apples,
McIntosh
220
330
200
380
320650
8501250
1100- 12001900 2500
110
220
280430
420640
5701200
9001500
140
250
310440
8301890
10302140
320
350
1390
2750
1670
4900
390·
550
680·
1150
13002100
1800·
3200
1950
3670
3340
8340
3340· 47308340
6010 8870
14270
5560- 9740- 1669018640 20030 30600
1220
3780·
4510· 9600
21220
Apples,
Early Cultivars
Apples,
Apples,
Average 0 f
Many Cultivars
Apricots
Artichokes,
Globe
Asparagus
C
b
Bananas,
Ripening
Beans, Lima
Unshelled
820- 12302020C 2700
1350-
Cb
25"C
Ref
13
6,
1840 Cb
Bananas,
Green
0.34
0.46
0.28
71
Commodity
Avocados
Miscellaneous
Honey
Maple Syrup Popcorn,
Unpopped Yeast,
Bakers,
Compressed
Heat of Respiration, kcal per Metric ton per 24 hr, al
Late Cultivars
Poultry Products
Eggs, Whole (Fresh)
Eggs, Whites
Eggs, Yolks
Eggs, Yolks (Sugared)
Eggs, Yolks (Salted)
Eggs, Dried (Whole)
Eggs, Dried (White)
Chicken
Turkey
Duck
Table 2 Heat of Respiration of Fresh Fruits and Vegetables Held
at Various Temperatures"
18003200
1800
3400
6120
7620
20005000
812010960
14
14
5.
15
5.16
6,1
7
14
14
6401840
1200
2200
1080
2140
1780
3730
Beans, Snap
Cb
Beets, Red, Roots
330
440
20902140Cb
560580
3340
3560
720830
Berries,
Blackberries
960·
1400
17502800
3200- 43005800 8900
Berries,
Blueberries
140640
560750
Cb
250280
Berries,
Gooseberries
420530
750830
Berries,
Raspberries
10801530
t 8902360
1700- 5030- 7000
3400 6200 15000
Berries,
Strawberries
7501080
1000
2030
3000
5800
4340- 62505640 11980
10340- 6, 14, 24
12900
Broccoli,
Sprouting
11401310
21109790
53820- 6.25,26
34250
Brussels Sprouts
940
147
0
1970
2970
3860
5170
10620·
17010· 20790
20850
5840- 55106530 11630
Beans, Lima
Shelled
Berries,
Cranberries
Cabbage,
Penn State
5,19
5,2
0
800012000
20903780
14
3170
5340
6701110
13301970
6.2
1
6,2
2
6.
14.23
5.20
7501100
1200- 22001650 2500
14
10801310
17802030
32803500
5.20
9501050
1450- 2250· 34001700 2600 3500
Cabbage,
White, Winter
300500
450850
Cabbage.
White, Spring
580830
470600
940
6,18
27
580620
Carrots, Roots,
Imperator, Texas
7230
7960
5200
5700
1030
1420
1370·
1940
240
Cabbage,
Red, Early
12930
16520
6,1
8
1200
4310
1920
2420
14
26
1977 Fundamentals Handbook
CHAPTER 29
29.6
Table 2 (continued)
Table 2 (continued)
Heat of Respiration, keel per metric ton per 24 hr, at
Vent of Respiration, kcal per metric ton per 24 hr, lIt
Commodity
O"C
5"C
IO"C
600950
15"C
1320
1730
27
190
410
Cauliflower, Texas
1090
1250
2070
2820
Cauliflower, U.K.
4701470
12001670
25002980
41205010
Celery,
440
670
Celery, U.K.
310440
560780
Celery,
Utah, Can. e
310
550
Cherries, Sour
360810
Carrots, Roots
Can.
Ref.
(18°C)
17904050
360740
Main Crop, U.K.
25"C
20
210420
Carrots. Roots,
20"C
2280
26
4910
O°
C
Commodity
C
Melons,
Watermelon
b
5°C
10°C
190250Cb
460
Mushrooms
17202670
4340
Nuts (kind
not specified)
50
100
Okra, Clemson
2
0
Onions, Dry,
Autumn Spice
3950
f
15°C
1060
1530
1613019360
200
200
300
5340
8920
15970
5801540
140
190
220410
180
210
440
680
6401360
10604170
22103600
40405950
Cb
Cb
190
390
750
1280
390
830
1390
280
720
780
690
9201330
12501610
19702620
N.Y. White
Cherries, Sweet
Corn, Sweet with
250
330
2600
1200
1670
23902560
(18°C)
20
1820
27
780810
16703060
23903060
580860
15302750
17201950
4750
9960
17640
6850
3250
4340
6,28
White Bermuda
Onions, Green,
New Jersey
Olives,
Manzanillo
Oranges,
6,29,30
24900
Onions, Dry.
26
Oranges, Calif.,
Husk, Texas
14101770
(13°C)
14702030
19002940
670810
13501410
30003870
34805810
560590
6701670
6101110
970
2000
Cucumbers,
Calif.
Figs, Mission
31
Valencia
Papayas
52005810
6, 32
5,33
Garlic
180670
360590
Grapes,
170
330
80140
190360
500
Grapes,
Thompson Seedless
120
290
470
13
Grapes,
Ohanez
80
200
440
13
Parsnips, U,K.
Parsnips, Canada
Hollow Crown
710950
5401070
220500
380940
2360
6,34
Peaches, Alberta
230
400
15301840
6,35
Peaches, Several
250390
390560
Concord
Grapes,
Emperor
610720
Cultivars
Peanuts, Cured
I
( 1.70C)
Peanuts,
Not
Cured
Virginia Bunch 1
Grapefruit.
560Cb 720
1080
1330
36
420Cb 780
970
1170
36
California
Grapefruit,
Peanuts, Dixie
Spanish
Pears, Bartlett
190420
310610
Pears, Late
160
220
360850
160300
450950
Florida
Horseradish
500
660
1610
2000
2730
Ripening
Kohlrabi
Leeks
610
1000
1920
3000
1200
1780
32804170
50607150
Pears,
5801000
5,20
1390
Lemons, Calif
Eureka
Lettuce, Head
Calif.
5601030
8101220
16702450
23602500
3670
Lettuce, Head
Texas
640
810
1330
2200
3480
Lettuce Leaf,
1410
5030
(27°C)
5,26
3850
6140
8960
(27°C)
26
1270
2170
2710
4190
6630
26
360640
4201140
9202780
Mangos
2750
45909260
7340
Cantaloupes
Melons
Honeydew
310530360Cb 610
C
b
190310Cb
Early
Ripening
Peas, Green in
Pod
18602860
33704670
Peas, Shelled
28904620
48405953
Peppers, Sweet
360
Persimmons
2410
Limes, Persian
Melons
36
1790
Texas
Lettuce, Romaine,
Texas
1590
Pineapple, Mature
Green
Pineapple,
Ripening
Plums, Wickson
6,37,38
Potatoes, Calif.
White Rose,
950
20602360
27303950
38104370
5,6,26
490
720970
12201460
16102110
6,26,39
13302390
Florida
Oranges, Calif.,
W. Navel
180
240550
Cb
720
120-
Immature
Potatoes, Calif.
White
Rose,
Mature
360420
20°C
13202830
960
2100
25"C
Ref
6,26
6,40
14
(29°C) 26
21110
Thermal Properties of Foods
29.7
Table 2 (continued)
Table 3
Change in Respiration Rates with Time
Heal of Respiration, kcal per metric ton per 24 hr, at
O°C
Commodity
5°C
1O°C
15°C
Heat of Respiration,
20°C
25°C
Ref
Days in
Commodity
potatoes. Calif.
White Rose, 1
C
b
310420
420
420610
560730
-
Storage
kcal(metric ton)
°C
Ref
5
Apples, Grimes
7
180
Very Mature
800
52
(lO°C)
Cb
potatoes, Katahdin
Can. m
240-
480-
260
620
220-
260-
potatoes, Kennebec
Cb
Radishes,
890-
1170-
1890-
4280-
1060
1280
2250
330-
470-
920-
360
500
970
500810
6701110
120-
290-
170
312
with Tops
Radishes,
Topped
Rhubarb, Topped
Rutabaga,
n
Spinach. Texas
-
Spinach, U.K.,
Summer
Spinach, U.K.,
Winter
Squash. Summer,
Yellow,
Straight-neck
Squash, Winter,
-
27
7590-
%80-
6
4760
8340
11790
1700-
2920-
4120-
2000
3000
4650
-
18902780
24503480
-
48
-
650-
-
-
27
-
26
6770
10940
14070
710-
1670-
3580-
-
11320-
1310
1970
4590
1070-
1790-
4170-
1550
3850
6320
720780C
8601140C
21402250
Cb
Cb
Cb
Sweet Potatoes,
Cb
Cb
b
b
20
13230
118°C)
-
(18°C)
45905560
1192014900
52005950
800-
980-
1350C
1350
860-
13501410
C
C
1960C
Cb
Cb
430Cb
920C b
Cured, Yellow Jersey
Sweet Potatoes,
Tomatoes. Texas,
-
Cb
3670
1530
2140
16
920
1590
I
3
16
4900
2410
1710
6430
3980
1840
16
Beans, Lima,
2
1830
2200
18
in Pod
4
1230
1770
6
1080
1620
I
2
440
162
3
350
15
Blueberries,
6
Broccoli,
Waltham 29
I
4
8
-
4530-
6
Corn, Sweet,
I
3140
2
2250
4
1880
I
800
2
12
730
730
10
30
240
370
550
920
in Husk
49
-
-
49
1250
2120
26 1 0
(27°C)
26
1630
2480
2950
(27°C)
26
Figs, Mission
180
Cb
-
1310-
1470
1470
1530
Turnip, Roots
530
Watercress
1190-
2680-
5060-
10130-
1610
2980
5660
12520
610
4470
2690
2020
54
-
26
-
32
33104480
Garlic
-
53
-
-
14702140
-
20
-
Tomatoes, Calif.
Pearson, Mature
Green
580-
2750
4
870Cb
Tomatoes, Texas,
Ripening
Cb
I
-
-
Mature Green
Cb
670
Blue Crop
1750
Noncured
Cb
1070
180
Asparagus,
Martha Washington
7470
Cb
180
80
960
2810
Cured, Puerto Rico
30
Artichokes, Globe
550
Butternut
Sweet Potatoes,
27
-
260
Laurentian, Can.
(day)
SOC
18302940
50
Olives,
20
-
Lettuce,
Great Lakes
860
2020
1040
1220
I
5
550
800
10
490
920
I
55
-
2390
56
(l5eC)
Manzanillo
-
33
5
1770
-
a
Column headings indicate temperatures al which respiration rates were determined, within
10
-
1350
1°C except where the actual temperatures are given in parentheses.
b
The
large leaner "C" denotes a chilling temperature. If the temperature is borderline, not
Onions, Red
damaging 10 some cultivars, or if exposure is short, a value is given.
C
Rates are for 110 2 mo and 2 10 4 mo storage, the longer storage having the higher rate. except
at DOC, where they were the same.
d
Rates are for I 10 2 mo and 4 to 6 mo storage. respiration increasing with lime only at
Plums, Wickson
15°C.
e
Rates are for J 10 2 mo storage.
I
100
30
150
-
57
120
200
2
120
240
6
120
430
18
180
550
47
f
Rates arc for 1 to 2 mo and 4 to 6 mo storage; rates increased with time at all temperatures
as dormancy was lost.
g
Rates are for I to 2 mo and 4 10 6 reo; rales increased with time at all temperatures.
h
Shel1cd peanuts with about 7flJo moisture. Respiration after 60 hr curing was almost
2
Potatoes
negligible, even at 30°C.
370
6
-
490
10
-
430
1
1080
1750
2
810
1880
5
810
2020
5
-
51
i
Respiralion for freshly dug peanuts, not cured, with about 35 to 40flJo moisture. During
curing, peanuts in the shell were dried to about 5 to 6070 moisture, and in roasting are dried further to about
2070 moisture.
2070 moisture.
Strawberries,
Shasta
j
Harvested 98 days after planting. 51
24
k 51
Harvested 126 days after planting.
I
Harvested 141 days after planting.
51
Tomatoes, Pearson,
m
Rates are for J to 2 mo and 4 to 6 mo with rate declining with time at 5°C but increasing at
15°C as sprouting started.
n Rates are for J to 2 and 4 to 6 mo; rates increased with rime, especially at 15°C where
sprouting occurred.
Mature Green
1960
(20°C)
15
20
-
1710
1470
50
1977 Fundamentals Handbook
CHAPTER 29
29.8
Table 4 Enthalpy of Frozen Foodsa
Water
Coolant
Product
Mean Specific Heal
h 4 tu 32°C.
kcal/(kg1 (dog C1
Temperature ºC
-40-JO-20-1S-)6-J4-12 -10
Enthalpy, kcal/kg u;'()
water nonfrozen c
2 4 6
9 10 12
Enthalpy,
10 I
070 (wI)
-9
8
-7
6
23
19
24
27
23
29
27
31
21
7
18
7
19
20
21
-4
Fruits and Vegetables
Applesauce
Asparagus. Peeled
82.8
Y2.6
0.89
0.95
kcal/kg
1 8 20
1417
12
1315
56
water unfrozen
Blueberries
85. 1
0.90
Entha1py, kcal/kg IJ/o
11
1213
7
8
1517
911
20
14
11
12 13
7
8
15 1 7
911
20
14
water unfrozen
Carrots
87.5
Enthalpy, calk
0"10
water unfrozen
Cucumbers
95.4
10 11
15
0.96
Enthalpy, kcal/kg fJfo
85.5
0.91
22
15
17
water unfrozen
Peaches.
85. 1
0.90
83.8
0.89
without stones
1719
1416
22
18
12 13 16
8 9 I1
Entha1py, kcal/kg 070
1719
1316
121416
9 10 12
Enthalpy, keeling 070
Plums, without
80.3
0.87
stones
Raspberries
22
18
0.89
Strawberries
90.2
89.3
0.93
0.94
o
131618
1 4 16 1 8
water frozen
o
I1
7
20 23
20 23
12 14
89
water unfrozen
I1
1618
1013
12
1314
6
Sweet Cherries,
77.0
water unfrozen
10 12 13
Tomato Pulp
75.8
o
water unfrozen
0.85
0.96
16
7
1416
18
79
11
14 16 18 21 24
1 5 1 7 1 9 21 26
23
19
10 11
Entha1py, kcal/kg 070
1 8 20
1618
23
21
12
1 315
17
5
6
7
water unfrozen
24
21
28
29
21
17
12
29
32
water unfrozen
18
8
Eggs
Egg White
86.5
0.91
Enthalpy, kcal/kg
0
Egg Yolk
Whole Egg with
50.0
66.4
0.74
0.79
Enthalpy, kcal/kg
0
070 water unfrozen
-
Enthalpy, kcal/kg
4 9 10 11
1214
- 10 -
070 water unfrozen
0
4
9 10 11
13 14
-
4
9 10 11
15
12 13
26
18
21
24
30
18
26
20
1
8
1
9
2
1
25
28
3
35
33
16
34
37
31
25
20
1
9
18
9
2
1
14
32
36
22
1
6
35
40
27
26
80.3
0.88
Haddock
83.6
0.89
Perch
79. 1
0.86
74.5
0.84
Beef. Lean Fresh
Beef, Lean, Dried
26. 1
0.59
Enthalpy, kcal/kg
070 water unfrozen
Entha1py, kcal/kg
% water unfrozen
0 5 10 11 13
10 10 11 12
0
8
Enthalpy, kcal/kg
O7owaterunfrozcn
Enthalpy, kcal/kg
070 water, unfrozen
Entha1py, kcal/kg
water unfrozen
12
5 10 1 I 13
8
9
JO
1416
18
J314
16
0 5 10 11 12
1415
17
10 10 II 12 12
13 14
15
0 5 10 11 12
1416
17
4 10 12 13
1415
1516
43
16
17
96 96 97 98 99 JOO
30
22
13
20
11
27
20
24
18
39
47
45
55
36
33
39
24
2
10
1
17
18
22
17
18
14
21
20
23
23
26
28
20
21
22
22
24
27
19
21
23
33
15
16
17
1
9
20
21
25
28
18
19
23
27
34
20
21
23
25
28
33
15
16
2
1
1
8
1
7
19
19
14
17
18
1
8
1
6
19
21
21
23
18
1 8 20
20
24
31
24
27
31
22
26
32
~
27 n
~ 31 40
22
20
18
23
22
17
1
37.3
0.62
Entha1py,
Whole Wheat Bread
42.4
0.64
Enthalpy, kca1/kg
kcal/kg
9 10 10
12 14
16
18
1I
13 15
1
21
9
a
Above -4()OC. To convert from kcal/kg to Btu/lb, multiply by 1.80. Adapted from Ref 4,65,66,81,82 and Ref 8. Temperature range limited
to 0 to 20°C for meats.
C
Total weight of unfrozen water = (total weight of food)(% water content/ 100)(070 Water unfrozen/ I (0). Calculated for a
weight composition of 58% white (86.5070 water) and 32070 yolk (50fJio water).
C
Date for chicken, veal, venison very nearly matched the data for beef of the same water content.8
40
40
16
1
9
18
Bread White
Bread
39
38
27
27
23
32
29
28
1
SO
38
42
1
9
14
17
13
10 10 11 12 13
0
35
29
15
1416
II 12
II
35
3
1
1
8
1
6
29
31
28
2
6
Fish and Ideal
Cod
1
28
26
23
18
33
30
1
34
25
26
22
23
2
6
7
24
30
26
1
9
Shelled
29
25
23
13
16
1
22
17
23
f170
12
24
27
33
25
Enthalpy, kcal/kg
1
7
24
27
29
121416
10 12 14
23
15
10
20
19
Entha1py, kcal/kg 070
water unfrozen
92.9
20
16
Entha1py, kcal/kg 070
withou1 Stones
Tall Peas
26
27
Enthalpy, kcal/kg fJ!o
5-6
0.86
22
19
4
33
6
20
Enthalpy, kcal/kg %
Spinach
1 7 19
1417
water unfrozen
Entha1py, kea1/kg %
82.7
1
5
water unfrozen
Pears, Bank-II
22
17
15
12 13 15
8 10 12
Enthalpy, kea1/kg 070
8
2
1
\.,'atcr unfrozen
Onions
36
37
44
2
1
1214
30
20
22
25
23
2
5
28
28
32
E.
D.
F.
Thermal Properties of Foods
29.9
90
70
60E
:''"::
~
50
'"
,,:
a.
...J
40
<t
:r:
>z
UJ
30
WATER CONTENT. % (by weight)
Fig. 1 Enthalpy of Beef (Adapted from Ref 4)
temperature range. Conversely, for a 60070 water content, freezing
starts at a much lower temperature, and appreciable freezing occurs
over a greater temperature range; because of the lower water content,
however, the energy associated with freezing is significantly less.
Fig. 2 does not give enthalpy of whole fruits and vegetables
G.
H.
130
because of the effect of solids (fibers, rind, membranes, stems, and
seeds), which are not a part of the juice, and do not participate in the
change of phase. From data for 16 fruits and vegetables, Riedel 65
obtained the following correlation between enthalpy of fruits and
vegetables, enthalpy of juice (Fig. 2), and percent solids-not-juice
(solids other than those present in the juice).
where
!J.h = enthalpy difference, kilocalories per kilogram.
X
snj
= solids-not-juice, percent by weight.
!J.hj = enthalpy difference of juice from Fig. 2, kilocalories per kilogram.
!J.T = temperature difference, degrees Celsius.
Eq 4 and Fig. 2 have been used to calculate enthalpy of the fruits and
vegetables investigated, with results shown in Table 4. Except for
plums and onions, enthalpy of fruits and vegetables, Table 4, differs
from Riedel's measured values by less than 5% of enthalpy at DoC.
Maximum deviation for plums and onions is 12%.
Using measured enthalpy values for egg white, yolk, and shell,
Riedel66 calculated enthalpy of whole egg with shell. These calculated
values are shown in Table 4. Also in Table 4: enthalpy of frozen egg
products. Enthalpy of frozen egg yolk of various water contents is
shown in Fig. 3.
Fresh Foods
Specific Heat. Above freezing, specific heat may be used instead
of enthalpy. Specific heat of fruits, vegetables, juices, meats, breads,
and eggs are shown in Table 4; selected data are shown as a function
of water content in Fig. 4. For juices, variation of specific heat with
water content is uniform (Fig. 4) and closely matches the equation:
WATER CONTENT. % (by weight)
Fig.2 Enthalpy of Fruit Juices and Vegetable Juices
(Adapted from Ref 65)
CHAPTER 29
29.10
1977 Fundamentals Handbook
Table 5 Specific Heat of Beef at Temperatures Below 64
40oe
1.
0
Temperature,
0.8
0.
6
°C
Beef, Chuck
-110
- 80
- 50
0.24
0.35
0.44
40
0.49
0.4
WHOLE EGG
0.2
L-
EGG YOLK
WHOLE WHEAT BREAD
WHITE BREAD
foods are nonhomogeneous and anisotropic; however, Eq 6 has been
used to find the thermal behavior of foods. 72-75 Thermal diffusivity
may also be defined:
ORIEO Bm
o
I
o
10
20
I
I
[
30
40
50
I
60
70
I
80
90
Specific heat,
kcal/(kg)(deg C)
Product
100
WATER CONTENT.
Fig. 4 Specific Heat of Food in the Temperature Range of 4 to 32°e (0
to 200e for Meats)
a = 0.0143 klQcp
(7)
where
a = thermal diffusivity, square centimeters per minute.
Cp =
0.40 + 0.006[O?owater (wt)1
(5)
where
cp = specific heat at constant pressure, kilocalories per
(kilogram)(degree Celsius).
When data are needed for juices not in Fig. 4, Eq 5 yields reasonably
accurate specific heat values.
For other foods, the correlation with Eq 5 is not as precise because
of distorting effects of the solids-not-juice content (fats, fibers, rind,
membranes, stems, and seeds). However, deviations are not great and,
when data are lacking, Eq 5 may be used to estimate specific heat.
In comparing data from Table I and Fig. 4, slight differences in
specific heat values may be noted for the same food product,
particularly at low moisture contents. This is because Table 1 data
were computed using Siebel's formulas I which, in its time,
represented the best information available for foods generally; while
Eq 5 is based on more recent experiments.
Data for meats (Fig. 4) were obtained in the temperature range of 0
to 20°C; caution is recommended in extrapolating the data into the
range of 20 to 50°C, particularly for meats with high fat content. For
beef fat, the change in enthalpy from 20 to 50°C is more than double67
the change in sensible heat due to specific heat alone; the additional
heat is required to melt the fat.
At temperatures between -40 and O°C, the specific heat of beef fat
is constant at 0.40 kcal/(kg)(°C).67 Above 50°C, it is constant at 0.45
kcal/(kgWC). Between 0 and 50°C, the energy required for a unit
change in temperature is highly variable, because beef fat components
change state at different temperatures. Similar data are available for
26 additional fats and oils. 67
Thermal Diffusivity. For non steady state heat transfer, the
important property is thermal diffusivity, a, defined by the Fourier
equation:
where
x,y,z = rectangular coordinates.
T = temperature, degrees Celsius. T =
time, minutes.
a = thermal diffusivity, square centimeters per minute.
Eq 6 has been solved for numerous conditions, and graphical
solutions are available. 68-73
Use of Eq 6, however, is limited to temperatures above freezing;
and, from a mathematically rigorous point of view, is restricted to
homogeneous, isotropic substances. Generally,
k = thermal conductivity, milli-watts per (centimeter)(degree
Celsius).
Q = density, grams per cubic centimeter.
cp = specific heat at constant pressure, kilocalories per
(kilogram)( degree Celsius).
The constant 0.0143 is required because of the units in which k, Q,
and Cp are defined. The denominator on the right-hand side of Eq 7
denotes heat absorbing ability; the numerator, ability of the material to
conduct heat through itself. Schneider 76 interprets thermal diffusivity
in terms of heating time:
"In a transient heating process the thermal capacity of the conducting
material dictates the quantity of heat absorbed and the thermal
conductivity of the conducting material sets the rate of this heat
addition. The reciprocal of the diffusivity, I/", = min/cm2, is a measure
of the time required to heat this material to some required temperature
level and evidently this time is directly proportional to the square of the
conducting path length."
Thermal diffusivity data for foods are scarce; but reasonable
estimates can be obtained from Eq 7, using values of thermal
conductivity, specific heat, and density, given elsewhere in this
chapter. A few experimental values are available (Table 6). Like other
thermal properties of foods, thermal diffusivity strongly depends on
water content, as shown by Riedel's correlation: 77
a = 0.053 + (aw - 0.053)[% water (wt)1
(8)
where
a = thermal diffusivity, square centimeters per minute.
a w = thermal diffusivity of water at the desired tem-
perature, square centimeters per minute.
Thermal diffusivity of water as a function of temperature is available
elsewhere. 3 When data are lacking, Eq 8 may be used to estimate
thermal diffusivity of foods; but its use must be limited to water
contents above 40% by weight. For water contents below 40%, there
is some question whether the water represents the continuous phase. If
another constituent (such as fat-usually a dispersed phase) replaces the
water as the continuous phase, there would be an abrupt drop in
thermal conductivity and thermal diffusivity.
Meats. Eq 8 applies to foods with variable amounts of water, fat,
and fiber; if the water content is reduced, it is assumed that the water
is replaced with fat. For this reason, the thermal diffusivity of 0.053
cm2/min, obtained from Eq 6 for zero water content, is reasonably
close to a computed value for fat (from Eq 7). Thus, Eq 8is applicable
only where a reduction in water content is compensated for by an
increase in fat content. Eq 8 cannot, for example, be used for freeze
dried samples, where a reduction in water content is compensated for
by an increase in air content.
Thermal Properties of Foods
29.11
Table 6
Product
Apple, Whole, Red Deliciousa
Applesauce
Bananas, Flesh
Cherries, Flesh b
Peaches b
Potatoes, Whole
Potatoes, Mashed, Cooked
Strawberries, Flesh
Sugar Beets
Codfish
HalibutC
Beef, Chuckd
Beef, Round d
Beef, Tongued
Corned Beef
Ham, Smoked
Ham, Smokedd
Water
Thermal Diffusivity of Some Foods
Water
content,
0/0 (wt)
85
37
37
80
80
76
76
78
78
92
Fat
content,
%(wt)
81
81
76
66
71
68
65
65
64
64
-
I
16
4
13
-
Apparent
density,
(g/cm3)
0.84
-
-
Temperature,
°C
o to 30
5
65
5
65
5
65
0 to 30
2 to 32
o to 70
5
65
5
o to 60
5
65
40 to 65
40 to 65
40 to 65
40 to 65
5
65
5
40 to 65
30
-
-
1.05
0.96
1.04 to 1.07
-
1.07
1.06
1.09
1.06
1.09
-
14
-
Thermal
diffusivity,
cm2/min
0.082
0.063
0.067
0.073
0.084
0.071
0.085
0.079
0.084
0.080
0.074
0.087
0.076
0.076
0.073
0.085
0.088
0.074
0.080
0.079
0.068
0.079
0.071
0.083
0.089
0.096
Ref
83
77
77
77
77
77
77
84
85
86, 87
77
77
77
75
77
77
88
88
88
88
77
77
77
88
3
3
a Data is applicable only to raw whole apple.
bFreshly harvested.
cStored frozen and thawed prior to test.
d Data is applicable only where the juices extruded during heating remain in the food samples.
Table 7 Thermal Properties of Food Container Materials (0 to 80°C)
Product
Stainless Steel (302)
Type 18-8 Austenitic
Glass, borosilicate
Nylon, Type 6/6c
Polyethylene, High
Density C
Polyethylene, Low
Density C
PolypropyleneC
Polytetrafluoroethylene C
Thermal
conductivity,
m W /(cm) (deg C)
160
Specific
heat,
kcal/(kg) (deg C)
0.12
Apparent
density,
g/ cm 3
7.9
Thermal
diffusivity, b
(cm2/min)
2.4
II
2.4
4.8
0.20
0.40
0.55
2.2
1.1
0.96
0.36
0.078
0.13
90
91
91
3.3
0.55
0.93
0.092
91
1.2
2.6
0.46
0.25
0.91
2.1
0.041
0.071
91
91
Ref
89
aTo obtain: W I(m) (deg C). multiply by 0.1; cal/(cm) (sec) (deg C). multiply by 2.39 x to -4; BlU/(hr) (rt) (F), multiply by 0.0578; kcal/(hr) (m) (deg C), multiply by 0.0856. bCa1culated; a ~ 0.0143
k/QCp)' To obtain in2/min, multiply by 0.155.
COata applicable only to monolayer materials.
When meat samples are heated to temperatures in the range of
40 to 65°C, juices sometimes exude, and heat transfer rates may
be altered significantly, depending on whether the exuded juices
remain in the sample and contribute to heat transfer, or drain away
from the meat and significantly lower thermal conductivity. The
data in Table 6 for the temperature range of 40 to 65°C apply only
where juices remain in the meat sample.
Fruits. Most data for fruits (Table 6) apply to the flesh of the
fruit; for products such as apples, cherries, and peaches, the data
can be used for the whole fruit (with rind) because the very thin
rind neither improves nor inhibits heat transfer.
Conversely, the relatively thick rind of grapefruits, oranges, and
lemons, has a pronounced effect on heat transfer rates, even
though thermal diffusivity of the rind is about the same as that of
the juice vesicle.78 It may seem that these equal thermal
diffusivities should result in equal heat transfer
rates through both components, But, the problem arises because
the thermal conductivity of the rind is only half that of the juice
vesicle.79 The rind has a spongy layer of loosely arranged cells
with many gas-filled intercellular spaces, producing an insulating
effect. Because of these spaces, the rind density is only 0.5 that of
the juice vesicle.78 The lower density compensates for the lower
thermal conductivity, leaving thermal diffusivity essentially
unchanged (Eq 7).
The rind's insulating effect results from the lower thermal
conductivity and correspondingly higher temperature gradient,
which reduces heat transfer rates through the rind. If the rind had a
thermal diffusivity and thermal conductivity equal to that of the
juice vesicle, there would be no insulating effect.
Data are available on the "effective" thermal diffusivity of
whole grapefruits, oranges, and lemons.71,74.78-80 However,
because of the rind's insulating characteristics, the reported
1977 Fundamentals Handbook
CHAPTER 29
29.12
values (except in Ref 74) are significantly lower than expected for
a food of high water content. These values do represent an
empirical coefficient for any given experiment, and may be used
to estimate heating and cooling times. They are dependent,
however, on rind thickness, fruit size, and time of harvest. 78 Since
the data do not meet the criteria of a basic thermal property, they
are not listed in Table 6.
Food Container Materials
In calculating heat transfer in foods, it may be necessary to
consider the effect of the food container. Thermal properties of
some food container materials are given in Table 7.
In much the same way as a thick rind insulates the flesh of fruit,
a food container may insulate food. Thermal diffusivities and
conductivities of glass and stainless steel are significantly greater
than those of foods (Tables 7 and 8). Consequently, these two
materials will not significantly delay heat transfer in foods.
Thermal diffusivity of low density polyethylene is considerably
lower than that of glass or stainless steel, but about the same as
that of beef (Table 6). A container fabricated from polyethylene
0.3 mm thick has about the same effect on heat transfer as an
additional 0.3 mm thickness of the food, provided there is intimate
contact between food and container, thereby preventing
accumulation of air spaces on the inside surface of the container.
Thermal conductivity of low density polyethylene is somewhat
lower than that of beef, and, if the container wall is thick enough,
it could reduce heat transfer rates to the food; but the effect is
negligible when the container diameter is greater than about 10
em and wall thickness less than about 0.4 mm.
The data for plastics (Table 7) apply. only for monolayer
materials, and not for plastic laminates. Thin plastic films can
have a thermal resistance much greater than indicated by their
thermal conductivities, due to imperfect contact between
laminated films and gas bubble buildup on the hydrophobic
surface of the plastic.
THERMAL CONDUCTIVITY
Heat conduction (as opposed to convection and radiation) can
be described as the transfer of heat associated with motion of the
particles (molecules, atoms, electrons) of a substance without
appreciable displacement or flow of those particles. This mode of
heat transfer depends on a property of substances called
coefficient of thermal conductivity: the quantity of heat that flows
in unit time through a plate of unit thickness and unit area having
unit temperature difference between its faces. For food
refrigeration, this is commonly expressed as MW /(cm)(°C). The
U.S. customary unit is [(Btu)(ft)/(hr)(ft2)(deg F)1; and the SI unit
for thermal conductivity is [(watt per square meter) per (Kelvin
per meter of thickness)1, written watt per (meter)(Kelvin), or, in
symbols, W/(m' K).
Thermal conductivity depends on many factors, including: kind
of substance (metal, dielectric, crystalline, amorphous, solid,
liquid, gas); composition (impurities, mixtures); structure and
structural orientation; temperature; and pressure. Thus, accurate
measurement and prediction of thermal conductivity may be
difficult for many foods, although a large amount of experimental
data is available, and estimations or predictions sufficiently
accurate for practical purposes can be made for many food
materials.
Thermal Conductivity of Mixtures
Thermal conductivity for mixtures of 60/0 gelatin gel and
butterfat arranged in several ways are shown in Fig. 5, which was
adapted from a more detailed study. 94 Since the ratio of
o
20
4
0
60
8
0
10
0
BUTTERFAT IN MIXTURE, % (VOLUME)
Fig.5 Thermal Conductivity of Gelatin Gel
16% (wO1-Butterfat Mixtures at 4°C. A. Alternate parallel layers
parallel to direction of heat f/ow (calculated).
B. Small spherical particles of butterfat dispersed in gelatin gel (calculated using
Maxwell-Eucken equation).
I. As for (2) but experimentally determined values up to 52"70 butterfat.
D. Alternate parallel layers perpendicular to direction of heat f/ow (calculated).
NOTE: Experimentally determined values for thermal conductivity of butterfat (1.76) and
gelatin gel (5.91) are used in calculations.
thermal conductivities of butterfat and 6% gelatin gel is roughly
the same as for fat and lean portions of meat, the curves give some
indication of the variability to be expected in the thermal
conductivity of meat. Conductivity is maximum for layers
arranged parallel to the direction of heat flow (Curve A) and
minimum for perpendicular layers (Curve D); other arrangements
fall in between. Curves B (calculated) and C (experimental) give
values for small spherical butterfat particles dispersed in the gel.
The calculated curve was obtained using Eucken's adaptation95 of
Maxwell's equation96 for conductivity of a mixture composed of
small spheres of one substance dispersed in another:
k = k 1 - [1 - a(kd/kc)1b
c
1 + (a - l)b
(9)
where
k = conductivity of the mixture.
kc = conductivity of the continuous phase. kd
= conductivity of the dispersed phase.
a = 3kc/(2kc + kd)·
b = Vd/(Vc + Vd)·
Vd = volume of dispersed phase. Vc
= volume of continuous phase.
The derivation of this equation assumes the dispersed particles are
sufficiently separated for their effects in disturbing heat flow to be
independent of each other.
Effect of Temperature
Temperature effects on thermal conductivity of a number of
meats and fats, as well as gelatin gel and ice, in the range of 10 to
-25°C are shown in Fig. 6 (composition of sample
Thermal Properties of Foods
29.13
J.
20
I
I
1
I
I
I
~
24
TURKEY
PORK
CODFISH(l) I
BEEF (II)
22
I
20% GEL
15
TURKEY
. -;i j;
PORK(l)~
SALMON(l)
SALMON 11!
BEEFI1!
~
10
TURKEY()
~
,
14
WA T E R
8
5
MEAT IAV.I
-25 -20 -15 -10 -5 o
5
TEMPERATURE °C
Fig. 6 Thermal Conductivity of Meats, Fats, Gelatin Gel, and Water
between 100C and -25° C
(II indicates heat floK' parallel to fiber structure; 1- indicates heat flow perpendicular
to fiber structure).
materials is in Table 8), also adapted from Ref 94. Rapid change of
phase and the possibility of sub cooling and metastable states make
values in the 0 to -10°C range more difficult to measure and less
reliable than at other temperatures. The effect of meat fiber or
structure orientation in the frozen state appears to be 10 to 20%.
Thermal conductivity of fats is affected relatively little by temperature
in the range studied.
Thermal Conductivity and Water Content
The relation between thermal conductivity and moisture content for
a wide range of food materials, based on a study 97 using the
aforementioned Maxwell-Eucken equation, is shown in Fig. 7. The
effect of temperature is also included. The curves represent data on
sugar solutions and fruit juices, 98 milk and evaporated milk, 99
butter fat and gelatin gels, 94 fats, 94.100 and meats, 94.100-102 with
an accuracy of ±100J0 if an allowance of ±7OJo is made for fiber
direction in frozen meats. The allowance is positive for heat flow
parallel to the fiber structure; negative for flow across the structure.
The study on which Fig. 7 is based differs from a number of others
94.98.99.103.104 in that water content was calculated on a volumetric
rather than a gravimetric basis, and a wider range of food materials
and temperatures is covered. In addition, only materials not containing
appreciable air were included. For the above-freezing temperatures,
the curves follow the Maxwell-Eucken equation, assuming water to be
the continuous phase, and the nonaqueous part the dispersed phase.
For below-freezing temperatures, the curves best fitting the
experimental data (Fig. 7) represent an average of the results
calculated assuming ice to be the dispersed phase in one instance, and
the nonaqueous part plus unfrozen water to be the dispersed phase in
the other instance.
o
1
0
20
30 40 50 60 70 80
90 100
WATER CONTENT %(VOL)
Fig. 7 Effect of Water Content and Temperature on Thermal
Conductivity of Food Materials
The Maxwell-Eucken equation is valuable in predicting thermal
conductivity from water content, even though the assumptions on
which it is based do not appear to be closely met, because:
I. The thermal conductivity of water is high compared to that of the
nonaqueous components, especially at below-freezing temperatures.
2. The thermal conductivity of the nonaqueous components falls within
a relatively narrow range-most organic substances between 1.4 and 2.0 m
W /(cm)(°C) with most fats in the 1.6 to 1.8 range.
3. The densities of fats, proteins, and carbohydrates fall within narrow
ranges which are relatively close together (values used in the stud y97 were
0.92, 1.35. and1 .55 g/cm3 for fat, protein, and carbohydrate, respectively).
Tabular Data
Thermal conductivity data for a wide range of foods and food
materials are given in Table 8, which is based on a compilation made
by the Thermal Properties Research Center at Purdue University under
ASH RAE sponsorship (RP-62). Since TC 11.9 used the TPRC report
as its data source without going back to the original literature, it cannot
accept responsibility for correctness of the abstractions made by the
TPRC, although care was used in selecting data for Table 8 to
minimize typographical or other errors. While the TPRC report does
not cover all literature on thermal conductivity (178 articles
representing most of the world's reasonably accessible literature on the
topic were reviewed), it was considered a good basis for Table 8.
To reduce the volume of data in the TPRC report and facilitate use
of Table 8, the data in some instances have been averaged,
interpolated, extrapolated, selected, or rounded off. For example,
where conductivity values were given for a range of conditions
(temperature, water content, pressure), the limits of the range were
usually included with a sufficient number of points in between to
represent the data. Where values for similar materials were given by
different authors, selection was based on completeness of information
and knowledge of the author's work by the committee's reviewers, as
well as other factors considered to favor one author over another. Data
from different sources were not averaged. Data of doubtful accuracy
or reliability were omitted.
29.14
CHAPTER 29
Table 8
Food or Food Material
Temp,
°C
1977 Fundamentals Handbook
Thermal Conductivity" of Food and Food Materials
Water
Coolant,
070 (wI)
k'
mW/(em) (deg C)
Rating
A,I,U
Ref'
Remarks-Compositionf
U
105
0.75 d
0.75 d
U
U
U
106
107
108
O.66d
A
109
Values taken from plot of
series of values given by authors
Grains, Cereals, and Seeds
Corn, Yellow
32
Flax Seed
Oats, White English
Sorghum
32
27
5
Wheat, No. I Northern
Hard Spring
Wheat, Soft White Winter
0.9
14.7
30.2
34
12.7
13
22
2
1.40
1.59
1.72
1.15
1.30
1.31
1.50
1.35
31
7
10
14
5
1.49
1.55
1.68
1.21
10
15
1.29
1.37
0.6R d
Hybrid Rs61 0 grain
110
U
105
Values taken from plot of series
of values given by author
U
II I
0.75 d; machine sliced, scalded,
Fruits, Vegetables, and
By-products
Beans, Runner
9
3.89
-13
-6
-16
9.20
3.R5
6.69
I
I
I1 I
III
Carrots, Puree
-8
12.6
U
III
Potatoes, Mashed
Potato Salad
Apple Juice
10.9
4.79
5.59
6.31
5.04
5.64
3.89
4.35
4.18
I
I
A
III
112
98
Apple
-13
2
20
80
20
80
20
80
8
Black Currants
-17
3.10
Gooseberries
-15
2.76
Grapefruit .Juice
Vesicle
Grapefruit, Ring
30
4.64
A
30
2.37
A
79
Grapefruit, Whole
25
3.26
A
113
Grape, Green, Juice
20
80
20
80
20
80
25
30
30
25
25
20
80
20
80
20
80
-16
-14
-15
5.67
6.39
4.96
5.54
3.96
4.39
4.39
4.35
1.79
4.90
4.10
5.50
6.29
4.75
5.32
4.02
4.46
2.47
11.0
9.6
A
98
packed in slab
Broccoli
Carrots
Lemon
Orange Juice Vesicle
Orange, Rind
Orange, Whole
Orange, Whole
Pear Juice
Plums
Strawberries
87
70
36
89
68
37
85
60
39
0.56 d; heads cut and scalded
0.6 d; scraped, sliced and scalded
0.89 d; slab
0.97 d; tightly packed slab
1.01d
Refractive index at 20°C=1.35
Refractive index al 20°C=I.38
Refractive index at 20°C= 1.45
A
74
Tasmanian French Crab,
whole fruit; 140g
I
III
I
111
O.64d
0.58 d; mixed sizes
79
Marsh, seedless; 786 p
Marsh, seedless; 812p
Marsh
Refractive index at 20°C= 1.35
Refractive index at 20°C=1 .38
Refractive index al 20°C=I.45
A
A
A
A
I
A
113
79
79
1 13
113
98
Eureka
Valencia; 786p
Valencia; 812p
Valencia
Washington navel
Refractive index at 20°C-I.36
Refractive index at 20°C-l.40
Refractive index at 20°C-l.44
!
I
111
III
0.6Id; 4 cm diam., 5 em long
Mixed sizes, 0.80 d slab
Mixed sizes in 57°10 sucrose syrup,
slab
Meat' and Animal By-products
Beef Brain
Beef Fat
35
35
35
77.7
0.0
20
4.96
1.90
2.30
A
A"
114
114
12% fat; 10.3% protein; 1.04d
Melted 100% fat; 0.81 d
0.86 d
Thermal Properties of Foods
Table 8
29.15
Thermal Conductivity' of Food and Food Materials (Continued)
Water
Food or Food
Materialb
Beef Fat .L b
Temp,
content,
°C
% (wt)
2
-9
35
Beef Kidney
Beef, Lean =b
35
3
-15
20
-15
6
Beef, Lean .L b
-15
20
Beef Liver
Beef, Lean =b
Beef, Lean =b
kC,
mW/(cm) (deg C)
9
6
-15
3
-15
6
4
6
3
30
20
-15
20
-15
3
-15
4
-15
20
-13
4
-15
20
-14
25
Beef, Lean .L b
Beef, Ground
Horse Meat .L b
Lamb b
Lamb =b
Pork Fat
Pork, Lean =b
Pork, Lean =b
Pork, Lean.L b
Pork, Lean .L b
Sausage
V eal.L b
Veal = b
A,I,U
Remarks-Composition1
Ref"
2.17
2.87
5.24
A
94
A
114
8.3% fat, 15.3% protein; 1.02 d
A
A
114
94
7.2% fat; 20.6% protein;
A
101
1.4% fat
76.5
4.88
5.06
14.2
4.30
14.3
4.00
A
101,
115
2.4% fat
79
13.6
4.80
A
101
Inside round; 0.8% fat
A
101, 115
76A
72
75
79
-15
Beef, Lean .L b
Rating d
89% fat
Sirloin; 0.9% fat
13.5
76
4.10
68
11.4
4.71
11.2
4.06
4.10
3.51
3.64
4.60
4.56
11.2
3.99
12.7
2.15
2.18
4.78
14.9
4.53
14.2
4.56
12.9
5.05
13.0
4.27
25
62
3.87
A
20
-15
28
75
4.70
13.8
A
118,
119
118,
119
101
4A5
A
101
120
120
74
67
62
55
53
70
72
71
6
72
76
76
72
76
75
-15
A
94
A
116
3% fat
Flank; 3 to 4% fat
12.3% fat; 0.95 d
16.8% fat; 0.98 d
18% fat; 0.93 d
22.2% fat; 0.95 d
I
A
117
101
Lean
8.7%fat
A
101
9.6% fat
A
94
93% fat
A
94
6.1 % fat
A
JOI
6.7% fat
A
94
6.1 % fat
A
101
A
Mixture of beef and pork;
16.1 % fat; 12.2% protein
Mixture of beef and pork;
24.1% fat; 10.3% protein
2.1% fat
2.1% fat
6.7% fat
14.6
Poultry and Eggs
Chicken, Breast .L b
Chicken, Breast with Skin
20
20
69-75
58-74
4.12
3.66
1
I
Egg White
36
88
5.58
I
Egg, Whole
Egg Yolk
-8
31
50.6
9.60
4.20
I
A
Turkey, Breast.L b
3
-15
4
-15
3
-15
74
4.96
13.8
4.97
12.3
A
94
2.1% fat
A
94
3.4% fat
A
94
2.1% fat
3
-15
83
94
0.1% fat
Turkey, Leg .L b
Turkey, Breast =.L
b
74
74
5.02
0-6% fat
0-30% fat
103,121
III
114
0.98d
32.7% fat; 16.7% protein; 1.02 d
15.3
Fish and Sea Products
Fish, Cod .L b
5.34
A
14.6
29.16
CHAPTER 29
Table 8
1977 Fundamentals Handbook
Thermal Conductivity' of Food and Food Materials (Continued)
Water
Temp,
kC
content,
°C
Fish, Cod
Fish, Herring
Fish, Salmon 1 b
% (wI)
5.60
3
67
5
73
16.9
8.0
5.31
12.4
4.98
5
4.3
2.19
-15
-15
Seal Blubber 1 b
-15
18
32
-9
-12
mW/(cm) (deg C)
1
-15
-19
Fish, Salmon 1 b
Whale Blubber 1 b
Whale Meat
Rating,d
,
Food or Food Material
11.3
1.97
2.09
6.49
14.4
12.8
A,I,U
Refe
1
122
Remarks-Composition f
123
1
A
III
94
0.91d; whole and gutted
12% fat; Gaspe-Salmo Salar
A
94
5.4% fat-B.C. Oncorhynchus
Tehawytseha
A
94
95% fat
1
1
117
106
1.04 d
1.07 d
I
III
0.5 It'7o fat; 1.00 d
Dairy Products
Butterfat
Butter
Buttermilk
Milk, Whole
Milk, Skimmed
Milk, Evaporated
Milk, Evaporated
Milk, Evaporated
Milk, Evaporated
Whey
6
-15
4
20
28
2
20
50
80
2
20
50
80
2
20
50
80
2
20
50
80
23
41
60
79
26
40
59
79
2
20
50
80
0.6
89
90
83
90
72
62
67
50
90
1.73
1.79
1.97
5.69
5.80
5.22
5.50
5.86
6.14
5.38
5.66
6.06
6.35
4.86
5.04
5.42
5.65
4.56
4.72
5.10
5.31
4.72
5.04
5.16
5.27
3.24
3.40
3.57
3.64
5.40
5.67
6.30
6.40
A
94
1
A
A
A
124
98
99
98
0.35% fat
3% fat
3.% fat
A
98
0.1% fat
A
98
4.8% fat
A
98
6.4% fat
A
99
10% fat
A
99
15% fat
A
98
No fat
A
125
A
98
Sugar, Starch, Bakery
Products, and Derivatives
Sugar Beet Juice
Sucrose Solution
25
0
20
50
80
0
20
50
80
0
20
50
80
0
20
50
80
0
20
79
82
90
80
70
60
50
5.50
5.69
5.35
5.66
6.07
6.36
5.04
5.35
5.72
6.00
4.73
5.01
5.36
5.63
4.43
4.70
5.02
5.25
4.13
4.37
Cane or beet sugar solution
29.17
Thermal Properties of Foods
Table 8
Thermal Conductivity' of Food and Food Materials (Continued)
Temp,
Water
content,
kC
Rating,d
,
Food or Food Material
°C
50
80
0
20
50
80
2
20
50
80
2
20
50
80
2
20
50
80
2
20
50
80
25
Glucose Solution
Corn Syrup
0-;0 (wI)
40
89
80
70
60
mW/(cm) (deg C)
4.67
4.90
3.82
4.04
4.34
4.54
5.39
5.66
6.01
6.39
5.08
5.35
5.71
5.99
4.78
5.04
5.38
5.65
4.46
4.70
5.01
5.29
5.62
4.84
4.67
3.46
Refe
A,I,U
A
Remarks-Composition!
98
I
126
U
127
Molasses Syrup
30
23
Fats, Oils, Gums, and
Extracts
Gelatin Gel
5
94-80
5.22
A
94
-15
-15
-15
5
4
35
94
88
80
21.4
19.4
14.1
2.33
1.76
1.70
I
U
I
U
U
U
U
U
124
128
103,
121
129
130
128
129
131
U
I
U
U
128
118
132
128
Margarine
Almond Oil
Cod Liver Oil
Lemon Oil
Mustard Oil
Nutmeg Oil
Olive Oil
Olive Oil
6
25
4
7
32
65
151
185
4
25
20
4
Peanut Oil
Peanut Oil
Rapeseed Oil
Sesame Oil
Freeze-Dried Foods
App1e
Peach
Pears
1.56
1.70
1.56
1.75
1.68
1.66
1.60
1.56
1.68
1.69
1.60
1.76
35
Pressure,
mmHg
0.020
35
0.156
1.43
21.6
0.045
35
0.156
1.16 d
1.31 d
1.34 d
Conductivity did not vary
with concentration in
range tested (6,12,20%)
6% gelatin concentration
12% gelatin concentration
20% gelatin concentration
1.00 d
O.92d
0.82d
1.02 d
0.94d
0.91 d
0.91 d
O.92d
0.91 d
0.92d
A
133,
134
Delicious; 88% porosity;
5.1 tortuosity factor; measured
in air
0.185
0.282
0.405
0.164
A
133,
134
Clingstone; 91 % porosity;
4.1 tortuosity factor; measured
in air
0.161
1.36
20.0
383
0.016
0.185
0.279
0.410
0.431
0.186
A
133,
134
97% porosity; measured
in nitrogen
0.146
1.42
16.1
530
0.207
0.306
0.419
0.451
29.18
CHAPTER 29
Table 8
Food or Food Materialb
Thermal Conductivity' of Food and Food Materials (Continued)
Pressure,
Temp,
°C
Beef =h
mmHg
35
Egg Albumin Gel
41
Egg Albumin Gel
Turkey = b
41
1977 Fundamentals Handbook
20.3
762
760
720
Turkey 1- b
kC
mW/(cmHdeg C)
0.0
11
0.1
71
1.7
9
0.382
Rating, d
A,I,U
Refc
Remarks-Composition r
I
133,
Lean; 64070 porosity; 4.4 tortu-
134
osity factor, measured in air
2070 water content; measured in
air
Measured in air
Cooked white meat; 68 to 72070
porosity; measured in air
0.412
0.532
0.620
0.652
0.393
U
135
0.0
33
0.0
40
0.1
1.1
13
9.8
0
3
0.0
42
0.129
0.287
U
U
135
136
U
136
0.1
1.0
42
9.3
4
9
0.0
32
1.3
6
0.174
0.221
0.417
0.586
0.091
0.144
0.291
0.393
0.443
0.706
0.861
0.927
0.170
Cooked white meat; 68 10 72"70
porosity; measured in air
657
Potato Starch Gel
16.6
772
U
135
Measured in air
3To obtain W 1(Il1)(deg C) multiply by nl cal/kl)(sL)(deg C) multiply by 2.39 x 10-4; Btu/{ft)(hr)(dg F) Multiply by 0.0578; kcal/(m)(hr)(cJcg C) multiply by 0.0856. 0The symbol .1 indicates heal flow
perpendicular 10 the grain or structure; the symbol = indicates heal flow parallel 10 the grain or structure.
"The symbol k is used for thermal conductivity.
The ring "A" indicates data considered reliable by reviewers from TC 11.9, within practical limits. The rating •• ," indicates data that appears to be reliable within practical limits, but for which background information
supplied (e.g. composition factors or conditions of measurement) was insufficient for a firm assessment. "U" indicates data un-ruled because it did not fall within the area of competence of any reviewer of the TC J 1.9.
c
References Quoted are those on which given data are based, although actual values in this whole may have been averaged. interpolated, extrapolated, selected, or rounded off. This column includes
density (d, in g/cm3), pressure (P. in mm Hg), fat content (D), and other details.
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• 8L. A. Hawkins: Governing factors in transportation ofperishabJe commodities
(Refrigerating Engineering, Vol. 18, 1929, p. 130).
29W. C. Micke, F. G. Mitchell, and E. C. Maxie: Handling sweet cherries for fresh
shipment (California Agriculture, Vol. 19, No.4, 1965, p. 12).
Thermal Properties of Foods
3°F. Gerhardt, H. English, and E. Smith: Respiration, internal atmosphere,
and moisture studies of sweet cherries during storage (Proceedings of the
American Society for Horricultural Science, Vol. 41, 1942, p. 119).
31 J. L. Eaks and L. L. Morris: Respiration of cucumber fruits associated
with physiological injury at chilling temperatures (Plant Physiology, Vol.
31,1956, p. 308).
32 L. L. Claypool and S. Ozbek: Some influences of temperature and carbon
dioxide on the respiration and storage life of the Mission Fig (Proceedings of
the American Society for Horticultural Science, Vol. 60,1952, p. 226).
33 L. K. Mann and D. A. Lewis: Rest and dormancy in garlic (Hi1j;,ardia,
Vol. 26,1956, p. 161).
3 .1. M. Lutz: Factors Influencing the Quality of American Grapes in
Storage (USDA Technical Bulletin, Vol. 606, 1938).
35W. T. Pentzer, C. E. Asbury, and K. C. Hamner: The effect of sulfur
dioxide fumigation on the respiration of Emperor grapes (Proceedings of the
American Society for Horticultural Science, Vol.
30) 1933, p. 258).
6Chapter 32, Table I, (1974 ASH RAE HANDBOOK & Product Directory,
New York, NY, p. 32.4).
37 H. C. Gore: Studies on Fruit Respiration (USDA Bur. Chern Bulletin,
Vol. 142, 1911).
J~D. V. Karmarkar and B. M. Joshe: Respiration studies on the Alphonse
mango (Indian Journal of Agricultural Science, Vol. 11, 1941, p. 993).
39H. K. Pratt and L. L. Morris: Some physiological aspects of vegetable and
fruit handling (Food Technology in Australia, Vol. 10, 1958, p. 407).
40W. H. Smith: The storage of mushrooms (Great Britain Agricultural
Research Council, Ditton and Covent Garden Laboratories Annual Report,
1963-64, p. 18).
41 E. B. Pantastico: Table 16.2, Postharvest Physiology (Handling and
Utilization of Tropical and Subtropical Fruits and Vegetables, Avi
Publishing Co., Inc., Westport, CT, 1974, p. 323).
42 W. W. Jones: Respiration and chemical changes of papaya fruit in relation
to temperature (Plant Physiology, Vol. 17, 1942, p. 481).
43M. H. Haller, P. L. Harding, J. M. Lutz, and D. H. Rose: The respiration of
some fruits in relation to temperature (Proceedings of the American Society
for Horticultural Science, Vol. 28, 1932, p. 583).
44H. Thompson, S. R. Cecil, and J. G. Woodroof: Storage of Edible
Peanuts, Georgia Agricultural Experiment Station Bulletin, Vol. 268,1951).
45R. U. Schenk: Respiration of peanut fruit during curing (Proceedings of the
Association of Southern Agricultural Workers, Vo1.56, 1959, p. 228).
46R. U. Schenk: Development of the Peanut Fruit (Georgia Agricultural
Experiment Station Bulletin N .S., Vol. 22, 1961).
47L. L. Claypool and F. W. Allen: The influence of temperature and oxygen
level on the respiration and ripening of Wickson plums (Hillardea, Vol. 21,
1951, p. 129).
4 H. W. Hruschka: Storage and Shelf Life of Packaged Rhubarb (USDA
Marketing Research Report, Vol. 771,1966).
49D. A. Lewis and L. L. Morris: Effects of chilling storage on respiration
and deterioration of several sweet potato varieties (Proceedings of the
American Society for Horticultural Science, Vol. 68, 1956, p. 421).
50M. Workman and H. K. Pratt: Studies on the physiology of tomato fruits;
II, Ethylene production at 20°C as related to respiration, ripening and date of
harvest (Plant Physiology, Vol. 32,1957, p.
33°1·5 L. L. Morris: Unpublished data, 1952.
52 P. L. Harding: Respiration studies of Grimes apples under various
controlled temperatures (Proceedings of the American Society for
Horticultural Science, Vol. 26, 1929, p. 319).
53R. E. Hardenburg: Unpublished data, 1966.
54L. Rappaport and A. E. Watada: Unpublished data, 1953.
55H. K. Pratt, L. L. Morris, and C. L. Tucker: Temperature and lettuce
deterioration (Proceedings of the Conference on Transportation of
Perishables, University of California at Davis, 1954, p. 77).
56E. C. Maxie, P. B. Catlin, and H. T. Hartmann: Respiration and ripening of
olive fruits (Proceedings of the American Society for Horticultural Science,
Vol. 75,1960, p. 275).
57D. V. Karmarkar and B. M. Joshe: Respiration of onions (Indian Journal
of Agricultural Science, Vol. 11, 1941, p. 82).
58S. E. Charm and P. Moody: Bound water in haddock muscle (ASH RAE
JOURNAL, Vol. 8, No.4, 1966, p. 39).
59W. R. Woolrich: Specific and latent heat of foods in the freezing zone
(ASH RAE JOURNAL, Vol. 8, No.4, 1966, p. 43).
6oH. E. Staph and W. R. Woolrich: Specific and latent heats of foods in the
freezing zone (Refrigerating Engineering, Vol. 59, 1951, p.1086).
29.19
61H. C. Mannheim, M. P. Steinberg, and A.!. Nelson: Determinations of
enthalpies involved in food freezing (Food Technology, Vol. 9,1955, p. 556).
62B. F. Short and H. E. Staph: The energy content of foods (Ice and
Refrigeration, Vol. 121, No. 11, 1951, p. 23).
63L. H. Bartlett: A thermodynamic examination of the "latent heat" of food
(Refrigerating Engineering, Vol. 47, 1944, p. 377).
64S. W. Moline, J. A. Sawdye, J. A. Short and A. P. Rinfret: Thermal
properties of foods at low temperatures (Food Technology, Vol.
15,1961,p.228).
65 L. Riedel: The refrigerating effect required to freeze fruits and vegetables
(Refrigerating Engineering, Vol. 59, 1951, p. 670).
6L. Riedel: Calorimetric investigations of freezing of egg white and yolk
(Kaltetechnik, Vol. 9, No. 11, 1957, p.342).
67L. Riedel: Calorimetric investigations of the melting of fats and oils (Fette,
Seifen, Anstrichmittel, Vol. 57, No. 10, 1955, p. 771). 68Chapter 37, (1964
ASH RAE HANDBOOK & Product Directory, New York, NY, p. 437).
69M. P. Heisler: Temperature charts for induction and constant temf,erature
heating (ASME Transactions, Vol. 69, 1947, p. 227).
7 P. J. Schneider: Temperature Response Charts (John Wiley and Sons,
New York, NY, 1963).
71 R. E. Smith, G. L. Nelson, and R. L. Hendrickson: Analyses on transient
heat transfer from anomalous shapes (ASAE Transactions, Vol. 10, No.2,
1967, p. 236).
72R. E. Smith, G. L. Nelson, and R. L. Hendrickson: Applications of
geometry analysis of anomalous shapes to problems in transient heat transfer.
ASAE Transactions, Vol. 11, No.2, 1968, p. 296.
73R. W. Dickerson: Computing heating and cooling rates of foods
(Symposium on Prediction of Cooling/Freezing Times for Food Products,
ASH RAE Bulletin NO-72-3, 1972, p. 5).
74R. Gane: The thermal conductivity of the tissue of fruits (Annual Ref:0rt,
Food Investigation Board, Great Britain, 1936, p. 21 I).
5E. Slavicek, K. Handa, and M. Kminek: Measurements of the thermal
diffusivity of sugar beets (Cukrovarnicke Listy, Vol. 78, Czechoslovakia,
1962, p. 116).
76p. J. Schneider: Conduction Heat Transfer (Addison-Wesley Publishing
Co., Reading, MA, 1955, p. 15).
77 L. Riedel: Measurements of thermal diffusivity on foodstuffs rich in
water (Kaltetechnik-Klimatisierung, Vol. 21, No. 11,1969, p. 315).
78A. H. Bennett, W. G. Chace, Jr., and R. H. Cubbedge: Thermal
Properties and Heat Transfer Characteristics of Marsh Grapefruit (USDA
Agricultural Research Service, Technical Bulletin No. 1413, U.S. Government
Printing Office, Washington, DC, 1970).
79A. H. Bennett, W. G. Chace, Jr., and R. H. Cubbedge: Thermal
conductivity of Valencia orange and Marsh grapefruit rind and juice vesicles
(ASH RAE TRANSACTIONS, Vol. 70, 1964, p. 256).
8oR. L. Perry, F. M. Turrell, and S. W. Austin: Thermal Diffusivity of Citrus
Fruits (Heat Transfer, Thermodynamics, and Education, ed., H. A. Johnson,
McGraw-Hill, New York, NY, 1964, p. 242).
81 L. Riedel: Calorimetric investigations of the freezing of fish meat
(Kaltetechnik, Vol. 8, No. 12, 1956, p. 374).
82L. Riedel: Calorimetric investigations of the freezing of white bread and
other flour products (Kaltelechnik, Vol. II, No.2, 1959, p. 41~.
3 A. H. Bennett, W. G. Chace, Jr., and R. H. Cubbedge: Heat
transfer properties and characteristics of Appalachian area 'Red Delicious'
apples (ASH RAE TRANSACTIONS, Vol. 75, Part II, 1969, p. 133).
84R. E. Parker and B. A. Stout: Thermal properties of tart cherries
(ASAETransactions, VoI.I0,No.4, 1967,p.489).
85 A. H. Bennett: Thermal Characteristics of Peaches as Related to
Hydrocooling (USDA Agricultural Marketing Service, Technical Bulletin No.
1292, U.S. Government Printing Office, Washington, DC, 1963).
86T. V. Minh, J. S. Perry, and A. H. Bennett: Forced-air precooling of white
potatoes in bulk (ASH RAE TRANSACTIONS, Vol. 75, Part 2,1969, p. 143).
87F. V. Mathews, Jr. and C. W. Hall: Method of finite differences used to
relate changes in thermal and physical properties of potatoes (ASAE
Transactions, Vol. 11, No.4, 1968, p. 558).
88R. W. Dickerson, Jr. and R. B. Read, Jr.: Thermal diffusivity of meats
(ASH RAE TRANSACTIONS, Vol. 81, Part I, 1975, p. 356).
89 Metals Handbook (The American Society for Metals, 1948, p. 555J.
9 N. A. Lange: Handbook of Chemistry, 10th ed. (McGraw-Hill, New
York, NY, 1961, p. 834).
91 Modern Plastics Encyclopedia: Plastics Properties Chart, Part I,
(Breskin Publications, New York, NY, 1963).
92Chapter 23, Table 4 (1963 ASHRAE GUIDE AND DATA BOOK,
Fundamentals and Equipment, New York, NY, p. 398).
93Chapter 37, Fig. 13, (1964 ASHRAE GUIDE AND DATA BOOK, Applications Volume, New York, NY, p. 446).
94C. P. Lentz: Thermal conductivity of meats, fats, gelatin gels,