Download Food Spoilage + vocabulary

(YDİ 339 İş hayatı İçin Yabancı Dil/ ENG 301 Mesleki İngilizce) Compiled by Ş. Tağı
FOOD SPOILAGE
It is an often overlooked fact that just about every food item we eat is biological in origin, i.e.
it comes from living organisms, so a knowledge of biology is important in all aspects of initial
food production, as well as preparation and distribution. In particular, we expect our food
to be fresh and wholesome, and not to contain any unnecessary added impurities (adulterants).
Food can deteriorate as a result of two main factors:
1) growth of micro-organisms - usually from surface contamination - especially important in
processed food - see below
2) action of enzymes - from within cells - part of normal life processes, (responsible for
respiration, for instance). It is important to note that many plants - fresh vegetables and fruit are still alive when bought and even when eaten raw, and meat from animals undergoes
gradual chemical changes after slaughter.
Micro-organisms are sometimes also called microbes (or the old-fashioned word "germs"),
and include the following groups:
bacteria and fungi (including yeasts)
Various members of these groups may cause changes in the character of food, which may be
classed as "positive" or "negative".
Products of "positive" microbial transformations include cheese, yoghurt, and wine, which
can be seen as increasing the nutritional value or keeping quality of products with a short
shelf life (see later topics).
"Negative" aspects of microbial growth include food deterioration and spoilage by decay, and
food poisoning, mainly caused by different and less widespread bacteria. As they grow,
micro-organisms release their own enzymes into the liquid surrounding them, and absorb the
products of external digestion. This is the main basis of microbial food spoilage, which lowers
its nutritional value. Bacteria and moulds may also produce waste products which act as
poisons or toxins, thus causing the renowned ill-effects.
It is perhaps worth noting that, viewed from another angle, bacteria and fungi have a major
positive role in the recycling of all forms of biological waste in nature, and that yet other
bacteria (together with viruses) are the main agents of infectious diseases in plants and
animals, including Man.
Conditions for microbial growth (and also for enzyme
action)
1) organic food (proteins, carbohydrates, fats) - same as humans!
2) suitable temperature
3) moisture (water)
4) [in some cases] air
5) suitable pH
1
For numbers 2-5, this (scientific) knowledge can be applied to (technological) processes in
order to control food spoilage.
Temperature treatments
For each 10 °C rise in temperature, the activity of micro-organisms and enzymes increases by
at least 2x, in the range 0-60 °C. Above this, heat quickly destroys enzymes and stops living
cells from working.
Decreased temperatures therefore work by slowing down these changes. The technology
involved may be fairly expensive, and is needed continuously, but it does not change the
flavour of food.
In a refrigerator (about 4 °C) food keeps longer because it decays more slowly. Bacteria are
not killed, but merely less active.
If milk goes off in 1 day on a warm summer day (24°C), how long will it last in a fridge?
> 4 days ( 10 °C warmer means 2x faster, 20 °C warmer means 2x2 faster )
In a freezer (about -15 °C) bacteria are completely inactive, but internal enzymes are still
active. For this reason, frozen vegetables such as peas are blanched by treatment with boiling
water before freezing.
Give 2 examples of food that is adversely affected by freezing. Think about the effects on
cell structure!
> celery etc
>
The cooling process may also have the effect of removing water from food, so it is necessary
to wrap it to prevent dehydration.
Where does the water go from unwrapped food, in a fridge or freezer?
> solidifies and freezes to the side of the freezer or cooling panel
Increased temperatures can have a more permanent preservative effect, and only require a
fairly brief treatment. They may also alter the flavour of food.
Gentle heating (about 60-70 °C, up to boiling, 100 °C) kills most bacterial cells in a few
minutes, but does not affect some species which form spores. It also denatures proteins, so it
deactivates enzymes. Most cooking does this, and pasteurisation of milk is carefully
controlled (63-66 °C for 30 minutes) to prevent flavour changes, although it does not quite
kill all contaminating bacteria.
Pressure cooking raises the temperature (usually to 120 °C or more), which kills bacterial
cells in seconds, although spores need about 15-20 minutes. This is called sterilisation.
Apparatus called an autoclave is used commercially, and for preparing sterile media for
growth of micro-organisms in the laboratory.
Ultra-high temperatures (UHT) - 132+ °C for at least 1 second) are at the basis of treatment
of liquids like milk, and fruit juices, so that these have a "long life".
After heat treatment, it is essential to ensure that foods cannot become contaminated by
contact with raw food, because they are now more easily colonised by bacteria.
List some food handling precautions to achieve this.
> keep on separate shelf of fridge (cooked above raw)
2
Removal of water
Many foods can be preserved by being simply dried (dehydrated, desiccated), perhaps in the
sun (not usually in England!). Water may be added to rehydrate it before consumption, or if
eaten dry, digestive juices moisten it and make it available to our bodies.
Give some examples of foods which are available in dried form:
> fruits e.g. apricots, raisins
Salted foods, and foods with added sugar are also effectively using the same technique, since
the water they contain is unavailable for microbial growth. Indeed, cells of micro-organisms
become plasmolysed when they come into contact with the surfaces of these foods.
What happens to the cytoplasm of any such micro-organisms? (Clue: think about
osmosis!)
> loses water: so micro-organism dies
Smoking foods, as well as drying, covers the outside (most exposed to microbial
contamination) with a thin film of antimicrobial chemicals. Some people even like the taste!
Removal of air
This technique is not usually used on its own - in fact some of the worst food poisoning
bacteria thrive in its absence.
Vacuum packing is, however, often used in conjunction with other techniques.
Give some examples of vacuum-packed foods, and say what other preservation methods
are combined with it.
> bacon (salting/smoking) > cheese (salt/low pH :see below)
Alteration of pH
Pickling, usually in vinegar or other acids, lowers the pH so that bacterial enzymes cannot
operate.
Combined treatments - provide extremely long keeping
qualities.
Freeze drying is a relatively recent method of preservation involving the removal of water
(as vapour) from frozen food under reduced pressure.
List and explain some advantages of the product of the process.
> lighter, and does not need refrigeration - lower transport & storage
Canning is heat-treatment in an autoclave, together with sealing of the food in an air-tight
container.
List and explain some disadvantages of the process.
> Heavy > Metal may contaminate
> Needs can-opener!
3
(YDİ 339 İş hayatı İçin Yabancı Dil/ ENG 301 Mesleki İngilizce)
Vocabulary list for “food spoilage” file
Düzenleme: Dr. Ş. Tağı
Kullanılan kısaltmalar:
abbr. Abbreviation, adj. Adjective, n: Noun, v. Verb, pl. Plural
Reference: American Heritage Dictionary
----------------------------------------------------------------------------------------------------------------o·ver·look v. To ignore deliberately or indulgently; disregard.
i.e. abbr. Latin. Id est (that is).
whole·some adj. 1. Beneficial, improving the moral or physical well-being; good for the health,
nutritive, nourishing; healthy: wholesome food; a wholesome climate. whole“some·ness n.
im·pu·ri·ty n., pl. im·pu·ri·ties. 1. The quality or condition of being impure, especially: a.
Contamination or pollution. b. Lack of consistency or homogeneity; adulteration. c. A state of
immorality; sin.
a·dul·ter·ant n. 1. A substance that adulterates. --a·dul·ter·ant adj. Serving to adulterate.
a·dul·ter·ate tr.v. To make impure by adding extraneous, improper, or inferior ingredients.
a·dul”ter·a“tion n. --a·dul“ter·a”tor n.
de·te·ri·o·rate v. de·te·ri·o·rat·ed, de·te·ri·o·rat·ing, de·te·ri·o·rates. --tr. 1. To diminish or
impair in quality, character, or value: , decay: The nation's highways are deteriorating at a rapid
pace. --de·te”ri·o·ra“tion n. --de·te“ri·o·ra”tive adj.
res·pi·ra·tion n. 1. The act or process of inhaling and exhaling; breathing.
slaugh·ter n. 1. The killing of animals for food.
slaugh“ter·er n. --slaugh“ter·ous adj.
trans·for·ma·tion A marked change, as in appearance or character, usually for the better.
de·cay v. de·cayed, de·cay·ing, de·cays. --intr. 1. Biology. To break down into component
parts; rot.
re·lease .v. re·leased, re·leas·ing, re·leas·es. 2. To free from something that binds, fastens, or
holds back; let go: released the balloons; released a flood of questions.
ab·sorb v. ab·sorbed, ab·sorb·ing, ab·sorbs. 1. To take (something) in through or as through
pores or interstices. –
4
ab·sorb·ent adj. 1. Capable of absorbing: absorbent cotton. --ab·sorb·ent n. A substance that is
capable of absorbing. --ab·sorb“en·cy n.
ad·sorb v. ad·sorbed, ad·sorb·ing, ad·sorbs. To take up by adsorption. [ad- + Latin sorb¶re,
to suck.] --ad·sorb“a·ble adj.
ad·sorp·tion n. The accumulation of gases, liquids, or solutes on the surface of a solid or liquid.
[From adsorb.] --ad·sorp“tive (-t¹v) adj.
ex·ter·nal adj. Abbr. ext. 1. Relating to, existing on, or connected with the outside or an outer
part; exterior
di·ges·tion n. 1. Physiology. a. The process by which food is converted into substances that can
be absorbed and assimilated by the body. It is accomplished in the alimentary canal by the
mechanical and enzymatic breakdown of foods into simpler chemical compounds.
re·nown n. 1. The quality of being widely honored and acclaimed; fame.
re·nowned adj. Having renown; famous.
fridge n. Informal. A refrigerator.
blanch also blench --v. To subject to or treat with boiling water:To scald (almonds, for example)
in order to loosen the skin. b. To scald (food) briefly, as before freezing or as a preliminary stage
in preparing a dish. --blanch“er n.
ad·verse adj. 1. Acting or serving to oppose; antagonistic: adverse criticism. ad·verse“ly adv. -ad·verse“ness n.
wrap v. wrapped or wrapt , wrap·ping, wraps. --tr. 1. To arrange or fold (something) about as
cover or protection: She wrapped her fur coat closely about herself. 2. To cover, envelop, or
encase, as by folding or coiling something about: wrapped my head in a scarf. 3. To enclose,
especially in paper, and fasten: wrap a package; wrapped up the peelings.
de·hy·drate v. de·hy·drat·ed, de·hy·drat·ing, de·hy·drates. --tr. 1. To remove water from;
make anhydrous. 2. To preserve by removing water from (vegetables, for example). See
Synonyms at dry. --intr. To lose water or moisture; become dry. --de·hy“dra”tor n.
de·hy·dra·tion n. 1. The process of removing water from a substance or compound. 2. Excessive
loss of water from the body or from an organ or a body part, as from illness or fluid deprivation.
re·hy·drate tr.v. re·hy·drat·ed, re·hy·drat·ing, re·hy·drates. 1. To cause (something
dehydrated) to take up fluid.
re”hy·dra“tion n.
al·ter v. al·tered, al·ter·ing, al·ters. --tr. 1. To change or make different; modify: altered my
will.
5
han·dle v. han·dled, han·dling, han·dles. --tr. 1. To touch, lift, or hold with the hands. 2. To
operate with the hands; manipulate.
SYNONYMS touch, treat
pre·cau·tion n. 1. An action taken in advance to protect against possible danger or failure; a
safeguard: He took every precaution but still got a bad deal on that used car.
des·ic·cate v. des·ic·cat·ed, des·ic·cat·ing, des·ic·cates. --tr. 1. To dry out thoroughly. 2.
To preserve (foods) by removing the moisture.
--des”ic·ca“tion n. --des“ic·ca”tive adj. --des“ic·ca”tor n.
mois·ten v. mois·tened, mois·ten·ing, mois·tens. To make or become moist
.--mois“ten·er n.
moist (moist) adj. moist·er, moist·est. 1. Slightly wet; damp or humid.
a·vail·a·ble adj. 1. Present and ready for use; at hand; accessible: kept a fire extinguisher available
at all times.
. --a·vail”a·bil“i·ty or a·vail“a·ble·ness n. --a·vail“a·bly adv.
un·a·vail·a·ble adj. Not available, accessible, or at hand. --un”a·vail”a·bil“i·ty n.
plas·mol·y·sis n., pl. plas·mol·y·ses . Shrinkage or contraction of the protoplasm away from
the wall of a living plant or bacterial cell, caused by loss of water through osmosis. -plas”mo·lyt“ic adj. --plas”mo·lyt“i·cal·ly adv.
plas·mo·lyzed, plas·mo·lyz·ing, plas·mo·lyz·es. --tr. 1. To subject to plasmolysis. --intr. To
undergo plasmolysis.
os·mo·sis n., pl. os·mo·ses . 1.a. Diffusion of fluid through a semipermeable membrane until
there is an equal concentration of fluid on both sides of the membrane.
thrive v. thrived or throve , thrived or thriv·en , thriv·ing, thrives. 1. To make steady
progress; prosper. 2. To grow vigorously; flourish: “the wild deer that throve here” --thriv“er n.
freeze-dry v. freeze-·dried, freeze-·dry·ing, freeze-·dries. To preserve (food, for example)
by rapid freezing and drying in a high vacuum.
can n. 1. A usually cylindrical metal container. 2.a. An airtight container, usually made of tincoated iron, in which foods or beverages are preserved. b. The contents of such a container.
--can tr.v. canned, can·ning, cans. 1. To seal in an airtight container for future use; preserve:
canning peaches. --can“ner n.
6