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Lipids
OBJECTIVES
1. To understand terminology and classification of lipids;
2. Important reactions of lipids;
3. Importance of lipids for food chemistry and food
technology;
4. Hydrogenation of lipids.
Lipids
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Classification – hydrolysable and non-hydrolysable lipids
Type
Simple
Hydrolysable
(having ester
bonds)
Complex
Nonhydrolysable
(without ester
bond)
Other
Subclass
Description
1. Waxes
Long chain alcohols and fatty acids
2. Acylglycerols
Glycerol + fatty acids
3. Phosphoacylglycerols
Glycerol + fatty acids + phosphate
+ N-containing compound
4. Sphingomyelin
Sphingosine + fatty acid +
phosphate + choline
5. Cerebrosides
Sphingosine + fatty acid +
carbohydrate
6. Isoprenoids
Polymers on the base of isoprene
7. Steroids
Sterane structure
Role of the lipids in the organisms
Lipids
Hydrolysable
Simple: Waxes – esters of higher alcohols with higher carboxylic acids
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Lipids
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Hydrolysable
Simple: Acylglycerols
*fats
*oils
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Lipids
Hydrolysable
Simple: Acylglycerols
*fats
*oils
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Lipids
! Simple: Acylglycerols – major carboxylic (fatty) acids
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Lipids
Simple: Acylglycerols – influence of fatty acids composition on melting point
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Lipids
! Simple: Acylglycerols – major carboxylic (fatty) acids
Human constitution (and some mammals) –
lack the enzymes with which could be
introduced double bond after the 9th C
atom (linoleic, linolenic acids – essential
fatty acids)
Benefits of ω-fatty acids
intake
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ω-fatty acids
Lipids
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Simple: Acylglycerols – major carboxylic (fatty) acids
Fat replacers
Category
Type and example
Function
Carbohydratebased
Cellulose (Avicel)
Dextrins, modified starches (Stellar)
Fruit-based fibre (WonderSlim)
Grain-based fibre (Betatrim)
Hydrocolloid gums (Kelgum)
Maltodextrin (Maltrin)
Pectin (Grinsted)
Binder, body, bulk, flavor, moisture retention,
mouth feel
Protein-based
Microparticulate protein (Simplesse)
Modified whey protein concentrate
(Dairy-Lo)
Mouth feel, water-binding, reduce syneresis
Fat-based
Altered triglycerides (Caprenin)
Sucrose polyesters (Olean)
Emulsion, mouth feel
Combination
Carbohydrate and protein (Mimix)
Carbohydrate and fat (Optamax)
Flavour, texture, mouth feel, water retention
Lipids
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Complex: Phospholipids
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Sphingolipids and Glycolipids
Sphingosine
Lipids
Complex: Phospholipids – building
the cell membranes
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Lipids
Non-hydrolysable (isoprenoids) – without ester bonds
Terpenes
Isopren
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Lipids
Non-hydrolysable (isoprenoids) – without ester bonds
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Gonane
Steroids
Squalene
Cholic acid
Cholesterol content of some food
Lipids
Non-hydrolysable (isoprenoids) – without ester bonds
Prostaglandins – inflammatory processes
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!
Lipids
Hydrogenation of lipids
Formation of trans fatty acids; isomerization of double bonds (position)
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Lipids
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Hydrogenation of lipids
Vaccenic acid – ω-7 – trans fatty acid
(in the milk – human, cow; butter; animals’ fats)
oxidative destruction
rumenic acid (anti cancer properties)
2-nonenal
old people smell
Lipids
Hydrogenation of lipids
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Transesterification (enzymatic)
Lipids
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Lipids – functional properties
Formation of
ordered structures
Arrangement of molecules of oleic acid
Molecular arrangement of trilaurin lattice
Lipids
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Lipids – functional properties
Consistency and polymorphism of triacylglycerols
Parameter
α-form
β'-form
β-form
Melting point
Lowest
Medium
Highest
IR absorption bands
720 cm-1 (singlet)
719 and 727 cm-1 (doublet)
717 cm-1 (singlet)
Density
Least dense
Intermediate
Most dense
Packing
Size of the molecule
Hexagonal
0.415 nm
orthorhombic
0.42, 0.38 nm
triclinic
0.46, 0.39 and 0.37 nm
Lipids
Lipids – functional properties
Consistency and polymorphism of
cocoa butter
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Lipids
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Lipids – functional properties
Fat consistency – melting and crystallization properties of fats
Several factors have important influences on the consistency of commercial
fats:
Proportion of solids in the fat. In general, the greater the solids
content, the firmer the fat. It has been estimated that plastic commercial fats,
at workable temperatures, increase in either firmness or viscosity by about
10% with each increment of crystals.
Number, size, and kind of crystals. At a given solids content, a
large number of small crystals produces a harder fat than does a small
number of large crystals. Larger, soft crystals are typically produced by slow
cooling. Crystals composed of highmelting acylglycerols provide greater
stiffening power than do those of lower melting acylglycerols.
Lipids
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Lipids – functional properties
Fat consistency
Viscosity of the liquid. Oils differ in viscosity at a given temperature
and this will influence viscosity of the melt, as well as consistency of a solidliquid lipid mixture.
Temperature treatment. If a fat tends to supercool excessively, this
can be overcome by melting the crystalline fat at the lowest possible
temperature, holding it for an extended period of time at a temperature just
above its melting point, and then cooling it. This facilitates formation of
numerous crystal nuclei, numerous small crystals, and a firm consistency.
Mechanical working. Crystallized fats are generally thixotropic; that
is, they become reversibly softer after vigorous agitation and only gradually
regain their original firmness. If a melted fat is mechanically agitated during
solidification, it will be much softer than if allowed to solidify in a static
condition. In the static state the growing crystals form structures of relatively
great strength. These structures can be deformed by mechanical working.
Lipids
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Lipids – functional properties
Fat consistency
Plasticity of the fats – determined
by the proportion of the solids
and liquid phase; interval of
melting;
The cocoa butter has large
amount of similar triacylglycerols – narrow range of
melting;
Lipids
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Lipids – functional properties
Mesomorphic states – liquid crystals
(b) and (c) - emulsions
Lipids
Lipids – functional properties
Emulsions and emulsifiers
Amylose – emulsifier complex;
prevention of bread ageing and lost of softness
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