Lesson 2 - Fats and Oils Flashcards
Nutritional Value
Produce 9 cal/g
Should contribute NO more than 30% of our caloric intake
Dietary fats/oils, essential fatty acids needed by the body to maintain proper health & functioning
What are fats?
Chemically known as triacylglycerols or triglycerides
Triglycerides (TG): Triesters of glycerol backbone & fatty acids
Chemical composition
Fatty acids: R1, R2, R3
Hydrocarbon chains with carboxylic acid (COOH) at one end and a methyl group (CH3) at the other end
R is referring to the rest fo the molecule which is quite large
Carboxylic acid (fatty acid) with more than 3 carbons
CH3-COOH acetic acid (not a fatty acid)
CH3-CH2-COOH propionic acid (not a fatty acid)
CH3-CH2-CH2-COOH butyric acid
Y: X(n-Z)
Y: number of carbon
X: number of double bonds
N: numbering of double bonds from methyl (CH3) end
Z: location number of first double bond
Cis configuration
Cis configuration: carbon chain segments on same side of the double bond
Bend toward each other… Kink in chains
Pack together kess tightly - lower melting point
- not linear, bend, cannot pack together easily
Trans fatty acids
- lose kink originally present in the cis form “pack close together” = the texture more semi-solid
- higher melting point than cis but less than saturated because structure is in between
Melting Point
The higher the number of carbon, the higher the melting point vice versa
The more saturated the fatty acid is, the more melting point
Saturated, unsaturated and polyunsaturated (in order)
Oxidative rancidity
(double bonds + oxygen) → products … off-flavours, (carcinogenic compounds…)
UFA or PUFAs + heat, light, oxygen → hydroperoxides → OHs
Only unsaturated fatty acids
Hydrolytic or lipolytic rancidity
(cleavage of the bond linking FA to glycerol → releasing free FAs
Lipase enzymes
Triglyceride + lipase → short-chain (free) FAs + glycerol (odorous)
Any fats
Reduce rate of oxidative rancidity:
Proper storage & packaging (away from light, oxygen, warm temp)
Limiting repeated exposure to high-temp
Don’t keep reusing oil
Addition of antioxidants (natural, like vit E and synthetic)
Hydrogenation
Hydrogenation
Also used by the food industry to “harden” liquid oils into semi-solid fats (e.g. margarine)
Hydrogen atoms are forced into the unsaturated double bonds of the UFA
Raises the fat melting point (MP)
Trans Fat
Behave like saturated fat
Raise LDL cholesterol → coronary heart disease (CHD)
Labelling required - the amount of trans-fat
Fats and Oils – Functional Properties
Mouthfeel - lubricant in food
shortening/tenderizing power
Carrier of aroma and flavour
High-temperature medium (deep fat frying)
Gradual softening
Emulsifiers
Emulsifiers
Lecithin (phospholipid) from egg yolk, soybean oil
2 FAs + phosphoric acid linked to glycerol
Help reduce interfacial tension → form an emulsion
Amphiphilic/amphipathic molecules:
Hydrophilic: water-loving (i.e. glycerol linked to an organic acid)
hydrophobic/lipophilic: water-hating or lipid-loving groups; (i.e. fatty acid)
**mayonnaise: egg yolk (2 components that can act as emulsifiers: lecithin & ??)
Stabilizers (not the same as emulsifiers)
Increase viscosity of the continuous phase
Keep the droplets suspended or dispersed
E.g. polysaccharides
Proteins
Contribute to 4 cal/g
Require 0.8 protein per kg body wt (adults)
Excess → converted to energy (4 cal/g) or stored as fat
Polymers or long chains of amino acids linked by peptide bonds
Amino group NH2 and acidic (carboxylic COOH) group on the same carbon atom
R = side chain (hydrophobic, charged, polar, aromatic)
Amino Acids
20 different amino acids naturally occurring in the human body and in foods
9 are essential (cannot be synthesized by humans). Must be obtained from food
Eg. leucine, phenylalanine (used in aspartame), tryptophan
Amino acid sequence and 3D structure of the protein determine the Functional Properties in food as well as Nutritive value of the proteins
complementation
Protein quality of foods can be improved by mixing
e.g. milk and cereal
supplementation
Done in industrial level
Functional properties
Emulsifiers
Amphiphilic molecules
Reduce interfacial tension;
Eg. egg yolk proteins in mayonnaise
Foam
Trap air bubb;es and form rigid 3D structure when heated or cooled → solid foams
Eg. meringues, bread, ice cream
Gels
Form 3D structure that can trap water
Eg. gelatin gels, yogurt, cheese, frankfurters
**gelatin is a protein
Enzymes
proteins that function as biological catalysts
Promote a chemical reaction that will not occur spontaneously
Inherent in the foods or added in processing
Desirable or undesirable reactions in foods
Eg. invertase, lactase, maltase, galactase, lipase
Allergies
Unable to digest certain proteins → exhibit symptoms of allergic reactions
The 12 most common food allergens/sensitivity promoters
Crustaceans and molluscs (shrimps, crabs), eggs, fish, gluten, milk, mustard, peanuts, sesame, soybeans, tree nuts, wheat and triticale, sulphites
Water
Important role: mixing effect and dispersion
Plays a key role in the quality of foods
Free vs bound water
