Lesson 2 - Fats and Oils

Question 1

Nutritional Value

Answer 1

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

Question 2

What are fats?

Answer 2

Chemically known as triacylglycerols or triglycerides
Triglycerides (TG): Triesters of glycerol backbone & fatty acids

Question 3

Chemical composition

Answer 3

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

Question 4

Y: X(n-Z)

Answer 4

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

Question 5

Cis configuration

Answer 5

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

Question 6

Trans fatty acids

Answer 6

• 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

Question 7

Melting Point

Answer 7

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)

Question 8

Oxidative rancidity

Answer 8

(double bonds + oxygen) → products … off-flavours, (carcinogenic compounds…)
UFA or PUFAs + heat, light, oxygen → hydroperoxides → OHs
Only unsaturated fatty acids

Question 9

Hydrolytic or lipolytic rancidity

Answer 9

(cleavage of the bond linking FA to glycerol → releasing free FAs
Lipase enzymes
Triglyceride + lipase → short-chain (free) FAs + glycerol (odorous)
Any fats

Question 10

Reduce rate of oxidative rancidity:

Answer 10

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

Question 11

Hydrogenation

Answer 11

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)

Question 12

Trans Fat

Answer 12

Behave like saturated fat
Raise LDL cholesterol → coronary heart disease (CHD)
Labelling required - the amount of trans-fat

Question 13

Fats and Oils – Functional Properties

Answer 13

Mouthfeel - lubricant in food
shortening/tenderizing power
Carrier of aroma and flavour
High-temperature medium (deep fat frying)
Gradual softening
Emulsifiers

Question 14

Emulsifiers

Answer 14

Lecithin (phospholipid) from egg yolk, soybean oil
2 FAs + phosphoric acid linked to glycerol
Help reduce interfacial tension → form an emulsion

Question 15

Amphiphilic/amphipathic molecules:

Answer 15

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 & ??)

Question 16

Stabilizers (not the same as emulsifiers)

Answer 16

Increase viscosity of the continuous phase
Keep the droplets suspended or dispersed
E.g. polysaccharides

Question 17

Proteins

Answer 17

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)

Question 18

Amino Acids

Answer 18

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

Question 19

complementation

Answer 19

Protein quality of foods can be improved by mixing
e.g. milk and cereal

Question 20

supplementation

Answer 20

Done in industrial level

Question 21

Functional properties
Emulsifiers

Answer 21

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

Question 22

Enzymes

Answer 22

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

Question 23

Allergies

Answer 23

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

Question 24

Water

Answer 24

Important role: mixing effect and dispersion
Plays a key role in the quality of foods
Free vs bound water

Question 25

Free water

Answer 25

Properties typical of water
Found in tissue food systems and dispersion
Available for all chemical enzymatic reactions and for microbial growth

Question 26

Bound water

Answer 26

Absorbed on macromolecules
Eg. proteins or polyssacharides
Bound to smaller molecules
Sugars and salt
Not readily available for chemical enzymatic or mibrocial activity

Question 27

water activity (free water)

Answer 27

Water activity (aw)
Closer to 0 is less free water, closer to 1 is more free water

can be controlled (adjusted) by:
Addition of solutes (sugars, salts) - bind free water
Physically removing free water from foods