Lesson 2.2

Question 1

Fats and oils in our diets

major component

Answer 1

• produce 9 Cal/g
• should contribute no more than 30% of our caloric intake
• dietary fats/oils, essential fatty acids are needed by the body to maintain proper health and functioning

Question 2

Chemical composition of fats

Answer 2

triglycerides (TG), which are triesters of glycerol and fatty acids
* glycerol: 3-carbon molecule containing 3 alcohol groups (OH)
* fatty acids: hydrocarbon chains (R1, R2, R3) with carboxylic acid (COOH) at one end and a methyl group (CH₃) at the other end

• FAs have more than 3 carbons (e.g. butyric acid with 4 carbons is the simplest) and R refers to the rest of the molecule, which is quite large
• broken down in the body by digestive enzymes (lipases)

Question 3

What holds fatty acids to glycerol in triglycerides?

or fats

Answer 3

esther bonds join OH groups of glycerol to COOH groups of fatty acids

Question 4

Most common fatty acids in food triglycerides

Answer 4

C-16, C-18
* some foods have shorter-chain fatty acids (e.g. coconut oil C-12)
* others also contain longer-chain fatty acids (e.g. salmon C-20, C-22)

Question 5

What are saturated and unsaturated fats?

Answer 5

saturated and unsaturated fatty acid constituents
* saturated have no double bonds C-C
* unsaturated have double bonds C=C (e.g. monounsaturated, polyunsaturated)

Question 6

Common formula of fatty acids

Answer 6

Y: X (n-Z)
* Y= number of carbons
* X= number of double bonds
* n= numbering of double bonds from methyl group (CH₃)
* Z= location number of first double bond

Question 7

3 examples of 18-carbon fatty acids

Answer 7

1. Stearic (saturated): CH₃(CH₂)₁₆COOH
2. Oleic (monounsaturated): CH₃(CH₂)₇CH=CH(CH₂)₇COOH
3. Linoleic (polyunsaturated): CH₃(CH₂)₄CH=CH-CH₂-CH=CH(CH₂)₇COOH

1. 18:0
2. 18: 1(n-9), an omega 9 fatty acid because its first double bond from the methyl end starts on carbon 9
3. 18: 2(n-6), an omega 6 fatty acid

Question 8

Animal fats

Answer 8

• usually solid at room temperature
• high in saturated fatty acids
• consist of linear chains that pack together tightly = higher melting point

Question 9

2 kinds of configurations in unsaturated fatty acids

Answer 9

1. cis configuration: carbon chains on the same side of the double bond that bend toward each other, creating a kink in the chain; less tightly packed = lower MP
2. trans configuration: carbon chains on either side of the double bond (or across); more tightly packed = more semi-solid texture and higher MP

trans FAs taste buttery!

Question 10

Vegetable oils

Answer 10

• usually liquid at room temperature
• high in unsaturated fatty acids (MUFA, PUFA)
• cis configuration so pack less tightly together = lower melting point

Question 11

Properties of unsaturated fatty acids

e.g. vegetable oils

Answer 11

• less stable and easily oxidized (oxidative rancidity) due to double bonds
• PUFAs more reactive than MUFAs

i.e. require less energy to be broken down

Question 12

Rancidity

and 2 types

Answer 12

process of breaking down fats and oils through improper storage, repeated exposure to high temp
1. oxidative
2. hydrolytic or lipolytic

Question 13

Oxidative rancidity

Answer 13

oxidation (double bonds + oxygen) results in products like off-flavors, carcinogenic compounds

e.g. UFA (or PUFA) + oxygen, heat, light (promote oxidation) > hydroperoxides > OHs

Question 14

Hydrolytic or lipolytic rancidity

unrelated to saturation/unsaturation!

Answer 14

hydrolysis (triglyceride + lipase enzyme) causes the bond between glycerol and FAs to break, releasing short-chain (free) FAs and glycerol (odorous)

Question 15

How can you reduce the rate of oxydative rancidity?

Answer 15

• proper storage and packaging (away from light, oxygen, warm temp)
• limiting repeated exposure to high temp
• adding antioxidants (natural and synthetic)
• hydrogenation

Question 16

Hydrogenation (partial)

to reduce the rate of oxydative rancidity

Answer 16

• hydrogen atoms are forced into the double bonds of the UFA, raising the MP and making it less prone to oxidize
• also used in food industry to harden liquid oils into semi-solid fats and can generate trans FAs (e.g. margarine)

newer margarines use blending to achieve the desired solid-liquid ratio and melting properties

Question 17

Trans fat

Answer 17

• behaves like saturated fat
• raises LDL (“bad”) cholesterol, which causes Coronary Heart Disease
• labelling required (amount of trans-fat)

Question 18

Functional properties of fats and oils

Answer 18

• mouthfeel (lubricant in food)
• shortening/tenderizing power (e.g. helps with entrapment of air in baked goods)
• carrier of aroma and flavor
• high-temperature medium (e.g. deep fat frying)
• gradual softening
• emulsifier

lubricant makes food softer and stay longer in palate (gradual swallowing)

Question 19

Lecithin

fats and oils as emulsifiers

Answer 19

• a phospholipid from egg yolk, soybean oil that consists of 2 FAs + phosphoric acid linked to glycerol (amphiphilic molecules)
• helps reduce interfacial tension to form an emulsion

Question 20

Amphiphilic/amphipathic molecules

fats and oils as emulsifiers

Answer 20

• hydrophilic: water-loving (i.e. glycerol linked to an organic acid)
  hydrophobic/lipophilic: water-hating or lipid-loving groups (i.e. fatty acid)

molecules stay connected and in uniform shape

Question 21

Stabilizers

not the same as emulsifiers!

Answer 21

increases the viscosity of the continuous phase by keeping the droplets suspended or dispersed (i.e. not precipitate toward the bottom)

e.g. polysaccharides

Question 22

Proteins in our diet

major component

Answer 22

• contribute 4 Cal/g
• require 0.8g protein per kg body weight in adults
• excess is converted into energy or stored as fat

Question 23

Chemical composition of proteins

Answer 23

polymers or long chains of amino acids linked by peptide bonds
* amino group (NH₂) and acidic group (carboxylic COOH) on the same carbon atom
* R, the side chain, is hydrophobic, charged, polar, aromatic

Question 24

Amino acids

building blocks of proteins

Answer 24

• 20 different amino acids naturally occurring in the human body and in foods
• 9 of which are essential (cannot be synthesized by humans) and must be obtained from food

e.g. Leucine, Phenylalanine (used in aspartame), Tryptophan, etc.

Question 25

What do the amino acid sequence and 3D structure of proteins determine?

Answer 25

* functional properties in food * nutritive value of proteins ## Footnote more essential amino acid = higher-quality protein

Question 26

Plant vs animal proteins

Answer 26

plant proteins... * are **less digestible** than animal proteins * have **less favorable ratio and quantity** of 1 or more essential amino acids * usually have **lower quality**

Question 27

How can you improve protein quality in foods?

Answer 27

mixing (complementation, supplementation) ## Footnote e.g. 30g of breakfast cereal when consumed with 125ml of milk represents a good source of protein

Question 28

Functional properties of proteins

Answer 28

* emulsifiers (e.g. egg yolk proteins in mayonaise) * foams (e.g. meringue, bread, ice cream) * gels (e.g. gelatin, yogurt, cheese, frankfurters) * enzymes * allergies (due to inability to digest)

Question 29

Enzymes ## Footnote functional property of proteins

Answer 29

function as **biological catalysts** * promote a chemical reaction that cannot occur spontaneously * inherent in food or added in processing * desireable or undesireable reactions in food

Question 30

Allergies ## Footnote functional property of proteins

Answer 30

inability to digest certain proteins may lead one to exhibit symptoms of allergic reactions ## Footnote **12 most common food allergens/sensitivity promoters:** **peanuts and tree nuts (most common)**, crustaceans and molluscs, eggs, fish, gluten, milk, mustard, sesame, soybeans, wheat and triticale, **sulphites** (not a protein but produces same reaction)

Question 31

Water ## Footnote major component

Answer 31

* plays key role in the quality of foods * comes in 2 forms: free and bound

Question 32

Free water

Answer 32

* properties typical of water * found in tissue food systems and dispersions * **available** for all chemical, enzymatic reactions and microbial growth

Question 33

Bound water

Answer 33

* absorbed on macromolecules (e.g. proteins, polysaccharides) * bound to smaller molecules (e.g. sugar, salt) * **not readily available** for chemical, enzymatic, or microbial activity

Question 34

Water activity (aw)

Answer 34

indication, not estimation, of water available for chemical reactions (primarily free water), microorganisms, etc. ## Footnote vs **water content** = total amount measured by weighing (e.g. an apple) before and after dehydration

Question 35

Are water activity and water content related?

Answer 35

**not always** * **salami:** 0.90 aw; 61% water content * **bread:** 0.96 aw; 35% water content

Question 36

How can water activity in foods be controlled?

Answer 36

* addition of solutes (sugars, salts), which bind to free water, reducing its availability * physically removing free water from foods through processing (e.g. freezing), concentration, dehydration

Question 37

Functions of organic acids in food ## Footnote minor component

Answer 37

* impart flavor and tartness * some used as antimicrobial agents * adjust pH or acidity of food (i.e. used as acidulants)

Question 38

Examples of organic acids

Answer 38

* malic acid (apples) * citric acid (citrus fruits, tomatoes, strawberries) * tartaric acid (grapes) * lactic acid (yogurt, cheese, olives, sauerkraut)

Question 39

2 ways to determine acidity ## Footnote organic acids

Answer 39

1. **taste:** sour or acidic taste is a positive indicator though highly subjective (individual differences in sensitivity) 2. **pH meter:** measure H+ concentration then convert to pH value ## Footnote **pH meters** are used by inserting a probe inside food and measuring the concentration of hydrogen ions

Question 40

What is pH? ## Footnote range and critical value

Answer 40

the measure of acidity * ranges from 0 (very acidic) to 7 (neutral) to 14 (very alkaline) * **4.6** is the critical pH value in the food industry, the borderline between acid and low-acid foods ## Footnote anything **below 4.6** inhibits microbial growth and foods with this pH are less susceptible to bacterial contamination

Question 41

What is the importance of pH in foods?

Answer 41

* determines the rate of chemical and enzymatic reactions * microbial growth/survival in foods

Question 42

Examples of acidic foods vs low-acid foods

Answer 42

* **acidic foods** (pH < 4.6): fruits and fermented products (e.g. citrus juices, apple juice, strawberries, apples, pickles) * **low-acid foods** (pH > 4.6): meat, fish, poultry, vegetables ## Footnote * **acidic foods** won't support growth of most disease-causing microorganisms * **low-acid foods** require a more intense process for preservation

Question 43

Total acidity vs pH

Answer 43

* **total acidity** (i.e. titratable acidity) measures the total acid concentration * **pH** (i.e. active acidity) quantifies H+ concentration

Question 44

Colors and pigments ## Footnote minor component

Answer 44

* naturally occur in foods * or extracted from natural or synthetic sources then added to foods

Question 45

3 classes of pigments

Answer 45

1. **carotenoids:** carotenes confer red in tomatoes (lycopene) and orange in carrots (beta carotene) 2. **anthocyanins** in blueberries, cherries, cranberries, plums, and red cabbage 3. **chlorophyll**

Question 46

Aroma and taste compounds

Answer 46

* **aroma compounds are volatile** while **taste compounds are non-volatile** * aroma and taste profiles of foods = **flavor** * complex flavors comprise 100s or 100s of compounds (e.g. aldehydes, ketones, acids, alcohols, fatty acids) * present as part of the **food matrix** (e.g. strawberries) **or modified** (e.g. cooked strawberries) ## Footnote **non-volatile** = do not readily evaporate at room temperature

Question 47

Vitamins and minerals ## Footnote minor component

Answer 47

* no effect on flavor, color, texture of food * low (or adequate) amounts in diet to maintain health ## Footnote **examples of minerals:** Ca, Mg, Na, K, Fe, Zn

Question 48

2 sets of vitamins

Answer 48

1. **water soluble:** vitamin C, B complex, folic acid 2. **fat soluble vitamins:** vitamins A, D, E, K ## Footnote some used as **food additives** like preservatives (antioxidants)