Chap 5: Food Chemistry

Question 1

Food Chemistry

Answer 1

encompasses the composition and properties of food components and the chemical changes they undergo during handling, processing, and storage

Question 2

Chemical Bonds

Answer 2

• Holds atoms and molecules together
• Requires energy
• Only electrons involved

Question 3

Types of Bonds

Answer 3

• Covalent
• Ionic
• Hydrogen

Question 4

Covalent Bonds

Answer 4

• Sharing one or more pairs of electrons
  (Fats, proteins, and carbohydrates incorporate covalently bonded atoms to form backbones of food molecules)

Question 5

Ionic Bonds

Answer 5

• Transfer of electrons

Question 6

Hydrogen (Bond)

Answer 6

• Type of covalent bond
  
  • Unequal sharing of electron
  • Compounds containing oxygen, nitrogen bonded to hydrogen

Question 7

Composition vs Decomposition

Answer 7

Composition - two or more substances combined to form a product A + B = AB
Sugars/Amino Acids —-> Polysaccharides/Proteins
Decomposition - One substance breaking down to form two or more products AB = A+B
Polysaccharides —-> Sugar

Question 8

Enzymes

Answer 8

• Biological Catalysts
• Speeds up reactions
• Lowers activation energy

Question 9

Desirable
Fermentation

Answer 9

Pickles, Tea, Yogurt

Question 10

Oxidation

Answer 10

addition of oxygen or removal of hydrogen

Question 11

Reduction

Answer 11

losing oxygen or gaining of hydrogen

Question 12

Browning of fruits and vegetables (catalyst)

Answer 12

Polyphenol Oxidase

Question 13

Browning of fruits and vegetables (melanin)

Answer 13

Oxidizes Polyphenols

Question 14

Properties of Water

Answer 14

• Acts at a dilutant and carrier of hydrophilic substances
• Fat replacer
• Dispersing/solvent action
• Medium for heat transfer
• Plasticizer

Question 15

Dipolar

Answer 15

Hydrogens share electron pair with oxygen

Question 16

Boiling and Freezing Point

Answer 16

BP: 100 C & 212 F
FP: 0 C & 32 F

Question 17

Solubility

Answer 17

Forming hydrogen bonds with water

Question 18

Hydration

Answer 18

Process by which water molecules surround and interact with solutes by acting as a solvent

Question 19

Amphiphatic

Answer 19

Containing both hydrophilic and hydrophobic ends

Question 20

Water disperses amphipathic substances by

Answer 20

Forming Micelles

Question 21

Types of Water

Answer 21

Free, Adsorbed, and Bound

Question 22

Free Water

Answer 22

Lightly entrapped
Easily pressed out
Easily boils and freezes
Flow properties

Question 23

Adsorbed Water

Answer 23

Structural

Question 24

Bound Water (bread, crackers)

Answer 24

Tightly chemical bound
Doesn’t exhibit typical properties of water
Doesn’t act as a solvent

Question 25

Polar (Ex)

Answer 25

Salts Minerals Carbohydrates Vitamins

Question 26

Amphipathic (Ex)

Answer 26

Phospholipids Sterols Proteins Vitamins

Question 27

Water Activity

Answer 27

Amount of water available for chemical, enzymatic, or microbial reactions Aw=P/Po Range = (None) 0.0 - 1.0 (Pure Water)

Question 28

Higher Moisture Foods

Answer 28

Water Activity Range - greater than 0.84 (microorganisms grow) Moisture Content Range - greater than 40%

Question 29

Intermediate Moisture Foods

Answer 29

Water Activity Range - (Chemical reactions take place, oxidation) 0.6 - 0.84 Moisture Content Range - 15%-40%

Question 29

Intermediate Moisture Foods

Answer 29

Water Activity Range - (Chemical reactions take place, oxidation) 0.6 - 0.84 Moisture Content Range - 15%-40%

Question 30

Low Moisture Foods

Answer 30

Water Activity Range - less than 0.6 Moisture Content Range - less than 15%

Question 31

Tartaric Acid

Answer 31

Leavening (bread)

Question 32

Phosphoric Acid

Answer 32

Cola beverage (preservation in cola, decreases pH)

Question 33

Amino Acid cysteine

Answer 33

reduced sulfhydryl groups

Question 34

SH groups are oxidized during processing

Answer 34

hardening of dough

Question 35

Fumaric acid added to

Answer 35

establish reducing conditions

Question 36

pH

Answer 36

potential of hydrogen ion concentration

Question 37

pH =

Answer 37

-log{H+}

Question 38

High acid foods

Answer 38

pH 4.6 and below Ex. Orange Juice and Canned Tomatoes

Question 39

Low acid foods

Answer 39

pH 4.6 and above Ex. Fermented foods