1. Enzymes

2. Overview
Enzymes -- proteins that catalyze a specific chemical reaction.
Each enzyme is specific to a specific chemical reaction.
The substance on which an enzyme acts is known as a substrate.
The structure of the enzyme does not change as a result of the reaction.
B Enzymes

3. Key Functions of Enzymes
Ripen fruits and vegetables.
Spoil fruits and vegetables after harvest.
Change flavor, color, texture, and nutritive value of food.
Decrease shelf-life if not inactivated.
Extract and purify commercially to:
Break down starch
Tenderize meat
Clarify wines
Coagulate milk
B Enzymes

4. Naturally-Occurring Enzymes
Trigger enzymatic browning
Found in large amounts in:
pineapple
papaya
figs
Meat tenderizers made from compounds in fruit
Bromelain -- Pineapple
Papain -- Papaya
Ficin -- Fig
B Enzymes

5. Enzymatic Reaction
B Enzymes

6. Factors that Affect Enzyme Activity
Two factors will affect enzyme activity:
water availability
amount of substrate
Enzymatic reactions generally occur in the presence of water.
B Enzymes

7. Water Availability
Water acts as a reactant and solvent in enzymatic reactions.
Less water available the slower the enzymatic reaction.
Reactions occur more slowly in dried foods (dried milk) than in moist foods (fluid milk).
B Enzymes

8. Amount of substrate Substrate is molecule upon which enzyme acts.
Substrate binds with the enzyme's active site and enzyme-substrate complex formed.
More substrate in a solution, the greater the rate of the reaction
Enzymes have more product with which to react.
B Enzymes

9. Denaturation of Enzymes9

10. Factors that Denature Enzymes
Enzymes are proteins.
Denaturation:
changes the structure of the protein
stops enzyme activity
Enzymes denatured by:
heat pH
salts
enzyme inhibitors
B Denaturation of Enzymes 10 10

11. B-3.03 -- Denaturation of Enzymes
Heat
Enzymatic reaction rates increase as temperature increases.
Denaturation occurs at 104°F or hotter.
Too much heat slows and stops enzyme activity.
Heating can destroy enzymes that alter food quality.
Example -- blanching vegetables to prevent spoilage during frozen storage.
B Denaturation of Enzymes 11 11

12. B-3.03 -- Denaturation of EnzymespH
pH and rate of enzymatic reaction
Specific to each enzyme
pH and denaturation of enzymes
Optimal pH range.
Most enzymes will denature if pH is too high or too low.
Changing the pH can speed up, slow, or stop enzymatic reactions
Lemon juice to apples
B Denaturation of Enzymes 12 12

13. B-3.03 -- Denaturation of Enzymes
Salts
Salt is commonly used in food production
Binds to enzymes in food that cause spoilage
Changes the water activity
B Denaturation of Enzymes 13 13

14. B-3.03 -- Denaturation of Enzymes
Enzyme Inhibitors
Substance that will prevent the enzyme-substrate complex
Enzymatic reactions slowed or stopped.
Naturally occurring
Egg whites
Pesticides that are naturally part of a plant structure
Synthetic compounds
B Denaturation of Enzymes 14 14

17. Enzyme Activity 17

18. B-3.03 -- Enzyme Activity in Food
Effects on Food
Positive effects:
Make food easier to eat – meat tenderizer
Preserve food – change milk into cheese
Improve flavor, quality, or appearance – add lactase to produce lactose-free dairy products.
Negative effects:
Enzymatic browning
Spoilage
B Enzyme Activity in Food 18 18

19. B-3.03 -- Enzyme Activity in Food
Make Food Easier to Eat
Meat tenderizers, enzymes that can be added:
during aging
prior to cooking
Enzymes break down tough protein fibers for a more tender product.
B Enzyme Activity in Food 19 19

20. B-3.03 -- Enzyme Activity in Food
Preserve Food
Converting milk into cheese increases shelf-life of milk.
Rennin (an enzyme) is added to coagulate milk proteins.
Some enzymes are also released by bacterial cultures to create unique flavors, textures, and colors.
B Enzyme Activity in Food 20 20

21. Improve flavor, quality, or appearance
Amylases – baked goods
Invertase – artificial honey and candy
Lactase – lactose- free milk
Pectic enzymes – fruit juices
Protease – baked goods, meat
Rennin -- cheese
B Enzyme Activity in Food 21 21

22. B-3.03 -- Enzyme Activity in Food
Enzymatic Browning
Reaction of oxygen and the enzyme (phenolase)
Results in desirable and undesirable color and structure changes
Desirable changes – browning of raisins, figs, dates
Undesirable changes -- fruit becomes discolored, mushy, bruised
B Enzyme Activity in Food 22 22

23. Preventing Enzymatic Browning
Prevent oxygen from combining with the enzyme phenolase
Cold storage slows enzyme activity.
Add preservatives, such as:
sulfites,
ascorbic acid,
citric acid, and/or
acetic acid
B Enzyme Activity in Food 23 23

24. B-3.03 -- Enzyme Activity in Food
Spoilage
Prolonged enzyme activity can cause food to spoil.
Overripening of fruit
Food processors control enzymatic activity by:
replacing oxygen to slow action of oxidases
B Enzyme Activity in Food 24 24

25. Phytochemicals 25

26. Definition and Benefits
Phytochemicals -- group of compounds naturally produced by plants
Found in vegetables, fruits, grains, herbs, spices.
Gives plant foods color and flavor.
Helps plants resist pests and disease.
Provides potential health benefits.
B Phytochemicals 26 26

27. Sources of Phytochemicals
B Phytochemicals 27 27

29. Seven Families of Phytochemicals29

30. B-3.03 -- Seven Families of Phytochemicals
Allyl sulfides
Carotenoids – carotenes, xanthophylls
Flavonoids – isoflavones
Indoles – isothiocyanates
Phenolic acids (or phenols) – polyphenols
Saponins
Terpenes
B Seven Families of Phytochemicals 30 30

31. Characteristics Scientists are examining their: Function structure,
stability in food, and
sources.
Function
Gives foods color and flavor.
Helps plants resist pests and disease.
Provides potential health benefits.
B Seven Families of Phytochemicals

32. B-3.03 -- Seven Families of Phytochemicals
1 -- Allyl Sulfides
Contain sulfur
Increase enzyme reactions
Sources -- onions, garlic, leeks, chives
Benefits in raw and cooked forms
B Seven Families of Phytochemicals 32 32

33. B-3.03 -- Seven Families of Phytochemicals
2 -- Carotenoids
Over 600 known carotenoids
Precursors to vitamin A
Subgroups
Carotenes
Xanthophylls
B Seven Families of Phytochemicals 33 33

34. B-3.03 -- Seven Families of Phytochemicals
Carotenes
Contain only carbon and hydrogen atom
Not readily destroyed by heat
Alpha-carotene – pumpkins and carrots
Beta-carotene – dark green & yellow vegetables
Lycopene – tomatoes, watermelon, guava, and red peppers
B Seven Families of Phytochemicals 34 34

35. B-3.03 -- Seven Families of Phytochemicals
Xanthophylls
Yellow and orange in color
Stability related to food source
Lutein and zeaxanthin
B Seven Families of Phytochemicals 35 35

36. B-3.03 -- Seven Families of Phytochemicals
3 -- Flavonoids
Most red and white in color
Responsible for flavor
Potential benefits
Anti-flammatory/anti-carcinogen
Sources
Apples
Broccoli
Cranberries
Onions
Red grape juice, and
Tea
B Seven Families of Phytochemicals 36 36

37. B-3.03 -- Seven Families of Phytochemicals
Isoflavones
Subgroup of flavonoids
Also called phytoestrogens or plant hormones
Genistein and daidzein are best known.
Sources:
Soy
Chickpeas
Licorice
Oriental vegetables -- Chinese cabbage and bok choy
B Seven Families of Phytochemicals 37 37

38. B-3.03 -- Seven Families of Phytochemicals
4 -- Indoles
Found in cruciferous vegetables
Broccoli, cabbage, kale, and cauliflower
Stimulate enzymatic reactions
Heating and thorough chewing speed these chemical reactions
Isothiocyanates
subgroup that forms aroma in Brussells sprouts, cabbage, turnips, mustard greens, watercress, and radishes
B Seven Families of Phytochemicals 38 38

39. B-3.03 -- Seven Families of Phytochemicals
5 -- Phenolic Acids
Weak acids
Sources:
Carrots
Citrus
Nuts
Raspberries
Strawberries
Tomatoes
Whole grains
B Seven Families of Phytochemicals 39 39

40. B-3.03 Seven Families of Phytochemicals
Polyphenols
Sources
Green and black teas (green are higher)
Red and purple grape products
Rosemary
Sunflower seeds, barley, and apples
B-3.03 Seven Families of Phytochemicals 40 40

41. B-3.03 -- Seven Families of Phytochemicals
6 -- Saponins
Product of a sugar and alcohol
Sources:
Spinach, potatoes, tomatoes, oats, beans, legumes, soybeans, sugar beets, peanuts, and asparagus
B Seven Families of Phytochemicals 41 41

42. B-3.03 -- Seven Families of Phytochemicals
7 -- Terpenes
Flavor compound in citrus, cherries and many seasonings and herbs
Taxol
Best known
Found in Pacific Yew tree
Can be very toxic
B Seven Families of Phytochemicals 42 42

43. Best Sources of Phytochemicals
Vegetables
Black and green tea
Dark green and orange
Herbs
Legumes
Nuts
Onions and garlic
Soy
Tomatoes
Fruits
Apples
Berries -- blueberries, raspberries, blackberries, and strawberries
Citrus peel
Dark orange fruits -- mango, papaya, apricots, peaches, nectarines
Red and purple grapes
B Seven Families of Phytochemicals 43 43