Food Science Lecture

Food Science Lecture Review for RD Exam

What will decrease the freezing point of water?

Salt and sugar will decrease

Climacteric vs non-climacteric fruits and veggies?

Climacteric: ripen after being picked (bananas, avocados, apples)

Non-climacteric: non-ripening and ready to eat at harvest but will rot (grapes, melons, berries)

Ripening process

Start with protopectin (green/non sugary) → Pectin (developing sugar) → pectic/pectinic acid (brown spots/sweetest)

green banana→yellow banana→brown banana

For climacteric fruits

What are phytonutrients?

Adds colors to fruits and veggies

How does color of Chlorophyll change with cooking?

Green + acid or heat (lemon juice)= Pheophytin (olive-brown color)

Green + base/alkaline solution (baking soda) = Chlorophyllin (bright green)

What are fat-soluble phytonutrients?

Chlorophyll and carotenoids

How does color of carotenoids (orange, yellow, reds) change with cooking?

Carrot + acid/heat = no change

Carrot + baking soda = no change

How does color of anthocyanins (flavonoids) change with cooking?

Purple + acid/heat = Red

Purple + base/baking soda = deep blue

How does color of anthoxanthins (flavonoids) change with cooking?

White + acid/heat = no change

White + base/aluminum pans = yellow

Onions or garlic

which phytonutrients are water-soluble?

flavonoids (anthocyanins/anthoxanthins)

Who is responsible for fruit and vegetable grading?

USDA

Fruit and vegetable grading by the USDA?

Canned:

Grade A- Fancy (desserts/salads)

Grade B- Choice (processed foods)

Grade C- Standard (pudding/pie filling)

Fresh: Fancy, Extra #1, #1, Combo, #2

Based on quality, color, firmness, uniform size/shape

What two connective tissue are in meat?

Collagen: becomes tender in heat and creates gelatin; use MOIST HEAT for touch cuts

Elastin: Resistant to heat (no change/yellow)

What are the two types of meat grading?

wholesomeness (mandatory) grading and quality (voluntary/ based on marbling of cut) grading

What are the quality gradings for meat?

Beef: prime, choice, select

Veal/lamb: prime, choice, good

Poultry: Grades A, B, C

Pork: Grade 1, Grade 2-4, Utility

When does casein curd?

Precipitates at its isoelectric point (pH 4.6) when in contact with acid or rennet enzyme

What is whey?

Liquid and contains lactose, lactalbumin/globulin

precipitated by HEAT

Grading for milk/dairy?

Grade A

Grade B (bad dairy)

Grading for butter/ eggs?

Grade AA

Grade A

Grade B

What part of the egg holds an egg in place?

chalazae

Air sac quality for new vs old eggs?

Big air sac for old eggs; new eggs have small air sac

Function of flour in baking?

Provides gluten (when gluten and gliadin are hydrated and mixed)

Provides elastic property of bread

Function of liquids in baking?

Hydrates gluten

Gelatinization

Starts chemical leavening process

Function of leavening agent in baking?

1. Air (angel food cake) - incorporate air to expand

2. Steam (popovers)

3. CO2 (yeast, baking powder, baking soda)

Function of salt in baking?

flavor

interferes with excess yeast growth

Function of egg in baking?

Stability, air, color, flavor, emulsification (lecithin in egg)

Function of fat of baking?

Tenderness because it impedes gluten formation

Chocolate chip cookies, think mouthfeel

Function of sugar in baking?

Tenderness, flavor, bind together with water to form gluten, feeds yeast

What is the difference between baking soda and baking powder?

Baking soda: Sodium bicarbonate; may require some acid to be activated

Baking powder: sodium bicarbonate + acid; doesn’t need acid adde

Mixing methods for baked goods?

Muffin method- quick bread; sift dry ingredients, mix wet/dry liquid, don’t overmix

Conventional- cakes; cream fat and sugar, add egg, sifted dry ingredients while alternating with milk

Mixing- pastries; cut fat into flour and salt, add liquid

What can cause a cake with a fallen center?

excess sugar, fat, baking powder

inadequate mixing

low temp

opening door early in baking

What can cause a yellow cake?

excess baking soda

Think of what happens when anthoxanthins in flour react with a base

What cause a tough or dry cake?

excess flour, egg

overmixing, overbaking

What causes a course texture cake?

Excess sugar, baking powder

Low temp

Inadequate mixing (mix to form gluten!)

What causes a cake that didn’t rise?

inadequate baking powder (adds volume)

inadequate sugar or fat

Examples of dry heat method?

No water:

frying

broiling

roasting

grilling

baking

Examples of moist heat?

Braising

Simmering

Steaming

Stewing

Boiling

Conduction heat transfer?

Heating with direct contact

Heat from stove to food dish

Pan on a regular stove

Convection heat transfer

Heating through movement of hot air through circulation of fans

Think baking; cuts time in half

Induction heat transfer

Heating through a magnetic field generated by an induction coil

Burner has no flame and doesn’t get hot

Radiation heat transfer

Microwave

Heating through waves the cause movements of water molecules

When using buttermilk instead of regular milk, how should you adjust the baking soda?

Increase the baking soda

What to do when baking at high altitudes?

decrease amount of leavening and increase amount of liquid

What are two starch molecules?

Amylose: gelling and linear structure (alpha 1-4 glycosidic bonds/linear)

Amylopectin: non-gelling and branched; (1-4 and 1-6 glycosidic bonds for branched); waxy starches contain no amylose (corn, rice, sorghum)

What is gelatinization?

When you add liquid to a starch and heat it

Affected by acid (creates runny/thin product) and sugar (increases translucency and thinness)

What is retrogradation?

The recrystallization of starch molecules (especially amylose) after gelatinization, causing gritty texture and staling

Enzymatic browning

Browning due to action of naturally present enzymes in food

Apples browning at room temp

Non-enzymatic browning

aka Maillard reaction

Browning due to combination of sugar with an AA (PRO)

Enhanced by: alkalinity, increased temp, little liquid; want to use a solid sugar (not honey/maple

How many cups are in a #10 can?

~12-13 cups

6 cans in a case

20-25 serving size

What do emulsifiers do?

allows two things to mix that don’t usually mix

ex. lechithin, disodium phosphate, monoglycerides

What do thickeners do?

thickens products

ex. pectin, cellulose, gelatin, gum, agar

What do humectants do?

Add moisture to foods

Ex. sorbitol, glycerol monostearate

What do sedimentation-preventers do?

prevent particles from settling out of fluid

ex. carrageenan in yogurt

What do mold-inhibitors do?

inhibits mold growth

ex. propionate, sodium benzoate

What do antioxidants do?

prevent oxidation by quenching free radicals

ex. propyl gallate, BHA/BHT, ascorbic acid (C), alpha tocopherol (E)

What do flavor enhancers do?

enhance flavor

Ex. MSG (unami flavor)

What do anti-caking agents do?

Prevents lump formation

Ex. calcium silicate, mannitol

What are isoflavones?

lower cancer risk; soy foods

functional food!

What are thioles?

cancer fighting; cruciferous veggies

functional food!

What are polyphenols?

heart protection/reduce CVD risk; cocoa, tea

functional food!

What are lignans?

prevent breast cancer; flax, wheat, bran, barley, oats

functional food!

What is lycopene?

prevent prostate cancer; tomato, watermelon, grapefruit

functional food!

What are plant stanols and sterols?

lower LDL cholesterol; fortified juice and margarine

functional food!

What is capsaicin?

fight pain and inflammation; black pepper, chili, jalopenos

functional food!