Food Chem Exam 1

What are the four major food components?

1) Proteins 2) Lipids 3) Carbs 4) Water

What are the three minor food components?

1) Vitamins 2) Minerals 3) Phytochemicals

Define Food Chemistry

The study of relations between structure & functional properties of foods in a molecular basis

What are the two reasons that Water has anomalous physical properties?

1) The size of Oxygen compared to Hydrogen 2) 104 bond angle

What is slow cooling?

Results in large ice crystals found only in extracellular areas

What is super cooling?

Freezing water w/ very low temps (less than freezing point)

What happens to crystallization speed as the supercooling rate increases?

Crystallization speed decreases

What are examples of charge - dipole interactions in aqueous solutions?

NaCl or CaCl2 in Water

What are examples of dipole-dipole interaction in an aqueous solution?

Sucrose or ethanol in water

What are 2 examples of dipole-induced-dipole interaction in aqueous solutions?

Oil or Proteins in water

What are the four colligative properties of water

Lower vapor pressure, Lower freezing point, Higher boiling point, Higher osmotic pressure

What is the difference between water content and water activity?

Water content = all water in a product, water activity = all water available for chem/bio rxn’s

What is the equation for water activity?

Vapor pressure of water in a sample / vapor pressure of pure water

What are the three types of water?

Free, Bound, Entrapped

Which type of water is NOT part of water activity?

Bound water

What is free water?

Water that can be extracted by pressing food sample between membrane filter paper

What is bound water?

Water in tissue membranes bound to other molecules & loses its ability to flow freely, does not freeze

What is entrapped water?

water immobilized in capillaries/cells

What does the water activity of a product have to be for it to be shelf stable?

0.6 AW or less

What water is present in Area A of sorption isotherm?

Tightly bound water (lost last during dehydration)

What water is present in Area B of sorption isotherm?

Entrapped water (lost second during dehydration)

What water is present in Area C of sorption isotherm?

Free water (lost first during dehydration)

What is hysteresis?

Collapse of capillary & cellular structures during the desorption process

What does water do as a plasticizer?

Weakens intermolecular forces, increasing plasticity and flexibility of food polymers

What is the general formula for carbohydrates?

C_x(H₂O)_y

Which types of carbohydrates are structure based?

Monosaccharides, Oligosaccharides, & Polysaccharides

Which types of carbohydrates are function based?

Glycogen, Starch, & Cellulose/gums

What is a monosaccharide?

Simple sugar that can’t be broken down smaller

What is the name of the 5 carbon ring structure formed by aldose?

Pyranose

What is the name of the 4 carbon ring structure formed by ketose?

Furanose

What is special about the carbonyl group in chain form vs ring form?

“free” in straight chain form, NOT “free” in ring form

What is reduction?

Gain of H or Loss of O

What is oxidation?

Gain of O or Loss of H

What is a reducing agent?

A molecule that gives away an e^-

What is the term for a sugar that donates an e^-?

Reducing sugar

What functional group is involved in both oxidation & reduction?

Aldehyde

Glucose is a reducing sugar: True or False?

True

Can carbonyl groups be reduced to alcohols?

Yes, catalytic hydrogenation

Where is galactose found in the body?

Glycolipids in the brain & myelin sheath of nerve cells

Galactose exists naturally in nature: True or False?

False

What is the sweetest sugar? (found in honey & sweet fruits)

Fructose

What type of sugar is glucose?

Aldose

What type of sugar is fructose?

Ketose

How many carbons are forming the ring of a pyranose?

5

What happens when glucose is dissolved in H₂O?

Hydroxyl group and aldehyde form a pyranose

What is the isomerization needed to convert glucose to fructose?

Aldose to ketose

What functional group confers the reducing properties of a sugar molecule?

Aldehyde

What is the term for a carbohydrate with 2-10 units (monosaccharides)

Oligosaccharides

What is a disaccharide?

Two monosaccharides joined together by a glycolytic linkage

What are the three common disaccharides found in foods? (all contain glucose)

Sucrose, maltose, lactose

What is required for disaccharide to be considered a reducing disaccharide?

Hemiacetal

What structure in lactose is the reason lactase is needed to break down glycosidic bond?

Beta bond

What is the term for when sugars attract and hold water to varying degrees?

Hygroscopicity

What is the relationship between temperature and absorption of moisture from the atmosphere?

Absorption increases as temperature increases

True or False? Solubility differs with the type of sugar

True

What are the two-types of non-enzymatic browning?

Caramelization and Maillard browning

What are the two required ingredients for Maillard browning?

Reducing sugars and amino acids

What is the general sequence of events during the Maillard reaction (4 elements)

Condensation reaction (loses H2O)

Schiffs Base

Amadori Compound

AGE’s

Are brown sugars more or less refined than white sugars?

More refined

What is the most common sugar available in crystalline form?

Sucrose

Which type of sugar is isomerized?

HFCS

What alternative sweetener was important in foods for diabetics?

Saccharin

How is aspartame made?

Combination of 2 amino acids

What is Acesulfame-K derived from?

Acetoacetic acid

How many times sweeter is sucralose than sucrose?

600-800

What is a polysaccharide?

Polymers of monosaccharides

What are some examples of polysaccharides as texture modifiers?

thickening and gelling agents

How are polysaccharides used as stabilizers?

Retard movement of droplets or other particulate matter

How do polysaccharides act as water binders?

Hold water within food product and prevent syneresis

What do polysaccharides do as encapsulants?

Encapsulate flavors or other functional ingredients

What is the range of degree of polymerization of polysaccharides?

200-3000

What is the general structure of starch molecules?

75% amylopectin, 25% amylose

What is amylose?

large molecule of more than 200 glucose units

How is amylose linked together?

1,4-a-glucosidic linkages

What is amylopectin?

Extremely large chains comprised only of glucose

What bonds does amylopectin use for branching?

a-1,6 linked D-glucose

How does gelatinization occur?

Heat energy breaks hydrogen bonds in the starch granules

True or False? Gelatinization reduces the amount of free water external to the granules

True

Define pasting (starch)

changes in starch as it heats in the presence of water (AFTER GELATINIZATION)

How does gelation (gelling) occur?

Cooling of starch mixtures promotes formation of H-bonds between amylose molecules, resulting in a gel

What is retrogradation in terms of starch?

Reforming of crystalline structures during cooling of starch

How do sugars effect starch?

Compete with starches for water, increase temperature required for gelatinization

How do heat and acid effect starch?

Break down starch into slightly smaller molecules