Food Chemistry

Name three ways one could reduce the occurrence of Maillard browning.

Increasing moisture levels to very high, lowering pH or temperature, removing one of the substances (usually sugar).

Describe the initiation, propagation, and termination steps of lipid autoxidation and explain how metal chelators inhibit the reaction.

Initiation forms lipid radicals, propagation generates peroxyl radicals and hydroperoxides, termination forms stable non-radical products. Chelators bind pro-oxidant metals (Fe²⁺, Cu²⁺), preventing radical initiation via Fenton reactions.

Explain the mechanism of lipid oxidation, including initiation, propagation, and termination steps.

Initiation involves the formation of lipid free radicals, often due to heat, light, or metal catalysts. Propagation occurs when lipid radicals react with oxygen to form peroxyl radicals, which then attack other lipids to form hydroperoxides. Termination happens when radicals combine to form non-radical, stable products.

What does the iodine value tell you about fat and what physical state is most likely for a lipid with a high iodine number at room temperature?

Iodine value refers to the degree of unsaturated fatty acids in a lipid or the number of grams of iodine absorbed by 100g of fat. A high iodine value is associated with an unsaturated fat, which is typically liquid at room temp.

Describe the flow direction of water across a cell membrane in an isotonic, hypotonic, and hypertonic solution.

Isotonic: no net flow (equilibrium); Hypotonic: water flows into the cell; Hypertonic: water flows out of the cell

Name two reasons why fats are hydrogenated.

It allows the conversion of liquid oils into semisolid or plastic fats; it improves the oxidative stability of the fat; Improves texture/mouthfeel; Used in shortening and margarine production

Name the properties and applications of three types of Carrageenan.

Kappa Carrageenan: Forms gels with potassium ions, known for their strong, brittle nature. It's widely used in dairy products like puddings and milkshakes, and in meat products as a water binder. Iota Carrageenan: Creates elastic gels that are thixotropic (break down with agitation and reform when at rest). This makes it suitable for applications like cold-filled dairy desserts and pet food gravy. Lambda Carrageenan: Primarily acts as a thickening agent, as it doesn't form a gel network. It's cold water soluble and used in applications like thickening solutions in personal care products.

Give an example of a food oil which contains as its principal fatty acid each of the following: Lauric Acid, Oleic Acid, Linoleic Acid, Linolenic Acid, Erucic Acid

Lauric: Coconut, Palm, Kernel; Oleic: Olive, Ground Nut, Rapeseed; Linoleic: Sunflower, Safflower, Soybean, Cottonseed, Maize; Linolenic: Linseed; Erucic: Rapeseed, Mustard Seed.

In the SI system what are the units that are applied to the following five dimensions or measurements; length, mass, time, electric current, thermodyanamic temperature?

Length = meter Mass = kilogram Time = second Electric current = Ampere Thermodynamic temp = Kelvin

Name 4 polyunsaturated fatty acids in foods and give the number of double bonds in each.

Linoleic (2), linolenic (3), arachidonic (4), EPA (5), DHA (6).

Rank the following fatty acids from lowest to highest melting point: oleic, elaidic, lauric, linolenic.

Linolenic, oleic, elaidic, lauric

Explain the mechanism of lipid oxidation and name two common antioxidants used to prevent it.

Lipid oxidation proceeds via initiation (radical formation), propagation (radical chain reactions forming peroxides), and termination (formation of stable products). Antioxidants such as BHA, BHT, or tocopherols donate hydrogen atoms to quench free radicals.

Differentiate between Maillard browning and caramelization.

Maillard browning involves a reaction between reducing sugars and amino acids/proteins (occurs at lower temps, gives savory notes); caramelization involves sugar degradation without amino acids (higher temps, sweeter notes).

Classify each emulsion types: margarine, mayonnaise, milk

Margarine: water in oil; mayonnaise and milk: oil in water

Give 5 initiators of lipid oxidation.

Metal ions, UV light, temp., oxygen, presence of conjugated double bonds, and free radicals

What is the percentage of chocolate in milk, sweet, bittersweet chocolate?

Milk chocolate ~10-15%, Sweet chocolate ~15-35%, Bittersweet chocolate ~35-60% or higher

Name five major food thickeners and stabilizers.

Modified starch, unmodified starch, guar gum, alginates, casein, carrageenan, xanthan gum, pectin, CMC, methyl cellulose, locust bean, gelatin.

Rank the relative sweetness of the following polyhydric alcohols: sorbitol, glycerol, xylitol, mannitol

Most to least: xylitol, sorbitol, mannitol, glycerol

Name three nonpolar, polar, and charged amino acids.

Nonpolar: Valine, Leucine, Alanine, Isoleucine, Proline, Methionine Polar uncharged: Serine, Threonine, Tyrosine, Asparagine, Glutamine Charged (polar): Positive: Lysine, Arginine, Histidine Negative: Aspartic acid, Glutamic acid

List 3 in vitro assays for determing alternative oxidase(AOX) activity.

ORAC, FRAP, DPPH radical, TEAC, CUPRAC, B-carotene-linolenic acid, PCL, TRAP, PSC