Food Chemistry

What are the described flavors of the following compounds: Diacetyl, acetic acid, acetaldehyde, ethyl hexanoate, propionic acid, 1-octen-3-ol?

Diacetyl – butter, acetic acid - vinegar, acetaldehyde – nutty or apple, ethyl hexanoate – fruity, propionic acid - Swisss cheese, 1-octen-3-ol – mushroom

Name the four types of chemical bonding that occur during bread dough mixing and kneading.

Disulfide interchange, hydrogen bonding, hydrophobic interactions, and ionic interactions

Name 5 chelating agents used in food.

EDTA, vitamin C, lactic acid, citric acid, acetic acid, malic acid, oxalic acid, pyrophosphate, proteins

Name 5 proteins with good foaming properties.

Egg white proteins, whey proteins, gelatin, soy proteins, bovine serum albumin

What are five functions of surfactants in foods?

Emulsification, aeration and foam stabilization, prevention of starch complexing, protein interaction, fat crystal modification, wetting agents, dispersion of flavors or colors

Explain the difference between enzymatic and non-enzymatic browning reactions, and give one example of each.

Enzymatic browning: Caused by polyphenol oxidase catalyzing oxidation of phenolic compounds (e.g., browning of cut apples). Non-enzymatic browning: Includes Maillard reaction (reducing sugars + amino acids) or caramelization (sugar heating).

Name 3 ways to slow or prevent lipid oxidation in a food.

Exclude oxygen (packaging), lower temp, protect from light, formulate w/antioxidants, inactivate lipoxygenase, or chelate metal catalysts

What are exopeptidases and endopeptidases?

Exopeptidases are enzymes that cleave amino acids or dipeptides in a stepwise manner from terminal end of protein. Endopeptidases are proteinases that hydrolyze linkages within the peptide chain, and don't touch the terminal peptide bonds.

Name 3 factors that influence the rate of lipid oxidation in foods.

Fatty acid composition, free fatty acid content versus the corresponding glycerols, oxygen concentration, temperature, surface area, moisture, pro-oxidants, antioxidants

What are the 3 forms of water in food and what is the difference between them?

Free water, adsorbed water, and water of hydration. Free water retains its physical properties and is available for reaction. Adsorbed water is held tightly to proteins. Water of hydration is the chemically bound water.

Name 4 colligative properties of water.

Freezing point, boiling point, vapor pressure, osmotic pressure; properties that depend on the number of solute molecules in water.

List three food sources that contain flavonoids.

Fruit, vegetables, nuts, seeds, stems, flowers, tea, wine, propolis, honey

Discuss starch gelatinization, including temperature range, molecular changes, and functional consequences.

Gelatinization occurs when starch granules absorb water and swell upon heating, disrupting hydrogen bonds and crystalline regions. Amylose leaches out, viscosity increases, and pastes or gels form, affecting texture and stability.

Gluten is a very unusual protein, partly because over 50% of the protein is composed of just 3 amino acid residues; name 2 of these 3 amino acids.

Glutamate, glutamine, proline

Name four compounds that may be used as humectants.

Glycerol, sorbitol, propylene glycol, honey, xylitol, or polyols

Name 3 physical agents capable of denaturing proteins.

Heat, Cold Mechanical Treatments, Hydrostatic Pressure, Irradiation, and Interfaces

Name 9 essential amino acids.

Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine (HIL PVT LMT)

What does HLB stand for and what does a high and low HLB value indicate?

HLB (hydrophilic-lipophilic balance); a low value (3-6) promotes water in oil emulsions and a high value (8-18) promotes oil in water emulsions.

Explain the chemical mechanism of lipid hydrogenation, and state its primary effect on the physical properties of a fat.

Hydrogenation is the process of chemically adding hydrogen atoms to the double bonds (C=C) of unsaturated fatty acids, converting them into single bonds (C-C). The primary effect is to increase the melting point and solid fat content of the fat, making a liquid oil more solid at room temperature and increasing stability.

Name four bonds involved in tertiary structure of protein.

Hydrophobic, ionic, hydrogen, disulfide