CCS Food Chemistry & Biochemistry 2 — Questions and Answers
Question 1: Which enzyme causes enzymatic browning in cut apples and potatoes when exposed to oxygen?
- Amylase
- Protease
- Polyphenol oxidase (Correct answer)
- Lipase
Correct answer: Polyphenol oxidase
Polyphenol oxidase (PPO) catalyzes the oxidation of phenolic substrates in the presence of molecular oxygen, producing brown quinone pigments.
Question 2: What is a protein's isoelectric point (pI)?
- The temperature at which a protein denatures
- The pH at which a protein has no net electrical charge (Correct answer)
- The molecular weight of the protein
- The protein concentration required for gelation
Correct answer: The pH at which a protein has no net electrical charge
At the isoelectric point, the number of positive charges equals negative charges on a protein, resulting in zero net charge and minimal solubility.
Question 3: Which type of dietary fiber is fermented by colonic bacteria to yield beneficial short-chain fatty acids (SCFAs)?
- Cellulose
- Insoluble fiber
- Soluble prebiotic fiber (Correct answer)
- Lignin
Correct answer: Soluble prebiotic fiber
Soluble fibers such as inulin, pectin, and beta-glucan are fermented by gut microbiota to produce SCFAs (butyrate, propionate, acetate) that nourish colonocytes.
Question 4: What is the primary antioxidant function of ascorbic acid (Vitamin C) in food systems?
- It thickens sauces by swelling
- It donates electrons to free radicals, preventing oxidation (Correct answer)
- It provides sweetness through receptor binding
- It releases CO₂ as a leavening agent
Correct answer: It donates electrons to free radicals, preventing oxidation
Ascorbic acid is a reducing agent that donates electrons to reactive oxygen species, preventing the oxidative degradation of lipids, pigments, and vitamins.
Question 5: Which monosaccharide is the primary circulating sugar in human blood and the central fuel for cellular metabolism?
- Fructose
- Galactose
- Glucose (Correct answer)
- Sucrose
Correct answer: Glucose
Glucose is the principal monosaccharide in blood (blood sugar) and the preferred substrate for glycolysis and ATP production in all cells.
Question 6: What distinguishes caramelization from the Maillard reaction at a chemical level?
- Caramelization requires amino acids; Maillard does not
- Caramelization involves only sugar thermal decomposition; Maillard requires amino acids and sugars (Correct answer)
- Caramelization produces no color; Maillard produces brown pigments
- Caramelization requires oxygen; Maillard is anaerobic
Correct answer: Caramelization involves only sugar thermal decomposition; Maillard requires amino acids and sugars
Caramelization is the pyrolysis and polymerization of sugars alone, while the Maillard reaction requires both amino acids and reducing sugars reacting together.
Question 7: Which lipid class provides the highest caloric density at 9 kcal per gram?
- Phospholipids
- Sterols
- Triglycerides (Correct answer)
- Glycolipids
Correct answer: Triglycerides
Triglycerides (triacylglycerols), composed of three fatty acids esterified to a glycerol backbone, are the storage form of fat and the most energy-dense macronutrient.
CCS Food Chemistry & Biochemistry 2
Which enzyme causes enzymatic browning in cut apples and potatoes when exposed to oxygen?