CFS CFS Food Chemistry & Biochemistry 2

Question 1

During starch gelatinization, what physical change occurs when starch granules are heated in water?

Accepted Answer

Granules swell irreversibly and absorb water

Answer

During gelatinization, starch granules absorb water, swell irreversibly, and lose their crystalline structure, causing a dramatic increase in viscosity.

Question 2

What is the isoelectric point (pI) of a protein, and why is it relevant to food processing?

Accepted Answer

The pH at which net charge is zero and solubility is minimal

Answer

The isoelectric point is the pH at which a protein carries no net charge, resulting in minimum solubility and maximum tendency to aggregate or precipitate — critical in dairy and soy processing.

Question 3

Enzymatic browning in cut fruits and vegetables is primarily catalyzed by which enzyme?

Accepted Answer

Polyphenol oxidase (PPO)

Answer

Polyphenol oxidase (PPO) catalyzes the oxidation of phenolic compounds to quinones, which polymerize into brown melanin pigments when plant tissue is cut and exposed to oxygen.

Question 4

In food emulsions, which type of molecule acts as an emulsifier by possessing both hydrophilic and hydrophobic regions?

Accepted Answer

Amphiphilic molecules (e.g., lecithin)

Answer

Amphiphilic emulsifiers like lecithin have a polar head (hydrophilic) and a nonpolar tail (hydrophobic), allowing them to stabilize oil-water interfaces and prevent phase separation.

Question 5

Retrogradation of starch refers to which post-gelatinization process?

Accepted Answer

Re-crystallization of starch polymers upon cooling

Answer

Retrogradation occurs when gelatinized starch cools and amylose/amylopectin chains re-associate into ordered crystalline structures, causing staling in bread and firming in gels.

CFS - Certified Food Scientist Practice Test

CFS - Certified Food Scientist Practice Test

CFS CFS Food Chemistry & Biochemistry 2