Food Chemistry and Microbiology Flashcards

A research chef replaces sucrose with sorbitol in a baked snack and notices far less surface browning. What best explains this?

Answer: Sorbitol is not a reducing sugar, so it does not participate in Maillard reactions

Sugar alcohols lack a free carbonyl group, so they cannot react with amino groups in Maillard browning.

Which enzyme treatment is commonly used to reduce acrylamide formation in fried potato products?

Answer: Asparaginase

Asparaginase converts asparagine, the main acrylamide precursor, into aspartic acid before frying.

A sauce thickened with native corn starch weeps liquid after one freeze-thaw cycle. Which starch modification best addresses this?

Answer: Hydroxypropylation (substitution)

Hydroxypropyl groups hinder amylose and amylopectin re-association, improving freeze-thaw stability and reducing syneresis.

Fresh pineapple added to a gelatin dessert prevents it from setting. What is the cause?

Answer: Bromelain, a protease, hydrolyzes the gelatin proteins

Bromelain breaks gelatin peptide chains so the gel network cannot form; heating the fruit first inactivates the enzyme.

Which pathogen is the primary concern when large batches of cooked beef stew are cooled slowly overnight?

Answer: Clostridium perfringens

C. perfringens spores survive cooking and germinate rapidly as large volumes cool slowly through the danger zone.

Under the FDA Food Code, cooked foods must be cooled from 135°F to 70°F within how long?

Answer: 2 hours

The Food Code requires cooling from 135°F to 70°F within 2 hours and to 41°F or below within a total of 6 hours.

Low-methoxyl (LM) pectin differs from high-methoxyl pectin because LM pectin forms gels primarily through:

Answer: Calcium ion bridges between carboxyl groups

LM pectin has more free carboxyl groups that are cross-linked by divalent calcium ions, allowing low-sugar gels.