Sample interview questions: Can you explain your knowledge of the chemical reactions involved in non-enzymatic browning of food?
Sample answer:
Chemical Reactions Involved in Non-Enzymatic Browning of Food:
1. Maillard Reaction:
- A complex series of reactions between reducing sugars (glucose, fructose, etc.) and amino acids, peptides, or proteins.
- Occurs during heating or storage of food.
- Leads to the formation of brown pigments (melanoidins) and flavor compounds.
Mechanism:
a) Initial Condensation:
– Sugar reacts with an amino group to form a Schiff base.
b) Amadori Rearrangement:
– Schiff base rearranges to form a more stable ketoamine.
c) Dehydration and Fragmentation:
– Ketoamine undergoes dehydration and fragmentation, leading to the formation of a variety of compounds, including reductones, dicarbonyls, and furans.
d) Polymerization and Melanoidin Formation:
– These compounds further react with each other and with amino groups to form brown pigments called melanoidins.
2. Caramelization:
- Non-enzymatic browning reaction involving the heating of sugars (sucrose, glucose, etc.) in the absence of amino compounds.
- Occurs during cooking or processing of foods, such as caramelizing onions or making caramel sauce.
Mechanism:
a) Initial Dehydration:
– Sugar loses water molecules and forms a caramel precursor.
b) Rearrangement and Polymerization:
– Caramel precursor undergoes a series of rearrangement and polymerization reactions.
c) Formation of Colored Compounds:
– These reactions result in the formation of colored compounds, ranging from light yellow to dark brown, and the development of characteristic caramel flavor.
3. Ascorbic Acid Oxidation:
- Non-enzymatic browning reaction involving the oxidation of ascorbic acid (vitamin C) in the presence of oxygen.
- Occurs in fruits and vegetables during processing, storage, or co… Read full answer