Unit 3

• Mechanisms of Maillard Non-Enzymatic Browning:
• Classical Pathway Steps (Hodge Scheme):

• Initial condensation of reducing sugar and amino group to form an uncolored Schiff's base (1).
• Isomerization via Amadori rearrangement (for aldoses) or Heyns rearrangement (for ketoses) (2).
• Dehydration, fragmentation, and Strecker degradation of $\alpha$-amino acids yielding aroma aldehydes and pyrazines (3).
• Final condensation into brown melanoidin polymers.
  • Gelation (4) is a protein/polysaccharide structural network phenomenon, NOT a biochemical reaction stage of Maillard browning.

• Conclusion: Gelation is not associated with Maillard browning (Option 4).

• Reaction Kinetics of Maillard Browning Color Formation:
• Zero-Order Kinetic Modeling:
• In both model sugar-amino acid mixtures and complex food products (milk powder, evaporated milk), the optical accumulation of brown melanoidin pigment ($\Delta A_{420}$) during continuous heating follows zero-order kinetics:

• Conclusion: Zero order kinetics (Option 4).

Correct option: (4) Zero order kinetics,

• The Order of Chemical Reactions:
• Kinetic Characteristics:
• The order of a reaction is an experimentally determined exponent in the rate equation:

• Can be zero (independent of reactant concentration), an integer/whole number (1, 2, 3), or fractional (common in complex free-radical mechanisms and enzymatic reactions).
• Conclusion: (A), (B) and (C) (Option 1).

Correct option: (1) (A), (B) and (C).

• Properties and Applications of Polypropylene (PP):
• Polymer Characteristics:
• Low density ($0.90 - 0.91\text{ g/cm}^3$) and high melting temperature ($160 - 165^\circ\text{C}$), allowing retort sterilization and microwave heating.
• Packaging Forms:
• Polypropylene is utilized in both rigid and flexible forms—rigid bottles, injection-molded closures, thin-walled thermoformed tubs, as well as flexible oriented films (BOPP) for snack pouches and bread packaging.
• Therefore, asserting that it is used only in rigid forms is completely incorrect.
• Conclusion: It is used only in rigid forms as in bottles (Option 2).

Correct option: (2) It is used only in rigid forms as in bottles