Unit 6

Matching the items of List I with List II for Milk clotting enzymes from different sources – microbial:

The correct combination is Option 2: (A) - (II), (B) - (IV), (C) - (1), (DB) - (Ill).

Correct option: (2) (A) - (II), (B) - (IV), (C) - (1), (DB) - (Ill)

• Antimicrobial Metabolites of Lactic Starter Cultures:
• Endogenous Antimicrobials Produced by LAB:
• Organic acids: Lactic and acetic acids lower pH and permeabilize bacterial cell membranes.
• Bacteriocins: Ribosomal antimicrobial peptides (nisin, pediocin) that create pores in bacterial cell membranes.
• Hydrogen peroxide ($H_2O_2$): Generates oxidative stress in catalase-negative pathogens under aerobic conditions.
• Phenols: Phenols are plant secondary metabolites or industrial chemicals, NOT metabolites synthesized by dairy starter cultures.
• Conclusion: Phenols (Option 2).

Correct option: (2) Phenols

• Function of Emulsifying Salts in Processed Cheese:
• Colloidal Role:
• Emulsifying salts (sodium citrates, disodium phosphate, polyphosphates at $2 - 3\%$) sequester calcium from the cross-linked calcium paracaseinate network of natural cheese during cooking ($70 - 85^\circ\text{C}$).
• This transforms insoluble paracaseinate into soluble sodium paracaseinate, which acts as a powerful amphiphilic emulsifier surrounding milk fat globules and preventing oil separation (free fat formation) upon heating.
• Conclusion: Prevent free fat formation (Option 1).

Correct option: (1) Prevent free fat formation