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Food Science and Technology QUESTION #5995
Question 1
Which is used as a cryoprotectant in freeze-drying (lyophilization) of dairy starter cultures?
  • Sodium chloride
  • Trehalose or skim milk — they protect cell membranes and proteins during freezing and dehydration by replacing water in hydrogen bonding (water replacement hypothesis)✔️
  • Calcium chloride
  • Glycerol at high concentrations
Correct Answer Explanation
Cryoprotectants during freeze-drying of LAB starters include: disaccharides — trehalose and sucrose (most effective) — stabilize membranes via the 'water replacement hypothesis' and vitrification; skim milk (traditional) — lactose \(+\) casein protect. Trehalose is preferred for commercial DVS (Direct Vat Set) cultures as it gives highest survival during freeze-drying and storage.