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Food Science and Technology QUESTION #5963
Question 1
The 'buffering capacity' of milk is primarily due to:
  • Lactose (a weak acid)
  • Casein (phosphate groups \(\text{p}K_a \approx 6.0\), carboxyl/amino groups), calcium phosphate, and \(\text{CO}_2/\text{HCO}_3^-\) system (\(\text{p}K_a = 6.1\))✔️
  • Fat-soluble vitamins
  • Chloride ions
Correct Answer Explanation
Milk has significant buffering capacity (effective at \(\text{pH}\;5.1\text{–}6.3\)) due to: casein phosphate groups (\(\text{p}K_a \approx 6.0\)) and amino/carboxyl groups; colloidal calcium phosphate equilibria; \(\text{CO}_2/\text{HCO}_3^-\) buffer (\(\text{p}K_a = 6.1\)); and whey protein histidine imidazole groups (\(\text{p}K_a \approx 6.0\)).