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Food Science and Technology QUESTION #6001
Question 1
Which of the following is used to detect the presence of Solids-Not-Fat (SNF) adulteration by addition of skim milk powder (SMP) to milk?
  • Alcohol precipitation test
  • Tyrosine index test or measurement of elevated non-protein nitrogen and reduced Whey Protein Nitrogen Index (WPNI) inconsistent with fresh milk (heat denaturation of whey proteins in SMP lowers WPNI)✔️
  • Clot on boiling test
  • Lactometer reading alone
Correct Answer Explanation
Detection of added SMP in milk involves: (1) Tyrosine index (proteolysis products elevated in SMP); (2) Whey Protein Nitrogen Index (WPNI) — lower in SMP-added milk due to heat denaturation of whey proteins; (3) Lactulose content (elevated in heated SMP); (4) Freezing point measurement inconsistencies. No single test is definitive; a battery of tests is required.