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Food Science and Technology QUESTION #5977
Question 1
Lactulose is formed in heated milk by:
  • Fermentation of lactose by lactic acid bacteria
  • Isomerization of lactose at high temperatures via the Lobry de Bruyn–van Ekenstein rearrangement: the glucose residue of lactose is isomerized to fructose✔️
  • Enzymatic hydrolysis of lactose by \(\beta\)-galactosidase
  • Oxidation of lactose by peroxidase
Correct Answer Explanation
Lactulose (4-O-\(\beta\)-D-galactopyranosyl-D-fructose) is formed from lactose during heat treatment via the Lobry de Bruyn–van Ekenstein rearrangement. Lactulose is used as a heat damage indicator: HTST milk \(<50\;\text{mg/L}\); UHT milk \(50\text{–}600+\;\text{mg/L}\); raw milk \(\approx 0\;\text{mg/L}\).