Q99: Which of the following can be used as an index... - Chemistry of Dairy Products - ICAR AIEEA PG Dairy Science 14 July 2023 Shift-1 Paper | Agrigyan

Lactulose (4-O-beta-D-galactopyranosyl-D-fructose) is an epimerization isomer of lactose that is completely absent in raw milk. When milk is heated, the Lobry de Bruyn-Alberda van Ekenstein transformation converts lactose into lactulose in a temperature- and time-dependent manner. Because lactulose levels directly reflect the cumulative thermal load, international standards (IDF/ISO) use lactulose content as an unambiguous chemical index to differentiate pasteurized ($\lt 50\text{ mg/L}$), UHT treated ($100\text{ to }600\text{ mg/L}$), and in-bottle sterilized milk ($\gt 600\text{ mg/L}$).

Option analysis:

• Urea content: Incorrect. Reflects cow nutrition and rumen nitrogen metabolism.
• Lactose content: Incorrect. High natural baseline varying little with normal heat treatments.
• Lactulose content: Correct. Synthetic heat-formed marker used internationally as an index of milk heat processing severity.
• Formic acid content: Incorrect.