Q23: Which one of the following best describes off-flavour of non-microbial... - Chemistry of Dairy Products - ICAR AIEEA PG Dairy Science 14 July 2023 Shift-1 Paper | Agrigyan

An oxidized off-flavour (cardboardy, metallic, oily, tallowy) in dairy products is strictly non-microbial in origin, initiated by abiotic chemical auto-oxidation of unsaturated fatty acids catalyzed by sunlight, fluorescent light, or transition metal ions like copper and iron. In contrast, malty is caused by Lactococcus lactis biovar maltigenes, bitty cream is caused by Bacillus cereus lecithinase, and rancidity is predominantly enzymatic/microbial lipolysis.

Option analysis:

• Malty: Microbial origin, caused by 3-methylbutanal from L. lactis biovar maltigenes.
• Bitty: Physical defect of microbial origin caused by lecithinase produced by Bacillus cereus.
• Oxidized: Correct. Purely abiotic chemical defect caused by free radical peroxidation of unsaturated phospholipids and triglycerides.
• Rancid: Predominantly caused by bacterial or native lipoprotein lipases hydrolyzing short-chain fatty acids.