Question

Which one of the following best describes off-flavour of non microbial origin in dairy products

• A. Malty
• B. Bitty
• C. Oxidized
• D. Rancid

Hint:

Oxidized flavor is often called "cardboard flavor." It is usually the result of chemical reactions catalyzed by light or metal ions (Cu/Fe), never bacteria.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Off-flavors in milk can be classified into several categories: microbial (caused by bacterial growth), chemical (oxidized or light-induced), enzymatic (rancidity), and absorbed (feed or barn odors).
The question specifically asks for an off-flavor that is non-microbial in origin.

Step 2: Detailed Explanation:
1.Malty: This is a microbial off-flavor caused by certain strains of Lactococcus lactis var. maltigenes. It develops when milk is poorly cooled.
2.Bitty: Also known as "sweet curdling" or "bitty cream," this is caused by the production of phospholipase C by Bacillus cereus. It is a microbial/enzymatic defect.
3.Oxidized: This flavor is described as "cardboardy," "metallic," or "tallowy." It is purely chemical in nature, resulting from the oxidation of milk phospholipids (lipid peroxidation). This is triggered by exposure to copper, iron, or sunlight. It has nothing to do with microbial growth.
4.Rancid: This is caused by the action of lipase enzymes on milk fat, releasing free fatty acids. While lipases can be endogenous (native to milk), they are also frequently produced by psychrotrophic bacteria (Pseudomonas spp.). Thus, it can be microbial or enzymatic.
Among the options, "Oxidized" is the only one that is strictly non-microbial and purely a chemical reaction involving fats.

Step 3: Final Answer:
The off-flavour of non-microbial origin is Oxidized.