Question:
Which one of the following best describes off-flavour of non microbial origin in dairy products?
Which one of the following best describes off-flavour of non microbial origin in dairy products?
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To distinguish milk off-flavors:
- Microbial origin \(\rightarrow\) Malty (L. lactis biovar. maltigenes) and Bitty (B. cereus lecithinase).
- Chemical/Non-microbial origin \(\rightarrow\) Oxidized (caused by light, air, or copper contamination).
- Microbial origin \(\rightarrow\) Malty (L. lactis biovar. maltigenes) and Bitty (B. cereus lecithinase).
- Chemical/Non-microbial origin \(\rightarrow\) Oxidized (caused by light, air, or copper contamination).
Updated On: Jul 23, 2026
- Malty
- Bitty
- Oxidized
- Rancid
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Verified By Collegedunia
The Correct Option is C
Solution and Explanation
Step 1: Understanding the Concept:
Off-flavors in dairy products can originate from microbial fermentation or non-microbial chemical changes.
Microbial off-flavors are caused by the growth and metabolic activity of bacteria, yeasts, or molds during storage.
Non-microbial off-flavors are caused by chemical oxidation, enzymatic activity from native milk enzymes, light exposure, or absorbed odors.
Step 2: Detailed Explanation:
Let us analyze the origin of each off-flavor listed in the options:
- (A) Malty:
This flavor is of microbial origin, caused by the growth of Lactococcus lactis subsp. lactis biovar. maltigenes.
This bacterium ferments leucine to produce 3-methylbutanol, which imparts a distinct malt-like flavor to milk.
- (B) Bitty:
This is a physical and textural defect in cream caused by Bacillus cereus.
The bacterium produces the enzyme phospholipase C (lecithinase), which hydrolyzes the phospholipids in the fat globule membrane.
This causes the fat globules to coalesce and form small, solid, floating particles of fat (bitty cream).
- (D) Rancid:
Rancidity is caused by the hydrolysis of milk fat, releasing free butyric and other short-chain fatty acids.
While it can occur spontaneously due to native lipoprotein lipase, it is often caused by heat-stable lipases produced by psychrotrophic bacteria like Pseudomonas.
- (C) Oxidized:
Oxidized flavor (often described as cardboard, metallic, or tallowy) is a purely chemical, non-microbial defect.
It is caused by the auto-oxidation of unsaturated fatty acids in phospholipids and triglycerides.
This chemical reaction is catalyzed by exposure to ultraviolet light, oxygen, or heavy metals (such as copper and iron) and does not require microbial activity.
Step 3: Final Answer:
The oxidized off-flavor is of purely non-microbial origin, caused by chemical lipid auto-oxidation.
Off-flavors in dairy products can originate from microbial fermentation or non-microbial chemical changes.
Microbial off-flavors are caused by the growth and metabolic activity of bacteria, yeasts, or molds during storage.
Non-microbial off-flavors are caused by chemical oxidation, enzymatic activity from native milk enzymes, light exposure, or absorbed odors.
Step 2: Detailed Explanation:
Let us analyze the origin of each off-flavor listed in the options:
- (A) Malty:
This flavor is of microbial origin, caused by the growth of Lactococcus lactis subsp. lactis biovar. maltigenes.
This bacterium ferments leucine to produce 3-methylbutanol, which imparts a distinct malt-like flavor to milk.
- (B) Bitty:
This is a physical and textural defect in cream caused by Bacillus cereus.
The bacterium produces the enzyme phospholipase C (lecithinase), which hydrolyzes the phospholipids in the fat globule membrane.
This causes the fat globules to coalesce and form small, solid, floating particles of fat (bitty cream).
- (D) Rancid:
Rancidity is caused by the hydrolysis of milk fat, releasing free butyric and other short-chain fatty acids.
While it can occur spontaneously due to native lipoprotein lipase, it is often caused by heat-stable lipases produced by psychrotrophic bacteria like Pseudomonas.
- (C) Oxidized:
Oxidized flavor (often described as cardboard, metallic, or tallowy) is a purely chemical, non-microbial defect.
It is caused by the auto-oxidation of unsaturated fatty acids in phospholipids and triglycerides.
This chemical reaction is catalyzed by exposure to ultraviolet light, oxygen, or heavy metals (such as copper and iron) and does not require microbial activity.
Step 3: Final Answer:
The oxidized off-flavor is of purely non-microbial origin, caused by chemical lipid auto-oxidation.
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