Question

End product of milk fermentation which acts as preservative

• A. Lactic acid
• B. Formic acid
• C. Malic acid
• D. Ascorbic acid

Hint:

Lactic acid bacteria ferment lactose to produce lactic acid. This lowers the pH of the product, acting as a natural preservative by inhibiting the growth of spoilage and pathogenic bacteria.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Fermentation is a natural biopreservation method used to extend the shelf life of perishable foods.
During milk fermentation, starter culture bacteria consume the milk sugar (lactose) and produce primary metabolic end products.
These end products create an unfavorable environment for the survival and multiplication of spoilage and pathogenic microorganisms.

Step 2: Detailed Explanation:
Homofermentative and heterofermentative lactic acid bacteria ferment lactose to produce lactic acid as their primary end product.
The accumulation of lactic acid has several preservative effects:
It reduces the pH of the milk from approximately 7 to below
The low pH protonates lactic acid into its undissociated form, which can cross the bacterial cell membrane, disrupt intracellular pH homeostasis, and inhibit spoilage organisms.
It creates an acidic environment that is highly inhibitory to most pathogenic bacteria, such as Escherichia coli and Salmonella.
Other acids listed (formic, malic, and ascorbic acids) are either present in trace amounts or are not the primary end products of milk fermentation.
Therefore, lactic acid is the primary end product responsible for the preservation of fermented dairy products.

Step 3: Final Answer
Lactic acid is the primary end product of milk fermentation that acts as a preservative.