Question

Given below are two statements:
Statement (I): Moseley count gives a better index of shelf life than aerobic mesophilic count as it determines the growth rate of bacteria when stored at low temperature.
Statement (II): Flavor rating at $7^\circ\text{C}$ is a useful shelf test as most of the enzymes responsible for off flavors are optimally produced and more active at this temperature.}
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is false but Statement (II) is true.

Hint:

Remember:
- Standard Plate Count (fresh milk) $\neq$ Shelf Life.
- Moseley Test ($7^\circ\text{C}$ storage for 5–7 days) $=$ Best predictor of shelf life because it measures cold-tolerant spoilage bacteria.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Evaluating the shelf life and keeping quality of pasteurized milk requires diagnostic tests that simulate typical storage and distribution conditions.
Traditional microbial counts do not always predict shelf life accurately.
Detailed Explanation:
Let us evaluate Statement (I): "Moseley count gives a better index of shelf life than aerobic mesophilic count as it determines the growth rate of bacteria when stored at low temperature."
This statement is correct.
The aerobic mesophilic count (or Standard Plate Count) on fresh pasteurized milk measures bacteria that grow at $30^\circ\text{C}$ to $35^\circ\text{C}$.
It does not measure how many psychrotrophic spoilage organisms (which grow at refrigeration temperatures) are present.
The Moseley keeping quality test involves storing pasteurized milk at $7^\circ\text{C}$ for 5 to 7 days, then performing a plate count.
The difference between the initial count and the post-incubation count indicates the growth rate of psychrotrophic contaminants, which are the main cause of milk spoilage.
Therefore, the Moseley count is a much more reliable predictor of shelf life.
Now let us evaluate Statement (II): "Flavor rating at $7^\circ\text{C}$ is a useful shelf test as most of the enzymes responsible for off flavors are optimally produced and more active at this temperature."
This statement is also correct.
Sensory analysis of milk stored at $7^\circ\text{C}$ (refrigeration abuse temperature) is a standard test for shelf life.
Psychrotrophic bacteria (like Pseudomonas species) grow at this temperature and produce extracellular lipases and proteases.
Interestingly, many of these enzymes are synthesized in higher quantities at lower temperatures (around $4^\circ\text{C}$ to $7^\circ\text{C}$) than at their optimal growth temperatures.
These enzymes remain active at refrigeration temperatures, hydrolyzing milk lipids and proteins to produce bitter, rancid, or oxidized off-flavors.

Step 2: Final Answer:
Both Statement (I) and Statement (II) are true.