Question

Aerobic spore former that produce bitty cream defect in pasteurized milk is ________.

• A. Bacillus cereus
• B. Bacillus coagulans
• C. Bacillus subtilis
• D. Bacillus mycoides

Hint:

Remember the enzyme pathway:
Bacillus cereus $\rightarrow$ Lecithinase $\rightarrow$ Hydrolyzes fat membrane (MFGM) $\rightarrow$ Fat coalesces $\rightarrow$ Bitty Cream.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
"Bitty cream" is a physical defect in pasteurized milk and cream.
It is characterized by the appearance of small, insoluble, flaky fat particles that float on the surface of the milk or pool when added to hot beverages like tea or coffee.
This defect is caused by the metabolic activity of specific heat-resistant spore-forming bacteria.
Detailed Explanation:
The primary causative agent of the bitty cream defect is Bacillus cereus, a Gram-positive, aerobic, spore-forming rod.
While pasteurization kills vegetative bacterial cells, Bacillus cereus spores can survive the process.
These spores germinate and grow during refrigerated storage.
Bacillus cereus produces an extracellular enzyme called lecithinase (phospholipase C).
This enzyme targets the milk fat globule membrane (MFGM), which naturally stabilizes the fat emulsion in milk by surrounding individual fat droplets with a layer of phospholipids (primarily lecithin) and proteins.
When lecithinase hydrolyzes the lecithin in the MFGM, the protective membrane is disrupted.
This destabilizes the emulsion, causing the exposed fat droplets to coalesce and aggregate.
These aggregated fat masses form the characteristic small, tough, insoluble flakes or "bits" on the surface, known as "bitty cream."
Other aerobic spore formers like Bacillus subtilis are proteolytic or amylolytic but do not produce sufficient levels of lecithinase to cause this specific fat-destabilization defect.

Step 2: Final Answer:
The aerobic spore former responsible for the bitty cream defect is Bacillus cereus.