Starter Cultures & Fermented Products

Delvotest is a standard broad-spectrum microbial inhibitor ampoule/plate test utilizing Geobacillus stearothermophilus var. calidolactis as the indicator organism:

• Statement (I) is false: Delvotest-SP is specifically sensitive to and designed for beta-lactams (penicillins) and sulfonamides. It has very poor sensitivity for aminoglycosides such as Streptomycin (detection limit is far too high to detect regulatory levels of streptomycin). Hence, claiming it is used for Streptomycin is technically false.
• Statement (II) is true: Delvotest is universally accepted as a standard reference diffusion test for detecting penicillin and beta-lactam residues in herd and silo milk.
  
  Option analysis:
• Both Statement (I) and Statement (II) are true: Incorrect.
• Both Statement (I) and Statement (II) are false: Incorrect.
• Statement (I) is true but Statement (II) is false: Incorrect.
• Statement (I) is false but Statement (II) is true: Correct answer.

Managing bacteriophage contamination in cheese production:

• Statement (I) is false: Phage rotation is an effective preventive strategy to minimize the build-up of specific virulent phages, but it cannot 'completely eliminate' phage growth, because new virulent mutant phages emerge and environmental contamination persists.
• Statement (II) is true: In commercial cheese factories, defined strain starter rotations are routinely implemented on a daily basis or from vat-to-vat during continuous operation to prevent phage amplification.
  
  Option analysis:
• Both Statement (I) and Statement (II) are true: Incorrect.
• Both Statement (I) and Statement (II) are false: Incorrect.
• Statement (I) is true but Statement (II) is false: Incorrect.
• Statement (I) is false but Statement (II) is true: Correct.

Butter is a water-in-oil emulsion. Proper 'working' of butter disperses moisture into billions of tiny micro-droplets ($\lt 10\;\mu\text{m}$), starving bacteria trapped inside due to limited local nutrients. In underworked butter, moisture exists in large droplets ($\gt 30\text{--}100\;\mu\text{m}$), which contain ample dissolved nutrients and water activity to support rapid microbial proliferation and premature spoilage.