Dairy Engineering- ICAR JRF/SRF 2024

• Methylene Blue Reduction Test (MBRT) in Milk Quality Control:
• Biochemical Principle:
• Dye reduction test measuring the metabolic activity and approximate bacterial load of raw milk.
• Proliferating bacteria consume dissolved oxygen, lowering redox potential ($E_h$), reducing the blue methylene blue dye to colorless leuko-methylene blue.
• Standard Grading:
• $\gt 5\text{ hours}$: Very Good ($\lt 2 \times 10^5\text{ CFU/mL}$).
• $3 - 4\text{ hours}$: Good ($2 \times 10^5 - 10^6\text{ CFU/mL}$).
• $1 - 2\text{ hours}$: Fair ($10^6 - 10^7\text{ CFU/mL}$).
• $\lt 30\text{ minutes}$: Poor ($\gt 10^7\text{ CFU/mL}$).
• Conclusion: Indication of bacterial load in milk (Option 1).

Correct option: (1) Indication of bacterial load in milk

• Determination of Solids-Not-Fat (SNF) via Lactometer Reading:
• Analytical Role:
• Corrected Lactometer Reading (CLR) measures specific gravity. Combined with Gerber fat percentage, it calculates % SNF (Solids-Not-Fat) using Richmond's equation:

• Vital rapid platform test for detecting illegal watering down or skimming of market milk supplies.
• Conclusion: SNF % in milk (Option 2).

Correct option: (2) SNF % in milk

• Indigenous (Bos indicus) Zebu Cattle Breeds:
• Sahiwal:
• Premier indigenous milch cattle breed originating from Montgomery district (now Sahiwal, Pakistan) and native to Punjab, Haryana, and Rajasthan.
• Characterized by reddish-dun coat, loose skin (Lola), high tropical heat tolerance, and average lactation yield of $2,000 - 2,500\text{ kg}$.
• Other Breeds:
• Holstein Friesian: Exotic taurine dairy breed from the Netherlands.
• Karan Fries & Karan Swiss: Synthetic crossbred strains developed at NDRI Karnal.
• Conclusion: Sahiwal (Option 3).

Correct option: (3) Sahiwal