Question

The idea about heat classification of milk powder can be obtained using :

• A. Whey protein nitrogen index
• B. Protein Digestibility Corrected Amino Acid Score
• C. Urea number
• D. Digestible Indispensable Amino Acid Score

Hint:

- Low-heat powder is preferred for recombined milk and cheese making.
- High-heat powder is preferred for bakery products because the denatured whey proteins improve loaf volume.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Skim milk powder is classified into different categories based on the cumulative heat treatment it received during processing.
These heat classes (low-heat, medium-heat, and high-heat) determine the powder's suitability for different industrial applications.
Detailed Explanation:
The heat treatment applied to skim milk during preheating denatures its whey proteins, causing them to complex with casein.
Because caseins are highly heat-stable, they do not denature, but the more sensitive whey proteins precipitate out of the soluble phase.
The Whey Protein Nitrogen Index (WPNI) measures the amount of undenatured, soluble whey protein remaining in the milk powder (expressed as milligrams of undenatured whey protein nitrogen per gram of powder).
The classifications are defined as:
- Low-Heat Powder: \(\ge 6.0 \text{ mg WPN/g}\) (subjected to minimal heat treatment).
- Medium-Heat Powder: \(1.51 \text{ to } 5.99 \text{ mg WPN/g}\).
- High-Heat Powder: \(\le 1.5 \text{ mg WPN/g}\) (subjected to intense heat treatment, causing extensive whey protein denaturation).
The other options (PDCAAS, DIAAS) are nutrition-related metrics used to evaluate protein quality and digestibility, rather than processing history markers.

Step 2: Final Answer:
The heat classification of milk powder is obtained using the Whey protein nitrogen index.