Question

Heat classification of milk powder based on WPNI mg/g is:

• A. High <1.5, Medium >1.5 – <6.0 and Low >6.0
• B. High >6.0, Medium >1.5 – <6.0 and Low <1.5
• C. High <2.5, Medium >2.5 – <6.0 and Low >6.5
• D. High <1.5, Medium >1.5 – <3.0 and Low >3.0

Hint:

Remember: High Heat treatment denatures more protein, leaving a low index of undenatured protein (\(<1.5\)). Low Heat treatment leaves a high index (\(>6.0\)).
{|l|l|} Heat Class & WPNI (mg/g)
High Heat & \(< 1.5\)
Medium Heat & \(1.5 \text{ to } 6.0\)
Low Heat & \(> 6.0\)

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The Whey Protein Nitrogen Index (WPNI) measures the amount of undenatured whey protein remaining in milk powder, which is used to classify the powder based on the heat treatment it received during manufacture.

Step 2: Detailed Explanation:
According to the American Dairy Products Institute (ADPI) standards, milk powders are classified into three heat categories:

• Low Heat Powder: Subjected to minimal heat treatment, leaving a high concentration of undenatured whey proteins:
\[ \text{WPNI} \ge 6.0\text{ mg of undenatured whey protein nitrogen / g of powder} \]

• Medium Heat Powder: Subjected to moderate heat treatment, causing partial denaturation:
\[ \text{WPNI} = 1.51\text{ to }5.99\text{ mg/g} \ (\text{or } >1.5 \text{ -- } <6.0\text{ mg/g}) \]

• High Heat Powder: Subjected to intense pre-heating, causing extensive denaturation:
\[ \text{WPNI} \le 1.5\text{ mg/g} \ (\text{or } <1.5\text{ mg/g}) \]
This matches the criteria in Option (A).

Step 3: Final Answer
The correct WPNI ranges are: High \(<1.5\), Medium \(>1.5\text{ to }<6.0\), and Low \(>6.0\).