Step 1: Understanding the Concept:
The alkaline phosphatase (ALP) test is a standard quality control method used in the dairy industry to verify that milk has been adequately pasteurized.
Alkaline phosphatase is a natural enzyme present in raw milk that has a thermal resistance slightly higher than that of the most heat-resistant, non-spore-forming pathogen commonly found in milk (Coxiella burnetii).
If the phosphatase enzyme is completely inactivated, it indicates that the milk has been successfully pasteurized.
Step 2: Detailed Explanation:
Let us review the historical contributions of the researchers listed in the options:
- Louis Pasteur (B): Discovered the process of pasteurization to destroy spoilage microbes in wine and milk, but did not develop the phosphatase test.
- Stephen Babcock (D): Developed the Babcock test in 1890, which is a rapid method used to determine the butterfat content of milk.
- Franz Schardinger (C): Discovered the Schardinger enzyme (xanthine oxidase) and developed early dye-reduction tests for milk quality.
- H. D. Kay and W. R. Graham (A): Developed the first practical alkaline phosphatase test in 1933--1935.
Their method used disodium phenyl phosphate as a substrate.
If active phosphatase is present in the milk, it hydrolyzes the substrate to release free phenol, which reacts with a color indicator to produce a blue color.
The intensity of the blue color can be measured to determine if the milk was successfully pasteurized.
Therefore, Kay and Graham developed the phosphatase test.
Step 3: Final Answer:
The alkaline phosphatase test for verifying adequate milk pasteurization was developed by Kay and Graham.