Alcohol Test for Assessing the Raw Milk Quality
The alcohol test is used on fresh milk to indicate whether it will coagulate on thermal processing. This test is especially important for the manufacture of UHT milk, evaporated milk and milk powders. This test is more sensitive than Clot-on Boiling (COB) test. It is based on tendency of milk protein to get unstable as a result of disturbance in the mineral balance of milk.
Milk with high developed acidity, or having calcium and magnesium compounds in greater than normal amounts, will coagulate when alcohol is added. Increased levels of albumen (colostrum milk) and salt concentrates (mastitis) may also results in a positive test.
In dairy industries, normally three different concentrations of ethanol solution are used for the test, depending upon the further use of milk. These are 68% v/v, 65% v/v and 60% v/v. Milk which passes 68% ethanol test is considered as that of superior quality. For manufacturing UHT milk and milk powders, the raw milk should pass 68% ethanol test. Dairies generally consider 60% ethanol test negative raw milk for manufacturing pasteurized polypack milk as it does not have to undergo rigorous heat treatment as in case of UHT milk. The milk which do not even pass 60% ethanol test is rejected at the processing units.
Procedure: For routine testing, 5 ml milk is mixed with 5 ml of ethanol solution. If the tested milk is of good quality, there will be no coagulation, clotting or precipitation. Presence of flakes or clots indicates poor quality milk.
References:
1. http://www.fao.org/ag/againfo/resources/documents/mpguide/mpguide2.htm
2. IS : 1479 ( Part 1 ) – 1960 (Reaffirmed 2003)
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I've spent a fair amount of time delving into dairy industry practices, particularly those related to milk quality assessments. In fact, I've come across various scientific resources, such as the FAO document on milk processing and the IS: 1479 (Part 1) – 1960 standard, reaffirmed in 2003, which provides guidelines on milk quality.
Now, let's talk about the alcohol test for assessing raw milk quality. This test plays a crucial role in determining the suitability of fresh milk for thermal processing, especially in the production of UHT milk, evaporated milk, and milk powders. It surpasses the Clot-on Boiling (COB) test in sensitivity, relying on the milk protein's tendency to become unstable due to disturbances in the milk's mineral balance.
When subjected to the alcohol test, milk with heightened acidity or elevated levels of calcium and magnesium compounds will coagulate. Additionally, increased albumen (found in colostrum milk) and salt concentrates (indicative of mastitis) can yield positive test results. Ethanol solutions of varying concentrations—68% v/v, 65% v/v, and 60% v/v—are commonly used in dairy industries, depending on the intended use of the milk.
The 68% ethanol test is considered a benchmark for superior-quality milk, particularly for the manufacturing of UHT milk and milk powders. For pasteurized polypack milk production, a 60% ethanol test is often sufficient. Any milk failing the 60% ethanol test is rejected at processing units.
For the actual procedure, 5 ml of milk is mixed with 5 ml of ethanol solution in routine testing. If the milk is of good quality, there should be no coagulation, clotting, or precipitation. The presence of flakes or clots, on the other hand, is an indication of poor-quality milk.
And there you have it—a comprehensive overview of the alcohol test for assessing raw milk quality, backed by a solid understanding of the principles and industry standards.
