New test to identify synthetic milk
ADULTERATION of milk is common. In January this year a survey by Food Safety and Standards Authority of India (FSSAI) found that about 70 per cent of the milk in the country does not conform to the standards set by it. The milk samples were found to have glucose, urea, hydrogen peroxide, vegetable fat, neutralisers, skim milk powder and even detergent in the samples tested.
Among these, detergents, though relatively new, are being widely used as an adulterant. “Their use has increased over the past five years due to absence of tests,” points out Y S Rajput, senior scientist at the National Dairy Research Institute (NDRI) in Karnal. He, along with other researchers at the institute, has now devised a way to detect the adulterant. The test is an improved version of an earlier method they designed, and can give results in less than two minutes. It is highly sensitive, too, and can detect even minute traces of detergent. Detergents are not natural components of milk. “Other chemicals like salt and glucose are naturally present.
Since these compounds are part of milk’s make-up it is difficult to detect the extra quantities milkmen add,” explains Rajput.
Detergents are used for a different purpose. “Milkmen remove milk fat and replace it with vegetable oil. However, vegetable oil is not miscible with milk, so they put detergent in it to make it miscible,” says Rajan Sharma, senior scientist with the dairy chemistry division of NDRI. The milk thus prepared is called synthetic milk. “This is done to increase the quantity of milk,” Sharma adds.
The test developed earlier in 2006 used a dye which gave a light blue colour when the milk was pure and turned dark blue when it was contaminated. But the industry pointed out that the test might be confusing for lay users.
To circumvent this problem, the team changed the chemistry of the test and used another dye, which they refused to name, so that pure milk gives violet colour and contaminated, blue. (see ‘NDRI innovation to tackle milk contamination’).
The kit was launched in December last year. It can detect all detergents that are being used to adulterate milk. “The USP of this test is that it will not show any false positive or negative results. Most of the other tests give five to six per cent false positive results,” says Rajput. He adds that it does not even throw up false positives in cases where there is residual detergent in the sample. This residual detergent can enter the sample through the utensils used to store milk.
The researchers add that their synthetic milk test has been field tested by Mother Dairy as well and they are now in talks with the company to commercialise it. Mother Diary is likely to outsource manufacturing to Benny Impex Private Limited, a company that supplies milk testing kits to it and to the National Dairy Development Board. “Most of the adulteration happens at the level of middlemen—the individuals who function as a link between the farmer and industry,” explains Sharma. Using the kit, companies can easily test the milk provided to them by middlemen, he adds. NDRI has also applied for a patent for the test.
Though there are no studies to show how chemicals in milk affect human health, experts warn that they are hazardous even in small quantities. Mukul Das, senior toxicologist at the Indian Institute of Toxicology Research in Lucknow, says, “Low doses of detergents over a period of time can dissolve membranes in the cells and interfere with their function.”
Naresh Kumar, a senior scientist in the microbiology division of the institute, adds that antibiotics in the milk can cause allergic reactions. The drug can also affect beneficial bacteria in the gut.
Aflatoxin M1—metabolites produced by the fungi Aspergillus flavus and Aspergillus paraciticus that enter milk through cattle feed—can impair the liver in large doses, he adds. Listeria monocytogenes—a bacterium found in milk if animals not kept under hygienic conditions—can lead to diarrhoea, fever and nausea. Chemicals like hydrogen peroxide added to the milk to preserve it can reduce the nutritive value of milk, says Rajput.
NDRI also has a testing kit for these chemicals. It can detect 11 other contaminants like starch, sugar, glucose, maltodextrin, urea, ammonium compounds, pond water/nitrate, common salt, neutralisers, hydrogen peroxide, formalin, and vegetable oil. The test kit, which costs Rs 5,000 and provides 100 tests, has sold 180 units in the past 10 years. Customers include dairy farms and small-scale dairy companies.
But similar kits are made by other manufacturers and are cheaper and easily available in the market.
The NDRI scientists are going to pitch the test kit to FSSAI in a few months. Speaking to Down To Earth, FSSAI chairperson K Chandramouli welcomed the innovation. “Our panel would be very willing to have a look at it.” he adds.
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