The common adulterants used in cow milk are water, starch, flour, urea, formalin, sodium hydroxide and cane sugar. Extension of milk with added water is the most common. These adulterants have effect on the nutritional quality of cow milk by decreasing the concentration of ingredients found and wholesomeness of the milk. This review examines the occurence of adulteration, as well as the methods to detect it.
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A three-dimensional paper-based microfluidic device has been designed and fabricated to simultaneously detect multiple chemical adulterants in milk using a visual colourimetric indicator.
It is intended as a quick and cheap screening test for use in developing countries.
The authors propose that it could be used by consumers to check milk before consumption.
It was shown to detect urea, detergents, soap, starch, hydrogen peroxide, sodium-hydrogen-carbonate, and salt which had been added to milk at concentrations between 0.05% and 0.2% v/v.
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Photo by Eiliv-Sonas Aceron on Unsplash
Milk has been a food involved with serious adulteration incidents in the past. In addition, where milk and milk-free products are manufactured and packed on the same lines, it is important to avoid cross contamination. With this in mind, SwissdeCode and Dutch microfluidics company DigiBio have joined together with the help of European Commission funding (€2.5m grant), and in collaboration with Vrije Universiteit Amsterdam in the Netherlands and EuroStars, an EU scheme to support new product development at small and medium sized enterprises (SMEs) to develop and produce an automated detection platform - BEAMitup. BEAMitup combines a digital microfluidics platform that slots into the production line with DNA testing to give results on milk adulteration in 30 minutes without the need of technical or laboratory personnel.
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The illegal practice of adding sucrose to milk has increased in recent years. Sucrose is used as an adulterant of reconstituted milk to increase the total solids content. This research developed the use of FTIR spectroscopy in combination with multivariate chemometric modelling for the differentiation and quantification of sucrose in cow milk. Trial samples of sucrose adulterated milk from 0.5 - 7.5% were prepared and analysed by FTIR. Chemometric analysis was performed on the spectra, and partial least squares regression (PLS-R) showed the best prediction of adulteration with a detection level of 0.5% w/v sucrose adulteration. The method is simple, non-destructive, quick and needs minimal samples preparation.
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Milk adulteration normally involves dilution with water or whey and adding other nitrogen sources such as ammonium salts, urea, melamine or non-dairy proteins. The established method for detecting added water in milk is to determine its freezing point depression, however, this method would not be effective to detect most milk adulterations. Brazilian researchers have developed a rapid and simple method to screen milk for adulteration, which involves precipitation of the milk proteins with copper sulphate and measuring the intensity of remaining copper salt after complexing with EDTA with a smartphone and a colorimetric app. The method was tested by adulterating milk with ammonium chloride, urea and melamine, and was able to detect the addition of 1% added water to the milk.
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Urea is added as an adulterant to give milk whiteness and increase its consistency by improving the non-fat solids content, but excessive amounts of urea in milk causes overload and kidney damage. A sensitive method for detecting and quantifying urea adulteration of milk has been developed using FT-NIRS (Fourier Transformed Near Infra Red Spectroscopy) coupled with multivariate analysis. The model was developed using 162 fresh milk samples, consisting of 20 non-adulterated samples (without urea), and 142 samples with the urea adulterant at 8 different concentrations (0.10%, 0.30%, 0.50%, 0.70%, 0.90%, 1.10%, 1.30%, and 1.70%), each prepared in triplicate. The NIR data coupled with the PLS‐DA (Partial Least Squares -Discriminant Analysis) model can be used to discriminate between the unadulterated fresh milk samples and those adulterated with urea. Furthermore, the NIR data coupled with PLSR (Partial Least Squares Regression) models may be used to quantify the level of the urea in milk samples.
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India is the largest producer of milk globally, producing 155 million tonnes/year worth nearly US$ 70billion. However, it has been reported that roughly 68% of all milk and milk products have been found to be in violation of the Food Safety and Standards Authority of India's (FSSAI) standards – despite the regulator's recent proposal of a penalty of around US$14,000, or a maximum of lifetime imprisonment for intentionally adding adulterants to food products. Adulterants found to be added in milk include white paint, refined oil, caustic soda, formalin, glucose, urea, salt, liquid detergent, boric acid, sodium bicarbonate, and hydrogen peroxide. Many of these pose a health risk to Indian consumers. The FSSAI has even produced a simple kit for consumers to test milk themselves for adulteration. The main problem being that only 66% of milk is handled in the main supply market and the rest is dealt with privately.
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