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Table 3 Rapid qualitative detection of different mixed adulterants in milk

From: Common milk adulteration and their detection techniques

Adulterant Procedure Observation Limit of detection (v/v) (Sharma et al. 2012) References
Detergent A. Take 5 ml in a test tube and add 0.1 ml 0.5% Bromocresol Purple (BCP) solution. Appearance of violet colour indicates the presence of detergent. Unadulterated milk shows faint violet color.   (Singhal, 1980); (Arvind Singh et al. 2012)
B. Take 5 mL of milk sample into a 15 mL test tube. Add 1 ml of Methylene blue dye solution and 2 ml chloroform. Vortex the contents for about 15 sec and centrifuge at about 1100 rpm for 3 min. Relatively, more intense blue color in lower layer indicates presence of detergent in milk. Relatively more intense blue color in upper layer indicates absence of detergent in milk. 0.0125% (Rajput, Sharma, & Kaur)
Pulverized soap Take 10 ml milk sample in a test tube. Add equal quantity of hot water to it, then add 1 – 2 drops of phenolphthalein indicator. Appearance of pink color indicates presence of soap.   (Arvind Singh et al. 2012); (Kamthania et al. 2014); (Ghodekar 1974)
Coloring matter A. Take 10 mL milk sample in attest tube. Add 10 ml diethyl ether. After shaking, allow it to stand. Appearance of yellow color in ethereal layer indicates the presence of added color.   (Batis et al. 1981)
B. Make the milk sample alkaline with sodium bicarbonate. Dip a strip of filter paper for 2 hours. Appearance of red color on filter paper indicates the presence of annatto. Treatment of this paper with stannous chloride gives pink color.   (Lechner and Klostermeyer 1981)
  C. Add a few drops of hydrochloric acid to milk sample. Appearance of pink color indicates azo dyes.   (DE Souza et al. 2000)