Study On The Methods Of Detecting Foreign Fat In Raw Milk

Detection methods for adulterate foreign fat in raw milk were studied in this paper. First, physical and chemical methods for detecting less than 0.5% plant butter in raw milk were reviewed, including iodine value, saponification value, refractive index, free fatty acid. The results showed that iodine value did not change, saponification value was in a decrease trend but was not significant under 0.1 level, the change of refractive index was not observed, free fatty acids had increase trend, while taste and smell was the same as without plant oil. Secondly, several fatty acids in raw milk adulterated with plant butter and powdered plant oil were determined by gas chromatography, and Bayesian discrimination formula was established, which was Pr (j | X) = exp (-0.5 Dj2 (X)) / SUMk exp (-0.5 Dk 2 (X)). The detection limits of adulterated plant butter and powdered plant oil in raw milk by Bayesian discrimination formula was 0.8% and 0.1%, respectively. Finally, volatility substance detection of milk fat was determined by two types of electronic nose, i.e. metal oxide sensors and GC with surface acoustic wave. Based on the sediments quality criteria, the detection limit by metal oxide sensors for adulterate plant butter in raw milk was 0.1%; the detection limit by GC with surface acoustic wave for adulterate plant butter and powdered plant oil in raw milk was 0.1%.In addition, as powdered plant oil contained reducing sugar, reducing sugar was detected with urine sugar test kit, and the detection limit of adulterate powdered oil in raw milk was 0.2%. As plant butter contained antioxidant BHT, spectrophotometer was used to detect BHT and the detection limit of adulterate plant butter in raw milk was 0.1%.