| Purpose: In this paper, the chromatographic conditions and sample pretreatment method were optimized to improve the method of quantitative analysis, which was used to detect the content of furosine in dairy products, and the relationship between the heat treatment and the content of furosine were also discussed in different dairy products.Methods:In this paper, the technique of HPLC was used to detect the content of furosine in dairy products.This method was optimized by improving chromatographic conditions and the microwave digestion. Both the detecting time of single sample and the sample hydrolysis time were shortened.The effect of different heat treatment under different temperature on the furosine content was further compared in dairy products.Both the middle infrared spectrum of dairy products and the NIR spectrum of different concentration reconstituted milk were collected and analysed to establish the accurate infrared model by which we could detect the reconstituted milk in dairy products.Results:1. The results of chromatographic conditions for HPLC showed that, by the method of improved ISO18329, the average retention time was3.59minutes.The single sample detection time could be reduced to25minutes, the CV was0.088, and the average recovery of furosine (%) was89.90%.2. The results of microwave digestion showed that, compared with acid hydrolysis, the hydrolysis time of mircrowave digestion was shortened from24to4hours. The average recovery of furosine in milk (%) was90.0%and the CV was0.013. The content of furosine in the mixed milk sample with5%reconstituted milk was6.0mg/100g protein, and it was over the upper limit of5mg/100g protein set by the GB. This method could be used to detect the reconstituted milk accurately that was adulterated into raw whole milk.3. The results of heat treatment showed that the content of furosine in reconstituted milk changed slowly from65to75℃, and reached159.81mg/100g protein at85℃. While in the raw whole milk, it reached32.50mg/100g, which was six times of the upper limit (5mg/100g protein) set by GB.4. The results of NIR spectroscopy model showed that the furosine had the characteristic peak of carbonyl group at1724.0cm-1, and the characteristic peak of carbonyl group in reconstituted milk was higher than that in raw whole milk. The PLS was used to predict the mathematical model, and the best region was7200.9cm-1-4481.76 cm-1. The fiber module was used to construct a infrared model, related coefficient was0.984, the RMSEP was0.045, and the RMSEC was0.075.Conclusion:1. The improved ISO18329chromatographic conditions had short retention time and single sample testing time. The sample stability and percent recovery of furosine were improved as well. Compared with acid hydrolysis pretreatment, the hydrolysis time of microwave digestion pretreatment could be reduced, as well as the repeatability and percent recovery of furosine were improved. The method was suitable for detecting the raw whole milk which had been adulterated with more than5%reconstituted milk.2. The results of heat treatment showed that the content of furosine increased with the increasing temperature in raw whole milk, pasteurized milk, ultra heat treated milk and reconstituted milk. At85℃, the content of furosine in raw whole milk was six times of the upper limit (5mg/100g protein) set by GB.3. The NIR spectroscopy model showed that furosine had the characteristic peak of carbonyl group at1724.0cm-1, and the best region was7200.9cm-1-4481.76cm-1. The model can be used to analyse the content of reconstituted milk in raw whole milk accurately. The milk samples did not need to be pretreated and the method was rapid and easy. This method was very suitable for detecting raw whole milk adulterated with more than5%reconstituted milk. |
