Development Of Novel Method For Detecting Vanillin In Milk Powder Based On FT-IR Spectroscopy

Milk powder is the main source of nutrition for infants who are not breastfed,and its security is a direct threat to the health of infants.With the sharp increase in milk consumption,milk safety problems have become an increasing concern,especially in recent years,with the"big milk","melamine"and other food safety incidents occurring frequently,milk safety problems has become a major problem affecting China's food safety and been one of the serious concerns of the whole society.In the safety of infant milk powder,vanillin as a high penetration rate of flavor,which exceed the standard is a neglected security problem.Vanillin has rich milk smell,easily induced infants to have preference for adding vanillin milk,thus promoting infant milk consumption.However,long-term consumption of vanillin can cause irreversible damage to the liver and kidney of infants.Therefore,the development of new and efficient detection method of vanillin is imminent.In various detection methods,infrared spectroscopy technology with its simple and efficient characteristic,has become one of the most preferred technologies of dairy products detection.However,the traditional IR technology is disturbed by the solid matrix,composition of trace vanillin is difficult to effectively detected in milk powder.Our preliminary study showed that vanillin has strong odor,volatile gas detection method is expected to effectively avoid the interference of complex matrix,and using the method of highly sensitive long path gas detection to achieve accurate detection of trace vanillin.Therefore,this paper innovatively proposes a method for rapid detection of vanillin based on long path infrared spectroscopy.Through the method of headspace sampling,we skillfully extract vanillin molecular information into the gas phase,and complete the corresponding high sensitive gas detection,thus effectively avoid the interference of solid matrix complexity,significantly improve the screening efficiency of milk powder doping.Following the principle of selecting typical targets and highlighting main contradiction,we adopt the uniform design method to detect the milk powder doped with vanillin.By the standard addition method,we analyzed the infrared absorption characteristic peaks of vanillin,and as a basis to accurately judge whether milk powder contains vanillin.Two characteristic peaks of vanillin at 1587 cm^-1 and 1515cm^-1were chosen to explore the relations between the peak height/peak area and the vanillin contents in milk powder.The results showed that there were good linear relations between vanillin contents,with the correlation coefficients were all over0.950.In order to further improve the sensitivity of quantitative analysis process,a multiscale modeling method was developed.This method combines discrete wavelet transform with partial least squares method,making full use of the gas infrared spectrum information in time/frequency multi-scale,to extract weak absorption information of vanillin from complex and changeable spectrum of milk powder.The results showed that the DWT-PLS algorithm can significantly improve the prediction accuracy and reliability,and promote the application of long path infrared spectroscopy technology in the detection of milk safety.In this paper we detected the volatile organic compounds releasing from doped milk powder,effectively avoid the interference of complex matrix formula.By using the long path infrared spectroscopy with high sensitivity and fast characteristics,we can significantly improve the detection efficiency and accuracy of milk powder.This method is simple,fast,having high accuracy,good feasibility and innovation,and is expected to achieve rapid detection of vanillin in milk products with low cost,and it will be further expanded to the rapid detection of other complex system.