Quality And Safety Evaluation Of Vinegars Using NMR Technology

Vinegar is widely consumed as a fermented food condiment around the world and its consumption amount is increasing year after year.Quality and safety evaluation of vinegar is closely related to people's health.By combing NMR method with multivariate statistical analysis,GC and GC-MS method,quality and safety evaluation of vinegars from home and abroad were carried out comprehensively and deeply.This work can provide data and method support for quality and safety control of vinegar industry.It is listed as four parts of two aspects as followings:1.Evaluation of vinegar quality1)Component analysis and type discrimination are two essential aspects for evaluation of vinegar quality.Three representative types of Chinese cereal vinegars and three representative types of European grape vinegars were chosen as subjects;NMR spectroscopy combined with multivariate analysis(PCA and OPLS-DA)has been applied to analyze the diversity of components and to extract key metabolites.The results showed that Chinese Aromatic Vinegar and Chinese Aged Vinegars were characterized by higher amount of amino acids and flavoring compounds while Balsamic Vinegar of Modena was clearly discriminated by higher amount of fructose and glucose.The flavoring compounds in Chinese Rice Vinegar(CRV)and grape wine vinegars are much less.These characters also corresponding to particular taste of different types of vinegar and coincide with the special raw materials and manufacturing process of individual vinegar.The detail one-way ANOVA analysis and Tukey's multiple comparisons test of component concentrations was conducted,and the results showed consistency with that of multivariate analysis and suggested that the concentrations of the characterized components could be used for the discrimination of different types of vinegars.2)Flavor is one of crucial index of vinegar quality.Volatile organic compounds(VOC)in vinegars are essential for their flavor.To carry out a comprehensive VOC analysis,isolate,detect and identify more VOC.Both sample injection and pretreatment methods for GC-MS detection were optimized.Finally,91 VOC were detected and identified.It was found that 10 same VOC were existed in six types of vinegars from different countries and areas.Many types of VOC which existed in caramel were detected in a type of aromatic vinegar.2(5H)-Furanone and 3-Furanmethanol which are threat to people's health were detected in some types of balsamic vinegar,aromatic vinegar and black vinegar.2.Evaluation of vinegar safety1)Detection of exogenous additive in vinegars is one of important aspects for safety evaluation.A vinegar fermentation process was established using mixed fermentation method and biogenic vinegar wsa obtained with this method.Signals distribute over the whole spectra with broad line widths in some types of Chinese commercial vinegar were analyzed using 1H NMR,T2 filter and DOSY experiments and we primarily deduced that those signals are from caramel.2)Distinguishing traditional vinegars from the blending or synthetic ones are crucial for safety evaluation of vinegars.Based on the principle of SNIF-NMR,1D and 2D heternuclear J-resolved pulse program and 1D 1H NMR pulse program were optimized to get 13C isotope distributions of different types of vinegars in a valid,general and simple way.According diversity of those distributions,blending or synthetic vinegars could be discriminated from traditional ones.The results suggested the method based on 1D 1H NMR pulse program is valid,non-destructive,general,and simple to achaive the discrimination.An improved GC-IRMS detection was also conducted and the results showed that carbon isotope distribution characteristics of different types of vinegars resulting from the new 1H NMR method are consistent with those from GC-IRMS method.