Study On Age Discrimination Of Zhenjiang Aromatic Vinegar Based On Colorimetric Sensor Array

Vinegar is one of the indispensable seasonings in people’s daily life; it is also a typical traditional fermented food in China. The vinegar not only gives us an enjoyment of taste, but also an unneglectable healthy function. As one of Chinese four major brewing vinegars, Zhenjiang aromatic vinegar has "color, aroma, acid, concentrated" characteristics, which is popular both at home and abroad. The age of aromatic vinegar is an important basis for consumers to choose products. Well-aged vinegar was not only more expensive, but also has a higher nutritional value.At present, our country has not set a mature identification standard about the ages of Zhenjiang fragrance vinegar, which leads to vinegar ages marked confusedly in the market. This phenomenon seriously injury consumers’ legal rights and interests, and also poses a threat to the healthy development of the enterprises. This research uses colorimetric sensor arrays to identify different ages of Zhenjiang aromatic vinegar quickly. In order to implement rapid and accurate identification of vinegars, this study activity and selectivity colorimetric sensors for different ages of Zhenjiang vinegar’s specificity gas by tuning the central metalions species and substituents to adjust the microstructure of porphyrins. The main contents of this study are as follows:1. Biomarkers screening of different ages of Zhenjiang aromatic vinegar. By using GC-MS with solid-phase micro-extraction, this study determined the volatile components from Zhenjiang aromatic vinegar in different ages which were new-made vinegar and the age of 1month/1year/2years /3 years. There were 46 kinds of volatile components were identified, and 2,3-Butanedione,2,4,5-Trimethyloxazole and Tetramethylpyrazine were found in minute amounts in new vinegar.With the increasing of aging time, the content of these ingredients increased significantly.We analyzed organic acids in different ages vinegar, experimental results showed that the content of lactic acid increased with the extension of aging time. Compared the changing trends of four types of compounds between the different ages of vinegar, the results proved that2,4,5-Trimethyloxazole could be used as a biomarker to identify vinegar ages.2. Identification of vinegar ages’ biomarker by olfaction visualization technology. This study evaluated the accuracy and stability of the visualization system, mainly to judge the stability of the sensor production and reproducibility of sensor arrays. The results indicated that the maximum spotting variation coefficient of four types of sensors was only 3.67%. Because sensor arrays had high precision and good repeatability, this olfaction visualization system was stable and reliable. From different metal porphyrins, this study screened sensitive materials for2,4,5-Trimethyloxazole. The results showed that metal zinc porphyrin and its derivatives: TPPZn,TPPZnF, TPPZnCl had good ability to identify different concentrations of2,4,5-Trimethyloxazole. The sensor made by the three kinds of zinc porphyrins could effectively recognize the different ages of Zhenjiang vinegar. Among them, TPPZnF had significant color variation in feature maps of Zhenjiang vinegar.3. By using UV-visible spectroscopy combined with the basic equation of thermodynamics,this study preliminary explored the maximum displacement, absorbance, coordination numbers and association constant between porphyrins and 2,4,5-Trimethyloxazole. The results showed that three kinds of metal zinc porphyrins were relatively sensitive with 2,4,5-Trimethyloxazole,and absorption spectrums had obvious peak displacement. This three kinds of porphyrins with2,4,5-Trimethyloxazole were formed 1:1 complexes. After finishing the comparative research,this paper also studied the TPPCl combined with 2,4,5-Trimethyloxazoleby means of the color sensors and UV-vis spectral change. The results showed that both zinc metal and electronic absorption(Cl) played a role in color reaction at the same time, and the zinc porphyrin played a leading role in the color reaction.4. Study on age discrimination of Zhenjiang aromatic vinegar based on colorimetric sensor array. As the research objects,new vinegar, vinegars samples storage for one year, two years,three years and four years, respectively were employed in this work. From 24 kinds of colorimetric dyes which including 18 kinds of porphyrins and 6 kinds of acid-base indicators, we screened cross colorimetric dyes for overall volatile gas of Zhenjiang aromatic vinegars. The results showed that optimal sensor made from four colorimetric dyes that were effective enough to identify the different ages of Zhenjiang vinegar. The four colorimetric dyes were CH3 OTPP b,CH3 OTPP a, bromocresol green and TPPZnF. Principal Component Analysis(PCA) and K-nearest neighbor(KNN) methods were used to discriminate vinegar samples. The result was evaluated by KNN whose recognition accuracy rate in the training set and test set achieved87.5% and 90.0% respectively.