Recently, the team of Professor Xu Zhenghong from the School of Bioengineering of Jiangnan University has made important progress in the screening of vintage liquor markers. The research results are”Identification of age-markers based on profiling of Baijiu volatiles over a two-year maturation period:Case study of Lu-flavor Baijiu” was officially published in LWT-Food Science and Technology (IF=4.006) (https://doi.org/10.1016/j.lwt.2021.110913).
Baijiu has been given the gift of time after aging. Under the four seasons, it has realized self-polishing and sublimation, which tends to be mellow and elegant. However, how to use scientific data to identify old wine is still a difficult problem. Liquor has undergone a series of physical and chemical transformations in the aging stage, and the flavor quality has gradually changed from the hot and spicy stimulus of the new wine to a mellow and coordinated. The sensory quality of vintage wine and its scarcity in the market result in a close relationship between the market price of vintage wine and storage time. However, there is still a lack of scientific, effective and easy-to-promote methods for identifying the years of liquor. Therefore, it is of great significance for the establishment of a vintage wine identification method to analyze the substance change law during the aging process of liquor, and to clarify the compound that marks the storage time.
Professor Xu Zhenghong’s team took Lu-type wine as a case, using headspace solid-phase microextraction-gas chromatography/mass spectrometry to track the dynamic changes of volatile components in the base wine during the 2-year aging process. A mathematical analysis method is used to obtain a series of compounds that mark the storage time, which improves the discrimination of base wines with different storage times. The changes in the volatile components of white wine summarized in this study provide important information for the establishment of a white wine vintage identification model, and the discovered landmark compounds also provide a powerful starting point for the establishment of a popularized identification method.
The main research results are as follows:
(1) Through the SPME-GC-MS method, the changes of volatile components of different batches of base wine during two years of aging were collected, and the analysis of similarities (Analysis of similarities) and unsupervised cluster analysis were performed , Found that in the two sample classification methods of aging time and different batches, the aging time distinguishes the samples more.
Figure 1. Principal component analysis shows that the volatile components of different types of base wine show a certain pattern with the aging time Sex
(2) Through partial least square discriminant analysis, correlation analysis and random forest, the importance of all volatile components to the storage time was analyzed, and a series of marker compounds were obtained. Compared with the full data set, the distinguishing degree of the landmark compound on the liquor samples with different storage time is significantly improved.
Figure 2. Time landmark compounds obtained through correlation analysis, partial least squares discriminant analysis, and random forest Importance ranking
(3) The study found that long-chain fatty acid ethyl esters are related to storage time, and their changing trend is significantly different from that of medium and short-chain fatty acid ethyl esters. This phenomenon has also been confirmed in bottled wine samples stored for 0-4 years, and compared with the data set of fully volatile components, the content of fatty acid ethyl esters is used as the sample parameter set, 0-4 The distinguishing degree of the bottled wine samples of the year has been significantly improved.
Figure 3. In different grades of bottled wine, short, medium and long chain fatty acid ethyl ester compounds are also reflected A differentiated trend is found, and the detection rate of long-chain fatty acid ethyl esters is positively correlated with storage time
Figure 4. Using principal component analysis to distinguish bottled liquor in different years, it was found that the use of long-chain fatty acid ethyl esters Compared with the full volatile component data set (A), the compound data set (B) significantly improves the discrimination of liquors with different storage time
Professor Xu Zhenghong is the corresponding author of the paper. Associate Professor Zhang Xiaojuan of the National Engineering Laboratory of Food Fermentation Technology and Technology of Jiangnan University, and Meng Lianjun, a 2018 master student in the School of Bioengineering, are the co-first authors. The above-mentioned research work was funded by the National Key Research and Development Program (2018YFD0400402) and the National First-level Disciplinary Project of Light Industry Technology and Engineering (LITE2018-11).