Research On Chinese Liquors Aroma By Ensory Analysis, Flavor Chemistry And Artificial Intelligence Sensory Technology

Chinese liquors, as one of the Seven Wonders of the World distilled spirits, have a long history and play important roles in people’s economic and social life. Due to their different fermentation materials and production process, distinctive flavor characteristics were formed. In order to regulate and improve the technical level and product quality, the liquors were divided into several flavor types and relevant sensory evaluation standards were established by the predecessors in Chinese liquor industry over a period of time. But as the development of flavors and varieties of Chinese liquors, the tasting demand was continuously changing. Therefore, the limitations of traditional evaluation for flavor types were increasingly prominent, In sensory evaluation, firstly, the "fixed" senses language in flavor standards were difficult to give scientific and quantified description for diverse product flavor characteristics; Secondly, the differences between different levels could not be quantified and the sensory results was difficult as the reference index for following research; Thirdly, the results from fewer tasters were as the leading results for the traditional evaluation standards and product design, and the relationship between them and consumers could not be established, so the contribution of flavor components to sensory evaluation need further study from physical and chemical indexes. In the physicochemical analysis, on the one hand, it was lack of screening methods of flavor components to the senses contribution; on the other hand, the quantitative data information was not formed between traditional experience sensory results and flavor components, and this led to the liquor flavor chemicals only staying in chemical analysis level and not explain the contribution relationship between the internal components and external aroma characters. Traditional evaluation method about Chinese liquor obstructed the sensory science and flavor chemistry, and a set of standard system which was internationally compatible and science was urgent to form.Therefore, the study research on Chinese liquors aroma by sensory analysis, flavor chemistry and artificial intelligence sensory technology. The sensory description analysis technology and establish unified flavor evaluation standards of Chinese liquor and to express the aroma characteristics; preference analysis method was applied to the sensory characteristics for consumer groups, and the relationships between product character and peoples’preference were established; flavor chemical analysis and multivariate statistical analysis methods were used to screen key flavor contribution components and dig deeper into the influence to sensory characteristics. This study was also the basic research of the Chinese national standard plan "20101030-T-607Guidelines for Flavor Components Threshold Determination of Chinese Spirits by Sensory Analysis","20101031-T-607Chinese Spirits Sensory Analysis and Evaluation Terminology","20101032-T-607Guidelines for Chinese Spirits Sensory Analysis". The research results would also promote the scientific sensory evaluation, strengthen the cultural understanding for consumers’ liquor tasting and help to control the product quality and development. The main contents and results were listed as follows:1. Quantitative descriptive analysis of Chinese liquor’aroma characteristicsTo overcome problems such as fuzzy index to evaluate and difficult to understand,10flavor types23kinds of Chinese liquors were taken as samples and analyzed by modern sensory quantitative descriptive analysis.(1) The aroma characteristic profile and style positioning were established, and the Chinese liquor aroma characteristics were expressed according to the aroma characteristics description language and strength combination. This makes the evaluation and expression more scientific and reasonable for Chinese liquor aromatic characteristics.(2) Principal component analysis of the locate and classify the samples by aroma characteristics, the type of Chinese liquor was firstly divided into two categories by the raw material, the first category is the samples based on sorghum as raw materials with vinegar, sweet aroma; roasted, sauced, rice as the main feature; The second category take rice as the raw material, with "Sweet aroma, Rice aroma, Grass aroma, Fat aroma and Floral aroma". Second, the former may continue due to differences in the fermentation process, the formation of Strong flavor (contains Nong jiang-flavor), Mild flavor (including Feng flavor, Laobaigan flavor), Jiang (including Zhima flavor, Te flavor). The study evaluated the location and classification of different white wine aroma style, verify the scientific basis of the senses of the traditional division of four flavor types.2. Preference characteristics research on Chinese liquor aroma for young peopleThe enterprise tasters were taken as the control and the preferences characteristics about young people to Chinese liquor was investigated. Results were that:(1) The aroma evaluation standard between experts and common tasters from enterprise were different; the young consumer groups were divided into six groups and this result was not affected by their gender and native, which indicated that there were diversified development trends and different preference criteria among young consumer groups.(2) The proportion, the products preference and their characteristics for different preference groups were analyzed by preference Map and PLSR. The result showed that the preference characteristics of bwtween consumers and tasters from enterprise, tasters and young people were different and all of them need to be noticed. Therefore, the discrepancy in product evaluation and design need to be noticed in product evaluation and design.3. Study on the evaluation about olfactory threshold determination method for the flavor components in Chinese liquorThe threshold determination method was based on screening the key aromatic components. Six kinds of typical flavor compounds (ethyl caproate, butyrate,2phenylethyl alcohol, furfural, isovaleraldehyde, tetramethylpyrazine) were taken as the representative components for this study:(1) Different threshold value determination methods were compared and results were that the results of BET calculation method (the geometric mean) were greater than the results of CF method (use curve fitting) and it was in three times acceptable ranges. And the results of TST method (Three-Alternative Forced-Choice) and AFC method (Three-Alternative Forced-Choice) were with no significant difference.(2) The influence of15%,30%,46%, and60%ethanol concentration to olfactory threshold of flavor components was studied. The results were that as the ethanol concentration increase, the threshold for most compounds began to rise. The compound thresholds in15%to60%ethanol are1/3-3times compared to46%ethanol and the compound characteristic was still to be considered. The establishment for simple and quick threshold determination would be beneficial for accelerating the research about the key aroma components; research on compounds’threshold change would provide powerful evidence.4. Research on key aromatic components in Chinese liquorThe composition of Chinese liquor was decisive factor for products’aromatic characteristics. In this part, according to the chemical content and olfactory threshold, the OAVs of71aroma compounds were determined to evaluate their potential influence on Chinese liquor aroma characteristic. Firstly, according to the ratio of OAVs,40representative aromas were extracted and analyzed by principal component analysis. Chinese liquor was divided into three categories based on the key components. The first category contained Strong, Feng-, Te-and Nong jiang-flavor types, and their key characteristic aromas were esters, aldehydes and ketones, alcohols, acids and pyrazines compounds. The second catergory contained Jiang and Zhima-flavor types; their contribution components were very complicated but their ratio was relative equilibrium; their key aroma components were aldehydes, esters, alcohols, acids (propionic acid, butyric acid), aromatics, and polyphenols and furan compounds. The third category contained Mild, Laobaigan-, Rice, and Chi-flavor types, and their key aroma components were n-octanol, acetic acid, and benzyl alcohol. Secondly, PLSR method was used to analyze the relationship between aroma characteristics and corresponding compounds and the comprehensive results of different components were uncovered.5. Evaluation and Improvement of the Chinese liquor aroma based on E-noseThe sensory evaluation methods are vulnerable to various subjective factors. The E-nose is an advanced intelligent sensory system, and the experiment employed PEN3portable electronic nose system to aroma detection.(1) Sensors S1(aromatic), S3(aromatic), S5(aromatic), S6(aromatic), S8(alcohols) and S9(sulfur compounds) can be used as the stable and effective sensors;(2) The determinination of flavor types by BPNN and SVM was far better than LDA, and their fitting accuracy were above90%, prediction accuracy above80%. The two pattern recognition algorithms would be adopted in flavor type’s discrimination.(3) The aromatic characteristics for high correlation characteristics with the six sensors was Floral, Rice, Sweet, Fruity aroma, and the corresponding compounds included aromatics, esters, alcohols, etc.; The aromatic characteristics for low correlation with the six sensors was Sauce, Grain, Vinegar, Roasted, Grass and Fat aroma; The six sensors were not sensitive to acids, phenolic components, aldehyde, esters and furfurans, these types of sensors need to add. The study showed that the e-nose can be feasible for aroma evaluation and flavor types’discrimination. Besides, the improved suggetion on the software (algorithms) and hardware (sensors) were proposed for commercial E-nose.