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基于可解释机器学习方法的茶本酒香气品质预测模型构建

Predicting study on aroma quality prediction model for tea-flavored liquor using explainable machine learning method

  • 摘要: 为实现茶本酒香气质量等级的精准预测、揭示影响其香气品质的关键挥发性成分,试验以110款茶本酒为研究对象,通过感官分析确定其香气品质等级,利用顶空固相微萃取-气相色谱-质谱测定主要香气成分轮廓,结合13种机器学习(machine learning,ML)算法和Shapley可加性特征解释(shapley additive explanations,SHAP),建立茶本酒香气品质预测模型,识别各等级茶本酒的关键差异性风味化合物并探索其作用模式。结果表明,在32个主要挥发性香气成分中,10种萜烯类物质、10种酯类物质和4种高级醇在不同等级酒样间具有显著差异。模型性能评价表明,径向基支持向量机(radial support vector machine)的曲线下面积最高(0.924),且准确度、精确度、召回率、F1分数均在0.8以上,综合性能优于其他ML算法,是茶本酒香气品质预测的最优模型。SHAP分析显示,里哪醇、茴香脑、水杨酸甲酯、橙花醇、十一酸乙酯、异戊醇的SHAP值高于其他成分,在模型预测中表现出较高的贡献度,是影响茶本酒香气质量等级的关键挥发性成分。其中,里哪醇、茴香脑、水杨酸甲酯、十一酸乙酯对茶本酒的香气品质具有积极影响;橙花醇对香气品质的贡献水平随其含量变化呈先上升后下降的趋势;异戊醇的大量积累则可能降低茶本酒的品质。研究揭示了影响茶本酒香气品质的关键挥发性成分及其潜在作用机制;通过对原料品质的把控,并在生产各环节对上述成分含量进行合理调控,可促进茶本酒风味品质的定向提升。

     

    Abstract: Tea-flavored liquor can often represent one of the most favorite alcoholic beverages in recent years. A combination of tea and liquor flavors can be produced after raw material preparation, tea maceration, sugar supplementation, alcoholic fermentation, distillation, aging, and blending. However, its aroma profile is characterized by pronounced complexity and variability. Substantial challenges also remained to accurately assess and then predict the aroma quality. In this study, an explainable machine learning (ML) framework was developed to predict the sensory quality grades of the tea-flavored liquor. The key volatile compounds were identified under quality differentiation. A total of 110 tea-flavored liquor samples were taken after identification. A tasting panel was selected for the standardized protocols of the sensory assessment. Each sample was assigned to one of three predefined quality grades (Grade A, high quality; Grade B, medium quality; Grade C, low quality) after evaluation. The aroma compound profiles of the tea-flavored liquor were then determined using headspace solid phase micro-extraction-gas chromatography-mass spectrometry (HS–SPME–GC–MS). Furthermore, the 13 ML models were benchmarked. The performance of the model was assessed using accuracy, precision, recall, F1-score, and the area under the receiver operating characteristic curve (AUC). Shapley Additive exPlanations (SHAP) were employed to quantify the contribution rates of the aroma compounds to the predictions, in order to enhance the model interpretability. According to the sensory evaluation, 28 samples were classified as Grade A, 42 as Grade B, and 40 as Grade C. Among the 32 volatile aroma compounds, 24 exhibited significant differences (P < 0.05) over the three quality grades, including 10 terpenes, 10 esters, and 4 higher alcohols. The samples of the RANK A and RANK B grades also displayed broadly similar aroma profiles, whereas most compounds in the RANK C were presented at significantly lower concentrations. Among the 13 ML models, the Radial Support Vector Machine (Radial SVM) achieved the best performance in the prediction, with an AUC of 0.92 and all accuracy, precision, recall, and F1-score values exceeding 0.8. The SHAP analysis further revealed that the terpenes constituted the largest subgroup among the top 20 most influential compounds, followed by 7 esters and 3 higher alcohols. Key aroma compounds contributed to the prediction, including linalool (floral), anethole (spicy), methyl salicylate (mint-like), nerol (floral), ethyl undecanoate (fruity), and isoamyl alcohol (alcoholic). Linalool, anethole, methyl salicylate, and ethyl undecanoate greatly contributed to the sensory quality of the tea-flavored liquor. While the nerol similarly shared a positive correlation, where its contribution rate followed a complex, nonlinear trend: Its positive influence first increased, then diminished as the concentrations rose. There was a synergistic interaction between esters and other terpene compounds at the lower concentrations. Collectively, the sensory perception of nerol was amplified after interaction. By contrast, the isoamyl alcohol was accumulated to diminish the overall aroma quality of the tea-flavored liquor. In conclusion, an accurate and interpretable ML model can be expected to identify the volatile compounds most critical to quality differentiation, particularly for the sensory quality grading of tea-flavored liquor. These findings can provide a scientific basis for the targeted optimization of the production, quality control, and flavor enhancement in the tea-flavored liquor. Future work can be expected to focus on the interactions among key aroma compounds, in order to enrich the theoretical foundation of the flavor chemistry in alcoholic beverages.

     

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