Comprehensive evaluation of taste quality of nonastringent persimmon based on texture analyzer and electronic tongue

Abstract:【Objective】The taste quality of fruit is one of the important factors to measure the commerciality of non-astringent persimmon, which is mainly evaluated by texture and taste. However, there is little known about the integrated evaluation system of fruit taste quality of different non-astringent persimmon germplasms in the same area. The instrument of texture analyzer has been widely used in the research on texture characteristics of various fruits and vegetables. The quantitative analysis could be realized by accurately transforming the complex and abstract taste of fruit into specific indicators. The specific results could reflect the texture characteristics of fruit, such as hardness, cohesiveness, springiness, adhesiveness and chewiness. The electronic tongue is a new type of analytical instrument used for imitating human tastes. The information of the liquid to be tested is obtained through the taste sensor array, which reflects the taste data of the sample. It is also famous for its characteristics of strong reliability, high sensitivity, and good repeatability. At present, the electronic tongue is mainly used in the classifica-tion and evaluation of tea beverages, alcohol and other liquid tastes (such as wine, vinegar and chemicals). The objective of this study was to use texture analyzer and electronic tongue to determine the texture and taste characteristics of the fruits of different persimmon germplasms. Then, we compared the differences in taste quality of non-astringent persimmon, utilizing statistical methods such as descriptive statistics, correlation analysis and principal component to analyze 20 accessions of non-astringent persimmon samples. Combined the comprehensive evaluation of fruit taste quality with sensory evaluation, we used the method of partial least square regression to establish a quantitative evaluation method for the taste quality of non-astringent persimmon.【Methods】The non-astringent persimmon fruits were collected from the plant nursery (Lanxi city, Zhejiang province). Indicators of non-astringent persimmon fruits, such as hardness, adhesiveness, cohesiveness, springiness, chewiness, sourness, sweetness, bitterness, saltiness, umami, astringency, aftertaste-B (bitter aftertaste), aftertaste-A (astringency aftertaste), richness (umami aftertaste) were measured by texture analyzer and electronic tongue. SPSS and Excel software were used for data analysis. Prior to the factor component analysis, the original data were transformed with Z-score normalization method. The number of principal components was determined according to the eigenvalue ≥1, and the scores of different non-astringent persimmon germplasm on corresponding principal components were obtained according to the score coefficient matrix of each component. The relative contribution rate of principal component variance was taken as the weights, and the comprehensive scores of different germplasms were added to obtain the principal component scores and the corresponding weight values. 20 non-astringent persimmons were ranked depending on the comprehensive scores. The sensory evaluation of non-astringent persimmon was evaluated as well. The methods of partial least squares regression analysis (PLSR) were utilized for the sensory evaluation and prediction model of the fruit taste quality of non- astringent persimmon.【Results】The fruit taste quality indexes of different non-astringent persimmon germplasms were significantly different. Among them, the differences of adhesiveness, chewiness, saltiness, umami, sweetness and richness were significant, the differences of other indexes (such as springiness, aftertaste-A and bitterness) were not significant. Three principal components with characteristic roots greater than 1 were extracted by factor analysis, with a cumulative contribution rate of 79.53%. The first principal component explained 31.250% of the fruit taste quality trait information that had high correlation with sweetness, umami, saltiness and bitterness. The second principal component explained 31.128% of the fruit taste quality trait information that had a high correlation with hardness, springiness, cohesiveness, chewiness and adhesiveness, and the third principal component showed high correlation with astringency aftertaste and richness and could explain 17.149% of the fruit taste quality trait information. According to the comprehensive scores of statistics, the sort of fractions of the fruit taste quality of the 20 non- astringent persimmon germplasms was as follows: Gosho > Yalin-46 > Luo tian-1 > Hana-gosho > Kazusa > Fuyu > Hazegosho > Suruga > Z5 > Z7 > Z1 > Yamafuji > Luo tian-2 > Sifangtianshi > Touyouichi > Shogatsu > Z2 > Z4 > Kanshu > Z6. According to the sensory evaluation scores, the sort of fractions of the fruit taste quality of the 20 non-astringent persimmon germplasms was as follows: Yalin-46 > Fuyu > Kazusa > Hana-gosho > Luo tian > Gosho > Suruga > Z5 > Haze-gosho > Touyouichi > Z7 > Kanshu > Luo tian-2 > Sifangtianshi > Z1 > Yamafuji > Z2 > Shogatsu > Z4 > Z6. The sensory evaluation results of different non-astringent persimmon germplasms were basically consistent with the comprehensive statistical scores. We concluded that Yalin-46, Kazusa, Fuyu, Hana-gosho and Luo tian-1 performed well in the fruit taste quality, while the fruit taste quality of Z4, Shogatsu and Z6 was poor. PLSR was used to analyze the correlation among the texture, taste index and sensory evaluation score. The prediction mod-el of non-astringent persimmon taste quality was as follows: comprehensive taste = 14.515+0.201X1+ 0.295X2-0.207X4-0.221X5+0.221X6+0.226X9+0.129X11. The R2 of the regression model reached 80.4%, and the model verification results showed that the correlation coefficient between the actual score of comprehensive taste and the predicted value reached 0.938.【Conclusion】Large variations in the fruit taste quality were found among the 20 non-astringent persimmon germplasms. Different germplasms of non-astringent persimmon could be distinguished well according to the evaluation of the texture analyzer and electronic tongue. Accurate and objective taste evaluation results of the fruit taste quality could be easily obtained by combining with sensory evaluation, texture analyzer and electronic tongue analysis. The established taste quality prediction model could realize the quantitative evaluation of the nonastringent persimmon taste.