摘要:
为研究游离氨基酸组分对白茶滋味品质的影响及通过氨基酸组分实现白茶品类的判别,采用全自动氨基酸分析仪对白茶主产区46个白茶试样进行分析,结果表明:①白茶游离氨基酸总量为16.19~51.00 mgg-1,平均含量为39.36 mgg-1,不同品类白茶氨基酸总量由高至低依次为贡眉(45.788.39)mgg-1、白毫银针(38.156.12)mgg-1和白牡丹(34.019.16)mgg-1。②白茶的茶氨酸含量占游离氨基酸总量的52.90%,是构成白茶鲜爽味的主要组分;脯氨酸、甘氨酸、天冬氨酸和苏氨酸是白毫银针甜味的贡献物质之一;亮氨酸、组氨酸和蛋氨酸对其苦味具有一定的影响;脯氨酸、缬氨酸、天冬氨酸和丙氨酸是贡眉甜味的贡献物质之一;苯丙氨酸、异亮氨酸、亮氨酸和缬氨酸对其苦味具有一定的贡献;谷氨酸可能是白毫银针与贡眉鲜酸味物质的主要贡献氨基酸。③在基于游离氨基酸组分白茶不同品类分析中,对品类判别的回判正确率均达到100%,采用该模型对27个市售样品分别进行预测,3种白茶的品类判别正确率分别为100%、88.89%、88.89%。白茶中的氨基酸构成依据品类的不同存在各自的典型特征;依据茶汤中4种游离氨基酸的含量,并结合PCA和LDA分析法能够实现对白茶品类的高准确率判别。
Abstract:
Flavor of the brewed white tea in relation to its constituents of free amino acids (FAA) was studied. The descriptive statistics, ANOVA, principal component analysis(PCA), and linear category identification were applied for the analysis. The FAA contents on 46 samples collected from 3 white tea-producing areas in the province were determined by using an automated analyzer. The results showed that(1)the total FAA in the tea ranged from 16.19 mgg-1 to 51.00 mgg-1, with an average of 39.36 mgg-1; (2) the highest FAA content of(45.788.39)mgg-1 was found in Kung Mee tea, followed by that of Silver Needle Pekoe tea at(38.156.12)mgg-1, while the lowest was White Peony tea at(34.019.16)mgg-1; (3) theanine in the tea accounted for 52.90% of the total FAA contributing to the cool and delightful taste of the tea; (4) proline, glycine, aspartic, and threonine were the main source of the sweetness of Silver Needle Pekoe tea; (5) leucine, histidine, and methionine brought about the hint of bitterness in Silver Needle Pekoe tea; (6) proline, valine, aspartic, and alanine gave the sweet note in Kung Mee tea; (7) phenylalanine, isoleucine, leucine, and valine tended to be slightly bitter on the taste; and, (8) glutamic acid might render the umami and sour tastes in Silver Needle Pekoe and Kung Mee teas; (9)the correct rate in classifying the white teas based on FAA constituents was found to be 100%. Subsequently,using the same model, 27 commercial samples of Kung Mee, Silver Needle Pekoe, and White Peony teas were evaluated to show the rates of correct identification to be 100%, 88.89%, and 88.89%, respectively. It was, thus, concluded that FAA composition of the 4 categories of amino acids in tea, combined with PCA and LDA analytical methods, could be used to accurately distinguish the white teas.
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