不同防冻措施茶园茶汤滋味差异的电子舌检测

为探讨轻度“倒春寒”对不同防护措施下3种茶园蒸青茶样的茶汤滋味影响,遂选品种和管理措施一致的安装防霜扇的茶园、松树林围绕的茶园以及未设防护措施的普通茶园,用电子舌综合评价3种茶园茶汤滋味、高效液相色谱检测茶汤游离氨基酸组分及含量。结果表明：基于电子舌检测数据的主成分分析、软独立建模分析和聚类分析结果揭示了普通茶园的茶汤滋味与防霜扇茶园和林间茶园的差异显著（P<0.05）;从9种茶样中皆检测出18种氨基酸,游离氨基酸质量分数介于19.691～30.947 mg/g 之间,茶氨酸含量占游离氨基酸含量的55.1%～70.5%;随着3种茶园气温的降低,游离氨基酸含量和茶氨酸含量呈升高趋势,3种鲜味氨基酸（天冬氨酸、谷氨酸、茶氨酸）、5种甜味氨基酸（脯氨酸、丙氨酸、甘氨酸、苏氨酸、丝氨酸）和5种苦味氨基酸（异亮氨酸、亮氨酸、苯丙氨酸、酪氨酸、缬氨酸）共占游离氨基酸含量在防霜扇茶园和林间茶园中分别出现升高、降低和降低趋势,而在普通茶园中变化与之不同。分析认为：轻度“倒春寒”可导致无防护措施的普通茶园茶叶滋味劣变,林间茶园能够减轻冻害,防霜扇作为防护手段不仅可以减免冻害,还可避免茶叶滋味品质下降。该研究结果为后续深入研究不同防护措施茶园茶叶品质提供参考。

Difference of taste among streaming tea soup from tea plantations under different measures against frost based on electronic tongue

Abstract: The late spring coldness is one of the natural disasters frequently occurring in recent years, which severely affects the yield and quality of tea, famous tea in particular. Because of the late spring coldness, the yield of spring tea decreases by 10%-20% every year, especially early-sprouting varieties. The tea plantation with protection measures can avoid frost and protect tea shoots from the injury of late spring cold, such as frost protection with the wind machine system, and shelterbelt planting. The electronic tongue, a kind of rapid analytical tool, has been widely used to assess the quality of food. The purpose of this research is to evaluate the difference in the steaming tea taste from 3 types of tea gardens with different measures against the frost. In this experiment, the steaming tea samples from 3 different tea gardens, i.e. tea garden installed with frost protection with the wind machine system (TGFPWMS), tea garden among shelterbelt planting (TGSP), and common tea garden without protection measures (TGWPM), were used as experimental targets. The fresh tea shoots were plucked from 3 different tea gardens in Yinchunbiya tea plantation, Danyang, Jiangsu, China in April 2015. Because the late spring coldness was coming, the plucking time was at 3 pm and 11 pm on April 2, 4 am on April 3, 2015. The plucked tea shoots were processed into the steaming tea by steamed tea processing technology, whose tea soup taste was detected by electronic tongue. The electronic tongue utilized was Astree from Alpha-MOS with 7 sensors (SRS, GPS, STS, UMS, SPS, SWS and BRS). The components and contents of the amino acids in tea soup were measured by high performance liquid chromatography (HPLC). The results showed that part of the sensors of electronic tongue could effectively analyze the variation of steaming tea taste, such as the sensor BRS, SWS, UMS and SPS. The statistic analysis results showed that both the principal component analysis (PCA) and the soft independent modeling of class analogy (SIMCA) analysis could effectively discriminate the steaming tea taste among 3 different tea gardens. The clustering analysis successfully clustered the steaming tea taste into 2 groups. The steaming tea taste from TGFPWMS and TGSP showed much closer relationship, and the steaming tea taste from TGWPM could be divided into the class separately. By means of HPLC, 18 kinds of free amino acids were detected from steaming tea samples from TGFPWMS, TGSP and TGWPM. The content of 18 kinds of free amino acids ranged from 19.691 to 30.947 mg/g. The percentage of the content of theanine occupying the content of free amino acids ranged from 55.1% to 70.5%. Accompanied with air temperature dropping, the contents of free amino acids and theanine appeared to rise. With the decreasing of the temperature, the contents of 3 kinds of delicious amino acids (asparagic acid, glutamic acid and theanine), 5 kinds of sweet amino acids (proline, alanine, glycocoll, threonine and serine) and 5 kinds of bitter amino acids (isoleucine, leucine, phenylalanine, tyrosine and valine) of steaming tea samples from TGFPWMS and TGSP respectively rose, declined and declined, while those of steaming tea samples from TGWPM varied irregularly. It was considered that the mild "late spring coldness" resulted that the steaming tea taste from TGWPM deteriorated, TGSP alleviated the cold damage, and the frost protection with the wind machine system could not only reduce the frost damage, but also avoid the decline in quality of tea taste. The research results can provide scientific basis and technical support for further researching tea quality under various protective measures.