| Summary: | 碩士 === 中臺科技大學 === 食品科技研究所 === 98 === Total 16 kinds of bottled tea drinks including green tea, oolong tea and black tea drinks with different brands were collected from Taiwan markets. Their physicochemical analyses, sensory evaluation including quantitative descriptive analysis and consumer test, and electronic tongue examination were carried out. The purposes of this study were to investigate the difference in physicochemical and sensory qualities of these bottled tea drinks, the degree of liking of these bottled tea drinks by university students using questionnaire survey and consumer test and the feasibility of using electronic tongue as a tool to evaluate the sensory quality of these bottled tea drinks by using all the data with multi-variance analysis.
From the physicochemical analysis results, the total catechins (TC), total polyphenols (TPP) and individual catechins (GC, EGC, C, EC, EGCG, GCG and ECG) in green tea drink G1 and oolong tea drink O1 which are labeled high contents of polyphenols were higher than those in other tea drinks. The results prove that the claim of this labeled high polyphenol contents by the brand is correct. In terms of TC, TPP, TAA (total amino acids), individual catechins and caffeine contents, the non-sugar green tea drinks were the highest while the black tea drinks were the lowest with low pH and dark color. By comparison, the contents of TPP and individual catechins of sugar-added tea drinks were lower than those of non-sugar tea drinks.
From sensory evaluation results, the bitter, astringent and sour tastes of the two high-content-polyphenols labeled tea drinks, G1 and O1 were significantly higher than those of other brand tea drinks. The sensory quality of non-sugar green tea drink G2 was significantly different from that of others. Its sensory scores for most attributes were all quite low. Other brand green tea drinks did not differ much in their sensory quality. Among oolong tea drink samples, the color of O3 was most reddish while the sweet aroma and aftertastes of sweet, salivated and aroma of oolong tea drink O4 were the most strong.
From the questionnaire survey data, tea drinks were the one university students most often to buy among all kinds of drinks because of the convenience for buying. And green tea drink was the most often to buy. The consumer tests using university students indicated that the appearance, bitterness and astringency of non-sugar green tea drink G2 and oolong tea drink O2 were most liked by the consumer-type university students. However, the sugar-added green tea drink G6 had the highest score on overall liking. The degree of liking on appearance, bitterness and astringency of high-polyphenols labeled tea drinks G1 and O1 was only higher slightly than that of sugar-added black tea drink sample. The possible reason may be due to the high content of polyphenols which resulted in high astringent and bitter.
From the results of principal component analysis for the electronic tongue data, non-sugar green tea drinks and oolong tea drinks could be well separated each other. The non-sugar green tea drinks with different brands were also well separated, while the non-sugar oolong tea drinks with different brands could be separated successfully. The sugar-added oolong tea drink was also not able to be separated from the sugar-added black tea drinks. In general, electronic tongue could well separate all samples including non-sugar, sugar-added and different brand tea drinks mostly.
The PLS2 results of electronic tongue and sensory descriptive analysis data indicated the sensors, CA, ZZ and BB were negatively correlated with the sourness, astringent aftertaste and astringency. It means that these two sensors could respond to the sourness, astringent aftertaste and astringency of tea drinks. On the other hand, from the results of the consumer test by university students, the hedonic scores of appearance, bitterness, astringency and overall liking were correlated to the sensor GA. Due to the ability of explanting the variation among the tea drink samples only reached 35%, therefore, it is a need to further study on the improvement of applying electronic tongue to examine the degree of liking by consumers on tea drinks.
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