Application Of Near Infrared Spectroscopic Techniques In Analysis Of Components In Green Tea Infusion And Establishment Of The Method For Instant Tea Brewing

Based on the large amounts of analyzing of major components in samples of green tea infusion, combining chemical analysis results with near infrared spectra of tea infusion samples scanned by near infrared spectroscopy. By comparing different spectral pretreatment methods, this paper established and optimized quantitative analysis models of water extract, tea polyphenols, free amino acids, soluble sugars, caffeine, total catechins, EGCG, EC, EGC, EGC and GA by using partial least squares(PLS) method. Each of the11predictive models was applied for the external inspection. Spectrum pretreatment method has standard normal variate (SNV), min/max, multiplicative signal correction (MSC), first derivative(FD), FD+MSL, minus a straight line. Results showed that almost all the decision coefficients of cross test and predictive models were exceed95%, except for EGC and GA. RPDs of models were exceed3, except for GA with a RPD of2.67. The established models present high stability and predictive accuracy. This paper provided a new method for the analysis of major quality components in tea infusion and tea beverages by near infrared spectroscopy.Instant brewing methods for four kinds of tea products were established. Results showed that water extracts of CTC black tea and Pu’er tea were most easily extracted, the relative water leaching rate of which can reached to more than92%within only2minutes, comparing with the method for standard tea brewing. Yet water extracts were difficult to be extracted from roasted green tea, white tea, yellow tea and oolong tea, unless the methods for special tea brewing were taken. Take roasted green tea as the research object, water leaching rate achieved over70%than that of which by using the method for standard tea brewing under the condition of secondary extract after in vacuo within45seconds. Over76%water leaching rate was obtained under the condition of hot water incubation in vacuo within2minutes. More than85%water leaching rate was obtained under the condition of boiling water bath within only1minute. Results indicated that the tea products easier to infuse should be manufactured by strengthening rolling processing with spring shoots.The typical samples of green tea, black tea, oolong tea and dark tea were brewed by Lepod machine. Water soluble components of loose Pu’er tea, Keemun black tea and Da Hong Pao were more easily to be extracted, concentrates of which can achieve more than80%of water leaching rate than that of which by using standard brewing method within only45seconds by a tea/water ratio of1:45(W/V). Ratios of tea/water were needed to increase to1:42or1:41to meet brewing requirement for Bi Luo Chun tea, roasted green tea, Nanjing yuhua tea, Lu’an Gua Pian tea and Tie Guan Yin tea. A much higher tea/water ratio of1:37was needed to satisfy people demands for Yong Xi Huo Qing tea, Longjing tea and Huangshan Mao Feng tea. As disadvantages, brewing with lepod machine will lead to tea waste, since there were still large amounts of water soluble components existing in the tea residue in Lepod cups which were abandoned after only one brewing. Results provided evidences for brewing with Lepod machine rapidly by choosing suitable tea products.