Quality assessment of fresh tea leaves by estimating total polyphenols using near infrared spectroscopy.

This paper reports on the development of an integrated leaf quality inspecting system using near infrared reflectance (NIR) spectroscopy for quick and in situ estimation of total polyphenol (TP) content of fresh tea leaves, which is the most important quality indicator of tea. The integrated system consists of a heating system to dry the fresh tea leaves to the level of 3-4% moisture, a grinding and sieving system fitted with a 250 micron mesh sieve to make fine powder from the dried leaf. Samples thus prepared are transferred to the NIR beam and TP is measured instantaneously. The wavelength region, the number of partial least squares (PLS) component and the choice of preprocessing methods are optimized simultaneously by leave-one-sample out cross-validation during the model calibration. In order to measure polyphenol percentage in situ, the regression model is developed using PLS regression algorithm on NIR spectra of fifty-five samples. The efficacy of the model developed is evaluated by the root mean square error of cross-validation, root mean square error of prediction and correlation coefficient (R2) which are obtained as 0.1722, 0.5162 and 0.95, respectively.

Micronutrients (B, Co, Cu, Fe, Mn, Mo, and Zn) content in made tea (Camellia sinensis L.) and tea infusion with health prospect: A critical review.

Tea (Camellia sinensis L.) is a perennial acidophilic crop, and known to be a nonalcoholic stimulating beverage that is most widely consumed after water. The aim of this review paper is to provide a detailed documentation of selected micronutrient contents, viz. boron (B), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn) in made tea and tea infusion. Available data from the literature were used to calculate human health aspect associated with the consumption of tea infusion. A wide range of micronutrients reported in both made tea and tea infusion could be the major sources of micronutrients for human. The content of B, Co, Cu, Fe, Mn, Mo, and Zn in made tea are ranged from 3.04 to 58.44 µg g-1, below detectable limit (BDL) to 122.4 µg g-1, BDL to 602 µg g-1, 0.275 to 13,040 µg g-1, 0.004 to 15,866 µg g-1, 0.04 to 570.80 µg g-1 and 0.01 to 1120 µg g-1, respectively. Only 3.2 µg L-1 to 7.25 mg L-1, 0.01 µg L-1 to 7 mg L-1, 3.80 µg L-1 to 6.13 mg L-1, 135.59 µg L-1 -11.05 mg L-1, 0.05 µg L-1 to 1980.34 mg L-1, 0.012 to 3.78 µg L-1, and 1.12 µg L-1 to 2.32 µg L-1 of B, Co, Cu, Fe, Mn, Mo, and Zn, respectively, are found in tea infusion which are lower than the prescribed limit of micronutrients in drinking water by World Health Organization. Furthermore, micronutrient contents in tea infusion depend on infusion procedure as well as on the instrument used for analysis. The proportion of micronutrients found in different tea types are 1.0-88.9% for B, 10-60% for Co, 2.0-97.8% for Cu, 67.8-89.9% for Fe, 71.0-87.4% for Mn, 13.3-34% for Mo, and 34.9-83% for Zn. From the results, it can also be concluded that consumption of three cups of tea infusion per day does not have any adverse effect on human health with respect to the referred micronutrients rather got beneficial effects to human.

Chromium in soil and tea (Camellia sinensis L.) infusion: Does soil amendment with municipal solid waste compost make sense?

In this study, two clones (TV1 and TV23) of tea (Camellia sinensis L.) plants were allowed to grow in earthen pots in a greenhouse, treated with municipal solid waste compost (MSWC) to study the effect of MSWC to the fractionation of chromium (Cr) ion, plant biomass production, plant uptake of Cr, fate of Cr in soils through risk assessment code (RAC) and Cr in tea infusion. Increasing rate of MSWC applications increased both total Cr and DTPA-extractable Cr in soil. Fractionation studies have revealed that Cr in soils was mainly associated with the organic and Fe-Mn oxide and the contribution of residual fractions is nearly 87.7-96.1%. The biomass yields of the tea plants were increased with the increase in MSWC, indicating that nutrient uptake of the plants from MSWC was dependent on the root-MSWC interface. High accumulation of Cr in the root of tea plants and its subsequent lower movement towards aerial parts corroborated the hypothesis that the root of the tea plants acts as a buffer. In this experiment the transfer factor was <1, indicating that the tea plants did not have a significant phytoextraction potential. In the application of 10tha-1 MSWC, Cr was found to be in medium risk for both clones whereas the application of 8tha-1 MSWC showed medium risk with respect to the Cr for TV23 clone applying RAC. Therefore, MSWC amendment rate above 8tha-1 increased the total biomass of the tea plants but posed a threat on environmental prospect with respect to Cr. It was also found that only 2.5µgL-1 to 4.8µgL-1 Cr was present in tea infusion when infusion was prepared from tea leaves receiving different doses of MSWC. Furthermore, stepwise regression technique was applied to choose the most significant regression variables to express the variability in leaves, stem, main root and feeder root biomass. The one-way analysis of variance along with the Dunnett's multiple comparison method was used to determine the significant differences between the means of different treatments. On the application of hierarchical cluster analysis, treatments were grouped in two distinct homogeneous groups.