UPASI TEA RESEARCH FOUNDATION

Nirar Dam BPO, Valparai-642 127 | Coimbatore (Dis), Tamil Nadu, INDIA.
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Tea Technology

Besides offering the analytical services and involving in inter laboratory ring test to validate the test methods, Tea Technology Division is concerned about quality of final produce in accordance with PFA Act requirements, storage studies, value added products and manufacturing aspects. The laboratory has been accredited by NABL under ISO/IEC 17025. It has been established that shelf life of black tea in terms of biochemical stability was seven months there after quality parameters declined. The division conducted a long term experiment on packing materials like aluminium foil pouches, jute bags and low density polyethylene bags on the shelf life of teas and found that aluminium foil and low density polyethylene bags retained the quality attributes of made tea for considerable period. Jute bags tend to absorb moisture rapidly and hence storage of black tea in jute bags deteriorated faster than that of low density polyethylene bags. Aluminium foil pouches resisted moisture absorption even at the ambient conditions. Additionally, the teas (Broken Orange Pekoe (BOP) & Pekoe Dust (PD)) were stored at warehouses at Cochin and at Coimbatore. The tea stored at Cochin absorbed more moisture than those stored at Coimbatore.

Under the long term project, “Chemistry of tea clones” modest results have been documented by the division in terms of biochemical constituents of crop shoots and commercially prepared black tea. These out come forms the basis for categorization of black tea quality as good, moderate and poor. Recently the division developed a protocol to determine the theanine content in crop shoots and its relative distribution in the shoot component. Among the clones, UPASI-3 recorded higher quantum of theanine, which accounts 45% of the total amino acids.

Tea Technology division is also engaged in applied aspects of tea culture considering the importance of quality of the made tea. The scientist evaluated the impact of foliar application of nutrients such as SOP, potassium nitrate and calcium nitrate on quality of made tea. It has been found that foliar application of recommended concentration of SOP (2%) significantly increased the total polyphenols, catechins, theaflavins, thearubigins, briskness and colour indices. Results of organoleptic evaluation confirmed the same. Foliar application of potassium nitrate significantly enhanced the biochemical precursors for quality while calcium nitrate application showed only marginal improvement or on par with standard treatment.

Time to time confirmatory studies on manufacture was conducted by the division. Biochemical analysis during fermentation using UPAS-3 harvested leaves showed a progressive decline in the levels of polyphenols and an increase in theaflavin content till the optimum fermentation time of 45 minutes. Analytical results of black tea and fractions of theaflavin coincide with the optimum fermentation time of 45 minutes. This is in agreement with the earlier finding on this aspect and clones exhibit variations in optimum fermentation time. Time for Optimum fermentation got reduced with the increase in temperature but the quality of the end product deteriorated.

Importance of quality of raw material on electrical power consumption was studied with particular reference to quality of CTC black tea. Crop shoots of the clone UPASI-9 were segregated into three portions comprising 100% fine leaves, 75% fine & 25% coarse leaves and 50% each of fine and coarse leaves. Two leaves and a bud, three leaves and a bud soft banji’s and single leaves were considered as fine leaf. Crop shoots with greater than third leaves, cut and mature leaves were considered as coarse leaves. Electrical power consumption was highest for the treatment involving 50% each of fine and coarse leaves and it decreased by 14% for 75% fine leaves followed by 24% for 100% fine leaves. Presence of higher proportion of coarse leaves in the harvest not only deteriorated the quality which also consumed more energy ultimately increased the cost of production.

Experiments carried out to standardize the optimum withering duration (16 hr), optimum withering temperature (25-35ºC), dhool temperature (25-30ºC), air flow as co-air current during fermentation, thickness of dhool (2.5 cm) and withering trough loading (3 kg/sq.ft.) and the same is being adopted by the tea factories for quality improvement. Impact of pre-withering machine on the physical/chemical withering in relation to quality attributes of black teas was attempted. A minimum of 2 hours and 10 minutes withering duration can be reduced when the pre-withering machine was used where the levels of theaflavin content enhanced. Similar trend in flavour index also observed when the machine was used for withering.

Optimization of temperature in withering and fermentation process was carried out using the miniature CTC facility. When harvested tea leaves withered at 25°C, TF formation was very high and there was a decline in TF content beyond 30°C. The study demonstrated that the optimum temperature for fermentation was between 25 and 30°C. Increasing temperature reduced the optimum fermentation time considerably at the cost quality deterioration. Impact of oxygen addition during fermentation on CTC black tea quality was evaluated. The made tea produced from the oxygen treated samples showed an overall improvement in the quality parameters which was substantiated by professional tasters.

Studies on “pacha” taint in CTC teas, a methodology to assay the lipase activity was standardized. A progressive decline in lipase activity was observed as the maturity of shoots increased. Miniature manufacturing unit trials on lipid degrading enzymes (lipase. lipoxygenase, alcohol dehydrogenase) and anti oxidants (butylated hydroxyl anisole & ascorbic acid) have shown encouraging results in terms of reducing “pacha”. Addition of combination of lipase and lipoxygenase reduced the quantity of lipids and improved the quality. Large scale trials conducted at commercial tea factories also confirmed the finding. Impact of different methods of withering (warm, freeze, ultraviolet and normal withering) on the total lipids and linolenic acid levels had been studied where UV radiation and warm withering resulted in higher levels of lipid degradation.

Comparative study on drum, drum cum floor and floor fermentation was done and the drum cum floor fermentation was found to be the best in terms of theaflavins and total liquor colour. Studies related to the day and night manufacture revealed that the teas produced in the night time resulted in maximum quality probably due to better control of temperature.

An alternative withering system for withering of tea leaves had been attempted. Freeze wither was done by keeping the leaves in a deep freezer at -20ºC and thawing was carried out by passing hot air (35ºC ) for 30 minutes. The effect of normal withering for sixteen hours had been brought about in two hours of freeze withering.

In order to contain the temperature build up during CTC rolling, an over head air cooling system for CTC has been designed, developed and successfully implemented in the factories. The department has developed a cooling system for rotor vane to bring down the dhool temperature below the critical temperature of 35°C. The system is successfully implemented by some of the factories to reduce the high pressure and building up temperature in the rotor vane.

Exogenous addition of pectinase has been standardised for the improvement of black tea quality and issued a recommendation for adoption. Dosage, mode and stage of addition of the enzyme had been standardized. There was a marked improvement in quality parameters like theaflavins and total liquor colour. This has also helped in maintaining the consistency of the black tea quality irrespective of the variations in the raw material and is being successfully employed by many tea factories. Methodology for the estimation of pectinase activity in tea had been developed which in turn helpful in determining the active ingredient of commercial formulations.

A methodology had been standardized for the incorporation of novel flavours into processed black tea with the help of binders which favoured in retaining the flavour for more than 90 days. Technology was developed for the preparation of polyphenol enriched black teas. Polyphenol enriched black tea had higher theaflavins content, total liquor colour and DPPH radical scavenging activity over the control. Apart from the value addition, antioxidant activities and reducing power of different types of tea was documented where white tea has higher DPPH radical scavenging activity followed by green and black teas.

Volatile flavour of Nilgiris teas were identified using the NIST mass spectral library. Among them, linalool was found to be the predominant flavour compound followed by geraniol, trans-2-hexenal, linalool oxides and methyl salicylate. Evaluation of flavors profile of Nilgiris teas had been carried out with orthodox tea sample (BOP grade) procured from different agro climatic zones of the Nilgiris. Highest flavour index (FI) was recorded in the month of January followed by October where the cool, dry weather could have the contributing factor for the improvement in flavour.

Refinement of existing analytical techniques is also taken as a priority area of research. A chilled tea beverage with natural tea flavour has been attempted with encouraging results. Further work on stabilization of the product with preservatives and stabilizers is in progress. Extraction of polyphenols from black tea and tea waste is also being standardized. Methods have been developed for the assessment of ascorbic acid in crop shoots of tea, reducing power and antioxidant activity of black teas.