Abstract
Spent tea, the main by-product of instant tea manufacture contains 20-30% crude protein. Though the spent tea is a suitable source of protein for animals, only about 20% of its protein is bioavailable for them when it is given as a feed in untreated form. Conventional protein isolation procedures are expensive, lengthy and result in protein with reduced nutritive value. Applicability of the membrane filtration technique in preparing a protein-rich feed from the alkali extract of spent tea was investigated. A suitable membrane for filtration was identified and operating parameters were optimized. Dried alkali extract and the concentrates obtained by dia-filtration of the alkali extract were analyzed for nutritionally important constituents. Membrane with molecular weight cut-off of 100,000 Da and operating temperature of 30°C and inlet and outlet pressures of 4.6 and 3 bars respectively, were found to be the most suitable for preparing the feed. The dried alkali extract contained 17.5% protein, 12.2% polyphenols, 2.8% caffeine and 18.1% total ash. The dried feed prepared by membrane filtration of alkali extract followed by two consecutive dia-filtrations, contained higher level of protein (24.2%), low level of polyphenol (7%), caffeine (0.9%) and total ash (12.3%). Further, this feed contained all essential amino acids except threonine.
Highlights
Tea which is consumed as a beverage after brewing is processed from the young shoot of tea plant (Camellia sinensis (L.)O.Kuntze)
While caffeine is the most well known nitrogenous compound of tea, other nitrogenous compounds like proteins/peptides and amino acids are present in tea leaf
Ten liters of pre-filtered alkali extract was taken and passed through four sheets of each of following membranes with molecular weight cut off point (MWC) of 250,000, 100,000 40,000, 30,000, 20,000 and 10,000 Da maintaining the feed temperature at 40 °C and inlet and outlet pressures at 5.6 and 4.8 bars respectively, using a membrane filtration pilot plant (Model–L, GEA Filtration, USA)
Summary
Tea which is consumed as a beverage after brewing is processed from the young shoot of tea plant (Camellia sinensis (L.). Perera et al (2007) optimized conditions for preparing Leaf Protein Concentrate (LPC) from refuse tea. This procedure includes alkali extraction of protein, precipitation of protein with trichloroacetic acid and recovery by centrifugation. The purified LPC obtained from refuse tea contained 42.8% crude protein, 0.9% crude fiber, 8.1% polyphenol, 5.1% ash and 1.6% ether extract (Perera et al 2007). This LPC prepared from refuse tea seems to be a promising source of protein for humans and /or animals. The present study was conducted to screen membranes, to optimize the membrane filtration parameters such as operating temperature and pressure for the preparation of protein-rich feed from spent tea and to evaluate the nutritional value of feed prepared
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