Application of Membrane Filtration Technique in Preparation of Protein-Rich Feed from Spent Tea

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.