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Withering timings affect the total free amino acids and mineral contents of tea leaves during black tea manufacturing
Authors:Saiqa Jabeen  Sahib Alam  Maria Saleem  Waqar Ahmad  Rukhsana Bibi  Farrukh S. Hamid  Hamid U. Shah
Affiliation:1. Department of Agricultural Chemistry, The University of Agriculture, Peshawar 25130, Pakistan;2. Food and Agricultural Organization of the United Nation, NARC premises, Park Road, Islamabad, Pakistan;3. Department of Chemistry, Hazara University Mansehra, Pakistan;4. National Tea Research Institute Shinkiari, Mansehra, Pakistan
Abstract:
The aim of the present study was to investigate the effect of withering timings (i.e. 0, 21, 22, 23 and 24 h) on the moisture, total free amino acids, ash, essential and toxic mineral element contents of tea (Camellia sinensis L.) leaves during black tea manufacturing. Moisture, ash, Na, P, Mg, Cu, Zn, Mn, Al, Ni and Pb contents were significantly (P < 0.05) affected by withering, whereas non-significant (P > 0.05) results were noted for total free amino acids, K, Fe and Cd contents. The highest moisture content (76.4%) was examined in fresh leaves that progressively decreased to 63.8% in 24 h withering. Total free amino acid contents gradually increased up to 23 h and then decreased. Ash, P, Cu, Zn and Mn contents showed an increasing trend with withering time. Conversely, significantly lowered amounts of Na (162.5 mg/kg) and Mg (803 mg/kg) were recorded in tea leaves after 24 h withering. Among the toxic elements, Al, Ni and Pb contents were progressively increased over withering time. It was concluded that tea is a potential source of essential chemical constituents and during processing proper care should be taken to produce high quality black tea.
Keywords:Corresponding author. Tel.: +92 919216903   fax: +92 91 9216520.  Black tea  Withering  Amino acids  Mineral contents  Ash  Fermentation
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