Effects of novel vacuum drying on orthodox and CTC tea processing

Abstract

Experiments were conducted on vacuum drying of tea leaves (orthodox, CTC) by following factorial design with three independent parameters: vacuum level, plate temperature and loading value, having three levels for their coded values (-1, 0, 1). The effects of these independent parameters were studied on the response, namely ?a (redness index of tea liquor), ?b (yellowness index of tea liquor) and aroma index (AI). Optimized values of independent parameters for orthodox tea were: vacuum level (670 mm Hg), plate temperature (75 C), loading value (0.15 kg dry solid m-2) and the corresponding values for CTC tea were: vacuum level (724 mm Hg), plate temperature (75 C) and loading value (0.18 kg dry solid m-2). Heat utilization efficiency for vacuum dryer was 2.14% for orthodox tea and the same figure for CTC tea was 1.23%.