Impact of microwave vacuum drying on quality of Liang (Gnetum gnemon var. tenerum) leaves powder

Abstract

Abstract Microwave vacuum drying is gaining popularity to maintain more active compounds compared with conventional drying. Liang (Gnetum gnemon var. tenerum) is a native plant with high consumer preference in Thailand. However, scientific information on the tenerum variety is not well documented. This study analyzed the effect of microwave vacuum drying on the quality of Liang leaves powder. Results showed that microwave vacuum drying at 50–60°C 3600 W for 12 min (G1) preserved better green color and maintained moisture content (%) and water activity (aw). G1 gave less moisture content and aw as 5.83 ± 0.07 and 0.42 ± 0.00, respectively compared to G2 which used lower temperature and longer drying time at 40–50°C, 2400 W for 15 min. Salmonella spp. and Staphylococcus aureus were not detected in either sample but pathogenic bacteria such as Clostridium perfringens, Escherichia coli, Bacillus cereus, and Coliforms were reported. The nutritional value of 100 g of powdered Liang leaves provided energy of 348–360 Kcal. G1 contained 25.5 g of protein with high and complete essential amino acids plus branched-chain amino acids and more carotenoids as β-carotenes (3,920 µg/100 g), with total dietary soluble and insoluble fiber 40.7 g/100 g. Consumers generally preferred the commercial green tea matcha drink rather than the Liang leaves drink, which had a strong unfamiliar smell and odor. Nevertheless, Liang leaves exhibited high potential as an ingredient to promote health benefits.