Effect of Drying Temperature on the Chemical, Sensory and Microbial Attributes of Black Tea from Kalanchoe pinnata, Cymbopogon citratus and Syzygium aromaticum

Abstract

Drying is the most imperative stage in tea processing, as many compounds are either lost, formed, or transformed. This study investigated the effect of different drying temperatures on black tea produced from Kalanchoe pinnata, Cymbopogon citratus and Syzygium aromaticum. The black tea was processed via washing, withering, rolling, and fermentation for 3 hours at room temperature. Then subjected to different drying temperatures. The samples were divided into two at varying drying temperature ratios (85:10:5 dried at 50℃, 60℃ and 70℃ while the second portion 75:20:5 was oven dried at 50℃, 60℃ and 70 ℃ respectively. Commercial Lipton black tea served as the control. The samples were evaluated for phytochemicals, vitamins, sensory and microbial properties. The phytochemical composition of the black tea samples reduced as drying progressed from 50 - 70℃ and ranged from (1.06 – 4.10 mg/100g) for alkaloids, saponins (0.11 – 0.22 mg/100g), terpenoids (7.30 – 14.95 mg/100g), phenols (3.63 – 3.66 mg GAE/g) and flavonoids (1.51 – 2.98 mg RE/g). Low temperature drying (50℃) significantly (p < 0.05) increased the vitamin A (14.92 mg/100g), B1 (11.60 mg/100g) and vitamin C (224.85 mg/100g) compositions of sample BLCA (85:10:5). In contrast, drying at 60 and 70℃ caused a progressive reduction in the vitamin compositions of the tea samples. The microbial analysis revealed that higher temperature drying (70℃) reduced the total viable and mould count from 20.46×101 to 9.83×101 cfu/g and 10.26 to 28.40×101 cfu/g, respectively. The sensory scores revealed that the black tea sample BLCA (85:10:5 dried at 50℃) was the most preferred when compared to the commercial brand (Lipton tea). This shows that low temperature drying of 50℃, conserves the chemical, nutritional and organoleptic properties of black herbal teas. This study depicts that black tea rich in antioxidant properties and vitamins could be produced from underutilized plant sources (Kalanchoe pinnata, Cymbopogon citratus and Syzygium aromaticum) other than Camellia sinensis.