Effect of Drying on the Nutritional and Microbial Quality of Tea (Camellia sinensis) using a Passive Solar Dryer

Abstract

Drying of food materials under direct sunlight predispose the food item to nutritional losses and microbial contamination. Drying of tea in a cabinet dryer is thus necessary to reduce nutrient losses in tea. This research studies the effect of using solar cabinet dryer on quality of dried tea. Tea from tea plant Camellia sinensis obtained from Cocoa Research Institute of Nigeria was dried using a passive solar dryer. Weight of tea was taken before loading into the dryer. Temperature and relative humidity were measured. Microbiological analysis was carried out on the representative samples of the dried tea leaves. Mean comparison of evaluation parameter for the variations in the temperature and relative humidity of the dryer and ambient were investigated using Analysis of Variance (ANOVA) and Least Significant Difference (LSD). Differences were considered significant at p ≤ 0.05. The pH, crude protein percentage and total dissolved solids (TDS) of tea leaves from the cabinet dryer were within the safe range and comparable with that dried in direct sunshine. The microbiological analysis of tea samples taken from Tray 1 (Partition A) showed only Trichoderma spp. (100%), while Penicillium chrysogenum (66.67%) and Aspergillus niger (60%) dominated samples obtained from the second and third partitions of the tray respectively. The phytochemical compounds present in the Camellia sinensis extract dried at ambient temperature was more than the chemical contents associated with extract dried in the dryer. The phytochemical compounds represented in tea extract dried at room temperature was at peak, 4336.00 (35%) and 4009.00 (35%) were absent at the Fourier transform infrared (FTIR) analysis of tea extract dried with a dryer. These peaks have the highest percentage in tea. However, tea can be dried using the solar cabinet dryer as it makes it safe and suitable for human consumption rather than tea dried under the sun which can allow contamination by microorganisms and weather conditions.