The Analysis of Optimal Factors for Reducing Microbial Quantity in Dried Ganoderma lucidum using Factorial Design Experiment

Abstract

The objective of this research was to investigate the optimal temperature and duration for microbial reduction in dried Ganoderma lucidum using a solar oven combined with electric heating coils. A 5x5 factorial experiment with three replications and a completely randomized design was performed. The factors studied included five temperature levels (40, 50, 60, 70, and 80ºC) and five drying time levels (4, 5, 6, 7, and 8 hours). The mean, standard deviation, factorial analysis of variance (ANOVA) with two components and the Kruskal-Wallis test were used to statistically examine the results. The total microbial count of bacteria, fungi, and yeast (CFU/g), moisture content (g/100 g), water activity (a_w) and dry weight were found to decrease in all samples with increasing temperature and duration of drying time. With exception of a_w, which did not exhibit any interaction, temperature and duration of drying time were found to have a significant effect on the total amount of microbial, moisture content, a_w and dry weight. This was determined by variance analysis at a significance level of 0.05. It was concluded that the optimal temperature for drying G. lucidum was 70ºC for 8 hours, as it resulted in the total microbial count, moisture content, a_w and dry weight of 2.70 x 10³ ± 0.15 CFU/g, 1.20 x 10² ± 0.05 CFU/g, 7.30 ± 0.04 g/100 g, 0.78 ± 0.01, and 32.18 ± 0.03 g, respectively, These values conform with the microbiological quality standards for food and food contact surfaces and the community product standards (TIS 136/2015). These results suggest that this temperature is safe for consumers.