The effect of gamma irradiation on microbial load of purple basil (Ocimum bacilicum L.) leaves dried in different methods

The effect of different drying methods on microbial load of the purple basil leaves was studied with sunlight drying, convective drying at 50 degrees C, a microwave drying at 460 W and freeze-drying. Microbial contamination control was evaluated using a gamma irradiation method at 10 kGy. Microbial analysis of total aerobic mesophilic bacteria and, yeast and molds count were performed. The results showed that the dried materials were contaminated with aerobic mesophilic bacteria which varied from 5.25 to 6.31 log cfu/g, and yeasts and molds 4.92-5.35 log cfu/g. The lower numbers of total mesophilic bacteria and yeasts and molds were counted in purple basil leaves dried by microwave and convective methods. According to the International standards, the dried purple basil leaves of the total aerobic mesophilic bacteria and yeasts and molds counts were unsatisfactory. No microorganisms were detected after gamma-irradiation dose of 10 kGy. Practical applications Basil (Ocimum basilicum L.) is an aromatic and medicinal plant for cooking and seasoning, and it is commercialized in both fresh and dried forms. The leaves can be used as a spice in fresh or dried form for adding distinctive aroma and flavor in food or for medicinal purposes such as inflammations, colds, headaches, and cosmetics. Several drying methods have been applied for the basil leaves. However, to reduce microbial load, it is important to implement the gamma-irradiation process. This study was done to investigate the microbial load and the effect of different methods of drying treatment (sunlight, convective, microwave, freeze-drying, and gamma irradiation) on microbial load of dried purple basil leaves.