Assessment of the impact of γ-irradiation on the piperine content and microbial quality of black pepper

Abstract

The major bioactive component of black pepper (Piper nigrum) is piperine which has demonstrated beneficial therapeutic properties. The purpose of this research was to investigate the effects of different irradiation doses on the content of piperine in black pepper. Samples were irradiated with 60Co γ-rays (at absorbed doses of 0.5, 1, 3, 5, 7, 10, and 12 kGy). Thin-layer chromatography (TLC) and UV-Vis spectrophotometry methods were used for measuring the piperine content in the samples. TLC was performed using three mobile phases (1. toluene:ethyl acetate, 7:3 v/v; 2. acetone:n-hexane, 6:4 v/v; 3. toluene:methanol, 8.5:1.5 v/v) and the retention factor (R f) value for piperine was equal to 0.66, 0.94, and 0.67, respectively. The content of piperine in γ-irradiated samples of black pepper was found to be between 0.04 and 1.05% w/w from the spectrophotometry analyses. Irradiation slightly decreased the piperine content of black pepper. It was found that piperine crude yield from black pepper was from 1.10 (the unirradiated sample) to 1.69, 1.07, 0.60, 0.90, 0.30, 1.20, 0.80% for irradiated samples, respectively. Microbiological analyses were performed with standard plate count method, which resulted in a decreasing number of the total cell count of microbial cells with increasing the radiation dose. Treatment with irradiation reduced the population of bacteria by 4 logs.