Abstract: This work aimed to explore the effect of gamma irradiation on the fermentation characteristics and the prebiotic functions of konjac glucomannan (KGM). KGM was irradiated with 60Co gamma at doses of 0, 10, 20 and 30 kGy. The influences of different radiation doses on the changes in pH, short-chain fatty acid (SCFA) content, the numbers of harmful and beneficial bacteria, the ratio between the numbers of bifidobacteria and Escherichia coli (B/E ratio) and prebiotic index (PI) were compared during in vitro anaerobic fermentation of feces from healthy volunteers. Results showed that the pH of the fermentation broth decreased whereas B/E ratio and PI increased significantly in the irradiation groups when compared with the positive control glucose. Meanwhile, gamma irradiation could also contribute to the production of SCFA, as well as the improvement of the microbial composition of the fermentation broth. The contents of SCFA and PI value increased with increasing radiation dose ranging from 0 to 30 kGy. PI values of KGM irradiated at 0, 10, 20 and 30 kGy were 0.48, 0.61, 0.76 and 0.78, respectively. Thus, KGM exerts a good prebiotic effect in the gut and its prebiotic functions can be enhanced by gamma irradiation. Taking PI into account, 20 kGy was recommended as a suitable irradiation dose for KGM.

Key words: konjac glucomannan, gamma irradiation, prebiotic, prebiotic index, short chain fatty acid