Preliminary Study On The Fermentation Of Red Fermented Rice By Monascus Using Glutinous Rice As Substrates

Red fermented rice(RPR)is prepared by inoculation of Monascus on steamed rice to produce pigments.It has been used for more than a thousand years in China.The fermentation substrate of RFR is mostly long-shaped rice.Studies have shown that the fermentation substrate may have an important influence on the growth and metabolism of Monascus.There are significant differences in nutrient composition and processing characteristics between long-shaped rice and glutinous rice.Therefore,the fermentation of red fermented rice using glutinous rice as substrates(GRFR)is a direction that deserves more research.However,to date,there have been few reports on GRFR at home and abroad.Therefore,this study intended to conduct a preliminary study on the preparation of GRFR by Monascus.The main results are as follows:(1)The optimal condition for activating the commercially available RFR samples by single factor and orthogonal experiment was as follows:peptone 0.1 g/L,pH 3,and temperature 30℃.(2)GRFR samples were prepared using nine activated RFR samples respectively,from which the best one was selected based on the ration of pigment and citrinin.A Monascus strain M1 was isolated and purified from the sample by the dilution-plate method,Then strain MI was identified as Monascus purpureus according its characteristics of morphology and 18 S rDNA sequence.(3)The single-factor and response surface method were used to optimize the culture condition of the preparation of GRFR by strain M1.The results showed that the optimized condition was as follows:initial pH 3.5,temperature 30℃,inoculum amount 13%.With optimized parameters,the content of pigment was increased by 0.84 times and citrinin content was reduced by 0.24 times.Compared with commercial available RPR sample 3#,the content of pigment and citrinin of the GRFR sample prepared under the condition were increased by 2.34 times and reduced by 0.19 times,respectively.(4)The stability of GRFR was studied and compared with RPR stability.The pigment of GRFR was more shelf-stable in dark conditions than that of RFR.GRFR was more suitable to be used in acidic food than RFR.However,the pigment of GRFR was more stable to common metal ions than that of RFR.