| Red mold rice(RMR),a well-known natural food and medicine supplement,which is widely used in the food industry,especially the application of functional RMR containing GABA in functional food has become a hot spot.In today’s health-oriented society,people no longer meet basic nutritional needs,but pay more attention to health-friendly functional foods.The development of high quality red rice products has promoted the development of functional health food in China.Red rice can not only replace chemical additives,but also have functional substances to promote health.γ-aminobutyric acid(GABA)has the biological activities of lowering blood pressure,stabilization,and nerve transfer,which has attracted much attention in the research and development of functional foods.Therefore,aiming at the actual production problems of low GABA content,high production process intensity and low production efficiency in Monascus rice,this study carried out the mutation breeding of high-yield GABA strains,the preparation of high-quality koji seeds,and the development of high-quality Monascus rice powder products,as follows:1.Breeding of Monascus with high GABA production.In view of the problems of low and unstable GABA production by Monascus,a mutant Monascus strain M162 was obtained by physical mutagenesis of Monascus with atmospheric and room temperature pressure plasma(ARTP)in this study.The stability of subculture,molecular biology identification and preliminary molecular mechanism of high GABA production were investigated.The results showed that under the conditions of 100W mutation power,10SLM gas volume and 2 mm distance,the relationship between the mutation time and the survival rate of Monascus spores was discussed,and 120 s was determined as the best treatment time.Using Monascus M-1 as the starting strain,a mutant strain named M162 was obtained by ARTP.The mutant strain could produce15.10 mg/g GABA by rice fermentation,which was 155.93%higher than that of the parent strain.The average GABA production was 13.9 mg/g after five generations of subculture,which proved that the mutant M162 had good genetic stability.The fungal universal primer ITS 4/5 was further used for molecular biological identification,and the mutant M162 was identified as Monascus purpureus.The reasons for its high GABA yield were discussed by real-time quantitative PCR.2.Preparation of high-quality starter based on response surface optimization.By single factor experiment and Box-Behnken response surface design experiment,the culture medium and culture process of Monascus were optimized,and the high quality starter rich in GABA was prepared.The effect of raw material selection on the number of live spores was investigated.The results showed that when brown rice flour was used as raw material.The number of viable spores was the largest,2.7×105 spores/g;when oat,bran,soybean powder and brown rice were added at a ratio of 1:9,the number of viable spores reached 1.5×106 spores/g,1.7×106 spores/g,1.75×106 spores/g,and the saccharifying power was 2625 U/g,2800 U/g,and 2450 U/g,respectively.Therefore,the ratio of brown rice to bran was 9:1.Furthermore,the inoculation amount of seed liquid turning time and culture time were investigated.When adding 20%seed liquid,the number of live spores increased to 1.2×107 spores/g.When the turning time was 12h,the number of live spores increased to 3.6×106 spores/g.When the culture time was7d,the number of viable spores increased to 4.O×106g/cell.On the basis of single factor results,the Box-Behnken design was used to optimize the preparation process.Finally,the medium and conditions of high-quality starter were determined as follows:brown rice:bran=9:1,inoculation amount was 21.5%,starter turning time was 9.06 h,and culture time was 7.19 d.The number of live spores of starter was 4.15× 107 spores/g,which was 94.75%of the predicted value.3.Production of rice flour rich in GABA.The brown rice bran koji seed optimized by Monascus M-1 and Monascus M162 was inoculated into rice flour medium to ferment a functional RMR flour that meets the standards.The appearance,section and fragrance of the sensory indicators are in line with QB/T 2847-2007;the moisture content in the physical and chemical indexes also decreased to less than 10%,but the content of Monacolin K was not detected.The GABA content of Monascus rice flour inoculated with M162 brown rice bran starter was 114.6%of that inoculated with M162 brown rice bran starter,318.8%of that inoculated with M-1 brown rice bran starter,270%of that inoculated with M-1 brown rice bran koji,and the pigment content of Monascus rice flour inoculated with M162 brown rice bran koji was 121.4%of that inoculated with rice bran starter.In the detection of health indicators,the coliform group,yeast and pathogenic bacteria of all Monascus rice flour were not detected,and the citrinin content of Monascus rice flour made from M-1 brown rice bran starter was 26.17%lower than that of Monascus rice flour made from M-1 rice starter.According to the verification of GABA solid-state fermentation kinetics,the time to reach the peak of GABA productivity was increased by 11.1%after the optimized brown rice bran starter was inoculated on rice flour compared with the original rice starter. |
PDF Full Text Request