Study On Enzymatic Degradation Of Phytic Acid In Brown Rice And Development And Digestion Characteristices Of Fermented Rice Cake Made From Brown Rice And Chinese Yam

Due to its fermented taste and fluffy texture,fermented rice cake is popular with middle-aged and older people.But fermented rice cake with white rice as the main raw material,has a poor mineral content and can quickly raise blood sugar levels.Not only having a hypoglycemic effect,yam is a rich source of minerals,amino acids,polysaccharides,and other physiologically active compounds but also enhance the sensory qualities and texture of fermented rice cake.Because of its large content of slow-digesting and resistant starches,brown rice possesses a variety of functions,including preserving the postprandial blood glucose homeostasis.Furthermore,as compared to other grains,brown rice is rich in several nutrients like calcium,iron,and zinc and low in protein allergenicity.However,brown rice contains phytic acid,which can lessen the bioavailability of minerals.This thesis used an enzymatic approach to lower the amount of phytic acid in brown rice in order to increase the bioavailability of micronutrients.What’s more,brown rice and yam were used to produce fermented rice cake,which addressed the issues of poor mineral content and high glycemic index of fermented rice cake.Finally,using an in vitro digestion simulation,the carbohydrate and protein digestion properties as well as the mineral availability in fermented rice cake made from brown rice and yam were assessed.The main study findings were displayed below.1.Study on enzymatic degradation of phytic acid in brown rice.A single-factor test was used to examine the effects of enzyme concentration,substrate concentration,enzymatic digestion time,and enzymatic digestion temperature on the degradation of phytic acid in brown rice.Orthogonal experiments were used to optimize the enzymatic degradation of phytic acid in brown rice.The phytic acid in brown rice was best degraded by phytase using the following conditions: enzyme concentration of 1.3 U/m L,liquid to material ratio of 3:1,temperature of 55°C,and time of 1.5 h.The degradation rate of phytic acid was 87.78% during this enzymatic process.The addition of 14 u/g cellulase boosted the degradation rate of phytic acid to 92.4% under the ideal enzymatic conditions for phytase,and the amount of soluble dietary fiber was 1.13 g/100 g.When brown rice was treated with enzymes,utilization of calcium,zinc,and iron rose by 13.39%,3.87%and 23.84%,respectively.Thermodynamic and pasting characteristics of brown rice flour revealed that the material’s thermal stability,cold paste stability and processing stability enhanced after enzymatic hydrolysis.2.Study on development of fermented rice cake made from brown rice and Chinese yam.Fermented rice cake was made from enzyme-digested brown rice and yam.Using the specific volume,texture traits,and sensory score of the fermented rice cake as evaluation indices,the recipe for fermented rice cake was optimized with the ratio of brown rice and yam,the percent of water,the percent of starch,the percent of baking powder,and the fermentation time.The results demonstrated that the fermented rice cake made from brown rice and Chinese yam had the right hardness and chewiness,moderate sweetness and sourness,rich yam flavor and soft texture when the ratio of brown rice,yam,and water was 10:6:8,the proportion of starch was 6%,the proportion of baking powder was 1%,and the fermentation time was 1.5 h.3.Study on digestion characteristics of fermented rice cake made from brown rice and Chinese yam.The viscosity and particle size of fermented rice cake were increased by yam and brown rice,which also had an impact on digestive characteristics of the carbohydrate and proteins.Fermented rice cake made from white rice,fermented rice cake made from white rice and yam,and fermented rice cake made from brown rice and yam all had protein digestibilities of 48.93%,47.82% and 35.42%,respectively.The nutritional value and amino acid content of fermented rice cake made from brown rice and yam were lower than those of fermented rice cake made from white rice and yam and fermented rice cake made from white rice,although brown rice raised the threonine content and yam enhanced the glutamic acid and arginine content of fermented rice cake.Fermented rice cake made from brown rice and yam had the highest starch hydrolysis rate,followed by fermented rice cake made from white rice and yam and fermented rice cake made from white rice,which had the lowest rate.The rapid digestive starch content of the fermented rice cake made from white rice and yam reduced by 8.91%,the resistant starch content increased by 2.83%,and the glycemic index decreased by 5.99% as compared to the fermented rice cake made from white rice.The rapid digestive starch content of the fermented rice cake made from brown rice and yam fell by 23% when compared to the fermented rice cake made from white rice and yam,while the slow digestive starch content climbed by 4.6%,the resistant starch content increased by 12.21%,and the glycemic index decreased by 26.20%.The amounts of soluble calcium,zinc,iron,and potassium in fermented rice cake made from brown rice and yam respectively increased by 39.16 mg/kg,1.22 mg/kg,6.89 mg/kg,and 211.88 mg/kg compare with fermented rice cake made from white rice.