Study On The Effect Of Enzyme Inactivation And Enzymatic Hydrolysis On The Properties Of Rice Bran Protein Hydrolysate And Dietary Fiber And Product Development

During the process of rice milling,the contact between active enzymes and the lipids of rice bran will lead to hydrolysis and rancidity,producing free fatty acids,which makes rice bran difficult to store.Due to the instability and dispersion of rice bran,few domestic enterprises have been able to achieve comprehensive utilization of rice bran.To solve these problems,it is necessary to carry out enzyme inactivation of rice bran to extend its storage period.Extrusion is an efficient,low-cost,and easy-tooperate industrial technology that is widely used in the food industry.Superheated steam enzyme inactivation can preserve the inherent nutrients of raw materials in an anaerobic environment,and there is a lack of research on grain enzyme inactivation.Therefore,this study selected extrusion and superheated steam as two enzyme inactivation methods suitable for large-scale production to explore their auxiliary effects on rice bran protein hydrolysis.In addition,in order to fully utilize rice bran resources,the rice bran residue of the extracted protein was further studied to prepare rice bran dietary fiber.Rice bran insoluble dietary fiber(RBIDF)and rice bran soluble dietary fiber(RBSDF)were obtained by modifying with cellulase,hemicellulase,and composite enzyme,and the effects of enzyme inactivation and hydrolysis on IDF and SDF were explored.Finally,in order to comprehensively use rice bran fiber resources,the optimum addition levels of RBSDF and RBIDF added to bread were found respectively,which provided practical guidance for the production of coarse grain bread.The main conclusions are as follows :(1)Both extrusion and superheated steam treatments could reduce the lipase activity of fresh rice bran.Both methods to some extent hindered protein hydrolysis.The type of enzyme determined the functional differences of the hydrolysates.Overall,alkaline proteinase had the best hydrolysis effect,while acidic proteinase had poor hydrolysis effect.RBPH-EX had the largest molecular weight,while RBPH-U had the smallest molecular weight.Extrusion and superheated steam treatment promoted the transformation of α-helix and random coil structures into β-sheet and β-turn containing structures.The molecular weight of rice bran protein hydrolysate(RBPH)treated by extrusion was the largest,the degree of hydrolysis of untreated RBPH was higher,and the solubility of overheated RBPH was better.The emulsification and emulsion stability of RBPH were improved by extrusion pretreatment.The DPPH free radical scavenging activity and total reducing power of untreated RBPH were better,but the metal-chelating capacity of extruded RBPH was higher.This study provides a basis for the development of rice bran protein products with specific functional properties,and expands the application of rice bran protein.(2)Extrusion processing promoted the conversion of RBIDF to RBSDF,and infrared spectrogram indicated that extrusion processing significantly altered the structure of RBIDF.The water holding capacity of RBIDF obtained by cellulase hydrolysis was better,and the oil holding capacity of RBIDF obtained by hemicellulase hydrolysis was better.The RBIDF treated by extrusion had the best water holding capacity and expansion,but its oil holding capacity was the worst.The ability of RBIDF to stabilize glucose and the viscosity of the solution showed extrusion >superheated steam > untreated;extrusion processing significantly reduced the particle size of RBIDF,and the particle size of RBIDF was opposite to the viscosity of the solution.The study elucidated that both extrusion and superheated steam improved the properties of RBIDF.(3)The main monosaccharide components of RBSDF were glucose,galactose,and xylose.The contents of glucose,rhamnose and galacturonic acid in RBSDF treated by extrusion increased significantly,and the content of galactose decreased significantly.The antioxidant activity of RBSDF showed a trend of extrusion >superheated steam > untreated,and the antioxidant capacity of RBSDF hydrolyzed by composite enzyme was higher.The rheological properties of RBSDF showed the trend of superheated steam > untreated > extrusion.The steady-state rheological properties and dynamic viscoelasticity were related to the monosaccharide composition of RBSDF,mainly related to the content of galactose and arabinose.The study showed that extrusion and superheated steam had different effects on the functional properties of RBSDF.(4)Appropriate addition of RBSDF and RBIDF improved the sensory quality of bread to a certain extent,enriched the nutritional value of bread,and extended the shelf life of bread.The addition of no more than 6 % RBSDF improved the overall quality of bread,and 6 % was the best addition amount of RBSDF.When the addition amount of RBIDF was 2 % and 5 %,the overall properties of bread were also good compared with the control group,but when the addition amount exceeded 10 %,the quality of bread showed a deteriorating trend,so the addition level of RBIDF was not more than 5 %.