Study On Improving Cooking And Eating Qualities Of Germinated Brown Rice By High-temperature Air Fluidization

Germinated brown rice(GBR)contains plenty of nutrients that benefit human's health.But GBR is not widely accepted by consumers due to its poor cooking and eating qualities because of the existence of bran layer.In order to improving the cooking and eating qualities of GBR,a high-temperature air fluidization(HTAF)method was employed in this paper.The changes in the starch physicochemical properties,in-vitro digestibility and storability of treated GBR(TGBR)were investigated.Firstly,the process conditions of HTAF were optimized based on the minimum cooking time and gelatinization degree of GBR.The optimal process conditions were obtained through single factor test and orthogonal experiment as follows: fluidization temperature 130 °C,feed rate 45 kg/h and fluidization time 60 s.Under this process,the gelatinization degree of TGBR was 29.16% and the minimum cooking time of GBR was 21.2 min which was 6.8 min shorter than the untreated germinated brown rice(UGBR).The cooking property of GBR was enhanced significatly.Secondly,the cooking and eating qualities of TGBR were evaluated.As results,TGBR showed better cooking quality since it had faster water absorption speed,greater water absorption capacity and volume expansion.The cooked TGBR was softer,stickier and smelled better because of the degradation of fat during the HTAF treatment.The sensory scores of TGBR were higher than that of UGBR.Then,the changes of physicochemical properties of GBR induced by HTAF were investigated.The results showed that:(1)The apparent amylose level increased significantly due to the degration of amylopectin during the HTAF processing.(2)The peak viscosity(PV),trough viscosity(TV),breakdown viscosity(BD),final viscosity(FV)and setback viscosity(SB)of UGBR decreased significantly.The pasting viscosity of TGBR was enhanced.(3)The onset temperature(To),peak temperature(Tp),conclusion temperature(Tc)increased significantly,whereas the enthalpy(?H1)maintained stable according to the DSC analysis.Meanwhile,a second endothermic peak between 104 to 114 °C was observed after treatment,indicating the formation of amylose–lipid complexes in the thermal processing.(4)After treatment,the starch granules showed less size and lost its irregular or polyhedral shape and were coated by the amylose leached out and induced the gelatinization of starch.Therefore,the surface was smooth but the edges of the granules were melted badly.(5)After treatment,the starch changed from A-type to A+V-type.And the relative crystallinity of A-type crystal structure significantly decreased,whereas that of V-type crystal structure increased significantly.(6)The LCM-Raman spectra analysis showed that the starch structure became loose and less orderly after HTAF treatment,which contributed to the formation of amylose-lipid complexes.Meanwhile,the changes in the nutritional quality and digestibility of GBR induced by HTAF treatment were studied.Results showed that the nutritional ingredients of TGBR such as GABA,Vitamin E and Vitamin B1 were degraded by heating treatment.However,the total antioxidant ability of TGBR kept stable owing to the release of combined flavonoid and combined phenols during HTAF treatment.Meanwhile,RDS level of GBR decreased from 47.91% to 31.18%,whereas the SDS and RS level respectively increased from 44.04% and 8.05% to 52.80% and 16.02%.Therefore,the GI value decreased from 86.26 to 78.60,which indicated the significant reduction in the starch digestibility of GBR after treatment.Finally,TGBR were packed with vacuum sealed plastic and stored in room environment.The lipase activity,fatty acid value and sensory quality of TGBR during storage were investigated.It was found that oxygen level was the main factor influenced the storability of TGBR.Samples packed with less ventilated plastic showed less lipase activity,lower growth rate of fatty acid value and higher sensory scores.