Optimization Of Brown Rice Germination Process And Application

After multiple milling,rice is processed into white rice(WR),which loses a lot of micronutrients and biologically active ingredients.Brown rice(BR)has high nutritional value due to the retention of the bran layer and germ,but it also leads to a rough taste,low cooking quality,and short storage time.Germinating is an effective approach for improving the nutritional and edible quality of BR.In this paper,a set of single-factor experiment was carried out,and then response surface methodology(RSM)was used to optimize the component concentration in germinated brown rice(GBR)culture solution to prepare GBR enriched with Gamma-aminobutyric acid(GABA).Effects of germination on the nutritional value,physicochemical properties,the cooking quality,texture characteristics and sensory properties of BR were investigated.First of all,with GABA content as the response value,the Box-Behnken design was used to perform RSM to optimize the concentration of the culture medium based on the single-factor experiments on the mass concentration of glutamic acid(L-Glu),calcium chloride(Ca Cl2),pyridoxal phosphate(PLP)and gibberellin(GA3).The optimized culture conditions were L-Glu concentration 5.40 mg/m L,Ca Cl2 concentration 2.28 mmol/L,PLP concentration 0.69 mmol/L,and GA3 concentration 0.2 mmol/L.Under these culture conditions,the GABA content in BR reached 158.94 ± 0.15 mg/100 g.Secondly,the effect of germination time on the nutritional value of BR was studied under the above-mentioned optimized process conditions.The results showed that:(1)With the extension of germination time,the GABA content in BR continued to increase during the0~48 h germination period,and the maximum value of 163.19 ± 2.53 mg/100 g appeared at48 h,which was an increase of 230% compared with BR;(2)The antioxidant capacity of BR gradually increased.The content of total phenols,total flavonoids,and ferulic acid continued to increase,and the free radical scavenging rate of ABTS and DPPH continued to increase;(3)Total starch,amylopectin,and amylose content continued to decreace,and the protein content gradually increases.Then,effects of germination on the physicochemical properties of BR was studied.The results showed that:(1)With the extension of germination time,the bud length of BR reached0.93 ± 0.06 mm in 24 h;(2)Microstructure of brown rice grains and brown rice flour occurred a significant change,that is,BR grains became soft,the structure became loose,and the network structure of starch and protein was gradually destroyed;(3)The color of BR flour was darker;(4)The gelatinization characteristics became worse,and the viscosity of the gelatinization system decreased.The gelatinization temperature of BR flour gradually increased,and initial temperature(To),peak temperature(Tp),and final temperature(Tc)increased significantly(p<0.05),and the To,Tp,Tc increased to 65.80,71.10 and 71.65 ?respectively after 48 h of germination;(5)Fourier Transform infrared spectroscopy measured the characteristic absorption peak at 1745 cm-1 due to-C=O for fat.With the extension of the germination time,the peak intensity of here gradually decreased until it disappeared,indicating a significant degradation of fat during the germination process.(6)As measured by X-ray diffraction patterns,the diffraction peaks at 2?=23.5° gradually diffused and gradually appeared as amorphous peaks,indicating that the V-type structure substance and amylose-lipid complex were reduced.Finally,effects of germination on the cooking quality,texture properties,and sensory properties of BR were studied.The results showed that:(1)Similar trends were obtained from the water absorption rate of BR grains at different germination times,and the rate gradually slowed down after rapid water absorption.The water absorption rate of BR germinated for 48 h at 30 min was greater than that of polished rice;(2)As the germination time increased,the solid content of the rice soup of BR gradually increased and the cooking time was gradually shortened.The heating water absorption rate and the volume expansion rate of BR showed a basically the same trend,showing that it first increased and then decreased,and the maximum value appeared at 24 h;(3)The iodine blue value and light transmittance of rice continued to decrease;(4)Brightness(L* value)of BR gradually decreased with the extension of the germination time,and red-green value(a* value)and yellow-blue value(b* value)gradually increased;(5)The hardness of BR gradually decreased.The elasticity first increased and then decreased,and the maximum appeared at 24 h after germination;(6)The sensory score of GBR was lower than that of polished rice,but germinating improved the sensory quality of BR.The acceptance score and total score of BR germinated for 12 h were the highest,which was significantly higher than that of BR.