Effect Of Germination On The Edible Qualities And Flavor Of Fermented Brown Rice Cake

As a traditional Chinese rice product,fermented rice cake has rich taste and soft texture.And as a kind of steamed cake,it has the advantages of low fat and low calories,which is in line with modern people’s pursuit of health.But it is prone to aging and unstable quality in the storage period,which limits its processing development.Germinated brown rice is more nutritious than white rice,and germination treatment can play a similar role as amylase and other quality amendments,and also meet the demand of "cleaning label",so it is of great practical significance to apply it to improve the quality of fermented rice cake.The objective of this study was to investigate the effect of different germination times(0-48 h)on the basic characteristics of brown rice pulp,the edible quality,and the storage quality of fermented brown rice cake(FBRC).The mechanism of flavor change was explored from the perspective of metabolite changes during germination.The results provided theoretical reference for improving the quality of fermented rice products.And the main results were as follows:The germination rate,bud length,amylase activity,small molecule sugar content of brown rice,rheological properties and microstructure of fermented brown rice pulp were applied to study the effects of different germination time treatments on basic properties of brown rice pulp.The results showed that the germination rate reached 89.62% and the bud length reached 4.47 mm when germinated 48 h.Germination treatment increased the highest amylase activity of brown rice pulp by 46.21%.The content of maltose in small molecule sugar increased the most,which increased from 13.19 mg/g to 57.14 mg/g after 48 h of germination.Meanwhile,the viscoelasticity of fermented rice pulp decreased,G ’and G "decreased significantly with the increase of germination time.The microstructure showed that the starch granules gradually gathered after germination,and the clumps were integrated into clumps.The color,specific volume,texture,stomatal distribution,sensory evaluation and volatile flavor of FBRC were applied to study the effects of different germination time treatments on the quality of FBRC.The results showed that compared with the non-germinated group,the color of FBRC was brighter,the redness and yellowness were decreased.The hardness,chewability and elasticity were decreased significantly,and the hardness was reduced by 46%at the highest.From the perspective of sensory quality,24 h germination time FBRC had the highest acceptability,which was soft and elastic with moderate viscoelasticity.A total of 14 characteristic volatile flavor compounds were determined by gas chromatography-mass spectrometry(GC-MS)and odor activity value(OAV).They were 3-methylbutanol,1-octen-3-ol,octanol,3-(methylthio)-1-propanol,phenyl ethanol,hexanal,octanal,nonanal,decanal,trans-2-nonanal,ethyl hexanoate,ethyl octanoate,ethyl acetate,2-pentylfuran.It was confirmed that germination treatment was beneficial to the further accumulation of these characteristic flavor compounds.The total content of volatile flavor compounds in 24 h germination time FBRC was the highest,which was 28% higher than that in the non-germinated group.The contents of free amino acid,crude fat,free fatty acid,volatile flavor compounds of brown rice pulp and correlation analysis were applied to explore the reasons for the effects of different germination time treatments on the flavor of FBRC.The results showed that after germination,the crude fat content in brown rice decreased,the contents of free amino acids and free fatty acids increased significantly,the maximum increase of free amino acids was 32.55%,the maximum increase of free fatty acids was 14.31%.At the same time,the change of flavor compounds in unfermented germinated rice pulp was monitored,and it was found that the content of flavor compounds increased with the increase of germination time.The correlation analysis showed that the flavor compounds were closely related to the contents of free amino acids and fatty acids of brown rice during germination.The aging rate,texture,thermodynamic properties,crystal structure,water migration and flavor changes,heat map analysis,principal component analysis(PCA)and partial least squares discriminant analysis(PLS-DA)were applied to study the effects of germination treatment on the quality changes of FBRC during storage.The results showed as follows: After 7 days of storage,the aging rate of FBRC after germination treatment decreased significantly.The aging rate of 48 h germination time FBRC was the lowest(734.68 g/d),which decreased by 43.82%compared with the non-germinated group.Meanwhile,the ΔH of FBRC decreased from 4.36J/g to 3.13 J/g,and the crystallinity decreased from 16.62% to 15.35%.LF-NMR showed that,compared with the non-germinated group,the germinated FBRC had less free water loss during storage period,and had stronger water retention ability,which was conducive to delaying the aging of FBRC.At the same time,it was found that although the contents of most flavor compounds after germination treatment were higher than those of brown rice cakes,the contents of characteristic flavor compounds of the two kinds of BR and GBR-24 h FBRC decreased to the same level after storage.Among them,ethyl acetate is the unique characteristic flavor compounds of FBRC,and 3-methylbutanol is the unique characteristic flavor compounds of germinated FBRC,which can be used as the identification index of odor change during storage.