Zinc Accumulation In Germinated Brown Rice And Nutritional Powder Development

The condition for zinc（Zn）accumulation in germinating brown rice and distribution of Zn binding with biological macromolecules and their antioxidant activities were investigated in this paper.The optimization of culture condition for Zn enrichment,the distribution of Zn in tissues and protein,polysaccharide and nucleic acid fractions of brown rice were studied.Effect of Zn-enrichment on antioxidant activities of different fractions was investigated and a kind of nutritional powder was developed.1.During ZnSO₄ soaking period,sucked time rate of brown rice showed a trend like"S",and didn’t change after 8 h,Zn²⁺ absorbed from external and concentrated in outer layers during soaking,declined substantially from the outer layers to the inner endosperm,total zinc（T-Zn）content of bran layer was the highest obtained after milling 10 s and white rice was the lowest obtained after milling 60 s,T-Zn content showed a decreasing trend with the germination time,however,organic zinc（O-Zn）content and O-Zn/T-Zn significantly increased（p<0.01）with germination time.Germination temperature had no significant（p>0.05）effects on T-Zn contents,but had a significant（p<0.01）impact on O-Zn contents.It was observed that the increase of Zn²⁺ concentration significantly（p<0.01）improved T-Zn and O-Zn contents in brown rice during germination,meanwhile gradually decreased O-Zn/T-Zn.Based on single factor experiments,the germination condition of germination time,temperature and Zn²⁺ concentration for O-Zn and O-Zn/T-Zn were optimized using Box-Behnken design（BBD）,the optimized condition was germinating for 3 days at 30.28 ℃ after 200 mg/L of Zn²⁺ soaking.Under the optimum condition,the maximum O-Zn content（304.71μg/g）and O-Zn/T-Zn（86.21%）were obtained.2.The DOM increased significantly（p<0.01）with the milling time from 0 to 60 s in Zn-enriched germinated brown rice;after being milled for 60 s,DOM reached 17.86%.T-Zn,O-Zn contents and O-Zn/T-Zn in the abraded parts decreased significantly（p<0.01）with milling time.After being rmilled for 60 s,an average of 55.25%and 49.95%in the loss of T-Zn and O-Zn was observed,which was nearly a half of Zn accumulated in the subsurface layer and accounted for 16.56%of total weight.Protein binding Zn concentration in the abraded parts decreased significantly（p<0.01）with the milling time,polysaccharide binding Zn content increased at the early stage of milling（0-40 s）,meanwhile had no significant change in the rest period.This trend of nucleic acid binding Zn content is the same as polysaccharide binding Zn,21.19%of O-Zn was found in the protein fraction,30.42%in the polysaccharide fraction and 1.24%in the nucleic acid fraction.Polysaccharide binding Zn of brown rice bran layer was extracted with different concentrations of ethanol alcohol,Zn are mainly located in the polysaccharide fraction precipitated in 60-90%ethanol alcohol concentrations,then polysaccharide fraction was separated by DEAE-52 cellulose anion-exchange column chromatography and SephadexG-100 gel chromatographic column,Zn largely distributed in BRP2-1,2 and BRP3-1 components and their molecular weight were mainly less than 5 KDa.3.Polysaccharide and protein extracted from different parts of brown rice has remarkable difference in hydroxyl,superoxide and DPPH anion free radicals clearance.With the extension of milling time,antioxidant capability of polysaccharide and protein decreased gradually.Antioxidant capability of polysaccharide and protein in Zn-enriched brown rice were improved.Investigating antioxidant capability of six polysaccharide fractions extracted from brown rice layer purified by DEAE cellulose-52 ionic sieve chromatography,it was found that BRP2 had the strongest capability of superoxide and DPPH radicals clearance,BRP3 has the strongest reducing power.4.The formula of germinated nutritional powder including Zn-enriched germinated brown rice,germinated soybean and germinated com was optimized by D-optimal mixture regression design and orthogonal design in which parameters of chromaticity,palatability,brewing and stability were evaluated.The optimal formula of nutritional powder was obtained:the ratio of germinated brown rice,germinated soybean and germinated com was 40.0%,21.9%and 38.1%,respectively.The sensory evaluation score reached 72.23 for this ratio.The optimum flavor of the nutritional powder was obtained at a ratio of sugar,maltodextrin,creamer and skimmed milk of 8%,11%,14%and 7%,respectively.O-Zn and GABA content reached 12.79 mg/100g,16.63 mg/100g for this formula.