| Rice as one of the important staple food in China, the development of correspondingfunctional brown rice and germinated brown rice products has positive significance forcomprehensive and reasonable improving national staple food nutrition. Three relatively largeplanting cultivars in Jiangsu region, Zhengxian96(ZX), Nanjing38(NJ), and Yannuo12(YN), which on behalf of indica, japonica and waxy cultivars, were chosen. Withcorresponding white rice or brown rice as a control, the effect of germination on thenutritional composition, antioxidant and immune function, starch properties and foodprocessing characteristics of brown rice were systematic studied, so as toprovide reference information for scientific selecting rice varieties, determining thegermination process, evaluating the Physiological effects of germinated brown rice anddevelopment of corresponding germinated brown rice product.Germination time significantly affected the important nutrients and antioxidants content ofbrown rice. Experiments confirmed that contents of seven kinds of essential amino acids Val,Pro, Met, Phe, Ile, Leu, Lys, four kinds of non-essential amino acids His, Thr, Ala, Tyr, andtotal amino acid were increased gradually as germination time increased. The contents of γ-aminobutyric acid, total dietary fiber content and total polyphenol also increased asgermination time increased. After five days of germination, total amino acids contents of ZX,NJ and YN increased by158%,185%and191%, GABA contents increased by17,13and15times, total dietary fiber contents increased by37%,39%and40%, total polyphenol contentsincreased by42%,40%and45%, respectively. Changes in γ-oryzanol, and vitamin E contentdiffered slightly among different rice cultivars: γ-oryzanol content reached a peak value onthe forth day of germination for rice cultivar ZX and on the third day of germination for ricecultivar NJ and YN, increased by23%,22%and20%respectively; tocopherol content contentreached a peak value on the forth day of germination for rice cultivar ZX and on the third dayof germination for rice cultivar NJ and YN, increased by40%,46%and51%respectively.In vitro experiments and animal test confirmed that germinated brown rice antioxidantand immune-enhancing effects. In vitro antioxidant activity of germinated brown rice increasewith the germination time, and the increase rate decreased after3days. Germinated brownrice that has undergone4days and5days germination showed similar antioxidant activity.After4days of germination, the reducing power, DPPH radicals and ABTS radicalscavenging effects, and the ability to inhibit the oxidation of linoleic acid increased by55%,35%,61%, and30%, respectively. Animal feeding experiments show that geminated brownrice has an effect of enhancing antioxidant activities and improving immune function in agedmice, and germinated brown rice from longer germination time overall exhibited a bettereffect. Compared with the control diet group, germinated brown rice(4days germination time)diet make Superoxide dismutase (SOD) activity of mouse serum, liver and brain increased by16%,17%and20%respectively, catalase (CAT) activity increased by18%,10%and15%respectively, glutathione peroxidase (GSH-PX) activity increased by27%,13%and21%respectively, total antioxidant capacity (T-AOC) increased by19%,20%and31%respectively,and the lipid peroxidation product malondialdehyde (MDA), reduced by36%,29%and35% respectively. Compared with the aged control group (AC), the spleen lymphocyte proliferationand NK cell activity in GBR4group were increased by19%and13%, respectively;Compared with the brown rice group (BR), the spleen lymphocyte proliferation and NK cellactivity in GBR4group were increased by10%and9%, respectively.The effect of germination time on starch composition, gelatinization, retrogradation,pasting, rheological, and morphological properties of flour and starch as well as andmolecular weight of starch during5days of germination were investigated. Germinationtreatment has little effect on the gelatinization temperature and enthalpy of brown rice flour,but led to a dramatic decrease in the retrogradation enthalpy, pasting viscosity values, storagemodulus (G′) and loss modulus (G″). After five days of germination, peak viscosity of ZX, NJ,and YN decreased from357cP,329cP and380cP to28cP,29cP and20cP respectively.Dramatic reduction of the total starch and the continuous structure of protein bodies of riceflour would be the reason resulting in significant changes during brown rice germination.Compared with rice flour, the overall changes in retrogradation, pasting and rheologicalproperties for the isolated starch were much less pronounced. Scanning electron micrographsof isolated starch showed that after three days of germination, pits and holes were discoveredon the surface of some starch granules. Germination had little effect on the average molecularweight of starch. These results indicate that, on the one hand rice starch was directly degradedinto soluble polysaccharides and small-molecule sugar during germination, few starchintermediate points; on the other hand high damaged starch lost during the extraction process,thus the isolated starch was mainly undamaged starch. Therefore, rice starch showed smallchanges during germination process, and this small change may also caused by changes in theamylopectin/amylose ratio.The cooking qualities, textural properties, flavor components and sensory qualities of fromdifferent germination stages were studied. Appropriate germination treatment can improve thecooking properties of brown rice through increasing water absorption and volume expansionrate, thus reducing the hardness and enhancing the viscoelasticity of cooked rice. After twodays of germination treatment, water absorption and volume expansion of NJ brown riceincreased from269%and283%to294%and308%respectively, rice hardness decreasedfrom1650to1222, viscosity and elasticity increased from146and0.83to164and0.87respectively. The flavor analysis results showed that a moderate germination process (1-3days of germination) may improve the flavor of brown rice through increasing the desirableflavors as well as decreasing objectionable flavors. Dimethyl sulfide, a new flavor ingredientwith the cooked corn flavor, was detected from cooked germinated brown rice which hasundergone2-5days germination. After germination treatment of2-3days, peak area ofdimethyl sulfide for ZX, NJ and YN brown rice increased from0to (3.44-15.31)×106,(14.89-28.67)×106and (6.05-32.73)×106, respectively. But duration of germination to4or5days produced too much aldehyde, phenolic compounds, and dimethylsulfide which may beconsider undesirable. Sensory evaluation showed that2-3days of germination treatment canimprove the taste, smell and taste as well as to improve the acceptance of cooked brown rice.After2or3days germination, respectively, the acceptability scores increased from4.79to7.42and7.13, total score increased from41.29to55.02and53.45, respectively. But after more than3days germination, mostly sensory index scores decreased significantly.The textural property, sensory quality and shelf life of our newly developed germinatedbrown rice products-germinated brown rice dumplings were studied. A comparison of texturalproperties and sensory qualities among white rice, brown rice and germinated brown riceshowed that germinated brown rice dumplings, the hardness, stickiness and chewiness ofwhich ranged between brown rice and white rice dumplings, possess moderate hardness andstickiness, good chewiness and elasticity, and more not easy retrogradation textural properties.The shelf model obtained through the sensory quality Weibull Hazard Analysis methods is:y=-0.0576x+7.0084; the shelf model obtained by measuring the acid value is: y=-0.529x+6.9723; the shelf model obtained by measuring peroxide value is: y=-0.0549x+6.9938.Shelf life in different storage temperature can be predicted according to these models, inwhich the shelf life of temperature below25℃is more than272days. |
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