Effects of glutelin and globulin on the physicochemical properties of rice starch and flour

The effect of two rice endosperm proteins, glutelin and globulin, on the physicochemical properties of rice starch and flour was investigated. Albumin, globulin, prolamin and glutelin were sequentially extracted from defatted rice flour with de-ionised water, 1.5 M NaCl, propan-2-ol and 0.1 M NaOH, respectively, followed by dialysis and lyophilisation. Globulin and glutelin were then added to pure rice starch at various concentrations, separately and together, and the pasting and textural properties of mixtures were analysed by the Rapid Visco Analyser (RVA) and TA-XT2 textural analyser, respectively. The presence of glutelin in rice starch caused an increase in pasting temperature but a decrease in the viscosity parameters of the starch paste. The concentration of glutelin was also positively correlated with the hardness and adhesive properties of the starch gel. The presence of globulin, on the other hand, resulted in a decrease in all the pasting and textural parameters except gel hardness and the changes were linearly correlated with the concentration of the protein for most of the physical parameters. When the two proteins were added to rice starch together, the outcomes in pasting and textural properties were generally dependent upon the relative concentrations of the two proteins, but were also influenced by the presence of the other two protein fractions, albumin and prolamin. The presence of globulin initially accelerated the rate of water absorption by starch during cooking while the presence of glutelin slowed it down, but in both cases, the ultimate amount of water absorbed was significantly lower than that by pure starch. The contrasting effects of the different protein fractions mean that it might be possible to manipulate the textural properties of rice starch and flour to achieve desirable sensory outcomes by varying the proportions of the protein fractions in product formulations.     

稻米蛋白质组分及总蛋白质含量与淀粉RVA谱特征值的关系

 利用低谷蛋白含量（low glutelin content, LGC）粳稻品种W1721与大面积应用的杂交粳稻恢复系轮回422构建了重组自交系群体。根据种子总蛋白质的SDS PAGE带型,推断各单株LGC位点的基因型。在排除脂肪的影响下,比较了基因型LGCLGC（谷蛋白含量较醇溶蛋白低）与基因型lgclgc（谷蛋白含量较醇溶蛋白高）在RVA谱特征值上的差异,以及同一基因型内总蛋白质含量与淀粉RVA谱特征值的关系。结果表明基因型LGCLGC的崩解值和回复值的平均值分别显著和极显著大于基因型lgclgc;LGC对崩解值和回复值的相对加性效应分别为3.91%和4.45%,贡献率分别为4.81%和12.81%。LGCLGC型的稻米,总蛋白质含量与崩解值和消减值分别存在显著的负线性回归和正线性回归关系,贡献率分别为9.86%和11.48%;lgclgc型的稻米,总蛋白质含量与消减值和回复值都存在极显著的负线性回归关系,贡献率分别为1341%和27.88%。结合前人研究认为,稻米食味品质受谷蛋白相对于醇溶蛋白的含量以及总蛋白质含量的影响;而总蛋白质含量对食味品质的影响因谷蛋白相对于醇溶蛋白的含量的不同而异。因此,育种工作中应当把谷蛋白相对于醇溶蛋白的含量以及总蛋白质含量同时作为选择指标。     

Effect of structured lipid on alveograph characteristics, baking and textural qualities of soft wheat flour

The effect of substituting canola oil/caprylic acid structured lipid (SL) for partially hydrogenated shortening (at 0, 25, 50, 75, and 100% levels) on the rheology of soft wheat flour dough (28.4% total lipid on flour weight basis, 43% moisture) was determined using the Alveograph. The effect of SL substitution on baking and textural qualities of sugar-snap cookies was also investigated. Addition of shortening to soft wheat flour dough resulted in a significant (P<0.05) decrease in dough resistance to deformation (P), dough extensibility (L), and dough baking strength (W), suggesting a less developed gluten network. SL substitution for shortening did not affect P and W. The cookies incorporating SL (50 and 75% SL substitution) were similar (P<0.05) to the shortening control cookies in both baking and textural qualities, but exhibited some baking and textural quality differences at the 25 and 100% SL substitution levels. Correlations (P<0.05) were found between some Alveograph characteristics, and baking and textural qualities.     

Effects of semidry flour milling on the quality attributes of rice flour and rice noodles in China

To investigate the effects of semidry-milling on the quality attributes of rice flour and rice noodles, the properties of rice flours and cooking properties of rice noodles prepared with wet-, dry- and semidry-milled rice flours were characterized. The level of starch damage of semidry-milled rice flour at 30% moisture was significantly decreased to the level of wet-milled rice flour (P < 0.05); the whiteness of dry-milled rice flour was decreased compared with wet-milled rice flour (P < 0.05), while that of semidry-milled rice flour was not; the wet- and semidry-milled rice flours showed similar morphology and water hydration properties; the dry milling method reduced significantly the hardness, chewiness, and resilience of rice noodles (P < 0.05) compared with wet-milling, but semidry-milling did not; the cooking qualities of rice noodles produced by semidry-milling were comparable to wet-milling. It indicated the semidry-milling at 30% moisture may provide the protective effects on the characteristics of rice flours, which could be used to produce similar qualities of rice noodles to the wet-milling.     

Amylopectin Fine Structure and Rice Starch Paste Breakdown

Ten rice starches with a fairly narrow range of amylose content, but wide variation in RVA pasting curves, were selected to study a possible relationship between amylopectin fine structure and RVA paste viscosity parameters. Amylopectin fine structure was found to significantly correlate with paste breakdown. Proportion of long chains of amylopectin (FrI) was negatively correlated (r=0·84, p<0·01) and proportion of short chains of amylopectin (FrIII) was positive correlated (r=0·89, p<0·001) with paste breakdown. The findings imply that amylopectin fine structure relates to the extent of breakdown of swollen granules and the viscosity after gelatinised starch granule structure is disrupted. The results suggest the possibility that lines can be selected with high proportion of amylopectin long chains for reduced paste breakdown.     

The Role of Dextrins in the Stickiness of Bread Crumb made from Pre-Harvest Sprouted Wheat or Flour Containing ExogenousAlpha-Amylase

Dextrins were extracted in water from bread made from pre-harvest sprouted wheat or standard flour supplemented with exogenousalpha-amylases. The dextrins were separated by gel permeation chromatography and the dextrin content (% of crumb weight) determined for different degree of polymerisation (DP) size classes; DP 1–2, DP 3–10, DP 11–50, DP 51–200 and DP >200. There were significant correlations between the dextrin content in each size class and crumb stickiness (r=0·84–0·91, 22 df ). The most significant correlation (r=0·96) was between total dextrin content and crumb stickiness. Addition of dextrins of various DP ranges from various sources to standard flour produced bread with sticky crumb. Again, the degree of stickiness was generally related to the amount of total dextrin in the crumb and not to size distribution of dextrins. In this instance, extensive enzymic hydrolysis of starch was not necessary to produce sticky crumb; the dextrins caused crumb stickiness directly. Addition of dextrins to reconstituted gluten–starch flour produced bread with unexpectedly low dextrin levels and correspondingly low stickiness scores. It is concluded that, to produce sticky crumb, high levels of dextrin of any size are necessary in the crumb; a sticky mass is produced when dextrins dissolve in the excess «free» water that is normally «bound» to starch, gluten and other insoluble components of bread crumb.     

Effect of jet-cooked wheat gluten/lecithin blends on maize and rice starch retrogradation

Vital wheat gluten and lecithin (GL) (50:50, w/w) were dry blended in a coffee grinder and a 9.5% (w/v) aqueous slurry was jet-cooked (steam pressures of 65 psi/g inlet and 40 psi/g outlet) to disaggregate wheat gluten and facilitate better dispersion of the two components. The jet-cooked material was freeze-dried and stored at 0 °C for future use. The GL blend was added to pure food grade common maize and rice starch at concentrations of 0 (control), 6, 11, 16, and 21%. Starch gelatinization and retrogradation temperature transitions were determined using Differential Scanning Calorimetry (DSC). From the DSC profiles, the change in the ΔH value was used as an indication of starch retrogradation, where a higher ΔH value indicated higher retrogradation. The ΔH values of the blends at 4 °C had higher values than the −20 °C and the ambient (25 °C) storage temperatures. Overall, the 21% GL/starch blends reduced retrogradation by 50%. The lower amylose content of rice starch relative to maize starch was reflected in Rapid Visco Amylograph (RVA) measurements of peak viscosity, and similarly, Texture Analyzer (TA) measurements indicated that maize starch gel is firmer than rice starch gel. Retrogradation was also evaluated by observing G′, the shear storage modulus, as a function of time after running a standard pasting curve. Using this method, it appears that GL has a significant effect on maize starch retrogradation, since low concentrations (<0.4%, w/w) reduced G′ up to 40%. The opposite behavior was seen in rice starch, where G′ increased directly with added GL. It appears that the amylose level in the rice starch is too low to be affected by the GL, and the increase seen in G′ is most likely due to added solids.     

Temperature during grain ripening affects the ratio of type-II/type-I protein body and starch pasting properties of rice (Oryza sativa L.)

The starch and protein properties of rice grain are important factors for sake brewing and these properties are reported to be influenced by temperatures during grain ripening. Amylose content, nitrogen content, protein composition, pasting properties measured by a Rapid Visco Analyser (RVA), and their relationship to temperatures during ripening were investigated in a rice cultivar, Yamadanishiki, which was grown under various conditions in the same experimental field. The average temperature after heading was significantly correlated with amylose content and RVA properties, but not with nitrogen content. Under high temperatures during ripening, a decrease in prolamin, which accumulated in type I protein body (PB-I), and an increase in glutelin, which deposits in type II PB (PB-II), were recognized. The ratio of PB-II/PB-I and RVA pasting temperatures were distinctly increased as the temperature became higher. High temperatures during grain ripening would lead to difficulties in digesting steamed rice grains by Aspergillus oryzae, together with ease in digesting rice protein. The average temperature of 11–20 days after heading showed a higher correlation coefficient than that of 1–10 or 21–30 days, implying that temperatures during the middle stage of grain development would be important in determining the rice component that relates to brewing properties.     

Effect of endosperm starch granule size distribution on milling yield in hard wheat

Increased flour yield in hard wheat is associated with increased endosperm rheology index, calculated from strength and stiffness as measured by the SKCS. A study of the fractured endosperm of hard wheat varieties grouped according to similar rheology index values was performed using environmental scanning electron microscopy (ESEM). Differing microstructures and fracture patterns were observed between each group. Specifically, the group representing high rheology index had a greater concentration of small starch granules in prismatic cells. Samples of diverse wheat germplasm were grown at two sites and subjected to laboratory milling. Starch granule size distribution (SGSD) analysis using a laser diffraction method was undertaken on a subset of samples in triplicate representing a range in flour yield. The results supported an hypothesis for a significant influence of SGSD on flour yield of hard wheat varieties. In addition, a significant part (R²>0.40 (p<0.05) at two sites) of the association appeared to be under genetic control. Results indicate a more even gradation of distributions involving an increase in the sample volume % of small granule (types B and C) and decrease in type A granules. This was associated with increased rheology index values and higher flour yield. The ratio of type A:C starch granules accounted for up to 58% (p<0.05) of the variation in flour yield in the samples studied. Thus, rheological parameters measured using a rapid SKCS screening method can be linked to the genetic regulation of SGSD with implications for the improvement of commercial processing performance of hard wheat.     

Impact of proteins on pasting and cooking properties of waxy and non-waxy rice

Changes of RVA viscosity and texture properties of waxy rice (n=9) and non-waxy rice (n=10) were analyzed through protein removal or disulfide bond disruption. Protease or DTT had similar effects on the pasting behavior of the waxy rice, but affected differently that of non-waxy rice. For all waxy rice flour treated with DTT or protease, the peak, breakdown and consistency viscosity values all significantly decreased, and the viscosity curves barely rose from the baseline. Pre-incubation of flours with a protease increased RVA pasting temperatures, decreased viscosities along all the points of the curves and the slopes of the linear parts of the curves for all non-waxy cultivars. DTT decreased RVA pasting temperatures and peak viscosities of all non-waxy flour, but increased breakdown viscosities in six non-waxy rice cultivars. With DTT-added cooking water, the hardness of cooked waxy and non-waxy rice, as determined by Instron, generally decreased. With DTT-added cooking water, the adhesiveness of all cooked waxy rice significantly decreased, while it increased significantly or remained the same in all cooked non-waxy rice. The above results indicated that the protein agent of a network linked by disulfide bonds increased the RVA gelatinized paste rigidity, the hardness and adhesiveness of cooked rice of all waxy cultivars, while in non-waxy cultivars, both the network and the increase of the gelatinized paste concentrations resulting from protein hydration contributed to the enhancements of the RVA paste rigidity and the cooked rice hardness.     

Characterization of rice storage proteins by SE-HPLC and micro z-arm mixer

While the effect of protein content and composition on the functional properties of wheat flour is well studied, our knowledge on the same properties of rice flour is limited. This work was conducted to study the relationship between the dough mixing properties of flour from different rice cultivars and protein content and composition. An efficient sonication-based two-step extraction procedure was applied to isolate rice flour proteins. The size-exclusion HPLC (SE-HPLC) method, originally developed for separating wheat proteins, was applied with some minor modifications in order to study the size distribution of rice flour proteins. Four fractions were distinguished on the SE-HPLC profile and were further characterized by SDS-PAGE. Fractions I–III consisted of glutelins, while fraction IV contained albumin, globulin and prolamin proteins. When rice dough was characterized on the basis of mixing parameters in a micro z-arm mixer, significant differences were observed depending on the protein composition of the flour. Statistical analysis results indicated that the functional properties of the flour from different rice cultivars were associated with the amount of polymeric proteins and their size distribution.     

Effect of Soaking on Wet-milling of Rice

Soaking is an essential step in wet-milling of rice flour. The effects of soaking duration and temperature (5 and 25 °C) on the properties of rice flour have been investigated. The uptake of water by rice kernels increased with temperature and reached a plateau at about 30–35%. Protein, lipid, and ash leached out during soaking. The moisture content after soaking appeared to be a key factor on loosening the structure of rice kernels, which resulted in the production of small particle flours with little starch damage. The particle size of flours did not alter the gelatinisation temperature (T_oand T_p) in DSC thermograms. Small particle and low lipid content flours appeared to have high peak viscosity measured by RVA. The change in microstructure of rice kernels during soaking was also examined by SEM.     

Effect of germination time on physicochemical properties of brown rice flour and starch from different rice cultivars

The present work was designed to obtain information on the effect of germination time on the selected physicochemical properties of brown rice flour and starch prepared from three different rice cultivars. Changes in total starch, amylose and amylopectin contents of flour, amylopectin/amylose ratio and molecular weight of starch, gelatinization, pasting, rheological, and morphological properties of flour and starch during 5 days of germination were investigated. Significant changes of pasting and rheological properties of brown rice flour were found during germination, but only small changes of these properties could be found in isolated starch. Scanning electron micrographs of flour showed that the continuous matrix structure of flour was highly destroyed after germination and scanning electron micrographs of isolated starch showed that after three days of germination, pits and holes were discovered on the surface of some starch granules. Germination had little effect on the average molecular weight of starch, but the polydispersity value in germinated brown rice (2–5 days germination) was higher than that in non-germinated brown rice. The changes observed in physicochemical properties of brown rice flour and starch after germination provided a crucial basis for understanding flour and starch modification mechanisms with potential applications for an industrial scale.     

In vitro starch digestibility,degree of gelatinization and functional properties of twin screw prepared cereal-legume pasta

The investigation explores the possibility of utilizing legume flour (pigeon pea:10–30%) and brown rice flour (35–45%) for production of pasta using twin screw extruder. RSM was used to analyse the effect of feed moisture (28–36%), barrel temperature (70–110 °C) and legume:brown rice ratio on quality responses (in vitro starch and protein digestibility, degree of starch gelatinization, cooking quality, pasting properties, color and textural properties) of pasta. Extrusion processing significantly enhanced in vitro starch and protein digestibility of prepared pasta. The in vitro starch and protein digestibility of pasta ranged between 15.00 and 26.77 g/100 g and 50.34–84.82 g/100 g respectively. Addition of brown rice flour and pigeon pea flour exhibited dominating positive effect on cooking quality of the pasta. Degree of gelatinization of prepared pasta was found in range of 52.13–90.10 per cent. Color characteristics viz. luminosity, redness and yellowness of pasta enhanced with feed moisture. Pasting properties revealed lower peak and final viscosity at higher processing conditions. Firmness of cooked pasta elevated with an increase in the barrel temperature. Acceptability score of health based pasta on the basis of sensory attributes was 8 as inferred from 9 point hedonic scale.     

稻米中蛋白质对淀粉RVA特征谱的影响

通过分析蛋白酶或还原剂二巯基苏糖醇（DTT）分别去除稻米蛋白质或打破蛋白质二硫键后,稻米RVA（Rapid Visco Analyzer）特征谱形成和特征值的变化,研究蛋白质对淀粉RVA特征谱的影响,以及对米饭食味品质的作用。在淀粉糊化过程中,蛋白质使RVA特征谱的峰值黏度、冷胶黏度等值升高,改变RVA线性上升段的斜率。蛋白质可能通过二硫键结合形成的蛋白质网络本身和通过吸水减少淀粉水合的有效水量,协同提高糊化多相体系的浓度,增强分散相与黏稠相的互作。蛋白质影响米饭食味品质,可能通过改变米粒的吸水性而起作用。     

Antioxidative properties of partially purified barley hordein, rice bran protein fractions and their hydrolysates

Antioxidative properties of proteins from barley and rice bran and their hydrolysates were examined. Three major hordein fractions of barley, B, C and D hordeins, were partially purified by gel filtration. Albumin, globulin, prolamin and glutelin fractions of rice bran were fractioned by the Osborne method. Hydrolysates of these protein fractions were prepared by digesting with pepsin followed by trypsin. Antioxidant properties in terms of antioxidative activity against linoleic acid peroxidation and reducing activity without the lipid adjuvant were investigated. The globulin fraction from rice bran protein revealed the strongest antioxidative activity throughout the incubation time of 7 days (p ≤ 0.05). The albumin fraction of rice bran protein showed the highest reducing activity (6964 μmol of Fe²⁺) followed by globulin, prolamin, glutelin and hordein fractions with activities of 2904, 2017, 1809 and 1333 μmol of Fe²⁺, respectively (p ≤ 0.05). Partially purified C hordein exhibited the highest reducing activity compared with B and D hordeins. Protein hydrolysates obtained after digestion with pepsin and trypsin exhibited much greater antioxidative, as well as reducing, activities than those from before digestion.     

Relationship between the Starch Properties of White-Core Tissue and Polishing Characteristics in Brewers’ Rice Kernels

References

The kernels of Hattan-nishiki No. 1 and Kairyo-omachi have larger air spaces in the white-core tissue and are broken easily during the process of polishing when compared with those of Senbon-nishiki and Yamada-nishiki. The polishing characteristics of brewers’ rice kernels are closely related with the structure of the white-core tissue of kernels. In this study, the varietal differences in the starch properties of white-core tissue of brewers’ rice kernels on polishing characteristics were studied. The starch properties were studied by rapid visco analysis (RVA) and differential scanning calorimetry (DSC); the amylose content of the rice flour of each variety was also analysed. No significant differences were observed in the amylose content among the four varieties. The two RVA parameters, peak viscosity and breakdown, were higher in Hattan-nishiki No. 1 and no significant differences were observed in them among Senbon-nishiki, Yamada-nishiki and Kairyo-omachi. The DSC parameters, gelatinization onset and peak and conclusion temperatures, were higher in Hattan-nishiki No. 1, lower in Senbon-nishiki and Yamada-nishiki, and intermediate between them in Kairyo-omachi. These results suggest that the polishing characteristics of brewers’ rice kernels are related with not only the endosperm structure but also the starch property of white-core tissue, except for Kairyo-omachi.     

Distribution of Water between Wheat Flour Components: A Dynamic Water Vapour Adsorption Study

The water adsorption properties of hard and soft wheat flours and flour components (starch, damaged starch, gluten, soluble pentosans, and insoluble pentosans) were determined at 25 °C using a controlled atmosphere microbalance. At different levels of relative humidity (from 10% to 95%), changes in sample mass (i.e., water gain) were continuously measured versus time and described using exponential models (R²≥0·994). Water adsorption isotherms were constructed for wheat flours and flour components and described using Guggenheim-Anderson-de Boer models (R²≥0·997). It was not possible to distinguish between the selected hard and soft wheat flours by their isotherms. The water-soluble pentosans had the highest water adsorption capacity. The theoretical distribution of water between the flour components (calculated using the Guggenheim-Anderson-de Boer parameters) was starch, 88%; gluten, 10%; and pentosans, 2%.     

Formulating low glycaemic index rice flour to be used as a functional ingredient

Amylose and resistant starch (RS) content in rice flour were manipulated. The experiment was conducted using a full factorial design. Rice flour with average amylose content of 20 and RS content of 0.5 g/100 g dry sample was fortified with pure amylose from potato and high RS modified starch to reach the final amylose content of 30, 40 and 50 and RS content of 2, 4 and 6 g/100 g dry sample. The fortified rice flours were examined for their gelatinisation properties, in-vitro enzymatic starch digestion and gel textural properties. It was found that amylose and RS significantly affect all the fortified rice flour properties (p < 0.05). High amylose and RS improved starch digestion properties, reducing the rate of starch digestion and lowering the glycaemic index (GI) values. Amylose had a more pronounced effect on the fortified rice starch properties than RS. In this study, the fortified rice flour which contained amylose and RS of approximately 74 and 9 g/100 g dry sample respectively was used to produce rice noodles. The noodles exhibited low GI values (GI < 55). However, amylose and RS affected the textures of rice noodles providing low tensile strength and break distance (extensibility).     

用糙米粉代替精米粉测定淀粉粘滞性的效果研究

研究了利用糙米粉代替精米粉测定RVA谱的效果,发现用3.0 g的糙米粉测得的RVA谱的最高粘度、热浆粘度和冷胶粘度约是用3.0 g精米粉相应值的76%,而用3.3 g糙米粉测定的RVA谱则基本与用3.0 g精米粉测得的RVA谱相近。在育种中,用糙米粉代替精米粉测定RVA谱可节省大量的人力和物力,从而可大大提高早期选择效率。