Preparation, physicochemical and texture properties of texturized rice produce by Improved Extrusion Cooking Technology

Using broken rice and rice bran as raw material, texturized rice (TR) was prepared by Improved Extrusion Cooking Technology (IECT) in which gelatinization is formed by means of low temperature and high pressure. The expansion of extrudate was hardly changed so that TR showed similar texture properties and shape with polished rices. The effect of rice bran addition (0% and 4%) and IECT conditions, including feed moisture content (26.6-33.4%), screw speed (20.1-32.6 rpm) and shearing compression metering zone temperature (SCMT, 69.8-120.2 °C) on the physicochemical, texture and nutritional characteristics of TR, were investigated by response surface methodology using Central Composite Design. When the bran addition was 4%, feed moisture content was 30%, screw speed was 26.6 rpm, SCMT was 95 °C, prepared TR contained 16.61 ± 0.02% of total dietary fiber, 9.40 ± 0.04% of protein, 3.68 ± 0.03% of fat, 2.42 ± 0.02 μg/g of thiamin, 0.52 ± 0.01 μg/g of riboflavin and 16.07 ± 0.12 mg/100 g of γ-oryzanol (dry matter content). The content increase of TDF for TR was 15.81% and the content increases of nutrients for thiamin, riboflavin, and γ-oryzanol were 1.39 μg/g, 0.24 μg/g, and 8.99 mg/g dry matter content, respectively, compared with those of polished rice.     

The relationship between reducing sugars and phenolic retention of brown rice after enzymatic extrusion

To investigate the relationship between reducing sugars and phenolic retention of brown rice after enzymatic extrusion, reducing sugars, total phenolic content, total antioxidant activity, and individual phenolic acids of brown rice extruded with different α-amylase concentrations (0.1%, 0.5%, 1%, w/w) were evaluated. Reducing sugars were produced during enzymatic extrusion and significantly increased with the increasing enzyme concentration. Compared with traditional extrusion, the enzymatic extrusion with 1% amylase significantly increased the phenolic retention, DPPH value, FRAP value, and ABTS value by 22.4%, 19.5%, 14.7%, and 41.5%, respectively. The retention of most free phenolic acids was also increased with the increasing enzyme concentration. Besides, the correlation analysis indicated that the content of reducing sugars was positively correlated with total phenolic content (r = 0.915), DPPH value (r = 0.882), FRAP value (r = 0.861), ABTS value (r = 0.867) and free individual phenolic acids (r = 0.595–0.943) of treated brown rice. These results suggested that reducing sugars might protect phenolic compounds during enzymatic extrusion.     

Relationships between upland rice canopy characteristics and weed competitiveness

Weed-competitive upland rices with an acceptable yield potential are needed for labor-limited systems in Africa, particularly where shortened fallow periods have increased weed pressure. Crosses between weed-competitive but low-yielding African rice, Oryza glaberrima, and improved Oryza sativa tropical-japonica rices, might reduce tradeoffs between competitiveness and yield potential. Parallel field studies under moist upland conditions were conducted during the 1996 and 1997 wet seasons at Mbe in Cote d'Ivoire to (1) characterize canopy properties, growth vigor and yield for O. glaberrima, O. sativa and interspecific progenies under monoculture, and (2) determine their competitiveness when grown in single rows in competition with natural weed growth, maize (removed 50 days after sowing [DAS]), the highly weed-competitive O. glaberrima IG10, and with themselves. In the monoculture study with 21 lines, dry matter, leaf area index (LAI), PAR extinction coefficient (K_df), mean tip elevation angle (MTA) and specific leaf area (SLA) were measured 31, 46 and 64 DAS. Across lines, LAI was positively correlated with SLA, dry matter partitioning to leaves (31 and 46 DAS) and K_df (46 DAS); and negatively with MTA (46 and 64 DAS). Plant height was negatively correlated with tiller number. In the competition study with 16 lines, the O. glaberrima landraces had superior relative yield (yield under interspecific competition/yield under intraspecific competition). Some breeding lines were competitive with specific competitors. Correlations between canopy characteristics under monoculture and competition indicated that LAI, SLA and tillering ability were predictive of competitiveness regardless of the competing species, whereas partitioning, K_df and MTA were correlated with competitiveness only for specific growth stages and/or competitors. Competitiveness was negatively but weakly correlated with yield potential, and positively, with crop duration. The authors conclude that SLA and tillering ability, which are major determinants of vegetative vigor, and crop duration, which affects the ability to recover from early competition, are useful traits in the selection of weed-competitive rices, particularly in breeding programs that use O. glaberrima. The traits are compatible with high yield potential if cultivars have large SLA during early developmental stages and small SLA during advanced stages. Major knowledge gaps remain on weed competitiveness under drought- and flood-prone conditions, which are frequently associated with weed problems.     

The relationship between rheological characteristics of gluten-free dough and the quality of biologically leavened bread

The rheological characteristics of gluten-free doughs and their effect on the quality of biologically leavened bread were studied in amaranth, chickpea, corn, millet, quinoa and rice flour. The rheological characteristics (resistance to extension R, extensibility E, R/E modulus, extension area, stress at the moment of dough rupture) were obtained by uniaxial dough deformation. Specific loaf volume of laboratory prepared gluten-free breads was in significant positive correlation with dough resistance (r = 0.86), dough extensibility (r = 0.98) and peak stress at the moment of dough rupture (r = 0.96). Even if the correlation between R/E modulus and the characteristics of loaf quality were not significant, the breads with the highest specific loaf volume were prepared from flours with R/E closer to the wheat check sample (18 N?mm-1). The results showed, in general, good baking flours exhibited stronger resistance to extension and greater extensibility, but differences found were not directly related to the results of baking tests.     

Sensory texture of cooked rice is rather linked to chemical than to physical characteristics of raw grain

This paper describes the multidimensional features of the texture of cooked rice (in particular the visual aspect and mechanical attributes) determined by sensorial analysis and links these attributes with a wide range of physicochemical characteristics of raw grain (in particular certain cell wall components). Textural classes of cooked rice did not fit classical grain ranking, which is primarily based on shape. For the classification of cultivars, it would be preferable to use chemical characteristics of raw kernels such as amylose content and Tgel (for prediction of firmness), but also protein (adhesiveness and stickiness) and arabinoxylan contents (deformation), which determine the textural properties of cooked rice. Leached amylose has been measured, and the particular role of soluble amylose on the surface behaviour (stickiness and adhesiveness) of the cooked grain is discussed.     

Features of the AFFRC model for evaluating the relationship between the water cycle and rice production

This paper introduces the Agriculture, Forestry and Fisheries Research Council of Japan (AFFRC) model, an integrated model that predicts future rice production in the Mekong River basin by taking into account the effect of global warming on both the water cycle and the rice economy. The model focuses especially on the water balance of paddy fields for different farmland water use systems. We defined six categories of irrigated paddies and three categories of rain-fed paddies on the basis of their systems of water usage. We included a process-based model to predict future rice production, accounting for daily changes in available water resources such as precipitation. Many models of crop production treat rice in the same way as other crops; the particular characteristics of rice farming are considered in more detail in our model. Our results show that it is possible to estimate future rice production in the Mekong River basin by taking into account changes in available water, and to model the resultant effects on the grain market.     

寒地水稻产量及构成要素关系研究

通过对影响水稻产量性状的灰色关联度、相关性及逐步回归分析,结果表明:产量构成四要素对产量的贡献依次为穗粒数>穗数/㎡>千粒重>结实率;穗粒数与实际产量之间有正相关性,其它与产量呈较弱的负相关性;产量构成因素与产量的多元逐步回归模型为■:=283.6605+0.4863X1+2.6405X2+0.6511X3+1.4269X4,回归方程中穗粒数偏回归系数最大。因此,在制定水稻高产栽培措施时,应在稳定平方米穗数的基础上,提高穗粒数,是获得高产主要途径之一。栽培上采取的措施是倒4叶后半叶酌情施N肥和倒2叶采用间歇灌溉。     

Acetylation of intact white rice grains to alter the physicochemical properties

The effect of acetylation of milled rice grains of selected varieties (TDK 8, YRW 4, Reiziq, Amber 33, and SHZ 2) with varying apparent amylose contents (3.8–26.6%) on their physicochemical properties was investigated. Milled rice samples were treated with different acetic anhydride concentrations (0.004–0.04 g per 100 g of milled rice samples in 225 mL of water). Results showed that glutinous (TDK 8), very low amylose (YRW 4) and low amylose containing varieties (Reiziq) were prone to acetylation even with 0.004 g of acetic anhydride. X-ray diffraction patterns showed an increase in the crystallinity in acetylated samples and formation of V-type crystals, suggesting the possible interaction of acetic anhydride with starch. Acetylation of rice grains resulted in reduced peak and final viscosities and gel strength, particularly in glutinous (TDK 8) and very low amylose (YRW 4) rice. Differential calorimetric study showed that acetic anhydride treatment resulted in reduced thermal transition temperatures and enthalpy of all varieties. Although increase in the retrogradation thermal temperatures was observed, the enthalpy of retrogradation was reduced with increasing acetylation, suggesting that the extent of starch retrogradation was lower in all varieties with more prominent reduction in the glutinous type. Furthermore, the texture of cooked acetic anhydride treated rice grains was less hard and showed more adhesiveness. This study demonstrated that the acetylation of rice grains (instead of flour) was successfully achieved, showing the potential of applying acetylation to alter the textural, pasting, thermal and retrogradation properties of rice.     

The relationship between architectural characteristics and regrowth in Trifolium pratense (red clover)

The relevance of particular architectural characteristics for a good regrowth has not been elucidated yet in red clover. Here, we present the shoot architecture and regrowth of six red clover genotypes analysed under controlled and field conditions, with and without competition from perennial ryegrass. Among the genotypes investigated, Lemmon and Crossway displayed the highest number of nodes and branches, the highest increase in the number of nodes in the basal 7 cm and the highest outgrowth capacity of the nodes in this zone resulting in the highest dry‐matter yields. Our results indicate that selecting genotypes with a high number of first‐order branches, short internodes and the ability to resume growth from the nodes that remain in the uncut zone will allow the development of cultivars with good regrowth.     

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.     

The effects of puroindoline b on the ultrastructure of endosperm cells and physicochemical properties of transgenic rice plant

Endosperm texture is an important factor governing the end-product quality of cereals. The texture of wheat (Triticum aestivum L.) endosperm is controlled by puroindoline a and b genes which are both absent in rice (Oryza sativa L.). It has been reported that the endosperm texture of rice can be modified by puroindoline genes. The mechanism, however, by which puroindolines affect the ultrastructure of rice endosperm cells remains to be investigated. In this study, we observed the ultrastructure of endosperm cells and the morphology of isolated starch granules of the transgenic rice expressing the puroindoline b gene. SEM and TEM observations indicated that compound starch granules were embedded within the matrix material in non-transgenic rice, Nipponbare, whereas they were surrounded by spaces in the transgenic rice. The morphology and size of each starch granule were not different between non-transgenic and the transgenic rice. However, the transgenic rice flour showed smaller particle size, higher starch damage, and lower viscosity during gelatinization than that of non-transgenic rice. These results confirm that puroindoline b reduces the grain hardness in rice. Moreover, the results also suggest that puroindoline b functions at the surface of compound starch granules, and not on polygonal starch granules in rice endosperm.     

Starch fine structure and physicochemical properties of specialty rice for canning

The long-grain, specialty rice cultivars, Bolivar, Cheniere, Dixiebelle, and L-205 are used for wet-pack canning. These cultivars have similar apparent amylose content but showed differences in canning, pasting, and gelatinization properties. Starch fine structures were analyzed to rationalize observed differences in functionality. Cheniere amylopectin had the lowest weight-average molar mass (M_w), shortest average chain length (CL), smallest z-average radius of gyration (R_z), lowest proportion of long chains (DP 37–65), and highest polydispersity; while its amylose had the largest M_w and R_z. These structural features were associated with more leached solids in the canning broth, lower volume expansion, lower peak and final viscosity, and lower gelatinization temperature and enthalpy. Bolivar amylopectin had the largest M_w, longest average CL, largest R_z, highest proportion of long chains (DP 25–65), and lowest proportion of short chains (DP 6–12); while its amylose had the smallest M_w and lowest polydispersity. These structures were associated with lower levels of leached solids, higher volume expansion, and higher peak and final viscosity. L-205 was similar to Bolivar in most structural and functional properties; those of Dixiebelle were either comparable to Bolivar or intermediate to Bolivar and Cheniere. These findings point to the importance of the molar mass of amylopectin and the proportion of long and short chains on the canning stability of rice.     

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.     

Moisture distribution of soaked rice grains observed by magnetic resonance imaging and physicochemical properties of cooked rice grains

Moisture distribution in individual polished rice grains was observed during soaking by magnetic resonance (MR) imaging, and a nuclear magnetic resonance (NMR) signal intensity profile (SI-profile) was generated from the MR image. The water penetration pattern during soaking roughly showed dissimilar trends between different varieties of japonica and japonica-indica hybrid rice. NMR signal intensity at the completion of water absorption varied within each grain; high at the periphery and the central region and low in the area between the periphery and the central region. High moisture content within the central region is due to loosely packed starch granules. The SI-profile was congruent for grains of the same variety harvested in different regions and years and characterized a grain moisture distribution for each variety. Moisture distribution was compared using SI-profiles for varieties with different amylose contents and new varieties bred for specific end-uses in Japan. The NMR signal intensity, which is related to the moisture content, at the surface of soaked grain was negatively correlated to the grain amylose content. The NMR signal intensities at the surface of soaked grain negatively correlated with the overall hardness of the cooked rice grain as measured by the single-grain low-high compression test.     

Genetic relationship between grain yield and the contents of protein and fat in a recombinant inbred population of rice

To study the genetic relationship between grain yield and the nutrient contents in rice, 209 recombinant inbred lines derived from a cross between indica rice Xieqingzao B and Milyang 46 were used to determine quantitative trait loci (QTLs) affecting the yields and contents of the two major nutritional components in brown rice. Seven traits were analyzed, including brown rice recovery (BRR), protein content (PC), fat content (FC), grain yield (GYD), brown rice yield (BRYD), protein yield (PYD) and fat yield (FYD). The nutrient contents were significantly negatively correlated with BRR, GYD and BRYD, and the variations on nutrient yield were mainly ascribed to GYD. A total of 22 QTLs distributed on 10 regions of eight chromosomes were detected. Two QTL clusters were found on the short arm of chromosome 6 and the long arm of chromosome 10, respectively. The former was responsible for all the seven traits, and the latter for all the traits except BRR and FC. In both regions, the maternal alleles decreased nutrient contents, but they increased the yields of grain, brown rice, protein and fat. Implication of these results for the breeding of rice varieties with enhancing nutritional capacity is discussed.     

自然生态与名茶品第成因关系的调研

为科学论证“高山好水出好茶”这一理念,针对本县名茶发展的新态势,如何合理配置资源,发挥优质资源优势,打造产品区域品牌,这是确保优质、立稳“名牌品牌”的关键。     

Effect of moisture transfer on texture uniformity of cooked rice after heat preservation with electric rice cooker

The texture uniformity of rice cooked by electric rice cooker (ERC) will deteriorate during the heat preservation process. In this study, the uniformity of rice texture and water dynamic were investigated by means of physical property analyzer and low-field nuclear magnetic resonance technique. The water content, distribution and migration in rice were compared to illustrate the effect of heat preservation mode with different temperature at pot cover. The middle-upper layer of rice was drier and harder after 24 h of heat preservation in conventional mode, while the outer-upper layer of rice absorbed water, swelled or even broken. The difference of water content between the two parts was 6.55%, and the difference of hardness was 333.31 g. The relaxation signal indicated that the binding force between immobile water of the two parts and the rice matrix became weaker after heat preservation. By adjusting the heat preservation mode with higher temperature of the cover, the moisture content difference between the internal-upper layer and the peripheral upper layer was decreased to 0.39% after 24 h of heat preservation, and the hardness difference was reduced to 2.99 g. These mean that the texture uniformity of the whole pot rice after heat preservation was maintained.     

世界稻米的饮食特色

水稻是世界主要粮食作物之一，全世界半数以上的人口以稻米为传统主食。但世界各国人民对稻米消费的喜爱迥然不同，这通常与各国的文化、经济背景和传统的生活模式密切相关。亚洲、非洲以稻米为主食，每年人均消费100kg，而不以稻米为主食的欧洲国家每年人均消费只有6～8k。拉丁美洲大部分国家以玉米为主食，但苏里南、圭亚那等国家与亚     

野生稻的优异特性及其在水稻育种中的利用

本文综述了野生稻的的抗病虫性、抗逆性、优良的稻米品质、细胞质雄性不育性和强大的生长优势等优异性状及其近年来在水稻育种中的最新利用；通过辐射诱变和生物技术方法对野生稻资源进行创新利用。