RELIABILITY OF THE FOCUS GROUP TECHNIQUE IN DETERMINING THE QUALITY CHARACTERISTICS OF MUNGBEAN [VIGNA RADIATA (L.) WILCZEC] NOODLES

Two commercial samples were evaluated in five focus group sessions to determine the reliability of the focus group technique in identifying the desirable and important sensory characteristics of dry and cooked mungbean noodles and to determine its quality characteristics. Each focus group consistently identified a similar list of desirable and undesirable characteristics. These results indicated that the focus group technique was a reliable method for determining consumer criteria for quality for mungbean noodles. When there is a need to determine consumers' definition of product quality at a stage when consumer testing is not desired, the focus group technique can be used as a valuable tool. Mungbean noodle quality was found to have two distinct aspects: appearance of the dry noodles and eating quality of the cooked noodles. Color, glossiness, and transparency are the most important characteristics of dry starch noodles while mouthfeel or texture is considered the most important characteristic of cooked starch noodles. Color, taste, and odor of the cooked noodles were considered not as important.     

Confocal laser scanning microscopy of dextran-rice starch mixtures

The microstructure of rice starch and dextran-rice starch mixtures was studied using confocal laser scanning microscopy (CSLM) and scanning electron microscopy (SEM). Surface pores and channels of rice starch were looked for. Channels could not be found in rice starch granules after reaction with 3-(4-carboxybenzoyl)-quinoline-2-carboxaldehyde (CBQCA). Fluorescein-labeled dextran was mixed with rice starch in order to locate hydrocolloid molecules in hydrocolloid-rice starch mixtures. The results showed that FITC-dextran (ave. Mw 4000; FD4) penetrated into raw rice starch granules, with the degree of penetration varying from granule to granule. FD4 could penetrate throughout cooked rice starch granules. FITC-dextran with an average Mw of more than 10,000 could not penetrate either raw or cooked rice starch granules.     

Changes in color and texture of wheat noodles during chilled storage

Wheat noodles cooked for different periods of time were stored at 5 °C, and color changes in their cross sections were quantitatively assessed by digital image analysis. The color of noodles with flattened moisture distributions whitened greatly during the early stages of chilled storage due to the retrogradation of starch, with the color change showing a significant correlation with the changes in noodle fragility. Color changes were also measured for wheat noodles and noodles containing modified starch with internal moisture distributions, and local changes within the noodles were kinetically analyzed. The addition of modified starch significantly reduced the color change in the noodle interior, where the moisture content was relatively low. Scanning calorimetric measurements indicated differences in the gelatinized state of modified starch and original wheat starch at low moisture contents, which affected the rate of color change in the interior of noodles containing modified starch.     

Some Physico-Chemical Properties of Non-Waxy Paddy Rice Starch in Niigata Prefecture

Fifteen samples of milled rice had protein contents ranging from 5.53 to 7.83% and amylose contents ranging from 17.6 to 22.1%. Eating and cooking qualities of cooked rice gave gross palatability indicies ranging from 100 to 61, cohesiveness values by balance method from 64 to 9, and starch-iodine color test values of milled rice from 0.297 to 0.574. Pasting characteristics of a 8% suspension of rice starch gave maximum viscosity values ranging from 550 to 380 Brabender Unit (B.U.), temperature at maximum viscosity from 82° to 92.5°C, break down values from 260 to 20B.U., and set back values from ?0.5 to 60B.U. Good correlations were found between cooking and eating qualities of rice and rheological property of starch, and between rheological property and amylose content of starch, respectively.     

Preparation of clear noodles with mixtures of tapioca and high-amylose starches

Ways to simulate the making of clear noodles from mung bran starch were investigated by studying the molecular structures of mung bean and tapioca starches. Scanning electron micrographs showed that tapioca starch granules were smaller than those of mung bean starch. X-ray diffraction patterns of mung bean and tapioca starch were A- and C_A-patterns, respectively. Iodine affinity studies indicated that mung bean starch contained 37% of apparent amylose and tapioca starch contained 24%. Gel permeation chromatograms showed that mung bean amylopectin had longer peak chain-length of long-branch chains (DP 40) than that of tapioca starch (DP 35) but shorter peak chain-length of short-branch chains (DP 16) than that of tapioca starch (DP 21). P-31 n.m.r. spectroscopy showed that both starches contained phosphate monoesters, but only mung bean starch contained phospholipids. Physical properties, including pasting viscosity, gel strength, and thermal properties (gelatinization), were determined. The results of the molecular structure study and physical properties were used to develop acceptable products using mixtures of cross-linked tapioca and high-amylose maize starches. Tapioca starch was cross-linked by sodium trimetaphosphate (STMP) with various reaction times, pH values, and temperatures. The correlation between those parameters and the pasting viscosity were studied using a visco/amylograph. Starches, cross-linked with 0.1% STMP, pH 11.0, 3.5 h reaction time at 25, 35, and 45°C (reaction temperature), were used for making noodles. High-amylose maize starch (70% amylose) was mixed at varying ratios (9, 13, 17, 28, 37, and 44%) with the cross-linked tapioca starches. Analysis of the noodles included: tensile strength, water absorption, and soluble loss. Noodle sensory properties were evaluated using trained panelists. Noodles made from a mixture of cross-linked tapioca starch and 17% of a high-amylose starch were comparable to the clear noodles made from mung bean starch.     

Effect of the Change During Storage in Lipid Composition of Rice on its Amylogram

There are many reports on the deterioration during storage of rice flavor, but no work has yet been done to relate the change during storage in rheological properties with the change in lipid composition. The present study revealed that the increase in amounts of free fatty acids during rice storage resulted in the increase in maximum viscosity of amylogram, i.e., deterioration in rheological property of cooked rice. The mechanism is explained by the formation of helical structure of starch molecule with fatty acid.     

Effects of Shading on Starch Pasting Characteristics of Indica Hybrid Rice (Oryza sativa L.)

Rice is an important staple crop throughout the world, but environmental stress like low-light conditions can negatively impact crop yield and quality. Using pot experiments and field experiments, we studied the effects of shading on starch pasting viscosity and starch content with six rice varieties for three years, using the Rapid Visco Analyser to measure starch pasting viscosity. Shading at different growth stages and in different rice varieties all affected the starch pasting characteristics of rice. The effects of shading on starch pasting viscosity at middle and later growth stages were greater than those at earlier stages. Shading enhanced breakdown but reduced hold viscosity and setback at tillering-elongation stage. Most pasting parameters changed significantly with shading after elongation stage. Furthermore, the responses of different varieties to shading differed markedly. The change scope of starch pasting viscosity in Dexiang 4103 was rather small after heading, while that in IIyou 498 and Gangyou 906 was small before heading. We observed clear tendencies in peak viscosity, breakdown, and pasting temperature of the five rice varieties with shading in 2010 and 2011. Correlation analysis indicated that the rice amylose content was negatively correlated with breakdown, but was positively correlated with setback. Based on our results, IIyou 498, Gangyou 906, and Dexiang 4103 had higher shade endurance, making these varieties most suitable for high-quality rice cultivation in low-light regions.     

Enzymatic Improvement of the Cooking Quality of Aged Rice: A Main Mode of Protease Action

This study aims to improve the stickiness and brightness of cooked rice from aged rice grains by removing its albumins and globulins with proteases. In newly–harvested grains, the proteins were easily removed by extraction with water which contained minerals from rice. In aged grains, however, the proteins were already denatured and extracted with difficulty. Proteases hydrolyzed even the denatured proteins to make them extractable. As a result, starch granules on the surface of grains were liberated. Some proteases also hydrolyzed a starch granule-associated protein, and consequently, made the starch highly gelatinizable by heating. The protease treatment of aged grains was effective for two main reasons: liberation of starch granules and removal of the granule-associated protein. During cooking of rice the liberated starch without the associated proteins gelatinized to give rise to stickiness. The gelatinized starch is considered to form a more isotropic film on the surface of every cooked rice grain to give brightness as well.     

Permanent Staining with Iodine Vapor

Sections of cooked rice have been stained with iodine vapor, and the method has given greater permanency than any heretofore reported. The method, which permits the use of a counter-stain, has been applied also to starches, starch pastes, uncooked rice flour, and cooked rice flour. The resulting color is of moderate intensity, so that structure is revealed and the birefringence of ungelatinized starch is not impaired. Preparations made more than a year ago have retained their characteristic blue or lavender color.     

Alkaliviscogram and Other Properties of Starch of Tropical Rice

In the alkaliviscogram of starch of 26 nonwaxy rices grown in the tropics, gelatinization normality correlated positively with final gelatinization temperature (BEPT) of starch (r=0.969^**) and negatively with alkali spreading value of milled rice (r= ?0.931^**). Peak viscosity was not linearly related to amylose content. Among samples of rice starch having a high amylose (>28%) content, peak viscosity was correlated with the gel consistency of starch (r=?0.690^**) and of milled rice (r=?0.644^**) (n = 18). These high-amylose starches showed the widest variation in peak viscosity. Amylose content, and gel consistency were inherited from the same parent in all nine varieties and lines studied, whereas peak viscosity, gelatinization normality and the final BEPT were inherited from either parent. The starch of five waxy rices showed higher peak viscosities even at a concentration of 1.8% as compared with a 2.0% nonwaxy rice starch.     

Molecular characterisation of soybean polysaccharides: an approach by size exclusion chromatography, dynamic and static light scattering methods

Water soluble polysaccharides from soybean (SSPS) have a pectin-like structure and are used as stabilisers in acidified beverages. Physicochemical properties such as structure, molecular weight and shape or conformation are primary factors controlling their functional properties. Two soybean polysaccharides, a native SSPS and a modified SSPS treated with beta-(1-->4)-D-galactosidase (GPase/SSPS) were studied by dynamic and static light scattering (DLS, SLS) and size exclusion chromatography (SEC). Consecutive filtrations using a range of membrane pore size removed a small fraction of macromolecular aggregates from dilute polysaccharide solutions with relatively little effect on the major component molecules as monitored by DLS and SEC measurements. Access to aggregate-free dilute solutions of SSPS and GPase/SSPS allowed the direct measurement of molecular characteristics. SLS results showed that SSPS had a weight average molecular weight of (645+/-11)x 10(3)g/mol and a radius of gyration, Rg, of (23.5+/-2.8)nm. By comparing R(g) with the hydrodynamic radius, Rh (21.1+/-0.5 nm) obtained from DLS, the structural parameter rho (Rg/Rh) was found to be 1.1, suggesting that SSPS has an overall globular shape due to a highly branched structure. The modified SSPS had a significantly lower molecular weight (287+/-18)x 10(3)g/mol but a similar radius of gyration (23.2+/-1.7 nm). The structure parameter rho of GPase/SSPS was higher (rho=1.3) because of a smaller hydrodynamic radius (17.7+/-1.8 nm). This suggests that GPase/SSPS has a much less branched structure yet still differs significantly from a linear random coil conformation (rho=1.7-2.0). The results derived from SLS and DLS are in agreement with the conclusions obtained from a chemical analysis where the reduction of molecular weight of GPase/SSPS was caused by the cleavage of galactan side chains.     

籼米淀粉粘滞性的基因型与环境互作研究

水稻精米中大约含有90%的淀粉,因此淀粉的特性对水稻的食味品质有很大的影响.淀粉粘滞性是预测稻米食用、蒸煮和加工品质的重要指标.本研究利用4个细胞质雄性不育系和8个恢复系配置的不完全双列杂交组合来分析淀粉粘滞性指标(崩解值、回复值和消减值)的胚乳、细胞质和母体基因效应及环境互作效应.结果表明在崩解值、回复值和消减值的遗传变异中,遗传主效应方差分量占了64%以上,表明它们主要受遗传主效应控制,同时也受到基因型与环境互作效应的影响.崩解值、回复值和消减值的总遗传率分别为67.8%、79.5%、79.5%,而且普通遗传率占了总遗传率的75%以上,表明对这些性状的早世代选择有效,且在不同环境中选择效果相对稳定.     

Measurement of resistant starch content in cooked rice and analysis of gelatinization and retrogradation characteristics

Digestion-resistant starch (RS) has many physiologic functions. The RS content is measured by enzymatically degrading flour samples according to the method of the Association of Official Analytical Chemists. Experiments have been performed with wheat, corn, and other grains, but there are no data for cooked rice grains in the form ingested by humans. Thus, we investigated a method to measure RS that is suitable for cooked rice grains using rice cultivars that are reported to differentially increase postprandial blood glucose in humans. Using a method for cooking individual rice grains and optimized enzyme reaction conditions, we established an RS measurement method. We also found that the amylopectin crystal condition affects the RS content measured using our method.     

Endosperm enzyme activity is responsible for texture and eating quality of cooked rice grains in Japanese cultivars

Eating quality of cooked rice grains is an important determinant of its market price and consumer acceptance. To comprehensively assess the variation of eating-quality traits in 152 Japanese rice cultivars, we evaluated activities of eight endosperm enzymes related to degradation of starch and cell-wall polysaccharides. Endosperm enzyme activities showed a wide range of variations and were lower in recently developed cultivars than in landraces and old improved cultivars. Activities of most endosperm enzymes correlated significantly with the eating-quality score and surface texture of cooked rice grains. Principal component analysis revealed that rice cultivars with high eating-quality scores had high stickiness of the grain surface and low levels of endosperm enzyme activities. These results suggest that endosperm enzyme activities control texture and eating quality of cooked rice grains in Japanese rice cultivars.     

Association of waxy gene single nucleotide polymorphisms with starch characteristics in rice (Oryza sativa L.)

The waxy gene, which encodes the granule bound starch synthase enzyme, is one of the key genes influencing starch synthesis in the rice endosperm. To investigate functional differences between GBSS alleles, we cloned and sequenced GBSS cDNA from a series of cultivars that differed substantially in apparent amylose content and starch viscosity characteristics. We found two single nucleotide polymorphisms in exons 6 and 10 that resulted in amino acid substitutions. These substitutions are associated with differences in apparent amylose content and viscosity characteristics. Subsequent sequencing of these regions from additional cultivars confirmed their association with particular rice quality characteristics. These point mutations could prove useful as molecular markers in the production of cultivars with superior eating, cooking and processing quality, and contribute to our understanding of the various structural and functional differences among granule bound starch synthase alleles.     

籼型杂交稻淀粉RVA谱特征值的杂种优势分析

以6个籼型三系不育系和5个籼型恢复系按不完全双列杂交设计配制的30个杂交稻组合及其亲本为材料,对其籽粒淀粉RVA谱各特征值进行了测定和分析。结果表明：（1）亲本间和杂交稻组合间的淀粉RVA谱各特征值均存在极显著的差异,其中变异最大的是消减值,最小的是糊化开始温度。（2）杂交稻组合淀粉RVA谱各特征值的变异系数均小于杂交稻亲本的变异系数;峰值粘度、崩解值、最低粘度和最终粘度的平均值杂交稻组合大于亲本,其他性状的平均值杂交稻组合小于亲本。（3）峰值粘度存在极显著的正向超亲优势;崩解值、最低粘度、最终粘度和回复值存在极显著的正向中亲优势;消减值和峰值时间存在极显著的负向中亲优势和正向低亲优势;糊化开始温度存在极显著的负向低亲优势;最终粘度、回复值和糊化开始温度表现为极显著的负向竞争优势,其他性状表现为正向竞争优势。（4）峰值粘度、崩解值、消减值和回复值等4个性状,各杂交稻组合与其母本、中亲值呈现极显著正相关,峰值时间与中亲值呈显著正相关。而与其父本的相关均未达显著水平。     

结实期相对高温对稻米淀粉粘滞性谱及镁、钾含量的影响

选用武育粳3号(粳稻)和扬稻6号(籼稻)两个水稻品种,利用人工气候室在水稻灌浆结实期进行控温试验,设置全结实期相对高温、结实前期相对高温、结实后期相对高温、全结实期适温(对照,日均温23 ℃)对照4个处理,探讨结实期不同时段相对高温(日均温度-30 ℃)对稻米淀粉粘滞性谱和Mg、K等元素含量的影响.结果表明：结实期相对高温使武育粳3号和扬稻6号淀粉粘滞性谱特征值发生改变,其中糊化开始温度、冷胶粘度、回复值和消减值升高,最高粘度、热浆粘度和崩解值下降;结实期相对高温促进了米粉中Mg、K、N含量的提高,特别是K含量的大幅提高,使稻米中Mg/K和Mg/(N·AC·K)明显降低;而2个水稻品种的直链淀粉含量（AC）对相对高温的反应截然相反,武育粳3号的AC降低、扬稻6号的AC升高.全结实期相对高温对稻米淀粉粘滞性谱和Mg、K等元素含量的影响最大,结实前期其次,结实后期的影响较小,开花后20 d内是稻米淀粉粘滞性谱和Mg、K等元素含量受温度影响的关键时期.Mg/K和Mg/(N·AC·K)与淀粉粘滞性谱特征值显著相关,可以作为稻米食味品质评价的参考指标.     

MutMapPlus identified novel mutant alleles of a rice starch branching enzyme IIb gene for fine‐tuning of cooked rice texture

Physicochemical properties of storage starch largely determine rice grain quality and food characteristics. Therefore, modification of starch property is effective to fine‐tune cooked rice textures. To obtain new resources with modified starch property as breeding materials, we screened a mutant population of a japonica cultivar Nipponbare and found two independent mutant lines, altered gelatinization (age)1 and age2, with moderate changes in starch gelatinization property. A combination of conventional genetic analyses and the latest mapping method, MutMapPlus, revealed that both of these lines harbour novel independent mutant alleles of starch branching enzyme IIb (BEIIb) gene. In age1, amino acid substitution of Met‐723 to Lys completely abolished BEIIb enzyme activity without significant reduction in its protein level. A transposon insertion in an intron of BEIIb gene reduced BEIIb protein level and activity in age2. Production of a series of the mutant lines by combining age alleles and indica‐type starch synthase IIa allele established stepwise alteration of the physicochemical properties of starch including apparent amylose content, thermal property, digestibility by α‐amylase and branched structures of amylopectin. Consistent with the alteration of starch properties, the results of a sensory evaluation test demonstrated that warm cooked rice of the mutants showed a variety of textures without marked reduction in overall palatability. These results suggest that a series of the mutant lines are capable of manipulation of cooked rice textures.     

Studies on the Cereal Starches

Significant correlations among amylograph characteristics or other relating properties of rice starch and flour were recognized by orderly rearrangement of previously obtained data. Linear regression of peak viscosity on breakdown was available for detecting a deteriorative damage of rice starch and grain. Alpha-amylase in white rice did not have close relation with peak viscosity of the flour. The ratio of breakdown to consistency and the corrected peak viscosity calculating the coincidence of the slurry concentration were significantly correlated with the starch iodine blue value and rigidity of the cold paste body respectively.     

Effect of gamma-ray irradiation on alcohol production from corn

Cracked corn was irradiated with gamma rays at 0-100 Mrad and the effects of the irradiation on sugar yield, susceptibility to enzymatic hydrolysis of starch, yeast growth, and alcohol production were studied. Gamma irradiation at 50 Mrad or greater produced a considerable amount of reducing sugar but little glucose. At lower dosages, gamma irradiation significantly increased the susceptibility of corn starch to enzymatic hydrolysis, but dosages of 50 Mrad or greater decomposed the starch molecules as indicated by the reduction in iodine uptake. About 12.5% reducing sugar was produced by amylase treatment of uncooked, irradiated corn. This amount exceeded the level of sugar produced from cooked (gelatinized) corn by the same enzyme treatment. The yeast numbers in submerged cultivation were lower on a corn substrate that was irradiated at 50 Mrad or greater compared to that on an unirradiated control. About the same level of alcohol was produced on uncooked, irradiated (10(5)-10(6) rad) corn as from cooked (121 degrees C for 30 min) corn. Therefore, the conventional cooking process for gelatinization of starch prior to its saccharification can be eliminated by irradiation. Irradiation also eliminated the necessity of sterilization of the medium and reduced the viscosity of high levels of substrate in the fermentation broth.