Fundamental study on protein changes taking place during malting of oats

During the malting process, storage proteins are degraded by proteolytic enzymes into small peptides and amino acids. The activity of these enzymes was measured during malting of oats and was found to be increased. To quantify proteolytic degradation, proteins of unmalted, germinating and malted grains were fractionated. After extracting the oat proteins (Osborne fractionation), protein fractions were analysed using a Lab-on-a-Chip technique, which separates the proteins – based on their molecular weight – by capillary electrophoresis. This new technique for the analysis of proteins was supported by using two-dimensional gel electrophoresis. In addition, amino acid analysis was carried out. In general a degradation of proteins to small peptides and amino acids could be observed in the globulin, prolamin and glutelin fractions. In the albumin fraction a protein increase was observed, which is due to the fact that this fraction contains the majority of the metabolically active proteins. Amino acid analysis supported the observation of increased protein amount in the albumin fraction and decreased protein amounts in the other fractions. Some proteins, which have not been described in the literature, were detected in the albumin and glutelin fraction, since Lab-on-a-Chip technique allows detection of proteins with low molecular weights of 4.5 kDa.     

Volatile metabolite profiling of malt contaminated by Fusarium poae during malting

A volatile metabolite-profiling approach based on solid-phase microextraction (SPME) combined with gas chromatography–mass spectrometry was used to investigate volatile metabolic changes over the course of a malting process contaminated by Fusarium poae to assess its influence on malt flavor. GC–MS analysis of time-serial samples revealed a broad spectrum of volatile compounds including aldehydes, ketones, alcohols, organic acids, aromatics and furans. Statistical assessment of the data via principal component analysis demonstrated that at the initial phase of germination, the influence of F. poae was relatively small. However, its influence increased over time, resulting in differences between contaminated and controlled samples at 120 h and 144 h. Analysis of the corresponding loadings showed that volatile metabolites from green malt were influenced by contamination with F. poae fungi during malting to an extent, especially for the volatile aldehyde fractions. These compounds can be formed during both primary and secondary metabolism, and the potential exists for metabolic perturbation resulting from F. poae.     

Physicochemical characterization and in-vitro digestibility of extruded rice noodles with different amylose contents based on rheological approaches

The physicochemical properties and in-vitro digestibility of extruded rice noodles with different amylose contents were characterized from a rheological point of view. Thermo-mechanical measurements showed that the rice flour with higher amylose contents exhibited greater stability to dual-mixing and higher degrees of starch gelatinization and retrogradation. In addition, greater elastic properties were clearly observed in the high amylose rice samples. The use of high amylose rice flour produced noodles with a harder texture, consequently contributing to reduced cooking loss. Furthermore, the rheological changes of extruded rice noodles were monitored in real time during the in-vitro starch digestion. The rice noodle digesta with higher amylose contents exhibited greater viscosities throughout the simulated oral-gastric-intestinal digestion steps. The flow behaviors of the rice noodle digesta consisted of the Power-law region and infinite shear plateau that were satisfactorily characterized by the Sisko model (R² > 0.99).     

高直链淀粉小麦西农836淀粉理化性质及消化特性分析

淀粉是人体摄入碳水化合物的主要来源,经消化后以葡萄糖的形式被人体吸收,其消化特性与人体健康密切相关。为探究小麦品种西农836淀粉理化性质与消化特性的关系,以商品粉金沙河、香雪、金龙鱼作为对照,测定其与西农836中直链淀粉含量、淀粉粒度和结晶度、糊化特性以及体外消化率的差异,并在小鼠体内模拟消化。结果表明,与金龙鱼、金沙河、香雪相比,西农836淀粉中直链淀粉含量和B型淀粉粒含量最高,与前3者差异显著（P<0.05）;西农836淀粉的峰值温度最高,峰值黏度和最终黏度最低;淀粉体外消化试验结果显示,西农836的快消化淀粉（RDS）、总消化淀粉（RDS+SDS）含量最低,抗性淀粉（RS）含量最高。小鼠体内消化试验结果表明,与金沙河相比,灌食西农836淀粉的小鼠血糖峰值较低,说明高直链淀粉小麦西农836有利于延缓消化和控制血糖升高。相关性分析结果显示,直链淀粉含量与抗性淀粉含量呈显著正相关（P<0.05）。     

Rheology and texture of starch gels containing iodine

The objective of this study was to investigate the textural and rheological properties of starch gels containing different levels of iodine. The research goal is to understand the architectural organization of granules by utilizing iodine as a marker. Corn (CS), wheat (WS), potato (PS) and tapioca (TS) starch gels containing varying concentrations of iodine were prepared in a Rapid Visco Analyser (RVA). The gels were analysed by using a rheometer for small-deformation properties and also by using a texture analyser for large deformation properties following storage for 1 or 7 days. With increasing concentration of iodine, the firmness of gels decreased and the extent of decrease varied for the different starches. The extent of change in complex modulus (G*) of the gels was highest in the A-type starch, CS, but was different from WS, which is also an A-type starch. The G* for PS gels (B-type) decreased with the addition of 0.1% iodine but there was no significant difference upon increasing the iodine concentration. The G* for the C-type TS gels was lower than 15 Pa. These observations suggest a difference in the microstructure of the starch gels formed, likely resulting from differential leaching of polymers.     

不同直链淀粉含量小麦淀粉理化性质与消化特性研究

为深入理解小麦直链淀粉含量与淀粉理化性质及消化特性之间的关系,以4份直链淀粉含量差异较大的小麦品种为材料,分析了其淀粉理化性质以及消化特性方面的差异。结果表明,随着直链淀粉含量的增加,回生值呈增加趋势;在体外消化前期,4个小麦品种的淀粉消化速率差异显著,西农836最慢,陕糯1号最快。这种差异与直链淀粉含量及回生值密切相关,说明直链淀粉比支链淀粉更易于回生,糊化后的冷却过程中更容易发生分子间部分重排和再结晶,重新组装成有序的聚集体,导致供试材料之间快速消化淀粉含量及总体消化程度不同。直链淀粉含量高的品种具有更多的B型小淀粉粒,但是大量B型小淀粉粒的存在并没有导致淀粉消化速率以及淀粉总体消化程度的提高,说明淀粉充分糊化后,粒度的差异并不改变淀粉消化特性。     

Crystallinity changes in wheat starch during the bread-making process: Starch crystallinity in the bread crust

The crystallinity of starch in crispy bread crust was quantified using several different techniques. Confocal scanning laser microscopy (CSLM) demonstrated the presence of granular starch in the crust and remnants of granules when moving towards the crumb. Differential scanning calorimetry (DSC) showed an endothermic transition at 70 °C associated with the melting of crystalline amylopectin. The relative starch crystallinity, as determined by X-ray and DSC, from different types of breads was found to lie between 36% and 41% (X-ray) and between 32% and 43% (DSC) for fresh bread crust. Storage of breads in a closed box (22 °C) for up to 20 days showed an increase in crust crystallinity due to amylopectin retrogradation both by X-ray and DSC. However, DSC thermograms of 1-day old bread crust showed no amylopectin retrogradation and after 2 days storage, amylopectin retrogradation in the crust was hardly detectable. ¹³C CP MAS NMR was used to characterize the physical state of starch in flour and bread crumb and crust. The intensity of the peaks showed a dependence on the degree of starch gelatinization.     

Kinetics of starch digestion and functional properties of twin-screw extruded sorghum

The time-course of starch digestion in twin-screw extruded milled sorghum grain was investigated using an in-vitro procedure based on glucometry. The sorghum grains were hammer-milled, and extruded at three levels each of moisture and screw speed. Irrespective of the extrusion conditions, extruded and non-extruded milled sorghum grain exhibited monophasic digestograms, and the modified first-order kinetic and Peleg models adequately described the digestograms. Extrusion increased the rate of digestion by about ten times compared with non-extrudates. Starch gelatinisation varied in the extrudates, and microscopy revealed a mixture of raw, gelatinised and destructured starch and protein components in the extrudates. Starch digestion parameters significantly (p < 0.05) correlated with extruder response and various functional properties of the extrudates. Extrusion conditions for maximum starch gelatinisation in milled sorghum grain for fastest digestion as an efficient animal feed were interpolated, as well as the conditions for directly-expanded extrudates with potential for human food, where minimum starch digestion is desired.     

Water stress during grain development affects starch synthesis,composition and physicochemical properties in triticale

Triticale, a man-made cereal crop developed from a cross between wheat and rye, has excellent agronomic traits to produce starch for bioindustrial applications. The effects of different levels of water stress on expression of starch synthesis genes and starch composition and physicochemical properties were investigated in this study. Three triticale varieties from 5 days post-anthesis were treated with three levels of water stress: low water stress (LWS) at 55–60% of soil moisture, moderate water stress (MWS) at 30–35% soil moisture and severe water stress (SWS) at 10–15% soil moisture. Water stress led to a significant reduction in seed weight at SWS (35–45%). A decrease in starch content was noticeable from MWS onwards and the values were decreased by 42–55% at SWS across all varieties. Such decrease was associated with the reduced expression of starch synthesis genes at 19 days of water stress (DWS). MWS favoured an increase of amylose proportion in triticale starch and it was accompanied by a significant up-regulation of GBSSI expression throughout the grain development. Triticale starch synthesized under water stress showed a reduced population of small granules and an increase of A-type to B-type ratio. SWS caused pitting on starch granules but did not alter the biconcave disc shape of mature granules. An inverse relationship between water stress and a range of starch gelatinization temperature was observed and the MWS environment specifically decreased the peak temperature (Tp) and increased the enthalpy. Our results signify that starch morphology, composition and physicochemical properties in triticale grains could be altered if triticale is grown under drought conditions.     

Effects of two novel Wx-A1 alleles of common wheat (Triticum aestivum L.) on amylose and starch properties

Common wheat (Triticum aestivum L.) has three Wx proteins (Wx-A1, Wx-B1, and Wx-D1), which are granule-bound starch synthases I and are responsible for the amylose synthesis of flour starch. The effects of two novel Wx-A1 proteins identified by gel electrophoresis on amylose content and starch properties were analyzed. The variant Wx-A1 protein coded by the Wx-A1i allele was present in smaller amounts and produced less amylose (7.3%) compared to standard lines with the Wx-A1a allele (21.5%). Wx-A1i generated altered starch properties; greater swelling power (SP), glucoamylase digestibility, starch paste clarity, and gelatinization enthalpy in differential scanning calorimetry. The starch from Wx-A1i also showed an altered pasting profile on a Rapid Visco-Analyzer, greater peak viscosity, smaller final viscosity, and lower pasting temperature. The Wx-A1i allele is a novel genetic resource for reducing amylose content in wheat. The other Wx-A1 protein coded by the Wx-A1j allele showed a more basic isoelectric point compared to Wx-A1a on an electrophoretic gel. The amylose content of Wx-A1j did not differ from standard Wx-A1a. Starch SP, paste clarity, and glucoamylase digestibility also suggested that Wx-A1j produced amylose as much as Wx-A1a.     

Effect of a gibberellin-biosynthesis inhibitor treatment on the physicochemical properties of sorghum starch

Inhibition of plant growth by Trinexapac-ethyl, TE, a gibberellin-biosynthesis inhibitor, can produce a shorter stemmed plant, requiring less nutrients and water to grow, while maintaining grain yield. Although TE and other plant growth regulators are commonly used in grain crops, their effects on starch biosynthesis in the grains have not been systematically examined. The changes in the structural and functional properties of starch in grains harvested from TE-treated sorghum (Sorghum bicolor (L.) Moench) were examined, and the results compared with those from the untreated controls. TE treatment had little or no effects on the molecular structures of starch, starch granule morphology, and starch and amylose contents, but increased the protein content of the grains significantly. Consistent with the lack of change in the molecular structure, there were no significant effects on the thermal properties of the starch. The pasting properties of TE-treated sorghum flours, however, showed lower peak viscosity, trough, and final viscosity, which were attributed to their higher protein contents. The TE treatment thus does not have an appreciable effect on the biosynthesis of starch during grain development in sorghum.     

Interaction of granular maize starch with lysophosphatidylcholine evaluated by calorimetry, mechanical and microscopy analysis

In this study we evaluated the thermo-mechanical properties of maize starch pastes (80% wt/wt) under the effect of exogenous lysophosphatidylcholine (LPC) using differential scanning calorimetry (DSC), dynamic mechanical spectrometry (DMS), and scanning electron microscopy (SEM). Particular attention was paid to the development of the amylose-LPC inclusion complex. Results from SEM and DSC showed that with no exogenous LPC, granular maize starch developed the amylose network structure for starch gelling at 80–95 °C. In comparison, at 1.86 and 3.35% of LPC, heating up to 130 °C was needed to develop the three-dimensional network required for starch gelling. Results showed that at these LPC concentrations LPC interacted mainly with amylose within the starch granule. At concentrations ≥8.26% the LPC interacted with amylose both inside the granule and on the granule's surface. At such LPC concentrations heating to 130 °C did not fully develop the starch network structure for gelling. These results suggested that a higher thermal stability was achieved by starch granules because of LPC inclusion complex formation. DSC or DMS did not detect the development of this complex, probably because its formation took place below the onset of gelatinization under conditions of limited molecular mobility. Subsequently, a lower level of organization (i.e. complex in form I) was achieved than in the complex developed at high temperature and water excess (i.e. complex in form II). On the other hand, the changes in the starch granule structure observed by SEM as a function of the time–temperature variable were well described by the phase shift angle (δ) rheograms for starch pastes with and without addition of LPC.     

Small-scale mashing procedure for predicting ethanol yield of sorghum grain

A small-scale mashing (SSM) procedure requiring only 300 mg of samples was investigated as a possible method of predicting ethanol yield of sorghum grain. The initial SSM procedure, which was conducted similarly to the mashing step in a traditional fermentation test, hydrolyzed just 38.5–47.2% of total sorghum starch to glucose. The initial procedure was simplified to contain only one liquefaction step, which did not influence subsequent saccharification. Thereafter, parameters such as temperature, pH, enzyme dosage, and saccharification time were optimized. Results showed that 91.2–97.5% of the total starch in 18 sorghum hybrids had been hydrolyzed to glucose using the following conditions: liquefaction at 86 °C for 90 min, 20 μL of α-amylase per 30 g of sample; pH adjustment by adding 50 μL of 2 M acetate buffer at pH 4.2 to each microtube; saccharification at 68 °C for 90 min, 200 μL of amyloglucosidase per 30 g of sample. There were strong linear correlations between completely hydrolyzed starch (CHS) from SSM and ethanol yields from both traditional (R² = 0.86) and simultaneous saccharification and fermentation (SSF, R² = 0.93) procedures. CHS was a better indicator for predicting ethanol yield in fermentation than total starch.     

Niacin status of humans as affected by eating decorticated and whole-ground sorghum (Sorghum Gramineae) grain,ready-to-eat breakfast cereals

Niacin utilization to humans from whole grain ground sorghum flour and decorticated grain ground sorghum flour was studied. During two, randomly-arranged experimental periods of 14 days each, the 10 healthy adult subjects ate constant, laboratory controlled diets which included 28 g per day of either a ready-to-eat cereal prepared from whole-ground-sorghum flour or one prepared from decorticated (polished) sorghum flour. All subjects received both experimental treatments, made complete collections of urine and stools, and gave fasting blood samples at the ends of both experimental periods. Although the whole ground cereal contained higher amounts of niacin than did the decorticated cereal, urinary losses of N-methylnicotinamine were higher when the decorticated cereal was fed than when the whole ground cereal was used. Blood serum levels of nicotinamide and N-nicotinamide were higher when the whole ground cereal was fed than the feeding of the decorticated cereal was given. Therefore, it appears that the niacin of whole ground sorghum is absorbed but then the need for niacin is either increased or its urinary excretion is inhibited.Published as University of Nebraska Division of Agriculture Research Journal Series No. 9494. Supported by Nebraska Agriculture Research Division Project 91-031 and U.S.D.A. C.S.R.S. Regional Research Project No. W-143.     

Barley genotype expressing “stay-green”-like characteristics maintains starch quality of the grain during water stress condition

The identification of “stay-green” in sorghum and its positive correlation with yield increases has encouraged attempts to incorporate “stay-green”-like traits into the genomes of other commercially important cereal crops. However, knowledge on the effects of “stay-green” expression on grain quality under extreme physiological stress is limited. This study examines impacts of “stay-green”-like expression on starch biosynthesis in barley (Hordeum vulgare L.) grain under mild, severe, and acute water stress conditions induced at anthesis. The proportions of long amylopectin branches and amylose branches in the grain of Flagship (a cultivar without “stay-green”-like characteristics) were higher at low water stress, suggesting that water stress affects starch biosynthesis in grain, probably due to early termination of grain fill. The changes in long branches can affect starch properties, such as the rates of enzymatic degradation, and hence its nutritional value. By contrast, grain from the “stay-green”-like cultivar (ND24260) did not show variation in starch molecular structure under the different water stress levels. The results indicate that the cultivar with “stay-green”-like traits has a greater potential to maintain starch biosynthesis and quality in grain during drought conditions, making the “stay-green”-like traits potentially useful in ensuring food security.     

The interaction between starch hydrolysis and acidification kinetic determines the quality of a malted and fermented sorghum beverage

Gowé is a traditional fermented Beninese soft cooked paste made from a blend of malted and non-malted cereals that is diluted with water/ice and sugar just before consumption as a thirst-quenching drink. Major differences in the processes used for the preparation of gowé, which includes natural lactic fermentation, result in variable quality. Acidity and free sugar content have been linked to the process parameters but also to the type of strains that can be used for inoculation. The aim of this study was to investigate the starch degradation mechanism in relation with the activity of degrading enzymes during the preparation of gowé and enzyme impact on the quality (sugar content and viscosity) of the final product. Our results point to a key role for malt α-amylase and its susceptibility to acidic conditions in the sequence of the preparation process and in the final quality of gowé. Pre-cooking and inoculation speeds up and increases acidification of the product thereby favoring its safety, but reduces the final free sugar content and increases the final viscosity of gowé, which are both organoleptic defects of the product.     

Influence of environmental temperature during grain filling period on granule size distribution of rice starch and its relation to gelatinization properties

High temperature (HT) is the major environmental factor affecting grain starch properties of cooking rice cultivars. However, little information has been available on the effect of environmental temperature on the starch granule size distribution of rice grains. In this paper, five indica rice genotypes, including the wild type (9311) and its four mutants differing in amylose content (AC), were used to investigate the effect of environmental temperature on the starch granule size distribution, as well as its relation to AC and gelatinization properties of rice starch. Two temperature treatments (HT and NT) at filling stage were imposed to rice plants under the controlled temperature chambers. The result showed that HT increased the average diameter of starch granules and enhanced the proportion of large starch granules (LSG, D > 2.6 μm) by number, volume and surface area, respectively. However, influence of HT on GT and starch granule size distribution was relatively independent of their alteration in AC level for different rice genotypes. Therefore, HT-induced increase in the average diameter of starch granules and LSG percentage was strongly responsible for the higher starch gelatinization temperature and inferior cooked palatability of HT-ripening rice grains, which be not inherently associated with their varying AC level.     

Storage retrogradation behavior of sorghum, maize and rice starch pastes related to amylopectin fine structure

Storage retrogradation behavior and properties of sorghum, maize, and rice starches were compared to better understand the relationship of amylopectin fine structure to quality issues. Long-term changes in texture of starch gels were attributed to amylopectin retrogradation. In starch pastes aged 7 days at 4 °C, change in the storage modulus (ΔG^′) during heating (representing intermolecular associations) was highly and positively correlated (r = 0.93, p < 0.01) with the proportion of fraction I (FrI) long chains from debranched amylopectin. One sorghum cultivar, Mota Maradi, showed a dramatic increase in the storage modulus (G′) over the 7 day storage period that was related to its high proportion of FrI. Pastes/gels made from starches with normal (20–30%) amylose content and higher proportions of FrI long chains from debranched amylopectin tended to become firmer with more syneresis during extended storage. Both degree of polymerization measurements and previous models for amylopectin structure indicate that FrI represents long B chains of amylopectin. Cereal cultivars having amylopectin structures with lower proportion of long B chains were speculated to give improved quality products with lower rates of retrogradation and staling. This is particularly an issue in sorghum foods where products generally lack storage stability and tend to stale relatively quickly.     

Potential longevity (Ki) of malting barley (Hordeum vulgare L.) grain lots relates to their degree of pre-germination assessed through different industrial quality parameters

Barley (Hordeum vulgare L.) grain germination is required to perform the malting process. Maintenance of barley seed viability during storage is crucial for the malt industry; and modern cultivars are bred for rapid grain dormancy release after physiological maturity. Low dormancy level combined with rain close to harvest induces pre-germination/pre-harvest sprouting damage. Pre-germination might not affect viability in the short term after harvest, but it could reduce potential longevity (K_i) of a barley seed lot. K_i value is inherent for each barley lot; however, its determination is time-consuming which precludes its assessment at an industrial scale. In this study we sought quantitative relationships between K_i and the pre-germination degree of barley grain lots, assessed through quality tests routinely performed by malthouses [Falling Number (FN), α-Amylase Activity and Carlsberg]. Field pre-germinated lots from one old barley cultivar (Quilmes Palomar) and artificially pre-germinated lots from major varieties currently grown in Argentina were used. Associations between K_i and values obtained from all quality tests analysed were found for Q. Palomar. However, FN was the parameter that yielded the best and simplest explanation of K_i variability. A significant positive linear K_i -FN relationship was also obtained for each modern barley cultivar.