Pasting Profiles and Solubility of Native and Cross-Linked Corn Starch inDimethylsulfoxide-Water Mixtures

The pasting profiles of native and cross-linked corn starch in dimethylsulfoxide (DMSO)–water mixtures were investigated with a Rapid Visco Analyser. The temperature profile included an isothermal step of 1 min at 30 °C, followed by a linear gradient to 75 °C in 3 min and finally an isothermal step of 20 min at 75 °C. The profiles were characterised by an initial peak (at 75 °C) followed by a trough, much as is the case with profiles of such starch in water. Increasing the DMSO concentration in the DMSO–water mixture from 70–97·5% (by weight), without changing the starch concentration, resulted in lower end-viscosities. The RVA pasting profiles of a series of sodium trimetaphosphate (STMP) and epichlorohydrin (ECH) cross-linked corn starches were investigated in 92·5% DMSO at different dry matter (d.m.) contents. At high starch concentrations (>60% d.m.), the end viscosity increased with the degree of cross-linking. At lower starch concentrations (<6% d.m.), the more highly cross-linked starches yielded lower peak- and end-viscosities than starches with lower degrees of cross-linking. The solubilisation of the starches in 92·5% DMSO was complete for the native starch and decreased considerably for the highly cross-linked starches. Light microscopy showed that the cross-linked starches, upon heating in DMSO–water, were converted to a biphasic system consisting of insoluble granule remnants and a starch solution.     

播期和密度对不同玉米品种淀粉糊化特性和子粒品质的影响

以农大108和青农105为材料,设置3个播期和6个密度处理,研究播期和密度对两个玉米品种淀粉糊化特性和子粒品质的影响。结果表明,品种间比较,淀粉峰值黏度、谷值黏度、崩解值、回复值、峰值时间、糊化温度差异显著;播期对糊化特征值及子粒淀粉、蛋白质含量的影响较大,密度的影响较小。晚播条件下,峰值黏度和谷值黏度显著升高,糊化温度显著降低;中播条件下,淀粉含量最低,蛋白质含量最高。因此,试验播期范围内,晚播有利于改良淀粉糊化特性,适期播种有利于改良子粒品质。     

不同肥料配比对贵州禾苟当1号产量及食味品质的影响

采用“3414”试验设计,研究不同肥料配比对贵州禾苟当1号产量及其构成因素、干物质积累量、稻米淀粉RVA特征谱及香味物质相对含量的影响。结果表明,不同肥料配比下N₂P₂K₂处理产量最高,为7.27t/hm²,与N₂P₀K₂和N₂P₃K₂处理差异不显著。从产量构成因素来看,各处理产量与有效穗数、总颖花量、结实率和千粒重呈正相关,其中与有效穗数达到显著水平。N₂P₂K₂处理在保证结实率和千粒重的前提下,有效穗数多,抽穗后期干物质积累量大,从而达到高产。从稻米品质来看,随着氮、磷、钾肥施用量的增加,峰值黏度和崩解值均不同程度降低,稻米食味品质降低。随着磷肥施用量的增加,籽粒香味挥发性主要物质相对含量逐渐上升,其中N₂P₃K₂处理香味物质相对含量最高。N₂P₃K₂处理可在保证产量的基础上增加籽粒香味。利用肥料效应方程分析得出,苟当1号获得最佳产量的施肥量为N 174.45kg/hm²、P₂O₅ 52.80kg/hm²和KCl 103.65kg/hm²,产量为6.86t/hm²。     

我国6个籼稻主产省93份水稻样品品质性状分析

以我国6个籼稻主产省的93份样品为研究对象，测定了加工品质、外观品质、蒸煮品质、蛋白质含量、RVA谱特征值以及米饭食味值。结果表明，所测定的22项品质指标中，15项指标的变异系数大于10%，说明收集的样品范围比较广，处于不同的品质水平，具有较好的代表性；垩白粒率、垩白度的测定值变幅较大，分别为1.0%～68.5%、0.3%～31.7%，且变异系数相对较高，分别为57.56%、73.25%，说明不同省份不同籼稻品种间的外观品质差异较大，尤其是垩白性状，已成为影响籼稻品质的一个重要因素。各指标间的相关性分析结果表明，垩白粒率、垩白度、直链淀粉含量、蛋白质含量均与食味值呈显著负相关，胶稠度、长宽比与食味值呈极显著正相关，热浆黏度、冷胶黏度、回复值、消减值与食味值呈极显著负相关，崩解值与食味值呈极显著正相关。直链淀粉含量、胶稠度和碱消值与RVA谱主要参数相关性较高。主成分分析表明，RVA特征值、直链淀粉含量、胶稠度、外观是影响籼稻食味品质特征的重要因素。     

粳稻食味相关品质性状的变异与相关性研究

为研究粳稻品种食味及相关品质性状的变异特点及相关性，对62份粳稻品种食味值、部分理化品质性状、淀粉的黏滞度进行分析。结果表明，62份粳稻品种测试性状变异系数在3.96%～90.00%,Shannon-Wiener多样性指数在1.279～2.038,62份粳稻品种在品质性状上可划分到4个类群。品种食味值、部分理化性状、RVA谱特征值之间存在显著或极显著的相关性，同时构建了3个回归方程。本研究结果为粳稻优质食味品种选育与性状选择提供了依据。