脂肪酸对小麦淀粉糊化特性及热特性的影响

为了解脂肪酸对小麦淀粉糊化特性和热特性的影响,在小麦淀粉中分别添加月桂酸、肉豆蔻酸、棕榈酸、硬脂酸,采用快速黏度分析仪(RVA)、X-射线衍射仪(XRD)、差示扫描量热仪(DSC)对淀粉-脂质复合物糊化特性、晶体结构和热特性进行分析。结果表明,小麦淀粉与四种饱和脂肪酸所形成的复合物的晶体结构均为V型晶型。加入脂肪酸后小麦淀粉的峰值黏度、热浆黏度和崩解值降低,而最终黏度和回生值升高,起始糊化温度(To)、峰值糊化温度(Tp)、终点糊化温度(Tc)略降,而糊化焓值(ΔH)则显著下降。综合来看,添加脂肪酸对小麦淀粉的糊化特性和热特性有显著影响,其中月桂酸对小麦淀粉糊化特性及热特性的影响最显著。     

灌浆期遮阴对小麦胚乳淀粉粒度分布及糊化特性的影响

为了解灌浆期遮阴对小麦胚乳淀粉粒度分布及淀粉糊化特性的影响,研究了灌浆期对扬麦13、宁麦13和烟农19进行30%遮阴后籽粒的淀粉粒度分布与糊化特性的变化。结果表明,小麦灌浆期遮阴显著降低了<10μm的B型淀粉粒体积和表面积占比,增加了>10μm的A型淀粉粒的体积和表面积占比,其中A型淀粉粒中主要增加了10~20μm淀粉粒的体积和表面积占比;遮阴处理对淀粉粒数目分布无显著影响。遮阴处理后,峰值粘度、低谷粘度、稀懈值、最终粘度、回升值等糊化参数指标均显著降低。小麦籽粒硬度、容重、出粉率等指标也因遮阴处理而显著降低。综上所述,遮阴处理改变了小麦籽粒淀粉粒粒度分布,降低了淀粉糊化参数和加工品质。     

不同生长期木薯块根淀粉糊化特性的差异

对木薯品种(系)SC8、南植199、C869、D346和E632在6～11个月生长期的块根淀粉糊化特性进行研究。结果表明,木薯的含粉量随生长期的延长呈先增后减趋势,不同品种的变化拐点各不相同;直链淀粉含量随生长期变化趋势因品种而异,表现出显著的品种效应和生长期差异性;峰值粘度在生长期为8个月后随生长期的延长而增加,其值与鲜薯含粉率、直链淀粉含量呈显著正相关关系;木薯淀粉糊化温度的生长期差异性显著,且变化趋势因品种的差异而略有不同,它与直链淀粉含量呈显著负相关关系。木薯淀粉恩氏粘度与直链淀粉含量呈显著正相关。     

Starch properties, in vitro digestibility and sensory evaluation of fresh egg pasta produced from oat,teff and wheat flour

Specific dietary requirements, e.g. celiac disease, as well as increased consumer demand for products of high nutritional value, makes the production of pasta from alternative cereals interesting. Raw material characterisation showed that the utilisation of oat and teff flour is beneficial as these ingredients contain higher levels of fibre and mineral composition is superior to that of wheat. Starch properties significantly influence pasta quality and therefore damaged starch levels, amylase activity, pasting properties and gelatinisation temperatures of the flours were investigated. Fresh egg pasta based on wheat, oat and teff flour was produced. Sensory properties of oat spaghetti were found to be very close to that of wheat pasta but improvement of smoothness and aroma is necessary, while teff spaghetti showed reduced sensory quality. An in vitro enzymatic digestion was performed using a dialysis system to mimic the behaviour of pasta as eaten and make predictions on the glycemic index (GI). The predicted GI was highest for wheat pasta, followed by teff and oat. Ultra structure was studied using confocal laser scanning microscopy, allowing the visualisation of differences in starch granule size and shape as well as gelatinisation occurring during the cooking process.     

Effects of monoglycerides on pasting properties of wheat starch after repeated heating and cooling

The effects of repeated heating and cooling on the properties of pastes prepared from a commercial wheat starch (Triticum aestivum L.) with added monoglycerides were studied using a Rapid Visco Analyser (RVA). The nanostructure of the freeze-dried pastes was determined by X-ray diffraction and small-angle X-ray scattering. Pastes prepared from the wheat starch alone, or from the starch mixed with tripalmitin, which does not form complexes with starch, produced regular viscosity profiles in the RVA when subjected to multiple heat-cool cycles. In comparison, the effects of adding monoglycerides (or monoacylglycerols) depended on the chain length and saturation of the fatty acid of the monoglyceride. Repeated heat-cool cycles in the RVA of the starch with different monoglycerides induced the formation of complexes of varying stability that influenced the viscosity trace of the paste during multiple heating and cooling cycles. Small-angle X-ray scattering in combination with X-ray diffraction proved useful in describing the nanostructural changes in the RVA pastes induced by monoglycerides and temperature cycling. The results indicate that the functional properties of starch pastes may be manipulated through the strategic selection of an added monoglyceride.     

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.     

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.     

小麦淀粉的粒度分布、组分及糊化特性对氮硫肥的响应

为明确氮硫肥对小麦淀粉粒度分布及主要理化特性的影响,以强筋小麦品种西农9718和中筋品种陕农138为材料,采用不同氮硫肥水平进行处理,系统分析了小麦A、B淀粉的粒度分布、淀粉组成、膨胀势及糊化特性对氮硫肥的响应。结果表明,强筋和中筋小麦品种的淀粉粒度分布基本一致。A淀粉粒体积分布占总淀粉的74.95%～75.43%,但淀粉粒数量远少于B淀粉粒。A淀粉的直链淀粉、峰值黏度、低谷黏度、崩解值、最终黏度以及回生值高于B淀粉,而B淀粉有更高的支链淀粉、膨胀势和糊化温度。不同氮硫肥处理改变了小麦淀粉的粒度分布,进而影响淀粉的组成和糊化特性。在施氮(230kg.hm-2)条件下,强筋品种西农9718和中筋品种陕农138的A、B淀粉分别在硫肥施用量为46和56kg.hm-2时有较低的直链淀粉含量、较高的膨胀势及较好的糊化特性。陕农138淀粉的粒度分布、组成及糊化特性对氮硫肥的响应比西农9718更敏感。适当的氮、硫肥配施有利于改善小麦的淀粉品质。     

Thermoplastic starch modified during melt processing with organic acids: The effect of molar mass on thermal and mechanical properties

Thermoplastic starch (TPS) was modified with ascorbic acid and citric acid by melt processing of native starch with glycerol as plasticizer in an intensive batch mixer at 160 °C. It was found that the molar mass decreases with acid content and processing time causing the reduction in melting temperature (T_m). As observed by the results of X-ray diffraction and DSC measurements, crystallinity was not changed by the reaction with organic acids. T_m depression with falling molar mass was interpreted on the basis of the effect of concentration of end-chain units, which act as diluents. FTIR did not show any appreciable change in starch chemical compositions, leading to the conclusion that the main changes observed were produced by the variation in molar mass of the material. We demonstrated that it is possible to decrease melt viscosity without the need for more plasticizer thus avoiding side-effects such as an increase in water affinity or relevant changes in the dynamic mechanical properties.     

Physical Properties and Gelation Behavior of a Low-Amylopectin Maize Starch and Other High-Amylose Maize Starches

This paper examines the effect of changes in fine structure due to hybrid breeding on gel formation and gel properties of high-amylose maize starches. Both small-strain oscillatory testing and uniaxial-compression testing ranked G′ and texture/strength, respectively, in the same order of HYLON® V starch <HYLON® VII starch <low-amylopectin starch (LAPS). The starch gels became more rigid and stronger as amylose content of the hybrids increased from HYLON V starch to LAPS. It was also noted in these studies that LAPS had the quickest onset of gelation and HYLON V starch had the slowest. The effect of preparation temperature on gel properties was also studied by cooking high-amylose starches at 250 °, 270 °, 290 °, 310 °, 330 °F in a mini-jet cooker with minimal steam. Temperature of jet cooking had an impact on the rate of sol-to-gel transformation of the starches, which in turn influenced the final gel properties. All three hybrids were strongest (highest fracture stress and strain values) when prepared at 270 °F. HYLON V had the narrowest cooking tolerance forming self-supporting gels from 270 ° to 310 °F, while LAPS was the most robust, forming acceptable gels throughout the range of temperatures tested.     

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。     

不同类型小麦品种大、小淀粉粒的分离和特性

为给小麦品质育种提供依据,以3个不同类型的小麦品种(济南17号、扬麦12号和扬麦9号)为材料,分离了大、小淀粉粒,并对它们的特性(形状、大小、膨胀势、晶体特性、糊化特性等)进行了测定和分析.结果表明,大、小淀粉粒形状为椭球形或球形,品种间无差别,但其大小和含量在品种间存在很大差异;大淀粉粒的膨胀势大于小淀粉粒.大、小淀粉粒都为A型淀粉晶体,大淀粉粒的相对结晶度差别不大,但小淀粉粒的相对结晶度差别较大,表现为济南17号＜扬麦12号＜扬麦9号.品种内大淀粉粒的起始温度To、峰值温度Tp值和吸收热焓△H高于小淀粉粒,终止温度Tc值却比小淀粉粒低.     

Functional study of raw and cooked blue maize flour: Starch digestibility,total phenolic content and antioxidant activity

The purpose of this study was to determine the chemical composition and antioxidant capacity of blue maize (BM) (Zea mays L.) flour and to investigate the effects of polyphenol-containing extracts and BM wholegrain flour on starch digestion under uncooked and cooked conditions; commercial white maize flour was used as control. Total phenolic content in BM flour (BMF) (164 ± 14 mg gallic acid/g of dry matter) was higher than white maize (127 ± 7 mg gallic acid/g of dry matter), and the presence of anthocyanins (2.0 ± 0.5 mg cyanidin 3-glucoside/100 g) was detected. Also, an important scavenging activity against ABTS (2,2’-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals and ferric reducing power (FRAP) was determined. Extracts of BMF reduced amylase activity (>90% of inhibition). BMF showed higher slowly digestible and resistant starch contents, thus exhibiting lower predicted glycemic index than white maize. Total anthocyanins (r = −0.89 and r = −0.79, p<0.05), antioxidant capacity (r = −0.86 and r = −0.96, p<0.05), total starch (r = 0.99 and 0.92, p<0.05) and resistant starch content (r = −0.99 and r = −0.92, p<0.05) were correlated with pGI for uncooked and cooked flours, respectively. These results indicate the potential use of BMF and its phenolic-rich extract as functional ingredients to develop antioxidant and indigestible carbohydrate-rich foods with potential health benefits.     

Improving the barrier and mechanical properties of corn starch-based edible films: Effect of citric acid and carboxymethyl cellulose

The films produced from pure starch are brittle and difficult to handle. Chemical modifications (e.g. cross-linking) and using a second biopolymer in the starch based composite have been studied as strategies to produce low water sensitive and relatively high strength starch based materials. A series of corn starch films with varying concentrations (0-20%, W/W) of citric acid (CA) and carboxymethyl cellulose (CMC) were produced by casting method. The effects of CA and CMC on the water vapor permeability (WVP), moisture absorption, solubility and tensile properties were investigated. The water vapor barrier property and the ultimate tensile strength (UTS) were improved significantly (p < 0.05) as the CA percentage increased from 0 to 10% (W/W). At the level of 15% (W/W) CMC, the starch films showed the lowest WVP values (2.34 × 10⁻⁷ g Pa⁻¹ h⁻¹ m⁻¹) and UTS increased from 6.57 MPa for the film without CMC to 16.11 MPa for that containing 20% CMC.     

The role of gluten in a sugar-snap cookie system: A model approach based on gluten–starch blends

The cookie making properties of dough made from blends of commercial wheat starch and gluten were determined. Higher gluten levels decreased dough piece weight, its density, stickiness and hardness. The largest spread was obtained when no gluten was added. However, this resulted in cookies of unacceptable structure. Higher gluten contents increased spread onset time, decreased cookie spread but generally had little impact on set time while additional water lowered spread onset time and likewise had no statistically significant impact on set time. The results showed that the final cookie diameter is quite dependent on the spread onset time which itself depends on the amount of water available to the non-gluten constituents in the system. Size-exclusion high performance liquid chromatography showed that during baking, proteins aggregated. This indicated that during the process the added gluten acquired the necessary mobility for interaction. However, because increasing levels of gluten increasingly decreased the relative level of water available to itself, and because the set time, and, hence, the set temperature, did not depend on the gluten level, we concluded that cookie dough setting was not determined by an ‘apparent’ glass transition. Furthermore, more protein aggregation went hand in hand with less spread.     

灌浆成熟期温度对水稻籽粒淀粉合成关键酶活性及品质的影响

 选用蒸煮食味品质不同的3个粳稻品种，利用温室高温和自然常温，研究了灌浆成熟期温度对水稻籽粒淀粉合成关键酶活性及蒸煮食味品质的影响。结果表明，灌浆成熟期高温条件下，水稻籽粒蛋白质含量提高，直链淀粉含量和味度值降低，劣质品种提高或降低的程度大于优质品种；RVA谱特性对灌浆成熟期温度的反应因品种和特性而异；灌浆过程中，籽粒ADPG焦磷酸化酶、可溶性淀粉合成酶和淀粉分支酶活性随灌浆进程，酶活性逐渐增加，达到峰值以后，酶活性又逐渐下降，呈单峰曲线，但不同品种酶活性达到峰值的时间和同一时期的酶活性大小有差异；ADPG焦磷酸化酶和可溶性淀粉合成酶的活性表现对温度的影响反应较为迟钝，而淀粉分支酶活性表现对温度变化的反应较为敏感，温度过高过低都降低该酶活性。     

环境和氮磷肥对强筋小麦品种郑麦9023淀粉糊化特性的影响

为了解环境和氮磷肥对强筋小麦淀粉糊化特性的影响,2007-2008年度在河南省安阳、三门峡、夏邑、漯河、南阳、信阳6个试验点,采用统一试验方案进行大田试验,研究了不同氮、磷配比对郑麦9023淀粉糊化特性的影响。结果表明,地点间淀粉糊化参数差异最大,达1%极显著水平;施氮量及地点×氮肥互作对淀粉粘度参数的影响达5%或1%显著水平;而施磷量及氮肥×磷肥、地点×磷肥互作对淀粉糊化参数无显著影响。表明对小麦淀粉糊化特性的影响效应依次为：地点＞氮肥＞磷肥。不同地点间以安阳和三门峡点的淀粉粘度参数较高,而低纬度的南阳点和信阳点较低。多个试验点施氮量从120 kg /hm2增加到240 kg /hm2时淀粉主要粘度参数有显著提高,不施氮肥也获得了较高的粘度参数値;而信阳（水稻土）则随施氮量增加淀粉粘度参数呈下降趋势。研究结果还表明,在施氮量240 kg /hm2、施磷量120 kg /hm2的氮磷配比下淀粉粘度参数较高。     

一个新的马铃薯GBSS基因5'侧翼序列克隆及调控活性研究

采用PCR技术,从马铃薯叶片基因组DNA中扩增到了约0.6kb的马铃薯GBSS基因的5'侧翼序列,经序列同源性分析所克隆的序列与已知序列同源性为97.41%,含有启动基因表达所需的主要调控元件CAAT盒和TATA盒。构建该序列与GFP的融合基因植物表达载体pBIGGFP,并用基因枪转化法将pBIGGFP导入马铃薯无菌苗茎段、叶片和微型薯薯片,用荧光显微镜观察转化组织中GFP的瞬时表达,结果表明GFP在上述器官中都得到了表达,说明所克隆的约0.6kbGBSS基因的5'侧翼序列是具有启动基因表达的功能。     

Effectiveness and economics of hermetic bags for maize storage: Results of a randomized controlled trial in Kenya

Maize is an important seasonal crop and year-round food staple in Africa. On-farm storage is therefore needed, but it suffers from storage pests. To study the effectiveness and economics of a new storage method, hermetic bags, a randomized controlled trial was organized in Kenya with 300 farmers in the treatment group using hermetic bags and 300 in the control group using conventional farmer practices. A subsample of 224 farmers was visited three times during the 2012–2013 major storage season: at baseline and after two and four months. Grain samples were taken and insect infestation, damage and weight loss observed. Results show that hermetic bags were highly effective in controlling storage insect pests: after four months, grain damage was 14% in the control and only 4% in the treatment; weight loss due to insect pests was 1.7% among control farmers, but only 0.4% in the treatment group. Economic analysis shows that hermetic bags become potentially profitable, under basic price and loss assumptions, if farmers use hermetic bags for storage for at least four months per season, and if the bags last for at least four seasons.     

Development of a Human-Clothing-Environment simulator for dynamic heat and moisture transfer properties of fabrics

A vertical skin model with two detachable environmental chambers was developed to simulate a Human-Clothing-Environment system and to evaluate heat and moisture transport properties of textile materials under severe conditions and during transient states. The construction of the system was described and data reproducibility and accuracy of the instrument were verified by using PEG treated nonwovens. Also advantages over a traditional static type experiment were demonstrated based on a series of experiments.