均质及大米蛋白对大米淀粉糊化和质构特性的影响

利用均质机在20～100 MPa压力下处理大米淀粉(RS),在添加或不添加大米蛋白(RP)情况下,考查大米淀粉理化性质、糊化和质构特性的变化。研究结果表明:随着处理压力的增加,RS的溶解度、膨胀率和透光率分别从1.90%、3.37%、6.27%上升至2.88%、5.38%、14.17%,凝沉性则下降;添加大米蛋白后,同一处理压力下,淀粉的溶解度、膨胀率下降,凝沉性上升。糊化特性分析发现,均质处理后,RS的最终黏度、崩解值和回生值分别下降了17.75%、24.47%和16.45%,说明其热稳定性提升,抗老化能力增强;原淀粉和60 MPa压力处理后的淀粉在添加氯化钠后糊化温度上升,黏度、降落值、回生值均有所下降,添加大米蛋白后淀粉黏度下降,回生值上升。质构特性分析发现,随处理压力的增加,淀粉凝胶的硬度从1 743 g下降到1 398 g,弹性则变化不大,大米蛋白使淀粉的硬度下降而弹性升高。     

氨基酸对大米淀粉糊化和流变性质的影响

以赖氨酸(lysine,Lys)、天冬氨酸(aspartic acid,Asp)和丙氨酸(alanine,Ala)分别代表带正电、负电、不带电3类氨基酸,采用快速黏度分析仪和流变仪研究氨基酸对大米淀粉糊化和流变性质的影响。结果表明,Lys和Asp均显著提高了大米淀粉的峰值黏度和崩解值(P0.05),但是降低了淀粉的最终黏度和回生值,而Ala对淀粉的糊化性质影响微小,在一定浓度范围内无显著差异(P0.05)。因此,带电的2种氨基酸(Lys和Asp)比不带电氨基酸(Ala)对淀粉糊化性质影响更强。此外,3种氨基酸对大米淀粉糊流变性质影响不同:动态流变学实验中,添加Lys和Ala使淀粉凝胶更具弹性,而Asp使淀粉凝胶变弱;静态流变学实验中,运用幂定律τ=kγm,对剪切应力τ和剪切速率γ进行了拟合,结果表明,原淀粉与添加氨基酸的淀粉的m值均小于1,表明淀粉及其氨基酸混合物都属于假塑性流体,并且Lys使淀粉假塑性增强,而Asp则相反。     

大米淀粉制备工艺对其糊化特性和粒度分布的影响

以籼米和粳米为原料,大米淀粉糊化特性和粒度分布作为评价手段,比较了碱法、中性蛋白酶法、碱性蛋白酶法(pH=8、pH=10)4种制备大米淀粉的工艺。结果表明,碱法制备的大米淀粉蛋白质残存率显著低于酶法,而3种酶法蛋白质去除率一致,但碱法部分破坏了淀粉颗粒的天然结构;经RVA糊化曲线分析,采用碱性蛋白酶法(反应条件pH=10)、中性蛋白酶法得到的籼米淀粉以及采用中性蛋白酶法得到的粳米淀粉能较好地保持天然淀粉的糊化特性;通过粒径分布检测,确定采用中性蛋白酶法处理粳米能制备得到粒径分布均匀的大米淀粉。综合各个评价指标,以粳米为原料,采用中性蛋白酶法可得到淀粉破坏小、粒径分布均匀、蛋白质残留率低的大米淀粉。     

Pasting Properties of Ohmically Heated Rice Starch and Rice Flours

ABSTRACT:  Pasting characteristics were examined for conventionally or ohmically heated rice starch and rice flours. Brown rice flour showed the greatest cooking stability and least retrogradation potential. Brown rice flour also showed the greatest pasting temperature and lowest peak viscosity, whereas commercial starch had the lowest pasting temperature. Nonstarch components of the brown rice flour, such as fat and protein, may have acted as stabilizers delaying water access into the granules and reducing swelling of the starch. Ohmic heating reduced pasting temperature for commercial rice starch, resulting in a starch that swelled faster. Furthermore, ohmic heating produced better cooking stability in white rice flour 1 and 2 than in the native sample, and caused white rice flour 2 to have less potential for retrogradation than the conventionally heated sample. At lower electric field strength (20 V/cm), ohmic heating resulted in the greatest cooking stable starches compared to higher voltages (40 and 70 V/cm) because more starch granules were disrupted from a longer cooking time, so there were fewer intact granules for pasting. Ohmic heating has been shown to alter rice starch and flour pasting characteristics with an added influence of lipids, proteins, and amylose contents.     

粳稻米淀粉糊化性质及其级分的研究

以3种粳稻米为原料，测定了粳稻米淀粉的RVA黏度特性、DSC热力学指标，以及对稻米淀粉进行高效液相色谱分析。结果表明：3种粳稻米淀粉的RVA峰值黏度、回生值差异较大，其余各项指标相差不大；DSC吸热曲线表明粳稻米淀粉起始糊化温度在65℃以下。吸热焓值略有差异；支链淀粉、中阃级分、直链淀粉在淀粉中的含量分为60％、22％、18％左右。     

Effects of Compositional and Granular Properties on the Pasting Viscosity of Rice Starch Blends

The changes in swelling power and pasting properties of suspensions of starch blends were studied in dependence on starch composition and at various isothermal temperatures (T_iso). Samples were prepared by mixing rice starches from Kaoshiung Sen 7 (KSS7, a high‐amylose‐content variety) and Taichung waxy 70 (TCW70, a waxy variety). Generally, mixing these starches at a comparable ratio caused significant decrements in overall swelling power, onset temperature of gelatinization or viscosity rise, and final viscosity of hot pastes after 30 min of isothermal stirring. Notable increases in the peak and conclusion temperatures of gelatinization and in the peak viscosity of the pastes were also observed. Generally, all viscosity parameters of the blends showed two linear dependencies on the starch composition, the graphs intersecting at a critical starch composition depending on the parameters concerned. The onset temperature of viscosity increase was related to the volume fraction of swollen granules when they were just closely packed in suspension. The volume fraction of KSS granules was smaller than that of TCW70. In addition, the rate of viscosity increase and the peak viscosity of the starch suspensions could be well described in terms of the swelling power (Q) when Q ≤ ∼27, and depending on the T_iso examined. From the photomicrographs of starch suspensions, the extensive shear‐induced disintegration of TCW70 granules in the co‐existence of rigid KSS7 granules was evident and in turn responsible for the reduced final viscosities of the hot pastes obtained from starch blends.     

蛋白组分对籼米粉糊化特性的影响机理探讨

通过逐一去除蛋白组分的方法研究了蛋白组分对籼米粉糊化特性的影响,并分析了影响这些变化的蛋白结构基础。RVA和DSC分析结果表明,不同组分的蛋白在去除之后,峰值粘度、热糊粘度和最终粘度均有不同程度的升高,崩解值、回生值及糊化温度均有不同程度的降低。SDS-PAGE和显微结构分析表明,各组分对糊化特性的影响机理应有差异:谷蛋白通过与纤维素类物质的紧密结合,在糊化过程中阻碍淀粉粒的溶胀;醇溶蛋白可能是通过蛋白体自身的溶胀与淀粉相互作用而影响;清、球蛋白通过活性蛋白对籼米成分的水解或合成等改变而影响;淀粉粒结合蛋白则可能对籼米的基础糊化特性影响较大。与分离重组法比较,逐一去除蛋白组分的方法因为蛋白组分之间的相互作用影响较大,对糊化特性的影响与分离重组法略有差异。     

损伤淀粉含量对米粉理化性质的影响

采用不同粉碎方法得到损伤淀粉含量不同的米粉,研究了损伤淀粉含量对米粉性质的影响。结果表明随着损伤淀粉含量的增加,米粉的总直链淀粉没有明显差异,可溶性直链淀粉和溶解度显著升高,溶胀度变化不大而透明度则显著降低。快速黏度分析(RVA)表明糊化温度由89.2℃降低到86.2℃,回生值由89.58 RVU降低到59.33 RVU,峰值黏度由139.29 RVU降低到85.08 RVU,谷值黏度由103.67 RVU降低到49.04 RVU,末值黏度由180.67 RVU降低到108.38 RVU。损伤淀粉含量9.05%米粉的衰减值最低。糊化后米粉凝胶的硬度和弹性显著降低。     

大米蛋白对小麦淀粉理化特性的影响

以小麦淀粉为原料,利用差示扫描量热仪(DSC)、快速粘度仪(RVA)、X-射线衍射等研究添加不同比例大米蛋白对小麦淀粉理化特性的热力学特性、糊化特性、流变学特性、X-射线衍射以及冻融稳定性的影响。结果表明,添加大米蛋白的小麦淀粉糊化温度增加,糊化焓值降低。随着大米蛋白添加量的增加,小麦淀粉峰值黏度、低谷黏度、崩解值、终值黏度降和回生值分别从5266、3098、2168、4755、1657 cP降低到4003、2969、1034、4439、1470 cP,糊化温度从72.50 ℃增加到76.00 ℃。大米蛋白会抑制淀粉中结晶的溶解。同时,添加大米蛋白会使小麦淀粉凝胶的储能模量和损耗模量均降低,凝胶强度变弱,冻融稳定性降低。     

大米淀粉及其不同取代度磷酸酯淀粉的糊化和流变特性

粳米淀粉与磷酸二氢钠发生酯化反应,通过改变反应温度得到取代度分别为0.028、0.049、0.073和0.14的磷酸酯淀粉。使用快速黏度分析仪和流变仪对比测定粳米淀粉及具有不同取代度的磷酸酯淀粉的糊化和流变特性。快速黏度分析仪测定的糊化特性显示PO43-与淀粉的结合降低了淀粉的糊化温度,升高了淀粉的峰值黏度,与粳米淀粉相比,磷酸酯淀粉更不易回生。流变仪测定的流变特性显示高取代度的磷酸酯淀粉抗剪切,随着取代度的增加,凝胶硬度降低,凝胶黏性增强。     

Oat Starch Part 1. Extraction,Purification and Pasting Properties

Starches have been isolated from a wide range of oat cultivars and their cooking behaviour determined with the new Ottawa Starch Viscometer. Gelatinization is typical of cereal starches but cooked granules appear more shear sensitive than corn, wheat or rice starch. The behaviour of oat starches on cooling shows striking differences from most other starches. High viscosity is rapidly developed and the cooled gels are clearer, less firm, more elastic, more adhesive and less susceptible to retrogradation than other cereal starches.     

Using Ozonation and Amino Acids to Change Pasting Properties of Rice Starch

ABSTRACT:  In this study, the effects of ozonation and the addition of amino acids on rice starches were determined in terms of pasting properties using a rapid visco-analyzer. Results from viscosity analysis showed that 30-min ozone treatment on commercial rice starch exhibited the greatest swelling extent among the treatments and least retrogradation tendency. The control pure oxygen treated sample had the best cooking stability. The addition of lysine (6%) to 30-min ozonated commercial rice starch significantly reduced peak viscosity (PV), minimum viscosity (MV), and final viscosity (FV) by 918, 1024, and 1023 cP, respectively. Moreover, it decreased Ptime, resulting in the faster swelling upon heating and less rigid gel formation upon cooling. Furthermore, the presence of lysine in 30-min ozonated starch isolate (WSI) also significantly reduced PV, MV, FV, pasting time, and total setback (TSB) and produced starch gel with the best cooking stability and the least retrogradation tendency. Ozonated starch exhibited similar pasting properties to those from oxidized starches treated with low concentrations of chemical oxidizing agents. The combination of lysine with ozonation resulted in pasting properties similar to starches treated with high levels of chemical oxidizing agents. The ozonated starch could be used as a thickening agent, whereas ozonated starch with lysine might be an alternative for a highly chemically oxidized starch. Therefore, ozonation alone or the combination of ozonation and addition of lysine might be used to develop new starch ingredients with various functionalities without using typical chemical modifications.     

小米淀粉与玉米淀粉糊性质比较研究

对小米淀粉和玉米淀粉糊性质进行较详细比较研究,包括透明度、冻融稳定性、凝沉性、膨胀力、酸解、酶解,和介质对糊粘度性质影响。结果表明,小米淀粉与玉米淀粉相比,糊的凝胶稳定性好、持水力强、膨胀力高、糊化温度高、热焓变值大、但透明度较差、冻融稳定性不佳、热稳定性差;且氯化钠及糖溶液对小米淀粉糊粘度性质影响较大。     

生物发酵处理对小米淀粉分子结构及糊化特性的影响

采用0.2 g/100 m L NaOH溶液提取发酵后的小米淀粉,研究自然发酵及优势菌(乳酸菌、酵母菌)发酵后对小米淀粉颗粒特性、结晶度、官能团、分子质量、糊化及老化特性的影响。结果如下:乳酸菌、酵母菌发酵后,淀粉颗粒表面有明显的侵蚀迹象,而自然发酵淀粉颗粒表面侵蚀迹象较轻;乳酸菌发酵后小米淀粉的结晶度较自然发酵增加1.49%而酵母菌发酵减少0.33%;发酵并未改变小米淀粉官能团区的峰位,但特征峰强度减弱,乳酸菌、酵母菌发酵后小米淀粉指纹区图谱消失;未发酵小米淀粉重均分子质量为1.5×10~4~5.9×10~5 g/mol,自然发酵分子质量在2.1×10~4~5.4×10~5 g/mol,乳酸菌发酵分子质量为1.6×10~4~5.3×10~5 g/mol,酵母菌发酵分子质量为1.6×10~4~4.7×10~5 g/mol,乳酸菌、酵母菌发酵后支链淀粉长链及直链淀粉比例减少而中间及短支链淀粉的比例相对增加;乳酸菌、酵母菌发酵96 h糊化温度较自然发酵下降0.84℃和1.13℃,热焓值上升1.00 J/g和0.78 J/g;二者的回生值较自然发酵分别下降743、471 mPa·s。自然发酵的优势菌(乳酸菌、酵母菌)使小米淀粉的分子结构、糊化及老化特性发生明显变化,并在小米自然发酵过程中起主导作用。     

Waxy Gene Factor and Residual Protein of Rice Starch Granules

Residual protein of rice starch granules prepared from milled rice by protein extraction with sodium dodecylbenzene sulfonate or alkaline protease treatment was related to amylose content. SDS-polyacrylamide disc gel electrophoresis confirmed that the major protein in nonwaxy starch granules was the Wx gene product with subunit molecular weight of about 60,000 daltons. The Wx gene product was absent in waxy starch granules.     

谷氨酰胺酶催化交联大米蛋白对大米淀粉理化特性的影响

为弄清谷氨酰胺酶(TG)催化交联前、后大米蛋白对大米淀粉理化特性的影响,测定淀粉的膨胀系数与溶解度、直链淀粉溢出率。采用红外光谱法、可见分光光度法、差示扫描量热仪(DSC)、快速粘度分析仪(RVA)等技术手段分析淀粉共混体系的结构特征和功能特性。结果表明,蛋白在TG酶催化下对淀粉的结构、消化率与其它功能特性均有显著影响,且大米蛋白与淀粉二者间相互作用增强,表现为:大米淀粉的膨胀系数由13.24 g/g降至最低,为7.02 g/g,其直链淀粉溢出量降低38.7%。在TG酶作用下,随着蛋白含量的增加,淀粉短程有序结构的稳定性逐渐增强。添加量为10%的蛋白在TG酶的催化下对淀粉消化性减轻效果更好。TG酶作用前、后蛋白对淀粉的热特性影响不大,而其糊化特性参数均明显下降,黏度也显著降低。TG酶催化蛋白使得淀粉颗粒网络结构更加致密且聚集。结论:TG酶催化交联蛋白对淀粉的改性效果显著。     

瓜尔豆胶对马铃薯淀粉消化性和糊化特性的影响

研究瓜尔豆胶对马铃薯淀粉消化性和糊化特性的影响,采用体外模拟消化性实验测定淀粉的消化性,比较与不同质量比(0:100、1:80、1:40、1:20)的瓜尔豆胶与马铃薯淀粉间糊化特性、热力学特性、结晶结构及微观结构的差异,从而探索瓜尔豆胶对马铃薯淀粉消化性影响的本质原理。研究结果显示:当瓜尔豆胶添加量较低时复配体系经糊化后冷却至37 ℃的体系较易被酶解,抗性淀粉含量低;随着瓜尔豆胶添加量的增大,瓜尔豆胶与淀粉颗粒缠结形成空间位阻从而抑制酶解,复配体系经糊化后冷却至37 ℃的体系不易被酶解,抗性淀粉含量较高。添加瓜尔豆胶增大了马铃薯淀粉的起始糊化温度和峰值温度,提升了马铃薯淀粉的吸热焓,延长糊化过程,增加吸热量。观察复配体系的结晶结构发现加入胶体后复配体系并没有新基团产生,胶体与淀粉间仅为物理作用,同时微观结构观察表明胶体与淀粉作用所形成空间位阻使得淀粉颗粒分布均匀,复配体系呈现出更加均一稳定的结构。     

Pasting Properties of Potato Starch and Waxy Maize Starch Mixtures

The pasting viscosity, morphological properties, and swelling properties of potato starch and waxy maize starch mixtures at different ratios were investigated. Pasting analysis of the starch mixtures (7% solids in water, w/w) using a Rapid Visco Analyser showed linear changes in peak viscosity and pasting temperature according to the mixing ratios of both starches, but not in breakdown and setback. The pasting profile revealed that the starches rendered mutual effects during pasting, more significantly when the amounts of potato and waxy maize starches were similar. The volume fraction of swollen granules and the presence of amylose appeared to be important parameters in the mutual effects of both starched during pasting. Under a light microscope, the swelling of potato starch granules was delayed by the presence of waxy maize starch. Overall results indicate that new pasting properties can be generated by mixing starches of different botanical sources.     

加热时间对大米淀粉特性及抗性淀粉含量的影响

采用不同的加热时间对大米进行处理,并从加热处理过的大米中提取淀粉,采用电镜扫描仪、差示扫描量热仪、质构仪、流变仪等检测仪器研究加热时间对大米淀粉的颗粒形貌、热力学性质、凝胶特性、流变等性质的影响,采用酶解法测定加热处理过的大米中抗性淀粉的含量。结果表明：随着加热时间的延长,淀粉的膨润力与溶解度先增大后减小;加热时间在0～10min 时,抗性淀粉含量减少,其范围为18.01%～8.10%;淀粉颗粒由单个独立的颗粒逐渐膨胀至相互粘连,糊化焓值降低;硬度、延伸性等都有不同程度的变化;淀粉糊的剪切稳定性降低。