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。     

Pasting and Crystalline Property Differences of Commercial and Isolated Rice Starch with Added Amino Acids

ABSTRACT This study compared effects amino acid structure and type on the pasting properties and crystallinity of rice starch isolated from flour. Amino acids were added at 2 and 6% of the starch (dry basis) for RVA analyses. Charged amino acids had more of an influence on pasting properties than neutral amino acids. Our results indicated that the negatively charged amino acids had a similar effect as that of the positive charged amino acids for decreasing cooking stability of the starch, but opposite effects on retrogradation tendency. Charged amino acids increased the crystallinity of the starch, potentially enhancing resistant starch nature.     

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.     

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。     

大米淀粉物化特性与糊化曲线的相关性研究

以不同品种的大米淀粉为原料，采用快速黏度分析仪（RVA）研究不同品种大米淀粉的糊化曲线的差异，碘兰值和酶解力等物化特性对糊化特性的影响。结果表明，不同品种大米淀粉的碘兰值、酶解力存在差异，以籼米淀粉的碘兰值最大，其次是粳米淀粉和糯米淀粉。粳米淀粉和糯米淀粉酶解力相对较大。糊化温度、最终黏度、最低黏度、回升值与碘兰值均呈不同程度的正相关。峰值黏度、最低黏度、最终黏度、回升值、糊化温度与酶解力呈不同程度的负相关。采用碘兰值、酶解力的指数模型描述大米淀粉的糊化特性可达到很高的拟合精度。     

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。     

Changes in Starch Pasting Properties Due to Sugars and Emulsifiers as Determined by Viscosity Measurement

The effects of sugars, emulsifiers, and their interactions on starch pasting properties were determined by the Rapid Visco-Analyser (RVA). Solutions of 50% sugars in water were used. The disaccharides, sucrose and lactose, delayed pasting more than did the monosaccharide, dextrose. Sugars’effects on starch pasting delay and on starch paste consistency varied with the starch. Addition of the same emulsifier (1%) to different starches did not result in the same change in paste consistency in the presence of high amounts of sugar. Both sucrose ester F-160 (SE) and polysorbate 60 (PS) reduced the hot paste consistency of starch-sugar mixtures, with SE having a greater effect than PS.     

应用RVA仪分析荸荠淀粉的糊化特性

为了更好地开发利用荸荠淀粉,以荸荠淀粉为原料,采用快速黏度分析仪(RVA)分析淀粉糊化特性,研究不同淀粉质量分数和同一淀粉质量分数下pH、蔗糖、食盐、黄原胶以及明胶对荸荠淀粉糊化性质的影响。结果表明,随着淀粉质量分数的增大,荸荠淀粉的糊化温度降低,凝胶性及凝沉性增强;pH值对荸荠淀粉的热稳定性、凝胶性和抗老化能力没有明显的影响,而在酸性条件下荸荠淀粉糊的凝沉性比在碱性条件下的稍好;加入蔗糖后淀粉的峰值黏度、谷值黏度、最终黏度均显著提高,糊化时间增长;食盐对荸荠淀粉的影响不大;加入黄原胶会影响荸荠淀粉的糊化;加入明胶后淀粉的峰值黏度、谷值黏度、最终黏度均显著降低。     

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。     

糯米淀粉的晶体性质和糊化特性

以不同产地、品种的糯米为原料,探讨糯米淀粉晶体性质和糊化特性的差异,并进行相关性分析,以期为糯米食品加工的原料选择提供参考。试验结果表明,糯米淀粉的结晶度为16.4%~25.3%,糊化温度为71.1~87.2℃,且结晶度和糊化温度均以珍珠糯最高,禾胜糯1次之,扬丰糯最低。其中,结晶性质主要取决于品种,受产地影响相对较小,而产地、品种的差异极大地影响糯米淀粉的糊化性质。相关性分析表明,糯米淀粉的碘蓝值、结晶度与糊化温度三者之间呈极显著正相关关系。因此,品种和产地对糯米淀粉的结晶性质和糊化特性均有较大影响。     

蕨根淀粉颗粒形貌与糊化黏度特性

以马铃薯淀粉和红薯淀粉为对照,研究了蕨根淀粉的颗粒形貌及糊化黏度特性。蕨根淀粉颗粒多为圆形或椭圆形,少数呈棒状,颗粒表面光滑。颗粒大小差异较大,粒径为5~31μm。蕨根淀粉颗粒具有可见偏光十字,偏光十字位于颗粒一端,呈"Ⅹ"。蕨根淀粉的起糊温度明显低于红薯淀粉,与马铃薯淀粉相当。蕨根淀粉糊具有较好的热稳定性,较高的回生值,适宜加工粉丝类产品。蔗糖、NaCl、碱面和明矾的添加及pH值对蕨根淀粉糊化特性有影响。蔗糖使蕨根淀粉糊黏度增大;NaCl可提高蕨根淀粉糊的热稳定性,延缓体系老化;碱面、明矾的添加使蕨根淀粉糊的热稳定性下降;蕨根淀粉糊耐酸性差,在酸性条件下,蕨根淀粉发生明显水解作用,体系黏度降低。     

用RVA仪分析玉米淀粉的糊化特性

以玉米淀粉为原料,利用RVA(快速黏度分析仪),研究了不同浓度玉米淀粉以及在同一浓度下氯化钠、蔗糖以及转速对淀粉糊化特性的影响,并且在此基础上将RVA糊化程序改为多重RVA程序,然后观察对淀粉的特性的影响。结果表明:随着玉米淀粉溶液浓度的增加,起始成糊温度降低,淀粉糊的热稳定性降低,凝胶性增强。随氯化钠浓度增大,起始成糊温度逐渐升高,到达峰值时间有所延长,热稳定性明显提高,但凝胶性降低。当蔗糖浓度增加时,淀粉成糊温度、峰值黏度、最低黏度和最终黏度都随之增加,热稳定性增强,冷却过程中淀粉糊形成凝胶的能力减弱。玉米淀粉在多重RVA程序中,淀粉胶体反复形成并且溶解。添加油脂后的玉米淀粉的黏度曲线的变化是复杂的,由淀粉和油脂之间的相互作用引起,油脂的水溶性以及淀粉颗粒与蛋白质的关系影响着它们的相互反应。     

大米谷蛋白对大米淀粉理化特性的影响

本文研究了低变性大米谷蛋白的添加对大米淀粉的持水、糊化、流变与质构特性的影响。结果表明,大米谷蛋白的添加(0~20%)会逐渐降低大米淀粉的持水能力,延迟其水化过程。淀粉的黏度特性曲线、糊化晗值、峰值黏度、崩解值和回生值随谷蛋白添加量的增加而逐渐降低,但起始糊化温度和峰值温度无明显变化。流变数据证实,蛋白添加量为0~10%时,淀粉-蛋白复合物的剪切应力和表观粘度随添加量增加而增加,当谷蛋白添加量为20%时,复合物的剪切应力和表观粘度迅速减小,大米淀粉的糊化特性和凝胶特性发生明显弱化。     

不同筋力小麦品种的搅拌值及其它淀粉糊化特性指标_注

以 5个小麦品种为材料 ,利用快速粘度分析仪 (RVA)研究了不同筋力品种间搅拌值的差异及搅拌值与其它淀粉糊化特性指标的关系。结果表明 ,不同品种间搅拌值有一定差异 ,酶浓度对搅拌值有显著影响。搅拌值与面团筋力无一致性 ,与糊化温度、糊化时间相关不显著 ,但是与高峰粘度、低谷粘度、粘度破损值、最终粘度以及回冷值等 5项淀粉糊化指标显著正相关。同时求出了这 5项淀粉糊化指标依搅拌值变化的回归方程。     

蕨根淀粉的颗粒形态与糊化特性研究

为探讨蕨根淀粉的糊化性能,以蕨根为原料,采用湿法提取淀粉,并进行提纯,对蕨根淀粉的颗粒形态、糊黏度曲线、糊冷热黏度、糊透明度、抗剪切性、冻融稳定性、凝沉性及抗老化性等特性进行了研究,并与玉米淀粉进行了比较。结果表明:扫描电镜观察蕨根淀粉颗粒表面光滑,大小均匀,呈椭圆或鹅卵石形,粒径范围10.23~26.14μm,长轴平均粒径19.09μm,稍大于玉米淀粉;布拉班德糊黏度曲线表明蕨根淀粉糊化温度为68.9~89.4℃,低于玉米淀粉糊,而峰值黏度为611 mPa·s,高于玉米淀粉;与玉米淀粉相比,蕨根淀粉稳定性好、透光性好、冻融稳定性好、抗老化性强,而凝沉性较弱、抗剪切性较差。蕨根淀粉较适于速溶、快餐、冷冻食品加工。     

Use of Iodine as a Tool to Understand Wheat Starch Pasting Properties

The ability of iodine to bind amylose has been used to understand a variety of structural and functional aspects of starch in food systems. In this study, the changes in starch granule swelling, polymer leaching and their relationship to pasting properties was investigated by adding iodine to the starch slurry at either room temperature or 95°C. The objective of the study was to investigate the contribution of leached and solubilized starch polymers on the pasting behavior of wheat starch. The addition of very small amounts of iodine (0.1%, dry basis, db) at room temperature increased peak and final pasting viscosities as compared to when no iodine was added. Further increases in iodine concentration resulted in a decrease in peak and final pasting viscosities. The amount of iodine required to completely inhibit granule swelling was more than that required to minimize amylose leaching from the granule. Adding increasing amounts of iodine at 95°C to the starch slurry resulted in the gradual decrease in peak and final pasting viscosities. The contrasting effects of iodine on paste viscosity behavior when added at room temperature or at 95°C suggest that the contribution of extra‐granular amylose on the setback viscosity is minimal and a larger proportion of amylose is retained in the intragranular spaces.     

脂肪酸对稻米淀粉流变性的影响

为了解脂肪酸对稻米淀粉糊流变特性的影响,利用旋转黏度仪测定了月桂酸、豆蔻酸、棕榈酸和硬脂酸与稻米淀粉结合形成复合物后淀粉糊的流变特性。结果表明,分别将1.0%、2.0%和3.0%的脂肪酸添加到稻米淀粉中,在95℃下蒸煮5、10和15 min,复合指数随脂肪酸量的增加而增加,随碳链增加而降低;黏度系数随复合物的增加而增加,而流变指数则随复合物的增加而降低;在4种脂肪酸中月桂酸与淀粉形成复合物的能力最强,对稻米淀粉的流变性影响最显著。     

预糊化淀粉对糯米粉糊化、流变性能及微观结构的影响

将预糊化淀粉以不同的比例(0%～8%)分别添至糯米粉中,通过测定预糊化淀粉-糯米粉复合体系的糊化、流变特性并分析其微观结构,旨在改善糯米粉的加工及品质特性。结果表明:预糊化淀粉的添加能够显著提高糯米粉复合体系的峰值黏度、回生值、稠度系数(K)、触变回复率及弹性模量(G’),降低其损耗角正切值(tanδ),且随着添加量的增加,其凝胶结构特性变化更明显,从而证实了预糊化淀粉的添加有利于糯米粉形成稳定高的强凝胶结构。此外,预糊化淀粉的添加能够增强预糊化淀粉-糯米粉复合体系颗粒表面结构的致密性,提高其相对结晶度,从而有利于糯米粉糊形成三维网状凝胶结构,显著改善其凝胶性能。