Changes in physico‐chemical and rheological properties of rice during flaking

Hydration, solubility, pasting and rheological properties of roasted‐parboiled rice and flakes were examined in comparison to raw rice. There was an increase in the hydration capacity, swelling power and solubility during roasting‐parboiling of rice as a result of gelatinization of its starch. Flaking caused further increase due to damage of starch by application of mechanical force. The changes were higher in flakes from roller‐flaker as compared to those from edge‐runner. Pasting characteristics of flour slurries in Rapid Visco Analyzer showed a typical profile for pregelatinized products viz. a higher initial viscosity but a lower peak viscosity for roasted‐parboiled rice and flaked rice than for raw rice. The viscosity curves and flow curves of the products over a wide range of shear rate indicated a non‐Newtonian, pseudoplastic behaviour for all the samples. All samples showed typical hysteresis loop in their viscosity curves indicating their thixotropic nature. Flakes from roller‐flaker exhibited lower viscosity but more thixotrophy indicating higher starch breakdown in them than in edge‐runner flakes, which seemed to have more of heat damaged starch.     

挤压预糊化淀粉的性能及其添加对糙米发糕品质的影响

通过挤压不同水分含量（45%、25%和18%）的大米淀粉制备预糊化大米淀粉,测定其分子量、结晶度、糊化度、水吸收指数、水溶解指数、冷糊黏度等指标,并考察了预糊化淀粉添加对糙米粉糊化特性及糙米发糕品质的影响。结果表明,与原大米淀粉相比,45%、25%和18%水分含量挤压制备的预糊化大米淀粉结晶度分别降低了51.93%、58.93%和59.04%;水吸收指数分别提高了1.56、4.69和6.11倍;水溶解指数分别提高了7.04、16.30和27.64倍;冷糊黏度分别提高了2.00、21.44和14.67倍。挤压还使大米淀粉分子发生降解,产生了更多的小链分子。预糊化大米淀粉性能变化与挤压过程中淀粉的水分含量有关。添加预糊化大米淀粉显著提高了糙米发糕的品质（P<0.05）,高的冷糊黏度和低的分子量（18%水分挤压）更有利于制备比容大（1.64 cm3/g）、孔洞细腻均匀、硬度低（338.59 g）和有弹性的糙米发糕。     

黑血糯米粉的物化性质研究

研究了黑血糯的营养成分,黑血糯淀粉的颗粒形貌和结晶性质,糊的凝沉性,冻融稳定性以及糊的粘度曲线。结果表明黑血糯的蛋白质含量高,氨基酸组成合理,结晶度高,糊化温度高,糊的凝沉性低,冻融稳定性一般。可知酸、碱可以促进黑血糯的糊化,而蔗糖则有一定的抑制作用。     

Properties of pregelatinized rice flour made by hot air or gum puffing

Three varieties of rice, TCW 70, TN 67 and TCN 1, with an amylose content of 1.0, 20.3 and 32.0%, were used to produce pregelatinized rice flour by using hot air fluidized‐bed puffing or gun‐puffing methods. Serious molecular degradation was introduced by the gun‐puffing process. However, there were no significant differences in the molecular weights of rice flour before or after the hot air fluidized‐bed puffing process. Pasting properties of pregelatinized rice flours were dependent on the rice variety and the types of pretreatment, and were significantly affected by the puffing method. Hydrothermal pretreatment had different effects on the pasting and hydration properties of pregelatinized rice flour, depending on whether it was made from waxy or non‐waxy rice. Various properties of pregelatinized rice flour could be attributed to the combined effects of gelatinization, retrogradation and degradation of starch molecules during processing.     

Starch Retrogradation and Starch Damage in Parboiled Rice and Flaked Rice

The equilibrium moisture content attained on soaking in water (EMC-S) of parboiled paddy was very high immediately after steaming and fell appreciably on storage, demonstrating starch retrogradation. The extent of retrogradation was dependent on the temperature of storage as well as the moisture content. It was maximum at about 25% moisture when stored at room temperature. Roasting of soaked raw paddy raised its EMC-S due to gelatinization. When stored at room temperature there was progressive retrogradation above 18% moisture. Flaking of roasted paddy and of moist milled rice, both raw and parboiled, also raised the EMC-S. This appeared to be caused by mechanical damage of starch granules. Flaked rice, too, showed retrogradation. — These results confirmed that many properties of parboiled rice are due to starch retrogradation while those of roasted and flaked rice are due to absence of retrogradation.     

大米淀粉及其磷酸酯的理化性质研究

对大米淀粉进行酯化,通过改变温度得到不同取代度的大米淀粉磷酸酯,使用扫描电子显微镜、质构仪、快速黏度分析仪、流变仪对大米淀粉及其不同取代度的淀粉磷酸酯的理化性质进行了测定。结果显示:大米磷酸酯淀粉的硬度、回复性、胶性和咀嚼性要低于大米原淀粉,凝聚性和黏着性要高于原淀粉,取代度越大硬度、回复性、胶性和咀嚼性越小,凝聚性和黏着性越大;大米淀粉磷酸酯的开始糊化温度要小于大米原淀粉,峰值黏度、最低黏度、最终黏度、崩解值、消减值要小于大米原淀粉,取代度增大,开始糊化温度降低,峰值黏度、最低黏度、最终黏度、崩解值、消减值增大。大米淀粉经过磷酸酯变性后,黏度增加了,不易回生,稳定性加强了,凝沉性减弱了,且取代度越高,这些性质越明显;大米淀粉磷酸酯和大米淀粉属于剪切稀化流体,在相同剪切速率下,取代度越大的大米淀粉磷酸酯表观黏度越大。     

Gelatinization of Rice Starch in Aqueous Urea Solutions

Addition of urea to starch slurry causes gelatinization of starch at room temperature. The time required for gelatinization, type of gel formed, rheological properties and apparent viscosity of starch suspension in urea solutions were determined. The latter did not decrease significantly after storing for up to 8 weeks whereas that of cooked starch decreased sharply after one week of storage. Suspensions of starch in urea solutions did not show any fermentation and retrogradation during 8 weeks storage. Its is suggested that urea interacts with starch to form adducts or urea starch complexes. The magnitude of the latter and its abundance is dependent on the concentrations of urea and starch. The urea starch complex acquires very high affinity to water thereby causing swelling and gelatinization of starch.     

黑糯米和血糯米淀粉结构及物化性质的对比分析

本研究从黑糯米、血糯米中提取淀粉,对其表观结构、球晶结构、支链链长、结晶结构、短程结构、黏度性质、糊化性质、老化性质进行对比分析。结果表明：两种淀粉颗粒形态类似,均具有双折射现象;黑糯米淀粉支链中A链、B2链所占比例较低,B1链、B3链所占比例较高;X衍射结果表明,两种淀粉均属于A型晶体,血糯米淀粉相对结晶度较高;红外结果表明,血糯米淀粉有序程度较高,无序程度较低;黏度结果表明,血糯米淀粉峰值黏度、崩解值较高,回升值、糊化温度较低;热力学结果表明,黑糯米淀粉起始温度、峰值温度、终止温度均较高,且更容易发生老化。两种淀粉在结构特性、物化性质方面存在差异,为指导糯米原材料的选用及其在食品工业中的合理开发利用和深加工提供理论依据。     

Rheological properties of black gram (Phaseolus mungo) batter: characterisation of flour from native and modified rice and their effect on batter viscosity

Rheological properties of black gram batter as a function of soaking time, and effect of flour from native and thermally modified rice on black gram batter have been studied. Greater increase in hydration capacity of black gram dhal was observed during 5–15 min of soaking, a gradual increase up to 90 min and a marginal increase beyond this period. Apparent viscosity of batter showed 100% increase up to 90 min and less than 20% increase beyond 120 min, and shear‐thinning nature of batter indicated that they were pseudo‐plastic in nature. Yield stress and consistency index showed greater changes after 90 min, while flow behaviour index did not show significant change beyond 90 min of soaking. Compared with the addition of native rice flour, incorporation of flaked rice flour and expanded rice flour into black gram batter significantly increased the cold paste viscosity of the batter, probably because of their greater water‐holding capacity, compared with that from native rice. Differences in physicochemical characteristics and pasting behaviour of these flour slurries, as studied by Rapid Visco Analyser, corroborated these results by the typical profile of pregelatinised products for flaked rice and expanded rice in comparison to native rice.     

The functional properties of popped, flaked, extruded and roller-dried foxtail millet (Setaria italica)

Foxtail millet grains were decorticated in rice‐milling machinery and the decorticated millet was processed to prepare flaked, extrusion cooked and roller‐dried products, whereas the native grains were subjected to high‐temperature, short‐time treatment to prepare popped millet. The nutrient composition and some of the functional properties of the products were determined, principally solubility and swelling power in water, oil absorption capacity and pasting characteristics. Carbohydrate and lipid profiles of the products were also studied. The changes in the starch granular structure caused by heat treatment were examined by scanning electron microscopy. The degree of starch gelatinization was highest in the case of roller‐dried millet followed by popped, flaked and extruded products. It was concluded that the cereal processing technologies that were investigated could be successfully applied to foxtail millet to prepare ready‐to‐eat or use products, thereby increasing its utilization as a food.     

二氢杨梅素对大米淀粉回生的抑制作

淀粉是大米中的主要成分,其回生程度直接影响大米制品的品质与货架期。该研究将属于多酚类化合物的二氢杨梅素（Dihydromyricetin,DMY）添加到大米淀粉中,研究不同添加量的DMY与大米淀粉的相互作用以及DMY对大米淀粉的溶解度、膨胀度、回生焓值、微观结构的影响,以期改善大米淀粉的回生特性。结果表明,随着二氢杨梅素的添加,大米淀粉的溶解度从4.49%增加至12.83%,膨胀度11.41%降至10.12%;淀粉表面由原来的紧密结构变化为疏松多孔结构;红外光谱1 047 cm-1/1 022 cm-1的比值从0.87降至0.78。较未添加的DMY的大米淀粉相比,低浓度的DMY已经显著影响大米淀粉回生特性。当DMY的添加量为5%时,大米淀粉的回生焓值、回生率以及相对结晶度分别下降了68.75%、71.86%、59.07%。总体而言,二氢杨梅素可以抑制大米淀粉的回生。因此,在淀粉制品加工时,可考虑添加DMY来调控淀粉基食品的回生现象。     

荸荠淀粉糊粘度特性研究

测定了荸荠淀粉糊的Brabender 黏度曲线,利用NDJ-8S数字显示黏度计研究了淀粉乳浓度、pH值、增稠剂、糖、盐等因素对荸荠淀粉糊黏度的影响以及荸荠淀粉糊的流变性。实验结果表明,荸荠淀粉糊化温度低,峰值黏度大,冷稳定性优良,不易发生老化,但热稳定性差。荸荠淀粉糊的黏度随淀粉浓度增加而呈幂次方上升;酸使糊黏度下降,碱使糊黏度上升;黄原胶与魔芋胶均使淀粉糊的黏度增加;葡萄糖和蔗糖对糊黏度的影响呈现先上升后下降的趋势;NaCl与CaCl2均能降低淀粉糊的黏度。荸荠淀粉糊属于非牛顿假塑性流体。     

香芋淀粉磷酸酯的糊化特性研究

研究了香芋淀粉磷酸酯的糊黏度、透明度、冻融稳定性、沉降稳定性、糊化难易程度、耐糖、耐盐和抗霉菌能力。结果表明,与原淀粉相比,香芋淀粉磷酸酯更容易糊化,透明度高,沉降稳定性好,冻融稳定性和抗霉菌能力有所改善,糊黏度减小。随着取代度的增加,香芋淀粉磷酸酯的糊化变得容易,耐盐和耐糖能力提高;透明度先增后减;糊黏度则先减后增。取代度的变化对沉降性和抗霉菌能力影响不大。     

聚葡萄糖对大米淀粉凝胶老化特性的影响

为探究聚葡萄糖(PD)对大米淀粉(RS)凝胶老化特性的影响,利用快速黏度分析仪(RVA)、差示扫描量热分析(DSC)、X-射线衍射分析(XRD)和扫描电子显微镜(SEM)研究聚葡萄糖对大米淀粉糊化黏度特性、热特性、晶体结构和微观结构的影响。结果表明,随着聚葡萄糖添加量的增大,大米淀粉糊化的峰值黏度、崩解值和回生值均显著下降(p<0.05);但是糊化温度升高,大米淀粉的糊化焓值和老化焓值均显著降低(p<0.05),大米淀粉凝胶的相对结晶度从14.09%降到8.61%。SEM结果表明添加聚葡萄糖后,大米淀粉凝胶孔洞变小,表面更致密、光滑,说明聚葡萄糖可以抑制大米淀粉凝胶的重结晶,延缓大米淀粉凝胶的老化。     

甘薯淀粉磷酸酯糊化特性研究

以甘薯淀粉为原料,与三偏磷酸钠反应,制得甘薯淀粉磷酸酯;并采用偏光显微镜、分光光度计、旋转粘度计等现代分析仪器,对所生成不同取代度的淀粉磷酸酯糊化特性进行了较为详细的研究。结果表明:甘薯淀粉磷酸酯糊化温度升高,其冷热粘度稳定性、冻融稳定性、耐盐能力较原淀粉有所提高,但透明度、凝沉性与原淀粉相比无明显优势;取代度的变化对这些性能有显著的影响。     

马铃薯淀粉凝胶形成及其品质影响因素研究进展

马铃薯淀粉黏度高、易糊化,淀粉糊稳定性及透明度高,被广泛应用于各类凝胶制品的加工中。温度、pH等环境因素以及盐类、多糖、蛋白质等食用成分对马铃薯淀粉的糊化特性及淀粉凝胶的回生特性、流变特性、微观结构等影响不同,进而影响马铃薯淀粉凝胶制品的品质。本文在分析马铃薯淀粉凝胶形成机制的基础上,综述了不同环境因素及食用成分对马铃薯淀粉凝胶品质特性的影响规律,揭示了不同食用成分与马铃薯淀粉分子之间的相互作用原理。旨在为高品质、高营养马铃薯淀粉凝胶及其制品的研究与工业化生产提供参考。     

荞麦淀粉糊化特性研究

本实验采用快速黏度分析仪及流变仪对荞麦(甜荞、苦荞)淀粉糊化过程中的黏度和流变特性进行系统分析,并测定荞麦淀粉膨胀度、凝沉性、冻融稳定性、透光率等糊化特性。结果表明,荞麦淀粉(甜荞、苦荞)的糊化温度高于绿豆淀粉,低于大米淀粉和小麦淀粉。苦荞麦淀粉膨胀过程与绿豆淀粉相似,而甜荞淀粉与小麦淀粉相似;荞麦淀粉(甜荞、苦荞)糊透明性好;荞麦淀粉(甜荞、苦荞)冻融稳定性高于大米淀粉,低于小麦淀粉和绿豆淀粉;荞麦淀粉(甜荞、苦荞)糊具有较好的凝沉稳定性;荞麦淀粉糊属于非牛顿流体中的假塑性流体,其流变曲线符合Sisko 方程。     

羧甲基化对马铃薯淀粉糊性质的影响

羧甲基化对改善马铃薯淀粉糊的性质具有重要作用。本文对马铃薯羧甲基淀粉糊的糊性质进行了详细研究 ,包括糊的冷热粘度稳定性、冻融稳定性、透明度、pH值和介质 (蔗糖、氯化钠 )对糊粘度性质的影响。结果表明 ,马铃薯淀粉经过羧甲基化后 ,糊的热粘度稳定性及冷粘度稳定性均有所降低 ,在pH为 6 5～ 8 5范围内 ,羧甲基淀粉糊有最大的粘度。蔗糖对羧甲基淀粉糊粘度有一定影响 ,氯化钠对羧甲基淀粉糊粘度有显著影响。马铃薯羧甲基淀粉具有易糊化、粘度大、糊凝沉性低、冻融稳定性好和透明度高的优良性质     

淀粉的种类及性质对微波膨化的影响

研究了 5种淀粉物料的微波膨化效果 ,以及淀粉的性质对微波膨化的影响。结果表明 :糯米及马铃薯淀粉等含支链淀粉较多的混合物料的微波膨化产品组织结构好 ,膨化率较高 ;淀粉糊化度大于 95%后 ,产品的膨化率将下降 ;淀粉的老化不利于微波膨化 ,并随着老化程度的增加 ,产品的膨化率不断下降     

RHEOLOGICAL AND HYDRATION PROPERTIES OF POPPED RICE

The cold-slurry viscosity, sediment volume and hydration power of popped rice, along with those of dry-heat parboiled rice and expanded rice for comparison, were determined. Values of all these properties increased with increasing severity of processing treatment but decreased with starch reassociation. The cold slurries of these products showed time-dependent thinning, indicating thixotropic nature. A yield value appeared beyond a certain minimum concentration. The viscosities of the products, their hydration power and sediment volume were all interrelated. The popped rice was well gelatinized with little or no starch reassociation.