Thermal Degradation of Starch in Parboiled Rice

Raw and variously parboiled Intan rice (intermediate-amylose variety) starch was fractionated in Sepharose CL-2B column into a larger-molecule (Fr I) and a smaller-molecule (Fr II) fraction. The amount of Fr I decreased and that of Fr II increased in parboiled as compared to raw rice, the extent of change increasing with increasing severity of processing. The proportion of polysaccharide and “amylose” in Fr I decreased from 70% and 40% of total, respectively, in raw rice to 16% in parboiled rice prepared by 3 kg/cm² gauge steam pressure. Simultaneously, the λ_max of its iodine complex increased from 570 to 588 nm in Fr I and decreased from 635 to 620 nm in Fr II. The change was marginal or low after steaming at ambient pressure or after sand roasting. The data show that thermal degradation of starch must be considered as another contributor, in addition to starch gelatinization and reassociation, to the peculiar properties of parboiled rice.     

The Significance of Starch Polymorphism in Commercially Produced Parboiled Rice

A study of eight commercial parboiled samples derived from two varieties of rice produced by four different processes has shown that depending on the parboiling process, the starch component itself can be present as native and/or retrograded starch in addition to the amylose-lipid complex. Further, it was demonstrated that the polymorphic states of starch can influence the texture and behaviour of cooked rice. The parboiled rice samples which had all three states of starch (i.e. ungelatinized and recrystallized amylopectin plus the amylose-lipid complex) possessed the hardest eating property but the lowest solubility. A negative linear relationship was demonstrated between the hardness and the solubility of cooked, parboiled rice. Overall, the observations suggest the existence of different forms of starch in parboiled rice which vary with the different parboiling protocols. The conditions governing their formation need to be established before investigating the specific functionality of individual forms within the rice. This study further confirmed that retrograded starch (amylopectin) in parboiled rice did not exhibit a B-tye X-ray pattern but mixed A+V patterns.     

Techniques for Canning Instant Parboiled Rice

The technology to produce an acceptable canned rice was investigated. Conventional raw and parboiled rice exhibit excessive starch leaching, loss of structural integrity, discoloration, unpalatable odors, and poor cooking qualities when canned. Instant parboiled rice which has been hydrated in boiling water before canning yields a superior product Objective color values are improved by flushing the hydrated rice with tap water before canning. Canned grains are free flowing and yield a product similar to freshly cooked rice. Without hydration, the product tends to be a solid mass of chalky and crumbly grains. A direct relation exists between subjective values for appearance and texture of canned rice.     

Crystallinity of Acid Treated Corn Starch

The hydrolysis of corn starch by 1N H₂SO₄-30% ethanol aqueous solution at 45°C increased linearly with increasing of hydrolysis time for 20 d. The relative crystallinity of native corn starch showed 0.350 by X-ray diffraction and it increased gradually with increasing of hydrolysis time up to 8 d. The increasing ratio of 1/hydrolysis residue to hydrolysis time increased more largely than that of relative crystallinity after 14 d. On the other hand, the relative crystallinity of native corn starch by deuteration showed 0.341 very near to the value by X-ray diffraction. Moreover, this increasing ratio of the crystallinity accompanied by acid hydrolysis showed an inclination similar to that given by X-ray diffraction. These facts suggest that the exchanging of OH for OD groups may be caused very a little in crystalline region of corn starch granules.     

Thin-layer Drying of Parboiled Rice at Elevated Temperatures

Experiments were conducted to dry thin layers of long-grain parboiled rice at air temperatures ranging from 38–158°C and relative humidities from 0.3–80%. A series solution of the diffusion equation, considering long-grain rice as infinite cylinder, was used to express the moisture ratio. During thin-layer drying experiments it was necessary to develop a computational method to determine the relative humidity of air above 100°C without the use of wet bulb temperature measurements. An empirical exponential expression for moisture ratio gave the best fit to the drying data at all conditions. Parboiled rice was found to have higher values of effective diffusivity than raw rice.     

Crystallinity of Raw Rice Starch Granules as Indexed by Corrosion with Hydrochloric Acid and Amylase

After 15 d in 2.2N HCl at 35°C, residual starch of 34 granular rice starches differing in apparent amylose content (AC) and final gelatinization temperature (GT) ranged from 1.3 to 20.8% and was verified to correlate significantly with GT (r = 0.69**) and AC (r = 0.44**). Residual starch after 5 h corrosion with crude Chalara paradoxa amylase ranged from 0 to 29.4% and also correlated significantly with GT (r = 0.45**) and AC (r = 0.70**). The amounts of residual starch after Lintnerization and after C. paradoxa amylase digestion were significantly correlated (r = 0.72**).     

Study on Relative Crystallinity of Moist Potato Starch

The relative crystallinity of various moist potato starches were measured by X-ray diffractometer. The diffraction patterns showed to become sharp with increasing of the amount of sorption moisture. Both areas of crystallinity portion were proportionally correlated with the amount of moisture. On the assumption that crystallinity of cellulose is 70%, that of native potato starch was showed to be 24%.     

变性淀粉结晶性和形态研究

利用光学显微镜和X射线衍射对玉米变性淀粉的颗粒形貌和结晶结构进行了研究和讨论，揭示出一定变性度下，不同的变性淀粉仍然具有球晶结构和结晶性，保持其刚性粒子特性。与原淀粉相比，变性淀粉的粒子形态未受到破坏。     

蒸谷米糠和普通米糠的理化特性分析

对蒸谷米糠和普通米糠的物理特性和化学特性进行了测定.结果表明,其物理和化学特性均发生了变化.在米糠综合利用上可以分级提取米糠油和米糠蛋白,即先分级收集一、二、三机米糠作为制油原料,生成的米糠粕与抛光机米糠混合提取米糠蛋白.     

微波处理对板栗淀粉结晶度的影响

研究了微波辐射对板栗淀粉的结晶度及α度的影响。结果表明,微波辐射可有效影响板栗淀粉乳的结晶度和α度变化,在微波辐射功率一定的条件下,板栗淀粉乳的浓度不同,经微波辐射后的样品结晶度和α度变化也不同,板栗淀粉的浓度与经微波辐射后的样品α度呈反相关,与经微波辐射后样品的X-射线衍图谱的结晶峰面积及样品的结晶度呈正相关。     

On the Relationship between Regain and Crystallinity of Starch

A formula for the relationship between regain and crystallinity of starch is given. Accessibility of crystalline portion of starch is in the range of that of cellulose. The saturated moisture state shows six molecules of water per glucose residue. The sorption cannot take place at the inside of crystalline portion of starch.     

微波辐射对马铃薯淀粉结晶度和α度的影响

采用酶水解法、X-射线衍射法等研究了微波辐射对马铃薯淀粉的结晶度和α度的影响。试验结果表明：微波辐射可有效改变马铃薯淀粉的结晶度和α度，在微波辐射功率一定的条件下，马铃薯淀粉乳的浓度不同，经微波辐射后的样品结晶度和α度变化也不同，马铃薯淀粉乳的浓度与经微波辐射后样品的X-射线衍射图谱的晶峰面积及样品结晶度的大小呈正相关，与经微波辐射后Ⅸ度的高低呈反相关。     

Changes of Relative Crystallinity of Potato Starch Under Gamma Irradiation

Indices of relative crystallinity of starch samples after gamma irradiation in dry form or in potatoes have been determined by differential and integral methods and compared with those calculated for corresponding reference samples. In the case of dry samples, the diminution of relative crystallinity was observed after gamma ray irradiation. In the case of starch samples extracted from irradiated potatoes, the influence of drying conditions was additionally observed. The diminution of relative crystallinity seems to be accompanied by destruction of long-range ordering as observed by SAXS experiment.     

On the Relationship between Specific Volume and Crystallinity of Starch

Specific volumes of starch, crystalline portion and amorphous portion are discussed and the crystallinity is calculated from the specific volume. The specific volume of starch is calculated from the density by extrapolation of the moisture content zero. The specific volumes of the amorphous portion seem to be almost the same as that of cellulose. One is 0.673 for potato, waxy corn and waxy rice and the other is 0.684 for sweet potato, tapioca, wheat and corn. The crystallinities of the starches calculated from the specific volumes with a special equation are reported.     

浸泡对早籼稻水分含量及蒸谷米品质的影响

以早籼稻为对象,通过改变浸泡时间和温度,测定分析浸泡条件对早籼稻的水分含量、蒸谷米VB1的含量以及蒸谷米品质的影响。结果显示,浸泡条件对蒸谷米品质影响明显,当浸泡温度为75℃、时间为3.5 h时,蒸谷米的品质最好,VB1含量最高。     

柠檬酸甘油共混热塑性淀粉的制备及性质研究

以糯米淀粉为原料,加入甘油、柠檬酸制备热塑性淀粉。通过试验得到热塑性淀粉制备的最佳工艺条件,即反应时间60 min、反应温度120℃、柠檬酸与糯米淀粉质量比为0.4∶1、甘油与糯米淀粉质量比为0.3∶1,热塑性糯米淀粉达到最高取代度0.118。并通过红外图谱分析和差示扫描量热检测,证明柠檬酸甘油共混制备的热塑性糯米淀粉与原糯米淀粉相比透明度明显提高,黏度显著降低。处理后的淀粉发生了部分酯化反应,其热稳定性明显提高,增强了热塑性糯米淀粉的生产加工能力。     

Changes in Crystallinity and Gelatinization Phenomena of Potato Starch by Acid Treatment

The hydrolysis of potato starch by 1-N H₂SO₄/30% ethanol aqueous solution at 45°C increased linearly with increasing of hydrolysis time for 14 d. The relative crystallinity of native starch showed 0.343 and 0.350 by symmetrical reflection and transmission techniques, resp. The increasing ratio of relative crystallinity to hydrolysis time corresponded very closely with that of 1/hydrolysis residue up to 14 d. These facts suggest that only the amorphous region of the starch granules will be hydrolyzed by the acid. By differential scanning calorimetry the calorimetric enthalpy of potato starch containing about 200% moisture content was found to stay largely unchanged by acid treatment for 6 d. The swelling power at 70° and 80°C of potato starch reached to the minimum value and, moreover, from the gel-chromatogram patterns of the acid-treated starches, the crystalline region of the starch granules may begin to deteriorate slightly by acid treatment for more than 6 d, although the relative crystallinity by the X-ray diffraction method increased slightly with passing of hydrolysis time.     

直链结晶淀粉形成过程中结晶度的变化

以蜡质玉米淀粉为原料,采用酶法制备直链结晶淀粉,优化酶法制备直链结晶淀粉的工艺参数,通过斐林试剂法和X-射线衍射技术考察酶相对作用量及作用时间对直链结晶淀粉DE值、结晶度的影响。采用酶法所制备的直链结晶淀粉有可能形成一种新的材料,可部分或全部替代价格昂贵的微晶纤维素,应用于药用辅料及片剂制品工业中。     

Internal Lipid in Rice Starch

The starch of a Japanese rice variety contained 0,69% of internal lipid. The ratio of neutral lipid, glycolipid and phospholipid in the total lipid was 37.0: 20.3: 42.7. The principal components of the neutral lipid were free fatty acid and monoglyceride; those of glycolipid were monoglycosylmonoglyceride and diglycosylmonoglyceride; those of phospholipid were lysophosphatidylcholine and lysophosphatidylethanolamine. All were monoacyl lipids, and they constituted more than 90% of the total internal starch lipids. The predominant fatty acid components were palmitic acid and linoleic acid. The component sugars of glycolipids were galactose and glucose, galactose being predominant. Lysophosphatidylcholine and monoglyceride were almost of the α-type.