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.     

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.     

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.     

蒸谷米的湿热处理与工艺优化

对浸泡,蒸煮,干燥等湿热自理对蒸谷米品质的影响进行了研究,结果表明,采用酸醇分步浸泡,高压蒸煮和高温高湿干燥相结合的新工艺生产的蒸谷米维生素Ｂ２的含量较高,且产品色泽好,饭香浓,出米率高,蒸饭时间短。     

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**).     

不同储藏年限稻谷的品质及蒸谷米加工适应性分析

为了解不同储藏年限的稻谷加工蒸谷米的品质变化,为蒸谷米加工原料的选择提供依据.以不同储藏年限的籼稻、粳稻各40份样品为研究对象,将其加工成蒸谷米,并对蒸谷米的蒸煮特性、外观及其制备米饭的食用品质与质构特性等指标进行测定,采用描述统计分析、方差分析、主成分分析等方法对蒸谷米的品质指标进行分析,采用聚类分析探讨稻谷的蒸谷米...     

淀粉结晶度计算的新方法

分析X射线衍射仪的不同衍射角范围、步长及扫描速率等测试因素对淀粉的X射线衍射图谱的影响;使用MDI Jade 软件采用两种方法实现淀粉结晶度的计算。结果表明：当设置衍射角范围为4～60°,步长为0.02°,扫描速率为10°/min时,分析测试结果较好;测试衍射角范围取4～30°之间时,计算结晶度的主观性因素影响相对减小,可快速、简便、可靠的计算结晶度大小,测得玉米、马铃薯、木薯淀粉相对结晶度分别为26.7%、18.4%和26.5%。     

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.     

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。     

蒸谷米加工工艺及品质的研究进展

蒸谷米是以稻谷或糙米原料,经过浸泡、蒸煮和干燥等一系列水热处理后,再经常规碾米工序得到的一类大米产品.蒸谷米在制备过程中发生水合-脱水、淀粉糊化和老化等系列理化变化,赋予其高营养、耐储存等特点,是一种营养健康的主食产品.该文综述蒸谷米加工过程及发生的理化变化,阐明加工和理化变化对蒸谷米产品品质的影响,以期为蒸谷米加工技...     

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。     

Nature of Crystallinity in Native and Acid Modified Starches

Crystalline characteristics of natural and acid modified starches (cereals, millets, pulses, root, and tuber) were examined by X-ray diffraction studies. The (hkl) planes were identified using A-, B- and C- type starch cell parameters. The size of crystallite along the direction [hkl] was calculated for all the reflections in the starches. Smallest crystallites (35 to 56 Å) are observed for the reflections at (2θ) 11.2 to 11.5° corresponding to (111) reflection plane, waxy rice showing the lowest value of 35 Å. Largest crystallite size of the order 200 Å is observed at 2θ 20.0 to 20.4° corresponding to (032) reflection plane with finger millet giving the highest value in the order of 289 Å. Acid modification leads to minor changes in ‘d' spacing but crystallite size changes quite considerably. It increases in some, decreases in others, and remains unchanged in few cases. There was no uniform pattern observed either with respect to acid used, source of starch or the peak at which the changes occur. In finger millet starch, crystallite size becomes homogeneous upon acid treatment.     

不同贮藏条件对发芽蒸谷米品质的影响

为探究不同贮藏条件(包装材料、氧气含量和温度)对发芽蒸谷米的理化性质、生物活性物质、抗氧化活性、微生物学特性的影响,将发芽蒸谷米在真空和常压状态下分别包装在铝层压聚乙烯(aluminum-laminated-polyethylene,ALPE)和聚酰胺-聚乙烯(polyamide-polyethylene,PAPE)包...     

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.     

不同工艺条件对蒸谷米品质的影响

以早籼稻为原料,设定浸泡温度65、70、75℃,浸泡时间3、3.5、4h,蒸煮温度90、95、100℃,蒸煮时间25、30、35 min,进行L9(34)正交试验,分别测定各参数组合处理所得产品的色度、营养品质和蒸煮品质。综合各品质指标选出生产蒸谷米的最佳工艺条件为:浸泡条件为65℃~70℃、3.5 h~4 h,蒸煮条件为100℃、30 min。