Effects of Hydrostatic Pressure/Heat Combinations on Water Uptake and Gelatinization Characteristics of Japonica Rice Grains: A Kinetic Study

ABSTRACT:  The combination effects of pressure (200 to 500 MPa) and temperature (20, 40, and 50 °C) on the water uptake and gelatinization characteristics of japonica rice (Tainung 71) grains were investigated. Pressure greater than 200 MPa at all temperatures increased the moisture content and volume of rice grains; meanwhile, the increase content of rice grain volume showed a high correlation with that of moisture content ( r ²= 0.96). The highest degree of gelatinization of 73% was observed at 500 MPa and 50 °C for 120 min, while gelatinization did not occur at pressures below 300 MPa and temperatures of 20 and 40 °C. The rate of gelatinization followed the 1st-order kinetics at each temperature and pressure. The higher pressures and temperatures would result in higher values of rate constant  k  which could be correlated with both pressure and temperature by combining Arrhenius and Eyring models.     

稻米淀粉期化进程研究

对不同初始粒径的稻米淀粉的糊化进程进行了研究。结果表明,淀粉的糊化具有上升,平缓和回落三个除段,在糊化温度以下（60℃）,淀粉颗粒仅存在吸水膨胀,糊化度曲线平坦,糊化温度以上,随加热温度和的升高,淀粉的糊化速度和糊化程度迅速增高,明显开成糊化过程的三阶段,较小的初始粒径会加快糊化进程,增大回落程度,但对糊化程度影响不大,加热温度对糊化特性的影响较淀粉的初始粒径大。     

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。     

Physicochemical and Gelatinization Properties of Starches Separated from Various Rice Cultivars

Morphological, viscoelastic, hydration, pasting, and thermal properties of starches separated from 10 different rice cultivars were investigated. Upon gelatinization, the G′ values of the rice starch pastes ranged from 37.4 to 2057 Pa at 25 °C, and remarkably, the magnitude depended on the starch varieties. The rheological behavior during gelatinization upon heating brought out differences in onset in G′ and degree of steepness. The cultivar with high amylose content (Goami) showed the lowest critical strain (γ_c), whereas the cultivars with low amylose content (Boseokchal and Shinseonchal) possessed the highest γ_c. The amylose content in rice starches affected their pasting properties; the sample possessing the highest amylose content showed the highest final viscosity and setback value, whereas waxy starch samples displayed low final viscosity and setback value. The onset gelatinization temperatures of the starches from 10 rice cultivars ranged between 57.9 and 64.4 °C. The amylose content was fairly correlated to hydration and pasting properties of rice starches but did not correlate well with viscoelastic and thermal characteristics. The combined analysis of hydration, pasting, viscoelastic, and thermal data of the rice starches is useful in fully understanding their behavior and in addressing the processability for food applications.     

Brewing of Chinese rice wine from rice roasted using superheated steam

The roasting of rice using superheated steam for brewing Chinese rice wine, saves energy and reduces environmental pollution. Three types of rice were adopted for studying rice gelatinization. The superheated steam achieved the best gelatinization under 200 °C. Meanwhile, the degree of gelatinization was the same when the heating period was within 20–40 s. The gelatinization parameters were strongly related to the gelatinization effect. Roasting influenced the properties of nonwaxy rice and waxy rice differently. The brewing of roasted rice was optimal when the raw materials were fed in batches. This produced rice wine with a lower amino acid N content and a lighter flavour. Copyright © 2012 The Institute of Brewing & Distilling     

Effect of Degree of Gelatinisation on the Rheology and Rehydration Kinetics of Instant Rice Produced by Freeze Drying

The effect of degree of gelatinisation on the rheology and rehydration kinetics of instant rice produced by freeze-drying was studied. A Rapid Visco Analyser (RVA) was used to analyse the pasting properties of mixtures of ungelatinized and completely gelatinized dried rice starch at varying ratios in order to develop a standard curve between degree of gelatinization and peak viscosity. The degree of gelatinization of instant rice starch prepared by precooking (gelatinization) for varying times was determined using the calibration curve. It was found that 30 minutes or more of precooking produced completely gelatinized rice. The (RVA) pasting profiles for instant rice precooked for varying times showed that the higher the degree of gelatinization, the lower the viscosity peak, and their decrease was proportional to the degree of gelatinisation. The degree of gelatinisation increased with increase in precooking time. A study of rehydration kinetics showed than an increase in pre-gelatinization time increased the rehydration speed. The kinetics data was analysed using the Peleg's model.     

12种杂粮米蒸煮特性研究

以12种杂粮米为原料,将其各分为2组,一组在蒸煮前进行浸泡处理,另一组未处理。蒸煮后,测定各种杂粮米的糊化度曲线,根据是否需浸泡预处理和延长蒸煮时间将各种杂粮米进行分类。在生产过程中,可以根据杂粮的特点,选择是否浸泡和设定蒸煮时间。结果表明,经浸泡预处理的杂粮米与未经处理的相比,糊化度较高;浸泡处理的样品组中,绿大米、紫大米、绿小米、白小米和玉米碴(小)糊化时间最短,容易熟化,高粱和玉米碴(大)最难糊化。焖制20min后,白大米和白小米糊化度最高,玉米碴(大)、高粱糊化度最低。白大米、白小米、黑大米、绿大米、紫大米可以不经过浸泡而直接蒸煮;黄小米和绿小米不经过浸泡也可达到同样的糊化度,但需要蒸煮较长时间;红大米、玉米碴(小)在蒸煮前必须浸泡才可以达到较高的糊化度;高粱米、荞麦米、玉米碴(大)均需要在浸泡后仍要延长蒸煮时间。     

大米挤压膨化对传统酒精发酵的影响

本文对大米的挤压膨化条件进行了优化，在此基础上，对酒精发酵进行了研究，并与传统的酒精发酵工艺进行了对照，摸索出了最佳工艺条件。当螺杆转速为３５０ｒ／ｍｉｎ，温度为１４０℃，进料量为１９０（表盘读数）时，膨化效果最佳，实验水平值为５．８４６，糊化率达８９．５４％；膨化工艺与传统工艺相比，缩短了时间，节约了能耗，出酒率提高了４１％，最高达７６％．     

Thermal characteristics of ohmically heated rice starch and rice flours

ABSTRACT:  Thermal properties of conventionally and ohmically heated rice starch and rice flours at various frequencies and voltages were studied. There was an increase in gelatinization temperature for conventionally heated rice starches since they were pregelatinized and became more rigid due to starch–chain interactions. In addition, there was a decrease in enthalpy (energy needed) for conventionally and ohmically heated starches during gelatinization; thus, the samples required less energy for gelatinization during DSC analysis. Ohmically heated commercial starch showed the greatest decrease in enthalpy probably because of the greatest extent of pregelatinization through ohmic heating. Brown rice flour showed the greatest gelatinization temperature resulting from the delay of starch granule swelling by lipid and protein. Enthalpy of ohmically heated starches at 20 V/cm was the lowest, which was most likely due to the lower voltage resulting in a more complete pregelatinization from a longer heating time required to reach 100 °C. Ohmic treatment at 70 V/cm decreased onset gelatinization temperature of white flour; therefore, it produced rice flour that swelled faster, whereas the conventionally heated sample showed a better thermal resistance.     

Rheological Properties of Certain Processed Rice Products

Two popular rice products, namely expanded rice and flaked rice, are prepared from parboiled rice. As about 90% dry weight of milled rice is starch, the behaviour of rice and its products reflects largely the behaviour of its starch. The above precooked rice products which undergo a high degree of thermal and/or mechanical treatment during processing have a high degree of gelatinization and display therefore properties like those of pregelatinized starch. Both expanded rice and flaked rice have high water binding capacity and cold-swelling properties. Under suitable moisture conditions they undergo retrogradation and show reduced hydration and viscosity. Normal steam-parboild rice shows much lower viscosity because of a comparatively low degree of starch gelatinization during processing and its subsequent retrogradation. Rheologically the cold slurry of these products indicates a thixotropic system demonstrating time dependent thinning. Further, a dependence on slurry concentration and degree of processing and a yield value behind a certain concentration were also apparent. The cold swelling properties of flaked rice and expanded rice show potential use of their flour as a possible subsitute for pregelatinized starch in food and other industries.     

不同糊化度籼米淀粉的结构及理化性质研究

本研究制备出糊化度分别为58%、80%、100%的籼米淀粉,探讨了糊化程度不同对籼米淀粉微观形貌、结晶特性、短程有序结构、层状结构及其热特性、黏度性质的影响。结构特性表明,随着糊化度的增加,籼米淀粉颗粒结构破坏程度加剧,双螺旋结构和分子有序排列被逐渐破坏,半结晶结构逐渐消失。热特性结果进一步证实,淀粉微晶结构随糊化度增加被破坏的程度加大,且不稳定的微晶优先被熔化使得剩余微晶的均匀性和稳定性有所提高。黏度性质表明,完全糊化籼米淀粉能在较低温度下吸水溶胀形成高黏度的溶液,但热糊稳定性差。尚余微晶结构的淀粉随糊化度的增加表现出更高的峰值黏度和更弱的热糊稳定性。     

富硒大米粉预糊化及其复配代餐粉的研制

以富硒大米为原料,采用喷雾干燥、真空冷冻干燥和滚筒干燥3种技术制备预糊化大米粉,考察不同预糊化加工方式对大米粉硒保存率及品质的影响,并以预糊化富硒大米粉为主要原料制备代餐粉。结果表明,预糊化大米粉硒保留率从低到高的顺序为:喷雾干燥<冷冻干燥<滚筒干燥,糊化度从低到高的顺序为:原料米粉<滚筒干燥<冷冻干燥<喷雾干燥。采用滚筒干燥制备的富硒大米粉(硒含量192. 08μg/kg)糊化度低、硒保留率最高(48. 82%)、呈片状结构,在冲调过程中易分散均匀。从硒含量、营养品质、溶解稳定性综合考虑,含硒大米代餐粉较适宜的配方为(g/100 g):富硒大米粉50,红枣粉5,黑芝麻粉0. 5,葛根粉5,山药粉24. 5,红豆粉5,薏米粉5,糙米粉5。     

二次挤压制备重组米的响应面优化及品质研究

本研究通过选取加工适用性较好的马铃薯,将其制粉并混配早籼米粉作为原料,用单螺杆挤压机将其预糊化,再用双螺杆挤压机制备马铃薯重组米,探究挤压工艺对重组米品质的影响,通过响应面优化预糊化挤压工艺,研究二次挤压和糊化度对重组米性质的影响。结果表明,预糊化最优工艺如下:进料水分37%,挤压温度72 ℃,螺杆转速34 r/min,在此条件下,挤出物品质良好,糊化度可达到75.95%。根据重组米质构结果可知,进料糊化度为50%时,重组米的硬度和粘聚性最接近早籼米;进料糊化度为30%时,重组米的咀嚼度最接近重组米;增加进料的糊化度可有效提高重组米的弹性。本文为改善重组米品质提供新思路和理论支持。     

A Model for Quantitating Energy and Degree of Starch Gelatinization Based on Water, Sugar and Salt Contents

A mathematical model defining the relation of moisture, sucrose and salt on the degree of starch gelatinization obtained from DSC, was developed. As moisture increased to 1.0g water, gelatinization rose to 85% and was complete at 1.5g water. Addition of 5% to 15% sucrose had no effect between 0.5 and about 0.8g water, but at higher moistures degree of gelatinization decreased with increasing sucrose. Salt showed a similar effect. The model covered 30% to 80% water, 0% to 15% sucrose, and 0% to 7.5% salt (R²=0.94). A test application of the model extended to rice and wheat starch, showed some correlation, but not conclusively.     

Physicochemical Properties of Rice Steeped in Hot or Warm Water

Prolonged steeping of rice grains in hot or warm water was examined to study the gelatinization process of rice starch. Rice treated at 75°C for 8–18 hr showed the same type “V” X-ray diffraction pattern as that of cooked rice. Rice treated at 50–60°C for 24–72 hr showed a strengthened type “A” pattern. The gelatinization degree of the 75°C treated rice determined by the β-amylase-pullulanase method and Brabender amylography was as high as that of cooked rice. The value of the 50–60°C treated rice was lower than that of raw rice. The gelatinization temperature of rice varied with the two types of treatment.     

直接挤出制备米粉(线)工艺的优化

为了获得直接挤压制备米粉(线)的最适工艺参数,采用响应面(RSM)方法设计试验方案,对挤压机挤压制作米粉的工艺参数进行优化分析。研究原料含水量、机筒温度、螺杆转速对米粉糊化度的影响。结果表明:3个因素对糊化度影响大小依次为机筒Ⅲ区温度>螺杆转速>原料含水量。通过响应面分析得出挤压米粉最佳工艺:原料含水量35.1%,Ⅲ区温度102℃,螺杆转速117 r/min。在此条件下,米粉糊化度为92.1。与3种市售产品对比,自制米粉在硬度、糊化度、咀嚼性和感官品质方面达到了市售产品平均水平。     

Relationship between the structure,physicochemical properties and in vitro digestibility of rice starches with different amylose contents

The in vitro digestibility and molecular and crystalline structures of rice starches (Long-grain, Arborio, Calrose, and Glutinous) differing in amylose content were investigated and the relationship between the structure and in vitro digestibility of starch was studied. Long-grain showed the highest amylose content (27.2%), whereas Glutinous showed the lowest amylose content (4.2%). Long-grain had the highest average amylopectin branch chain length (18.8) and proportion (8.7%) of long branch chains (DP ≥ 37), and the lowest proportion (26.9%) of short branch chains (DP 6–12). Among the non-waxy rice starches (Long-grain, Arborio, and Calrose), Calrose had the lowest average chain length (17.7) and the lowest proportion (7.1%) of long branch chains (DP ≥ 37). The relative crystallinity of rice starch followed the order: Glutinous (33.5%) > Calrose (31.4%) > Arborio (31.0%) > Long-grain (29.9%). Long-grain had the highest gelatinization temperature and the lowest gelatinization temperature range, whereas Glutinous showed the highest gelatinization temperature range and gelatinization enthalpy. Arborio had the highest melting enthalpy for amylose–lipid complex among the tested rice starches. Pasting temperature, setback, and final viscosity increased with increasing amylose content, whereas the peak viscosity and breakdown showed negative correlations with amylose content. The rapidly digestible starch (RDS) content of the tested rice starches followed the order: Glutinous (71.4%) > Calrose (52.2%) > Arborio (48.4%) > Long-grain (39.4%). Contrary to this, the slowly digestible starch (SDS) and resistant starch (RS) contents showed an opposite trend compared to RDS. Digestibility (RDS, SDS, and RS) of the rice starches was significantly correlated (p ≤ 0.05) with amylose content, proportions of DP 6–12 and DP 13–24, relative crystallinity, intensity ratio (of 1047 cm⁻¹ to 1022 cm⁻¹ from Fourier transform infrared spectroscopy), swelling factor, amylose leaching, onset temperature of gelatinization, gelatinization temperature range, gelatinization enthalpy, pasting temperature, peak viscosity, breakdown, setback, and final viscosity.     

浸泡和超高压预处理对大米品质的影响

对浸泡和高压处理条件对大米品质的影响做了初步研究。实验表明,用0.8%的柠檬酸溶液浸泡大米有助于提高其糊化度,随着压强的升高,大米淀粉的糊化度逐渐增强,400 MPa压强下糊化度的边缘效应,能够显著降低大米的老化度,提高米饭的品质。     

大米垩白度与米饭蒸煮品质的相关性研究

本文研究了五种垩白度不同的原料米饭在高压蒸煮工艺条件下的蒸煮品质,并对垩白度与多种蒸煮品质指标进行了相关性分析;同时为了满足少量米饭品质测定需要设计了微波蒸煮米饭的工艺条件,研究微波蒸煮工艺条件下不同垩白面积对米饭糊化度的影响。研究发现:大米蒸煮后米饭的膨胀率和吸水率与原料米的垩白度呈负相关,但是均未达到显著性水平;质构特性与垩白度的相关性分析表明垩白度主要影响米饭的硬度,对米饭粘度、粘聚性、回复性、弹性、胶粘性和咀嚼性有一定影响,但影响并不显著;原料米的垩白度与米饭形态呈极显著负相关;与口感呈显著负相关;与色泽、滋味、香气均有一定相关性,但均未达到显著水平;微波蒸煮试验显示全垩白米样糊化速度较无垩白米样在3~15 min阶段都要快,且最终糊化度值全垩白米样比无垩白米样大。     

Effect of Extrusion Cooking on Functional Properties and in vitro Starch Digestibility of Barley-Based Extrudates from Fruit and Vegetable By-Products

ABSTRACT:  Barley flour and barley flour–pomace (tomato, grape) blends were extruded through a co-rotating twin-screw extruder. The aim of the present study was to investigate the effects of die temperature, screw speed, and pomace level on water absorption index (WAI), water solubility index (WSI), degree of starch gelatinization, and in vitro starch digestibility using a response surface methodology. The selected extrudate samples were examined further using differential scanning calorimetry (DSC) and polarized light microscopy, respectively. The WAI of barley–pomace extrudates was affected by increasing pomace level. Temperature had significant effect on all types of extrudate but screw speed had significant linear effect only on barley and barley–grape pomace extrudates on degree of starch gelatinization. Although no gelatinization peak was detected, an endotherm was observed on all selected extrudates. In general, extrusion cooking significantly increased in vitro starch digestibility of extrudates. However, increasing level of both tomato and grape pomace led to reduction in starch digestibility.