Studies on parboiled rice: Part 1—Comparison of the characteristics of raw and parboiled rice

Various properties of raw and parboiled rice were compared in an effort to elucidate the factors responsible for the changes induced by parboiling.The parboiled rice was less prone to disintegration on cooking, the kernels remaining well separated and less sticky than the non-parboiled sample. The solids leached into the cooking water and the extent of solubilisation of the kernels on cooking were both considerably lowered by parboiling. Amylograms of flour prepared from the rice revealed that this was due to the resistance of the starch in the parboiled rice to swelling and solubilisation in hot water.From the results of X-ray diffraction spectra it was concluded that the behaviour of parboiled rice is influenced by the presence of an insoluble helical amylose complex and not, as is generally assumed, by retrogradation.     

Comparative studies on the physicochemical properties and microstructure of raw and parboiled rice

The protein and mineral salts of rice were found to have increased while water-soluble substances were found to have decreased as a result of parboiling. Parboiling resulted in marked changes in the amylograph properties of rice paste, as well as increasing its resistance to alkali dispersion. The grains were shorter but wider, with lower water absorption and swelling capacity during cooking than those of raw-milled rice.The differences in ultrastructure between dry and cooked raw-milled and parboiled rice were studied with a scanning electron microscope. Complete deformation of the starch granules was evident in the raw-milled rice after cooking for 9 × 10² and 12 × 10² s, while those of parboiled rice showed great resistance to deformation. Variations in the over-cooked grains of both raw-milled and parboiled rice were studied.     

The breakage susceptibility of raw and parboiled rice: A review

Rice (Oryza sativa L.) is one of the most important cereals in the world. Before it is consumed, it is common to remove the hull, bran and germ from the rough rice kernel which is either parboiled or not. During such processing, rice kernels are subjected to mechanical stresses which cause some rice grains to break. A main challenge of the rice industry is to minimize the quantities of broken rice. We here review the factors impacting the breakage susceptibility of rice kernels. Their tendency to break is primarily determined by fissures, chalkiness, immaturity and rice kernel dimensions, properties which are both cultivar and rice grain history dependent. The intensity of processing of any given rice feedstock determines the actual level of broken rice kernels. If performed properly, parboiling, a three-step hydrothermal treatment consisting of soaking, heating and drying of rough rice, substantially reduces the level of broken kernels.     

Studies on parboiled rice—Part 3: Characteristics of parboiled rice on recooking

The apparent solubility and cookwater loss of samples of parboiled rice, subjected to various steam treatments, were measured after recooking the rice in boiling water. Both parameters were reduced according to the severity of treatment received, the reduction of apparent solubility being the most marked.The results showed a highly significant, negative linear correlation (r = 0.972) between apparent solubility and the relative amount of complexed amylose in the starch. This confirmed the suggestion made in Part 1 of this paper that complexed amylose was responsible for the resistance of the starch towards solubilisation.Estimation of the amylose and amylopectin released into the cooking water and solubilised inside the kernel revealed that both fractions were insolubilised to a similar extent. It was proposed that amylose was insolubilised by complexing with free fatty acids and the amylopectin insolubilised by interaction with the complexed amylose.     

Nutritive value of raw,parboiled, stabilised and deoiled rice bran for growing chicks

The proximate analysis of different types of rice bran (raw, parboiled, stabilised and deoiled) showed wide differences in the oil, fibre, ash and available carbohydrate contents. Free fatty acids in the fat extracted from the raw, parboiled and stabilised rice brans were 500.6, 277.8 and 163.1 g kg^?1 respectively. Palmitic, oleic and linoleic acids constituted about 94.5% of the total fatty acids in oils extracted from those rice bran types. In chick growth trials, the average metabolisable energy of raw, parboiled, stabilised and deoiled rice brans was found to be 12.34, 11.67, 12.11 and 9.08 MJ kg^?1 DM, respectively. The bodyweight gain of broiler chicks over a period of 6 weeks was depressed by 183, 79, 49 and 200 g when the level of the respective brans was raised from 200 to 400 g kg^?1 in the diet. However, the food and protein conversions were significantly depressed at both levels of rice bran in the diets.     

蒸谷米糠膨化工艺的研究

考察了膨化方式、原料水分、入料温度、机膛温度等工艺条件对蒸谷米糠膨化效果的影响.实验结果表明,湿法和干法膨化均可获得较好的膨化效果,最佳工艺条件为:干法,原料水分控制在8％ ～9％,入料温度50C,机膛温度100 ～ 110℃;湿法,原料水分控制在6％ ～7％,入料温度60℃,机膛温度120 ～130℃.蒸谷米糠膨化料在实验室模拟浸出卖验中获得了较好的浸出效果.     

Technological properties of microwave parboiled rice

Two rice varieties, a short grain (Giza 175) and a long grain (Giza 181), were parboiled by soaking in water at 80–85 °C for 1.5 h and then dried in the microwave oven for 3, 5, 6 and 8 min. The effect of such parboiling treatment on milling output and technological properties (cooking and eating quality) of milled rice were studied. There was a negative significant correlation between head rice and the drying time and a positive correlation between the drying time and the broken grains. The effect of such treatment on the chemical composition of milled parboiled rice, i.e. amylose, protein, fat and ash contents, showed that the amylose content of Giza 175 variety significantly decreased while not affect in Giza 181 variety. No significant differences were obtained in protein, fat and ash contents by increasing drying time. Microwave drying was more pronounced on Giza 175 variety rather than Giza 181 one. However, the optimum cooking time of the parboiled samples of the two varieties was not affected as a result of increasing the microwave drying time.     

蒸谷米快速浸泡工艺研究

研究不同浸泡工艺包括温度-时间、微波、酸碱溶液、低浓度乙醇、酶对稻谷吸水率的影响,结合蒸谷米外观品质及米饭质构分析,筛选有效的快速浸泡工艺。结果表明,在稻谷∶水为1∶1(g/mL)、温度60~70℃、浸泡4~5 h时,便达到浸泡工艺要求,吸水率达到30%;能显著提高稻谷吸水率的方法是质量比5%的纤维素酶浸泡4 h,吸水率达30.07%;能显著缩短浸泡时间方法是5 min、700 W微波浸泡,吸水率为31.69%。且2种浸泡工艺对蒸谷米的外观品质和米饭质构无不良影响,有望作为蒸谷米快速浸泡工艺进行应用。     

蒸谷米生产工艺简析

介绍了中粮(江西)米业有限公司的蒸谷米生产工艺。     

蒸谷米浸泡工艺参数初探

通过研究浸泡温度、浸泡时间、浸泡压力对蒸谷米含水量的影响,采用正交试验优化蒸谷米浸泡工艺参数,经过中试试验修正的工艺参数为:浸泡温度55℃、浸泡压力400kPa、浸泡4 h.     

Effect of modified atmosphere packaging on the quality of germinated parboiled brown rice

Germinated parboiled brown rice (GPBR) is a healthy Thai food. To extend the quality of GPBR cv. KDML 105 with 8.06% moisture content, the effects of three packaging conditions on the characteristics of GPBR were investigated. GPBR in laminated (nylon/LLDPE) bags was sealed as follows: vacuum-sealed, 40% N₂-sealed with 60% CO₂ (60% CO₂+40% N₂), or 100% N₂-sealed before storage under ambient conditions (30±2°C, 70±5% RH) for 15 months. GPBR in all the packages exhibited delayed fungal proliferation and very low aflatoxin B₁ contamination (<0.82 μg/kg). The 100% N₂-sealed package was the best treatment to preserve GPBR quality, as indicated by the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and free fatty acid content as well as the least rancidity and brownness. As observed through a scanning electron microscope, compared with vacuum-sealed packages and those sealed with 60% CO2+40% N₂, the lowest hardness texture and the least elongation of cooked rice in 100% N₂-sealed package were linked to a lesser compact GPBR endosperm ultrastructure.     

Swelling and solubility behaviour of parboiled rice flour

Parboiled rice flour swelled and dissolved more than raw rice flour in water at temperatures below 70°C, but less than raw rice at higher temperatures. This difference between raw and parboiled rice increased with an increasing degree of parboiling. A sample of parboiled rice produced by dry-heating soaked paddy in hot sand behaved differently; but when it was wetted and tempered to favour reassociation of starch, its properties fell in line with normal steam-parboiled rice. The above behaviours of raw and parboiled rice flour were similar to those of corresponding whole-grain rice. They also reinforce the earlier suggestion of starch reassociation in conventional parboiled rice.     

蒸谷米生产中干燥工序工艺参数的研究

以糙米为原料进行干燥工序工艺参数的研究。通过对快速干燥温度和时间、慢速干燥温度和时间以及缓苏时间进行单因素试验和正交试验,最终确定干燥工序的最佳工艺参数为快速干燥温度为70℃、快速干燥时间60 min、缓苏时间为40 min、慢速干燥温度65℃和慢速干燥时间40 min。     

Effect of milling on colour and nutritional properties of rice

Brown rice (long-grain variety Puntal) was abrasively milled (0–100 s) to various degrees of milling (DOM, 0–25%). The non-linear relationship between milling time and DOM indicated a variability in hardness within the different rice fractions. The hardness of the bran layers increased from outer to inner bran layers, while the different endosperm fractions were of comparable hardness. The colour parameters L^*, a^* and b^* and extinction measurements of water-saturated butanol extracts of flour, from rice with different DOM, indicated that bran contained much more yellow and red pigment than endosperm. The levels of yellow and red pigment decreased from the surface of the brown rice to the middle endosperm (DOM = 15%). Once bran (DOM = 9%) and outer endosperm (additional DOM = 6%) were removed, the yellowness and redness of the middle endosperm of the raw rice remained constant, indicating that the pigments were uniformly distributed in the middle endosperm. Cooking of rice containing residual bran layers (DOM < 9%) increased rice brightness (L^*) and decreased its redness (a^*) and yellowness (b^*), as expected from a dilution effect resulting from the uptake of water, as well as from leaching of pigments in the cooking water and diffusion of bran pigments to the endosperm. Cooking of rices with DOM > 9% resulted in products of constant brightness and redness but with yellowness which decreased as a function of DOM. Proteins, minerals and starch were not uniformly distributed in the brown rice kernel. The endosperm (DOM > 9%), contained most of the rice kernel proteins (84.2%), and proteins were mostly concentrated in the outer endosperm (9% < DOM < 15%). Bran (0% < DOM < 9%) contained most of the minerals (61.0%), and starch (84.6%) was concentrated in the core endosperm fraction (DOM 25%).     

Geographical traceability of “Arròs de Valencia” rice grain based on mineral element composition

The geographical traceability of rice grain samples involves the use of analytical methodologies that allow their differentiation on the basis of the rice composition, thus confirming their authenticity. In this paper, trace element determination of rice samples by inductively coupled plasma optical emission spectroscopy (ICP-OES) has been addressed to achieve a complete geographical origin classification. Samples (107) from Spain including Valencia, Tarragona, Murcia and Extremadura, Japan, Brazil and India were employed as training set whereas the validation set was formed by 46 samples of the aforementioned geographical origins. Data were processed by linear discriminant analysis (LDA), using as analytical variable the concentration of 32 elements (Al, As, Ba, Bi, Cd, Ca, Cr, Co, Cu, Fe, Pb, Li, Mg, Mn, Mo, Ni, K, Se, Na, Sr, Tl, Ti, Zn, La, Ce, Pr, Nd, Sm, Eu, Ho, Er and Yb), enabling a 91.30% of correct classification for the validation set.     

黄酒及其原料中微量氰化物的测定

基于氰化物衍生化及LC-MS/MS联用技术,建立了适用于黄酒及其原料中游离态氰化物及总氰化物测定的方法,该方法具有良好的准确度、精密度和灵敏度,检出限为0.01μg/L,相对标准偏差低于5%,回收率在93.6%~106.0%。利用该方法对不同黄酒及其酿造原料中的游离态和总氰化物的含量进行了分析检测。结果表明,黄酒酿造原料大米和麦曲及黄酒中均含有微量氰化物。其中,麦曲氰化物含量相对较高,其游离态氰化物含量20.35~93.73μg/L,总氰含量98.09~1 032.03μg/L。黄酒中游离态氰化物的含量低于15μg/L,总氰含量一般低于30μg/L,表明在黄酒储存和销售过程中,氰化物可能不是影响黄酒氨基甲酸乙酯(EC)增加的主要因素。该研究结果为进一步明确黄酒中氰化物与EC的关系提供了技术手段和研究基础。     

超声波辅助浸泡对稻谷含水量和蒸谷米品质的影响

以早籼稻为材料,研究超声波功率、超声波处理时间及料液比对稻谷含水量、蒸谷米的整精米率以及糊化特性的影响,并采用正交试验对超声波辅助浸泡工艺进行优化。结果表明:在超声波功率为600W,超声波处理时间为25min,料液比为1∶3(g/mL)时的工艺组合条件最优,整精米率达68.82%,蒸谷米的品质最好。     

Limited multilayer desorption of brown, parboiled rice

Two mathematical models, the BET-equation and the Caurie-equation, are used to analyse experimental desorption isotherms of two long-grain varieties of brown, parboiled rice at different temperatures. Monolayer moisture contents and maximum number of sorbed water layers, estimated by the Caurie-model, decrease with increasing temperature. From the temperature dependence of the desorption isotherms, isosteric heats of desorption are calculated. For both varieties, the differential heats of desorption are already very small (1.4 kJ/mol) at a moisture content of 20%. Thus, additional moisture behaves almost like pure water.     

Effect of soaking medium on the physicochemical properties of parboiled glutinous rice of selected Laotian cultivars

The effect of various soaking mediums, viz. water (control), 3% NaCl and 0.2% acetic acid, and without soaking on the physicochemical properties of parboiled selected glutinous (TDK8 and TDK11) and non-glutinous (Doongara) was investigated in the present study. Results showed that the chemistry of soaking had a significant effect on the head rice yield (HRY), grain hardness, crystallinity, color, pasting and thermal properties, textural attributes, and glycemic index of these rice varieties. Soaking with NaCl and acetic acid significantly increased the grain hardness and HRY than control and without soaking treatments. Acetic acid and NaCl soaking significantly affected crystalline regions of starch resulting in reduced crystallinity in X-ray diffraction analysis and thermal endotherms in DSC analysis. NaCl soaking induced swelling of starch granules resulting in high peak and final viscosities. However, acetic acid restricted swelling resulting in reduced peak and final viscosities. NaCl and acetic acid soakings also resulted in increased hardness and adhesiveness of cooked grains than normal water soaked and un-soaked parboiled rice samples. Interestingly, change in textural attributes was prominent in parboiled glutinous rice. The color difference value for fresh parboiled samples was significantly lower for acetic acid soaked samples compared to NaCl soaked and un-soaked samples probably due to bleaching effect of acetic acid. Moreover, parboiling also resulted in significant reduction in glycemic index of glutinous rice. These findings revealed the potential application of parboiling with modified soaking techniques to improve the grain quality.     

Effects of trace element supplementation on milk yield and composition in camels

Objective of the study was to determine milk yield and quality (fat, protein, mineral content) of camels reared in north-east Africa, supplemented with trace elements for the first nine months of lactation. Twelve multiparous lactating camels were divided into two groups: control and treated (trace element supplemented). Addition of trace elements did not affect milk production and milk fat and protein content (respectively 3.09 vs. 3.51 kg d⁻¹; 2.86 vs. 2.56%; 3.31 vs. 3.19%, treatment vs. control). Calcium and zinc contents of milk were significantly higher in treated animals (1.20 vs. 0.94 g L⁻¹ and 3.16 vs. 2.52 mg L⁻¹; P<0.01). Mineral status of lactating camels and of their calves was assessed by analysis of plasma. Camel control diet was deficient in copper and supplementation did not allow reaching, neither in milk nor in plasma, the threshold values. Results suggest that oral trace element supplementation could increase zinc excretion in camels’ milk, despite the low levels of zinc in plasma.