Effects of Cultivar and Processing Condition on Physicochemical Properties and Starch Fractions in Parboiled Rice

Starch can be classified into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) according to its resistance to amylolytic enzymes. This study investigated the effects of cultivar and feedstock under varying parboiling conditions on the physicochemical properties and starch fractions of parboiled rice. Rice (rough or brown) was soaked, steamed under pressure, dried immediately or stored at room temperature for 24 hr prior to drying, and then treated with or without a repeated steam cycle prior to milling. The storage treatment significantly increased the retrograded amylopectin enthalpy and amylose‐lipid complex melting temperature of parboiled rice. Parboiled rice samples prepared from brown rice feedstock had higher peak melting temperatures but lower enthalpy values of retrograded amylopectin than samples prepared from rough rice after the storage treatment. The pasting viscosity of parboiled rice was most affected by the repeated autoclaving treatment and cultivar. Starch fractions in parboiled rice were significantly affected by cultivar and storage and by the interactions of cultivar and parboiling conditions. The storage treatment significantly increased SDS and generally decreased RDS in parboiled rice. Parboiled rice with different SDS and RS contents can be produced by varying rice cultivar and parboiling conditions.     

低支链淀粉品种米的储藏性和食味品质评价

摘要：储藏米的生理品质与食味品质变化程度对于消费者的认可度至关重要。本研究讨论了不同储藏温度对低直链淀粉品种米（Yumepirika）的储藏性和食味品质影响。稻谷具有比糙米更加优越的储藏性。在低温条件下储藏,稻谷脂肪酸含量增加2.9 mg,糙米脂肪酸含量增加15.8 mg,这表明低支链淀粉糙米应该在更低的温度下保存。食味试验表明室温条件下储藏的糙米具有最低黏度值和综合评价值。经过2 a的储藏期,超低温储藏和低温储藏能够保持米的活力和食味品质与基准米相似的水平。     

Analysis of Ferulic and p‐Coumaric Acids in Japanese Rice for Sake Brewing

Ferulic and p‐coumaric acids were analyzed in 50 rice (Oryza sativa L.) samples from 32 cultivars harvested in Japan. In brown rice, ferulic and p‐coumaric acid levels ranged from 309 to 607 mg/kg and from 49 to 100 mg/kg, respectively. In 70% polished rice, ferulic and p‐coumaric acid levels ranged from 27 to 103 mg/kg and from 0.4 to 3.5 mg/kg, respectively. Ratios of average phenolic acid levels in the 70% polished rice to the brown rice were 13.9% for ferulic acid and 1.9% for p‐coumaric acid. The ferulic acid level was highly correlated between brown and 70% polished rice (R = 0.815; P < 0.01), but there was no clear correlation for p‐coumaric acid. Phenolic acid levels in the 70% polished rice did not show any clear correlations between the analytical index measurements for sake brewing suitability (weight of 1,000 grains, water absorption, digestibility, crude protein, and potassium content). Phenolic acid levels in the 70% polished rice directly affected levels in the rice koji enzyme digest. The results indicated that phenolic acid levels in sake were affected by the levels in ingredient rice grains, which may then influence the sensory quality of sake.     

Bulk Density of Long- and Medium-Grain Rice Varieties as Affected by Harvest and Conditioned Moisture Contents

The effect of harvest and conditioned moisture contents (MC) on bulk density (BD) of rough, brown, and white rice was determined for several long- and medium-grain rice varieties harvested from different Arkansas locations. The results indicated that harvest MC (HMC) significantly affected the BD of freshly harvested and conditioned rough rice. Higher HMC levels resulted in lower BD levels for rough rice over the conditioned MC range from 11 to 29% (wb). There was a strong linear relationship between rough rice BD and conditioned MC for a given HMC. The harvest location had a more pronounced effect on rough rice BD of long-grain varieties than of medium-grain varieties. The BD of brown and white rice was less dependent on harvest location and conditioned MC than the BD of rough rice. Rice harvested at low MC level (≈13%) gave a higher BD for both brown and white rice than that harvested at higher MC levels. Medium-grain varieties showed a higher BD for brown and white rice than did long-grain varieties.     

硒对镉胁迫下寒地水稻镉含量与分配的影响

【目的】研究施硒对不同镉污染土壤上镉在水稻各器官中的分配及稻米中镉含量的影响,探讨通过施硒降低水稻镉吸收量及在稻米中分配的可行性。【方法】采用盆栽试验,以垦鉴稻6号为材料,研究添加不同浓度镉(0、2、4和8 mg/kg土壤)的条件下,施硒(0、0.07和0.14 mg/kg土壤)对水稻不同器官镉含量和镉分配的影响。成熟期整盆收获,分别测定叶片、叶鞘、茎秆、根系和糙米、精米镉含量、硒含量和干物重,计算镉积累量和分配比例。【结果】1)当土壤镉浓度在0 4 mg/kg时,水稻各营养器官和糙米、精米中镉含量随土壤镉浓度增高而显著增加,但当土壤中镉浓度4 mg/kg时,糙米和精米中镉含量增加不显著。未施硒(Se0)时,Cd2(4 mg/kg)和Cd3(8mg/kg)处理糙米中镉含量分别为0.221 mg/kg和0.234 mg/kg,分别是Cd0处理的15.8和16.7倍,均超过我国国家食品安全标准中稻米镉的限量(0.2 mg/kg),精米镉含量未超过国家食品安全规定的限量,Cd3处理精米中镉含量最高,为0.174 mg/kg。2)相同镉浓度下,随着硒浓度的增加,水稻各营养器官和糙米、精米的镉含量和镉积累量均显著下降,糙米和精米的镉含量均低于我国国家食品安全规定的稻米镉限量,且Se2(0.14 mg/kg)处理优于Se1(0.07 mg/kg)处理。其中Cd1(2 mg/kg)浓度时,Se2处理的精米镉含量下降幅度最大,比Se0降低31.5%(P0.01)。3)镉在各器官中的分配比例为根系茎鞘稻谷叶片。随着硒浓度的增加,镉在根系中的分配比例增加,在地上部的分配比例减少,在稻壳中的分配比例增加,在精米中的分配比例下降。在Cd1浓度时,根系镉分配比例范围为60.9%67.8%,稻谷镉分配比例为12.6%13.8%;Se2处理稻壳中镉分配比例比Se0增加5.2个百分点,而精米中镉分配比例则下降了6.2个百分点。4)相同镉浓度下,随着硒浓度的增加,植株各营养器官干物重均增加,Se2处理对干物重的影响优于Se1处理。Cd1、Cd2和Cd3浓度下,Se2处理比Se0处理稻谷干物重分别增加了6.4%(P0.01)、5.2%(P0.05)和11.3%(P0.01)。【结论】施硒可降低镉污染土壤上水稻各营养器官和糙米、精米的镉含量,并能显著降低精米中镉的分配比例,保证稻米的食用安全性,尤其在Cd加入量为2mg/kg土浓度下,施硒效果最显著,以施Se量为0.07 mg/kg处理的效果最好。     

基于同位素示踪技术的糙米加湿后精米吸水率的试验研究

该研究以糙米为原料，应用同位素示踪技术研究糙米加湿调质各工艺参数对精米吸水率的影响规律。在糙米加湿调质中用氚水(H₂³O)为同位素示踪剂对所加水分标记，通过放射性测量(cpm值)确定样品吸水率；采用二次旋转正交组合试验方法设计试验，用Reda软件包处理试验数据，得出了各试验参数对精米吸水率影响关系的回归方程，分析了各试验因素对精米吸水率的影响规律，试验结论可以为掌控糙米加湿调质后精米含水率提供理论依据。     

Silicon decreases the arsenic level in rice grain by limiting arsenite transport

Silicon (Si) reduces arsenic (As) levels in rice shoot and grain. However, the underlying mechanisms remain unclear. In this study, we examined the effect of Si application to three rice paddy soils on the dynamics of Si, iron (Fe), phosphorus (P), and As in the soil solution, As accumulation in rice straw, flag leaf, husk, brown rice, and polished rice, and on As speciation in polished rice. Silicon application to soil increased the concentrations of Si, Fe, As, and P in the soil solution, while the redox potential was unaffected. Arsenic concentrations of straw, flag leaf, and husk were reduced by half by Si application, while As concentrations of brown and polished rice were decreased by 22%. The main As species in polished rice was arsenite, As(III), with a fraction of 70%, followed by dimethylarsinic acid (DMA) and arsenate, As(V), with 24% and 6%, respectively. Silicon application to the soil did not affect DMA or As(V) concentration of polished rice, while the As(III) concentration was reduced by 33%. These results confirm that Si reduces As(III) uptake and translocation into the shoot. Furthermore, data indicate that decrease of As concentration of polished rice is due to decreased As(III) transport into grain. Possible underlying mechanisms are discussed.     

Distribution of total aflatoxins in milled fractions of hulled rice

Two varieties of hulled rice artificially contaminated with aflatoxins at five different levels were processed by dehulling and polishing methods. Contamination levels ranged from 356 to 818 microg/kg and from 244 to 645 microg/kg in medium and long grain rice, respectively. After physical processing, four different milled fractions were obtained (hull, bran, polished broken grains, and polished whole kernels). The fractions were analyzed for total aflatoxins (B1, B2, G1, and G2) by enzyme-linked immunosorbent assay (ELISA). Aflatoxins were removed in fractions intended for human consumption (polished broken grains and polished whole kernels) at rates up to 97%. They were found throughout all fractions, but higher contamination levels were detected in hull and bran fractions than in unprocessed kernels and polished fractions. Regardless of the rice variety, the aflatoxin distribution pattern depended on the initial contamination level and type of milled fraction but not on the duration of polishing.     

Storage Stability of Flour‐Blasted Brown Rice

Brown rice was blasted with rice flour rather than sand in a sand blaster to make microperforations so that water could easily penetrate the brown rice endosperm and cook the rice in a shorter time. The flour‐blasted American Basmati brown rice, long‐grain brown rice, and parboiled long‐grain brown rice samples were stored in Ziploc storage bags under atmospheric conditions and in vacuum‐packed bags. They were periodically tested for over 10 months for changes in water absorption, free fatty acid (FFA), peroxide value (POV), viscosity changes of flour using the Rapid ViscoAnalyser (RVA), and texture of whole cooked kernel using a texture analyzer during cooking. Flour‐blasted brown rice absorbed less water but needed less cooking time than its counterpart that was not flour‐blasted. There was an increase in FFA, POV, peak viscosity (PV), final viscosity (FV), breakdown viscosity (BD), and setback viscosity (SB) during storage of flour‐blasted brown rice for 300 days, but no change was observed in texture (hardness, gumminess) and water absorption. The combined coefficient of correlation (including all types of rice) between FFA and FV is r = 0.86 and between FFA and SB is r = 0.90 at P < 0.0001.     

Impact of Feedstock,Parboiling Condition,and Nutrient Concentration on Simultaneous Fortification of Two U.S. Long‐Grain Rice Cultivars with Iron and Zinc

This work investigated the effect of parboiling on simultaneous fortification of rice with iron (Fe) and zinc (Zn) using rough rice and brown rice as feedstocks. Three fortificant concentrations (0, 100, and 200 mg/L for both Fe and Zn) were tested, and two long‐grain rice cultivars (CLXL745 and RoyJ) were used as test samples. Cultivar had little impact on the retention of Fe and Zn; steaming combined with soaking significantly increased the migration of Fe and Zn into the endosperm compared with soaking only. The Fe and Zn contents of the resultant parboiled head rice were related to the initial concentrations in the soaking water and were 7.2–17.6 and 21.8–31.9 mg/kg, respectively, when rough rice was used as a feedstock, and they significantly increased to 32.4–84.9 mg/kg for Fe and 45.8–78.4 mg/kg for Zn when brown rice was used as a feedstock. Mineral retention after simulated washing was 87.5–95.1% for Fe and 81.1–84.3% for Zn. Dilute‐HCl extractability as an indicator of mineral bioavailability was 66.2–72.4% for Fe and 83.4–92.0% for Zn. The results indicate that brown rice is a better feedstock than rough rice for mineral fortification via parboiling.     

Policosanol Contents and Compositions in Wax‐Like Materials Extracted from Selected Cereals of Korean Origin

Policosanols, long‐chained alcohols, have been reported to have beneficial physiological activities. Content and composition of policosanols in wax‐like materials extracted from selected cereals of Korean origin were determined. Wax‐like materials were extracted using hot hexane. Yields of wax‐like materials from unpolished grain sorghum, polished grain sorghum, brown rice, purple rice, wheat, and maize were 223, 37, 33, 61, 10, and 10 mg/100 g of dry kernels, respectively. Policosanol contents, as determined using HPLC, in the wax‐like materials from the cereals were 33, 29, 6, 0, and 2% (w/w, db), respectively. Major alcohols in the policosanols from grain sorghum were octacosanol and triacontanol. Docosanol was the major alcohol in the policosanols from brown rice, purple rice, wheat, and maize.     

Dry Matter Loss for Hybrid Rough Rice Stored Under Reduced‐Oxygen Conditions

The objectives of this research were to characterize dry matter loss of hybrid long‐grain rough rice during storage under reduced‐oxygen conditions and develop a new approach to predict the dry matter loss by using storage temperature and relative humidity data as input. Two long‐grain hybrid rice cultivars, CL XL745 and XL760, harvested in the year 2015 were stored in rough‐rice form in sealed glass jars at moisture contents of 12.5, 16, 19, and 21%, (wet basis) and temperatures of 10, 15, 20, 27, and 40°C for a total of 16 weeks, with samples taken at 2, 4, 6, 8, 10, 12, and 16 weeks of storage. Results revealed no differences in dry matter loss connected with the rough‐rice moisture content levels and temperature during the storage duration. However, the dry matter loss was statistically different based on rough‐rice cultivar. Experimental data were fitted to a dry matter loss equation for long‐grain rice found in literature. The dry matter loss equation developed for conditions of grain storage without oxygen limitation did not accurately predict rough‐rice dry matter loss under reduced‐oxygen conditions. Equation constants generated for reduced‐oxygen storage conditions were significantly lower than the typical constants used for long‐grain rice in literature. Hence, integration of rice cultivar and storage conditions such as oxygen supply is crucial for accurate determination of kinetics of dry matter loss during storage of hybrid long‐grain rough rice.     

不同早稻品种对喷硒的响应

通过田间试验研究了海南省主栽的12个早稻品种对叶面喷施亚硒酸钠的响应,结果表明,与对照相比,喷硒分别提高糙米和精米平均硒含量43%和34%,差异达极显著水平。不同品种对喷硒的响应不同,与对照相比,喷硒显著提高丛优629和特优5735的糙米硒含量,因此,在海南低硒地区可选择种植这两个水稻品种生产富硒大米。     

Determination of selenium concentration of rice in china and effect of fertilization of selenite and selenate on selenium content of rice

A method of hydride generation atomic fluorescence spectrometry was applied to the determination of the selenium concentration of regular polished rice in China and selenium-enriched polished rice obtained by foliar application of selenium-enriched fertilizer in the forms of selenite and selenate. The average selenium content of regular rice was 0.025 +/- 0.011 microg g(-)(1). On the basis of a daily dietary rice intake of 300-500 g suggested by the China Nutrition Society, the total selenium intake from regular rice was calculated to be 7.5-12.5 microg per person per day for an adult. The selenium contents of rice were significantly increased to 0.471-0.640 microg g(-)(1) by foliar application of selenium-enriched fertilizer at rate of 20 g of Se ha(-)(1) in the forms of sodium selenite and sodium selenate. The selenium content of rice by application of a fertilizer of selenate was 35.9% higher than that by a fertilizer of selenite, which showed that Se-enriched fertilizer in selenate exhibited greater efficiency in increasing Se content in rice products. The Se-enriched rice products can increase daily Se intake on average by 100-200 microg of Se per day by the consumption of 400 g of rice products if the Se level of rice products is controlled at 0.3-0.5 microg of Se g(-)(1). Because rice is a staple food in China, selenium-enriched rice obtained by bioenrichment of selenium to increase the Se content of rice could be a good selenium source for the population in selenium-deficient regions.     

Contribution of dimethyl sulfide to the aroma of Syrah and Grenache Noir wines and estimation of its potential in grapes of these varieties

The contribution of dimethyl sulfide (DMS) to the aroma of Syrah and Grenache Noir wines from the Rhone Valley of France was investigated by sensory analysis, and its levels in these wines were measured. The potential DMS in the corresponding grapes and wines, susceptible to release during wine aging, was evaluated. Free DMS and potential DMS assessed by a heat-alkaline treatment were measured in grape juices and wines by SPME-GC-MS using methods previously reported and slightly modified. A relationship between potential DMS from grapes and the total DMS levels in wine was demonstrated. Furthermore, a linear regression between the ratio of free DMS levels to these total DMS levels in wine and time of storage was found. Free and potential DMS levels in grapes and wines depended on grape variety, vintage, and vine location. DMS imparted a noticeable and complex contribution to the aroma of the wines investigated, depending on the mode of sensory perception used, either before or after glass swirling. It significantly enhanced the fruity notes of the wines, and additional truffle and black olive notes.     

基于Micro-CT图像处理的稻谷内部损伤定量表征与三维重构

在水稻脱粒、储运、加工过程中,外界机械作用力是造成稻谷损伤破损的主要方式,造成的内部裂纹肉眼无法观察但影响稻谷的存储、加工以及种子的发芽率等.该文利用质构仪对稻谷进行挤压力学特性试验,分析稻谷损伤破碎过程;对受不同载荷的稻谷进行CT扫描试验,结合数字图像处理方法对稻谷进行损伤表征分析与三维重构,旨在提出一种新的稻谷内部损伤定量评价方法.结果表明:伪彩色图像处理可以提高CT图像的视觉分辨率;灰度值以及灰度直方图分析可以识别稻谷的胚、胚乳以及裂纹大小,并定量分析;对分割后的二值图像进行像素点统计分析得到80,100,120,140,160N载荷下的损伤度分别为0,0.26%,0.39%,0.93%,1.79%;重构的三维模型可以看出裂纹一般沿着短轴方向扩展,随着载荷增大,原有裂纹逐渐变宽,并产生新的沿着长短轴的混合裂纹,直到糙米断裂.该研究可为谷物内部损伤定量表征分析提供新思路.     

糙米机械破碎力学特性试验与分析

为了研究糙米机械破碎力学特性及其与籽粒结构特性的关系。采用物性测试仪对糙米的锥刺、三点弯曲、剪切、挤压4种机械破碎力学特性进行测试与分析,并对糙米和精米的破碎力学特性(三点弯曲)进行了比较。结果表明:糙米的断裂是由于内部胚乳组织不均匀,在外力作用下首先形成内部裂纹,裂纹尖端处的应力集中又进一步促进裂纹扩展,最终导致籽粒断裂;厚度为(1.0±0.5)mm的不同样品锥刺破碎力在10N左右,各样品籽粒内部的结合力相差较小,籽粒的断裂主要与厚度及胚乳特性有关,其中三点弯曲力更能反映籽粒的破碎特性,糙米的糠层对籽粒有一定的保护作用,糙米力学特性比精米好。该文为糙米储藏加工技术参数的确定提供依据。     

Induced Postharvest Yellowing in Southern U.S. Rice Cultivars

Rice can yellow during storage if moisture levels and temperatures are allowed to increase. This postharvest yellowed (PHY), or stackburn, rice is reduced in value but no study has investigated the inherent potential within rice germplasm for limiting PHY. To screen a large number of cultivars for propensity to PHY, a laboratory method for PHY using a small amount of rice was used. Ninety‐eight popular southern U.S. rice cultivars were yellowed under laboratory conditions. Additional samples of the low‐yellowing and high‐yellowing cultivars were retested after two and three years of storage as rough rice using higher amounts and larger containers. All cultivars showed greater color change with the higher amounts of rice and when yellowed as milled rather than as rough rice. Length of time of storage and storage temperature did not affect the degree of PHY. The low‐ and high‐yellowing groups remained distinguishable but the overall high level of coloring in southern U.S. rice cultivars indicates that a more diverse germplasm should be investigated to increase the likelihood of identifying low‐PHY cultivars.     

不同生境下水稻稻米品质因子分析

运用因子分析法对不同生境下62个水稻品种中13个稻米品质性状研究结果表明,以前5个主因子对变异的累计贡献率>89％统计,垩白(垩白粒率和垩白度)、加工品质(糙米率、精米率、整精米率和碎米率)、粒形(糙米宽厚比、糙米长宽比)是影响早季稻米品质主要因素;糙米宽、整精米率、精米率、糙米长和直链淀粉含量是影响晚季稻米品质的主要因素。主因子之间早季垩白与碎米率、糙米宽厚比和糙米长宽比、碎米率与糙米宽厚比表现正向相关,晚季糙米宽与精米率和直链淀粉含量、精米率与糙米长和直链淀粉含量、糙米长与直链淀粉含量表现正向相关。主因子之间早季垩白与糙米率、精米率和整精米率,糙米率、精米率、整精米率与碎米率、糙米宽厚比和糙米长宽比,碎米率与糙米长宽比,糙米宽厚比与糙米长宽比表现负相关,晚季糙米宽与整精米率、精米率、糙米长和直链淀粉含量,整精米率与糙米长,精米率与直链淀粉含量表现负相关。     

水稻对~(134)Cs的吸收和~(134)Cs在水稻-土壤中的分配

试验表明,水稻对~(134)Cs的吸收,孕穗期吸收速率最快;土壤理化性质不同,吸附~(134)Cs的能力有差异;不同生育期灌溉~(134)Cs溶液,水稻对其吸收量不同,离成熟期近,吸收得多;灌溉次数多和灌溉水中~(134)Cs活度高,水稻吸收的~(134)Cs也多。糙米经精白加工后,可使~(134)Cs的污染减少22.6—45.6％;~(134)CS在水稻各部位比活度大小的顺序为糠>根>稻草>谷壳>精白米;活度以稻草中最高,占水稻植株总活度的51.4％,糙米、根和谷壳分别占28.4％。11.8％和8.4％:~(134)Cs在土壤中移动很少,有95.1％集中在0—2.5cm的表土层内;~(134)Cs在水稻-土壤中的分配为6.1％:93.9％;K~+抑制水稻对~(134)Cs的吸收,K~+浓度与水稻中~(134)Cs比活度之间呈指数回归形式。