Effect of drying air temperature and storage on industrial and chemical quality of rice grains

The drying air temperature and storage time can change the milling yield and chemical composition of rice grains. Therefore, the objective was to verify the industrial quality and chemical composition of rice grains, white and integral subgroups, in response to drying air temperature and storage time. For such, the rice grains were subjected to drying in a column dryer with a grain capacity of 1 m³, using 55 and 65 °C drying air temperatures. After, they were stored in PP Woven Bags under environmental conditions for 240 days. After drying and every 60 days the milling was performed, aiming to evaluate the industrial quality and chemical composition of the grains. The whole grains yield was negatively affected by the increase in drying air temperature for both subgroups. The increase in the drying air temperature led to a reduction in the lipid content and an increase in the ash content for grains of white subgroup. The storage time promoted an increase in the whole grains yield in the white subgroup when the grains were dried with the highest drying air temperature. The lipids and proteins contents decreased, while the fibers and ash contents increased during storage for the white subgroup grains. The chemical composition of grains from the brown subgroup did not change during storage, regardless of drying air temperature.     

Storage effects on nutritional quality of commonly consumed cereals

Storage effects on nutritional quality of commonly consumed cereal grains are studied. Freshly harvested wheat, maize and rice grains were stored at 10, 25 and 45 °C for six months. A significant decrease in pH and an increase in titratable acidity was observed during storage of these three cereal grains at 25 and 45 °C. A gradual decline in moisture, total available lysine and thiamine contents was observed during storage. Total available lysine contents decreased by 6.50% and 18.5% in wheat, 14.3% and 20.7% in maize and 23.7% and 34.2% in rice during six months of storage at 25 and 45 °C, respectively. Six month’s storage of rice, maize and wheat grains at 25 and 45 °C resulted in reduction of thiamine contents by 16.7% and 29.2%, 17.2% and 24.1% and 21.4% and 29.5%, respectively. About 36.4–44.4% decrease in total soluble sugars at 45 °C and 9.30–31.8% increase in total soluble sugars were observed at 10 and 25 °C during six months storage of these cereal grains. Protein and starch digestibilities of cereal grains also deceased during six months of storage at 25 and 45 °C. No significant change in nutritional quality was observed during storage of cereal grains at 10 °C.     

Utilization of germinated and heat-moisture treated brown rices in sugar-snap cookies

Utilization of germinated brown rice (GBR) in sugar-snap cookies and effect of heat-moisture treatment of the GBR were investigated. Brown rice was germinated at 30 °C for 48 h and then a heat-moisture treatment was conducted for the moistened GBR (17 g/100 g moisture content) at 100 °C for 4 h. Sugar-snap cookies were prepared with white rice, brown rice, GBR and the treated GBR flours, as substitutes for wheat flour (30–100 g/100 g). All cookies containing rice flours, regardless of germination and heat-moisture treatment, required significantly less force to compress than did the wheat flour cookie, and this softening effect was increased as the level of rice flour substitution increased. The cookies made with the GBR flour displayed inferior physical characteristics compared to those with wheat flour, but the cookies containing the treated GBR flour showed improved physical properties with lower moisture content and higher spread factor than those containing untreated GBR flour. The cookies containing the treated GBR flours showed relatively a low degree of firming during the ambient storage. The overall results showed that the cookies with acceptable quality and improved nutrition could be prepared by partial or complete replacement of wheat flour with the heat-moisture treated GBR flour.     

Milling breakage susceptibility and mechanical properties of parboiled brown rice kernels

Parboiling, a hydrothermal treatment of paddy or brown rice, impacts both head rice yield and texture and nutritional characteristics of cooked rice. Here, milling breakage susceptibility of parboiled brown rice was investigated on both bulk and kernel level. Brown rice was parboiled by soaking at 40, 55 or 65 °C and steaming at 106, 120 or 130 °C. The breakage susceptibility and changes in starch and proteins of bulk samples were related to the properties of individual rice kernels. An increase in milling breakage susceptibility from 1% to 11% corresponded to a decrease in average bending force of individual kernels from 34.9 to 14.6 N. Furthermore, both white bellies and fissured parboiled rice grains were more breakage susceptible. Their average bending force was respectively 14.1 N and 17.6 N compared to an average of 39.6 N for intact parboiled rice grains. Whereas the level of proteins extractable with sodium dodecyl sulfate containing medium had no impact, the degree of starch gelatinization was critical in determining the presence of both white bellies and fissured parboiled rice grains. More in particular, complete starch gelatinization ensured the absence of white bellies and minimized fissuring in the parboiled end-product, thereby decreasing milling breakage susceptibility.     

Oxidative stability of fried dough from rice flour containing rice bran powder during storage

The aim of this study was to evaluate the efficiency of rice bran powder on lipid peroxidation inhibition of fried dough from rice flour during storage. Rice flour dough containing rice bran powder at 5, 10 and 15 g rice bran powder/100 g mixed rice flour were fried in soybean oil at 160 °C for 1 min and stored in dark at 60 °C for 10 days. Lipid peroxidation of fried dough was determined by change of fatty acid compositions, oxygen absorption in vial headspace, lipid hydroperoxides, TBA values including decreasing tocopherol and gamma-oryzanol contents during storage. Polyunsaturated fatty acid decreased rapidly in fried dough without rice bran powder, while an increase of oxygen absorption in vial headspace, lipid hydroperoxide and TBA values were significantly lower (p?0.05) in fried dough containing rice bran powder. In addition, tocopherol degradation was significantly lower in fried dough containing rice bran powder during storage (p?0.05). However, there was no significant difference in gamma-oryzanol contents among fried dough during storage (p>0.05). These results demonstrated that rice bran powder shows the antioxidative effects on fried dough during storage.     

辐照糙米储藏过程中淀粉脂和非淀粉脂组成及变化

目的：研究低剂量60Co-γ辐照对储藏糙米的淀粉脂和非淀粉脂的粗脂肪含量和脂肪酸组成的影响,为辐照糙米储藏提供数据支持和理论依据。方法：晚粳米收获后进行60Co-γ辐照,设0.2、0.5、1.0 kGy和2.0 kGy 4 个不同的辐照剂量水平,之后恒温（15±0.5）℃储藏12 个月,每3 个月进行一次品质测量。结果：辐照糙米在储藏12 个月的过程中,非淀粉脂含量变化不显著（P＞0.05）,淀粉脂含量在储藏过程中持续下降,储藏12 个月后,淀粉脂含量显著降低（P＜0.05）。在储藏过程中,非淀粉脂和淀粉脂的各个脂肪酸组成的含量表现出不同的增加或减少趋势。在同一时期,辐照糙米和未辐照糙米的粗脂肪（淀粉脂和非淀粉脂）含量没有显著差异（P＞0.05）,说明辐照不会影响粗脂肪含量,辐照对各糙米的脂肪酸组成没有显著的影响。结论：低剂量的辐照处理不会改变储藏过程糙米的脂类组成,储藏对糙米的淀粉脂和非淀粉脂有不同的影响。     

Effect of ageing-induced changes in rice physicochemical properties on digestion behaviour following storage

The changes in rice grains structure and digestion behaviours were investigated following storage at 4 °C and 37 °C, respectively. Pasting study indicated that rice samples stored at 37 °C demonstrated a consistent increase in the time to peak viscosity of the Rapid ViscoAnalysis parameters, implying a quick ageing progress. Compared to the rice stored at 4 °C, aged rice (stored at 37 °C) showed a coarser morphology after cooking by SEM, suggesting a limited starch gelatinization. Consistently, ageing process led to a decrease in the leaching of starch molecules in cooking residual water, which further confirmed that starch granules in aged rice grain caused less hydration and swelling. The analysis of the amount of cell wall remnants showed that rice stored at 37 °C caused a significant increase in the amount of cell wall remnants along the storage at 37 °C, which might suggest that the cell wall structure of the rice grains became more lignified because of the ageing. Furthermore, the ageing process significantly reduced rice digestion kinetics both in rate and extent. Thus, it is assumed that ageing process leads to the cell walls becoming more strengthened and lignified, which makes the rice grain more organized in its structure, and subsequently reduces starch granules disruption and molecules leaching during the cooking. Therefore, this study suggests that the changes in digestion behaviours of rice are highly associated with the changes in rice physical and chemical properties occurred during storage and the ageing process might be another option for manipulating rice digestion properties.     

Efficacy of methoprene for multi-year protection of stored wheat,brown rice,rough rice and corn

Hard red winter wheat, brown rice, rough rice, and corn were treated with the insect growth regulator (IGR) methoprene at rates of 1.25 and 2.5 ppm, held for 24 months at ambient conditions in buckets on the floor of a grain bin, and sampled every two months. Bioassays were done by exposing 10 mixed-sex adults of Rhyzopertha dominica (F.), the lesser grain borer, and Tribolium castaneum (Herbst), the red flour beetle, on wheat, R. dominica and Sitotroga cerealella (Oliver), the Angoumois grain moth, on brown rice and rough rice, and T. castaneum and S. cerealella on corn. Sample size for all commodities was about 80 g, and these samples were held for 3 months at 27°C-60% r.h. Both rates of the IGR completely suppressed adult progeny development of R. dominica with little resulting feeding damage, sample weight loss, or insect damaged kernels (IDK). Some adult progeny production of S. cerealella and resulting IDK occurred at both rates on rough rice, brown rice, and corn, but was far less than in untreated controls. There was little adult progeny production but some feeding damage caused by larval T. castaneum in the treated wheat and corn but again far less than in untreated control. Allowing continual exposure of parental adults on grains treated with an IGR, rather than exposing those parental adults for a short time period, may give more accurate evaluations of residual efficacy. Results show that methoprene used as a grain protectant will give residual control of stored product beetles for 24 months, but complete control of S. cerealella may require inclusion of a contact insecticide.     

Speciation and localization of arsenic in white and brown rice grains

Synchrotron-based X-ray fluorescence (S-XRF) was utilized to locate arsenic (As) in polished (white) and unpolished (brown) rice grains from the United States, China, and Bangladesh. In white rice As was generally dispersed throughout the grain, the bulk of which constitutes the endosperm. In brown rice As was found to be preferentially localized at the surface, in the region corresponding to the pericarp and aleurone layer. Copper, iron, manganese, and zinc localization followed that of arsenic in brown rice, while the location for cadmium and nickel was distinctly different, showing relatively even distribution throughout the endosperm. The localization of As in the outer grain of brown rice was confirmed by laser ablation ICP-MS. Arsenic speciation of all grains using spatially resolved X-ray absorption near edge structure (micro-XANES) and bulk extraction followed by anion exchange HPLC-ICP-MS revealed the presence of mainly inorganic As and dimethylarsinic acid (DMA). However, the two techniques indicated different proportions of inorganic:organic As species. A wider survey of whole grain speciation of white (n=39) and brown (n=45) rice samples from numerous sources (field collected, supermarket survey, and pot trials) showed that brown rice had a higher proportion of inorganic arsenic present than white rice. Furthermore, the percentage of DMA present in the grain increased along with total grain arsenic.     

Rheology and tribology properties of cereal and legume flour paste from different botanical origins

Paste made from eight types of cereal grains (low fiber containing grains [LF grains]: rice, sticky rice, black rice, and millet; and high fiber containing grains [HF grains]: wheat, buckwheat, oat, and barley), and four types of legumes (soybean, red bean, kidney bean, and mung bean), were studied in terms of particle size, rheological, and tribological properties. Sticky rice and soybean pastes showed lower yield stress, viscosity and consistency coefficient than other pastes. Most cereal pastes showed a major peak at approximately 160 µm except for oat and barley, while legume pastes showed mono modal profiles except for soybean. Tribological results showed that starch tended to develop type A friction profiles, showing a typical Stribeck curve; bran/fiber tended to develop type B profiles, showing an ascent curve with clear onset of hydrodynamic regime; protein and lipids promoted type C profiles, showing a flat plateau shaped curve. Water soluble polysaccharides in grains or legumes could improve the paste lubrication. In general, 5% of the black rice paste and sticky rice in the LF grain group, and the soybean paste in the legume group, showed a low friction coefficient (μ) in the entire entrainment speed range; barley paste and oat paste in the HF grain group showed relatively low μ at low entrainment speed (0.5 mm/s) and medium entrainment speed (5 and 10 mm/s), respectively.     

Status of glycemic index of paddy rice grain (Oryza sativa L.) on infestation by storage pest Sitotroga cerealella

The harvested paddy rice grains are normally stored by growers under normal conditions. Paddy rice grains are natural food for storage pests like Sitotroga. cerealella, a major insect that appears during paddy storage. The changes in grain composition due to such insect infestation in relation to human health especially the alteration in their Glycemic Index (GI) value have not been studied so far. The present investigation was aimed at studying the effect of S. cerealella infestation on rice grain quality and glycemic index of stored paddy grains. Five diverse rice genotypes with different quality traits were evaluated for grain quality after S. cerealella infestation. The tolerance to insect and variation of grain quality varied with rice genotype significantly. The glycemic index, glycemic load, total carbohydrate, amylose content and resistant starch were affected to a great extent. The consumption of affected grains may create health issue due to imbalance in nutrition and unhygienic condition. Improper storage of paddy after harvesting and processing results in infestation by pests at a large scale. Thus, the grain quality needs to be evaluated to judge the suitability of affected grain for consumption.     

Susceptibility of Ethiopian wheat varieties to granary weevil and rice weevil infestation at optimal and sub-optimal temperatures

Integrating varietal resistance with temperature manipulation during storage may provide a better option for protection of stored grains and may decrease reliance on the use of synthetic chemicals. The current study was conducted to determine the susceptibility of different varieties of wheat seed to the infestation by the granary weevil, Sitophilus granarius (L.), and rice weevil, Sitophilus oryzae (L.), at optimal (30 °C) and sub-optimal (19 °C) temperatures. Kernels of six wheat varieties namely, Danda'a, Digalu, ET-13-A2, Kakaba, Millennium, and Pavon-76 were examined over a period of 90 d. Significant interactions were detected between wheat varieties and storage temperature for progeny emergence, percentage of insect damaged kernels, grain weight loss, and amount of powder produced per gram of wheat. Kernels of Danda'a, infested with S. oryzae at 30 °C exhibited significantly lower mean progeny counts (13.3 live insects), lower percentage of grain weight loss (4.2%) and insect-damaged kernels (6.4%), and powder production (1.5 mg/g). Kernel weight and hardness index were negatively associated with percentage of insect damaged kernels and grain weight loss. Kernel diameter was positively associated with both of percentage of insect damaged kernels and grain weight loss. Wheat varieties with high Zeleny sedimentation values had lower percentage of insect-damaged kernels and grain weight loss. These results indicated that kernel weight, hardness index, and protein content are predominant factors contributing to wheat resistance against S. granarius and S. oryzae. The varieties Millennium and Danda'a can be considered with other integrated pest management approaches to reduce stored grain losses of wheat in Ethiopia.     

Effect of radio frequency heating on the mortality of Rhizopertha dominica (F.) and its impact on grain quality

The use of radio frequency (RF) heating to reach temperatures lethal to stored product pests has significant potential. We examined the lethal effects of RF on the stored grain pest, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), under four different RFs, three types of grain, and different moisture contents of rice. The quality of two rice cultivars, after RF heating, was also tested. When heated to 58 °C by RF, R. dominica adult mortality reached 100%. The mortality of R. dominica adults reached 100%. The fastest mortality rate occurred at 50–52 °C. With an increase in RF, the time needed to attain a lethal temperature decreased. The heating time to reach 100% mortality differed among the three types of grain; for example, the heating time of wheat was faster than corn or rice. Kernel size and chemical composition was the main factor influencing the RF lethal rate in the different types of grain under the same experimental conditions. There was a significant linear relationship between moisture content (m.c.) and heating time (Y = −38.05 X + 15.501, R = 0.9803) in rice. RF heating of rice to 58 °C did not significantly affect milling quality, storage quality, or seed quality. Thus, heating time, types of grain, and the m.c. of the grains are three important factors that should be considered in RF heating to control stored product pests. These results indicate that RF heating could be an effective physical method for killing stored grain pests.     

Impacts of Storicide II on internal feeders of Brown rice

Protectants applied to grain can reduce damage caused by insect feeding during storage. Although these protectants are effective against many external feeders, they may also reduce damage caused by internal feeders as they often interact with the exterior surface of the grain during their larval or adult stages to feed or oviposit. For this study, we investigated impacts of Storicide® II applied to brown rice on three different internal feeders: Rhyzopertha dominica (Fauvel), Sitophilus oryzae (L.), and Sitotroga cerealella (Olivier). We also investigated the effects of this protectant at three different temperatures and when it was combined with different percentages of untreated brown rice. Time-series clustering was also performed to determine whether treatments caused disruptions to the timing of progeny emergence. Overall, R. dominica was the most susceptible as mortality and knockdown were observed in mixtures containing 10% treated brown rice. In contrast, S. cerealella was the least susceptible as mixtures containing at least 50–75% treated brown rice were required to reduce progeny production. However, lowering the temperature to 22 °C did reduce the amount of treated brown rice required to reduce progeny emergence and also reduced the number of progeny that emerged synchronously, which would likely reduce mating and reduce population levels over time. Similar effects on progeny were observed for S. oryzae and R. dominica. Overall, these findings suggest that Storicide II can reduce population levels of internal feeders and that combining this protectant with cooler temperatures can provide additional protection.     

Accelerated aging of jasmine brown rice by high-temperature fluidization technique

After being cooked, newly harvested brown rice becomes a pasty mass and swells only slightly. To modify these undesirable brown rice properties, the paddy needs to be stored for at least 3–6 months. However, problems arise since brown rice has short shelf-life (3–6 months) due to accumulation of free fatty acids (FFA) leading to rancidity during storage. In the present study, high-temperature fluidized-bed drying technique in combination with tempering step was tested to alleviate the above-mentioned problems. The quality of rice dried at temperatures of 130 and 150 °C and tempered for 30 up to 120 min was compared to that of brown rice stored at ambient temperature (approximately 30 °C) for 7 months. The experimental results showed that the cooking and eating properties of the fluidized bed dried brown rice, i.e., hardness, solid loss, volume expansion and elongation ratio, changed in a similar fashion to those of the conventionally aged brown rice. The drying temperature and tempering time affected significantly the brown rice properties. The texture of cooked thermally treated brown rice was significantly firmer than that of the conventionally aged brown rice. In addition, it was found for the thermally treated brown rice that the contents of free fatty acids increased only slightly during storage while the glycemic index reduced from high to low-medium level.     

Persistence and activity towards Sitophilus zeamais (Coleoptera: Curculionidae) of pirimiphos-methyl sprayed at different temperatures on maize

The air temperature in storage units in tropical areas frequently exceeds 50°C during the warmest periods of the day. Since protectant insecticides are sprayed on grains under these conditions, such high temperatures may interfere with the insecticidal activity. To assess this possibility we sprayed maize grains with pirimiphos-methyl 500 EC (0.8 ml c.p./l and 1.5 l/t) at different temperatures (25°C, 30°C, 35°C, 40°C, 45°C, and 50°C) and 55% r.h. The grains were then maintained at 27±1°C and 55±5% r.h. throughout the experiment which lasted 90 days. Residues of pirimiphos-methyl on the sprayed grains were analyzed every 30 days. Grain samples were assessed every 15 days after the insecticide spraying for their effect on the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Insect mortality was evaluated after 24 and 48 h of exposure to the treated grain. The level of pirimiphos-methyl residue on maize grains decreased with an increase in storage period and air temperature during the insecticide spraying (varying from 11.0±0.1 to 1.1±0.1 ppm, corresponding to the residue levels at 25°C on the day of the spraying and after spraying at 50°C and 90 days of storage). The same trend was observed for mortality of the maize weevil, which dropped from 95.4±13.3% to 2.5±2.5% after 90 days storage after insecticide spraying at 50°C. These results indicate that temperature at spraying can affect insecticide persistence and activity during storage.     

Analysing the freshness of intact rice grains by colour determination of peroxidase activity

Freshness is an important palatability characteristic of rice grains. However, this characteristic deteriorates rapidly during dry storage. In the present study we have developed an indirect method to examine the freshness of rice grains harvested in different crop seasons or stored under conditions known to accelerate deterioration. Bulk samples of intact brown rice grains were soaked in dianisidine solution containing guaiacol and H₂O₂, and the optical absorbance of the incubation solution was determined colorimetrically. Alternatively, intact brown rice grains were incubated in a similar solution in the wells of a 96‐well microplate, with one grain per well, and the optical absorbance of the incubation solution was measured by a microplate reader. The results indicated that cultivar, storage duration and temperature significantly affected the activities of grain peroxidase. Marked differences in the development of purple colour in the incubation solutions and in vitro peroxidase activity were also found among the brown rice grains sampled in different seasons. The changes in colour of the incubation solutions measured by either of the above methods paralleled the changes in grain activity of peroxidase assayed using an in vitro method. The proposed method can differentiate brown rice grains harvested in different seasons. Moreover, this method, if combined with suitable statistical clustering procedures, can detect the blending status of fresh/old brown grains in a sample. The advantages of this test method using A₃₈₅ over the conventional enzyme activity assay are the rapidity and simplicity with which A₃₈₅ can estimate the in vitro determination of peroxidase activity of tested rice grains. Copyright © 2003 Society of Chemical Industry     

鲜湿糙米线品质劣变机理及调控技术研究进展

全谷物以其对营养健康的重要作用在全世界得到了广泛关注。鲜湿糙米线作为营养健康的全谷物主食食品存在更易腐败、老化变硬、易断条、蒸煮损失率高等问题。系统阐述了鲜湿米线品质影响因素,鲜湿糙米线在储藏过程中的水分含量、pH值、蒸煮品质、水分迁移、质构、微观结构等品质变化规律,分析了鲜湿糙米线品质劣变机理;并进一步对选择糙米原料、外源添加物、糙米全籽粒磨粉及回填法制备工艺等鲜湿糙米线品质调控技术2016—2023年最新研究进展进行了综述,为鲜湿糙米线的品质调控和品质提升提供参考。     

Effects of flameless catalytic infrared radiation on Sitophilus oryzae (L.) life stages

A laboratory benchtop flameless catalytic infrared emitter was evaluated against all life stages of the rice weevil, Sitophilus oryzae (L.), an insect species associated with stored wheat. The emitted infrared radiation was in the 3-7 μm range. A non-contact infrared thermometer measured grain temperatures continuously during exposures of infested wheat. Insect mortality was a function of the final grain temperature attained. In general, higher grain temperatures were attained when using 113.5 versus 227.0 g of wheat, and at 8.0 cm from the emitter versus 12.7 cm, and during a 60 s exposure versus a 45 s exposure. Complete mortality of all life stages of S. oryzae was achieved at 8.0 cm from the emitter using 113.5 g of wheat, with a 60 s exposure; the mean grain temperatures attained ranged from 108.4 to 111.8 °C. The log odds ratio tests showed that eggs (0 days old) were the least susceptible stage to infrared radiation, followed by adults within kernels (28 days old), pupae (24 days old), young larvae (7 days old), larvae that were 14-21 days old, and adults (42 days old). These data using small amounts of grain indicate infrared radiation from the flameless catalytic emitter to be a viable option for disinfesting wheat containing various life stages of S. oryzae.     

Gamma-oryzanol content,phenolic acid profiles and antioxidant activity of rice milling fractions

This study was aimed to determine γ-oryzanol content and total phenolics, individual phenolic acid profile and the antioxidant activity of the free and bound extracts of rice milling fractions namely, brown rice, unpolished rice, white rice, chalky rice, raw seed and rice bran. Gamma-oryzanol content of milling fractions which is designated with a simple chromatographic method was in the range of 12.19–3,296.5 mg/kg. The whitening and polishing steps reduced approximately 94% of γ-oryzanol of the brown rice when becoming the white rice. The contribution of bound phenolics to the total phenolic content was approximately 40%. Ferulic and p-coumaric acids were the most abundant phenolic acids in bound phenolic extracts and their amounts were 119.98 and 18.10 μg/g, respectively, in rice bran. The best source of γ-oryzanol, phenolics and antioxidants was clearly rice bran and followed by raw seed and brown rice.