Rice Milling Quality Research Articles

Effects of Harvest Time on Grinding Quality, Appearance Quality and Physical and Chemical Quality of Japonica Rice.

Harvest time is very important to rice due to its high correlation to rice yield, eating quality, etc.; however, the impact of harvest time on quality is still unclear. In this study, Nangeng 5718, a japonica rice planted in three regions in Jiangsu Province of China, was used to analyze and compare the milling quality, appearance quality, and physicochemical quality of japonica rice at different harvest times. The results showed that the 1000-grain weight of Nangeng 5718 exhibited no significant change at different harvest times (p > 0.05). The brown rice rate and rice yield at different harvest times were 82.3-85.4% and 66.3-76.1%, respectively. Harvest time had no significant effect on the brown of rice (p > 0.05). However, Nangeng 5718 planted in Nanjing had the highest rice yield at 50 days after heading, which was significantly different from that of rice harvested 65 days after heading (p < 0.05). Nangeng 5718 planted in Huai'an had the highest rice yield at 55 days after heading, which was significantly different from that of rice harvested 60 days after heading (p < 0.05). Harvest time had little effect on the length, width, and thickness of rice. The immature grain rate showed a decreasing trend with the increase in maturity. There were little differences in the protein content of Nangeng 5718 at different harvest times. Nangeng 5718 planted in Nanjing had the highest protein content at 50 days after heading. There was a significant difference between the rice harvested and the rice harvested 60 days after heading (p < 0.05). There were no significant differences between the other two regions (p > 0.05). The accumulated temperature in Nanjing was relatively high, and the RVA curve and RVA eigenvalues of rice varied greatly. The setback value of rice harvested at 50 days was significantly lower than that at 55 days and 60 days (p < 0.05). Rice has good gelatinizing properties. Therefore, timely harvesting and appropriate accumulated temperature could increase 1000-grain weight and rice yield, reduce the immature grain rate, and improve the gelatinization characteristics. Overall, the quality of Nangeng 5718 reached a good level when it was harvested 50 days after heading, with the accumulated temperature reaching 1051 °C. In fact, the harvest time should be chosen flexibly according to the weather conditions. Nangeng 5718 planted in Nanjing should be harvested earlier than 50 days, and rice from Huai'an and Lianyungang was of better quality when the harvest time was 50 days.

Fluidized Bed Heat Treatment for Controlling the Lesser Grain Borer (Rhyzopertha dominica) and Sawtoothed Grain Beetle (Oryzaephilus surinamensis) on Paddy cv. Khao Dawk Mali 105

The efficacy of fluidized bed (FDB) heating was studied for controlling stored product insects on rough rice using laboratorial heat-fluidized bed equipment, and the milling quality of rice was later examined. Rough rice cv. Khao Dawk Mali 105 (13% wb) infested with insects was treated with FDB. The lesser grain borer (Rhyzopertha dominica, Fabricius) (internal feeders) had a higher tolerance for heat than the sawtoothed grain beetle (Oryzaephilus surinamensis Linnaeus, external feeders). At a hot air velocity of 3.7 m/s at 55°C for 90 s, the mortality of the lesser grain borer treated by FDB significantly differed (P &lt;0.05) between all stages and from the untreated control. The pulpal stage, as an FDB-tolerant stage of the lesser grain borer, was treated with 55–65 °C for 60–150 s. FDB heat treatment at 55°C for 150 s, 60°C for 90 s, and 65°C for 60 s caused 100% mortality. At a hot air velocity of 3.7 m/s at 40°C for 120 s, the mortality of the sawtoothed grain beetle significantly differed (P &lt;0.05) between all stages and the untreated control. The egg stage, as the FDB-tolerant stage, was treated at 40–50 °C for 60–150 s. FDB heat treatment at 45°C for 150 s and 50°C for 60 s caused 100% mortality. Some of the adults that survived FDB exposure were able to reproduce, but there were significantly less progeny than in the untreated control. Heat FDB slightly affected rice quality in terms of physical and chemical properties. Keywords: Heat, Fluidized bed heat, Paddy, Stored insect pests

Effects of elevated CO2 concentration gradients on rice grain quality under two cultivation practices in cold region

AbstractBackground and ObjectivesThe effect of elevated atmospheric CO2 (eCO2) on rice (Oryza sativa L.) grain quality has been widely studied, but mostly under two contrasting levels of CO2 concentration. Our study was conducted in a new version of CO2 Gradient Tunnel (CGT) to study the responses of grain quality of japonica rice cv. Wuyoudao no.4 (WYD4) and Songjing no.9 (SJ9) to five CO2 concentrations (390–600 μmol·mol−1) gradient levels at two cultivation practices: traditional flooding (TF) and non‐flooded plastic film mulching (PM).FindingsThe results showed that the response of SJ9 to eCO2 was more pronounced under TF cultivation. When the CO2 concentration increased to 450 μmol·mol−1, the brown rice ratio and milled rice ratio of SJ9 decreased by 4.2% and 17.7%, respectively. However, when CO2 concentration increased to 600 μmol·mol−1, the brown rice ratio increased by 3.7%. These results reveal that different gradients of eCO2 have different effects on rice quality. Besides that, eCO2 decreased the nutritional quality of SJ9 by decreasing the protein content and amylose content, while eCO2 improved rice appearance and eating quality. Different from SJ9, when CO2 concentration increased to 500–600 μmol·mol–1, the milled rice ratio and head rice ratio of WYD4 increased by 5.9%–7.5% and 16.7%–19.5% under PM cultivation. Furthermore, eCO2 decreased the chalky grain rate or chalkiness by 34.5%–80.5% and 53.1%–77.1%, respectively.ConclusionsUnder PM cultivation, the rice milling quality and appearance quality of WYD4 were promoted by eCO2. Rice nutritional quality was significantly decreased in both cultivation practices. In the comparison of rice quality between the two cultivations, except for rice eating quality, the other grain quality parameters of SJ9 under PM cultivation were better than those under TF cultivation. The opposite was true for WYD4.Significance and NoveltyUnder future production conditions with eCO2, the high‐yielding SJ9 cultivar is more suitable for water‐saving cultivation with mulching film, while the high‐quality WYD4 is suitable for TF cultivation.

Influence of Nitrogen Applications during Grain-Filling Stage on Rice (Oryza sativa L.) Yield and Grain Quality under High Temperature

High temperature frequently occurs during rice’s early grain-filling period in the south of China, negatively affecting rice yield and quality and posing a major threat to local rice production. This experiment researched the influence of 3.5 °C warming during the first 20 grain-filling days on rice yield and quality and emphatically investigated the effects of the low-broadcast nitrogen fertilizer application level (LBN), high-broadcast nitrogen fertilizer application level (HBN) and foliar nitrogen fertilizer application (FN) at heading on the rice organ temperature, leaf photosynthesis, chlorophyll fluorescence, yield and grain quality, pasting and thermal properties under high temperature in 2020 and 2022, with a widely planted japonica rice variety, “Wuyunjing31”, in order to explore the practical mitigation measures for reducing the adverse impact of high temperature on rice productivity. The results showed that high temperatures during grain filling increased the rice plant temperature, damaged the chlorophyll fluorescence system and decreased the net photosynthesis rate. This led to a decline in the seed-setting rate and grain weight, resulting in a 7.0% and 13.9% yield loss in 2020 and 2022, respectively. In addition, high temperature caused a decline in the head rice rate and an increase in chalk occurrence and pasting temperature, thereby deteriorating rice grain quality. Under high temperatures, HBN enhanced the rice yield by 3.6% and 13.0% in 2020 and 2022, respectively, while FN enhanced the rice yield by 11.5% in 2022. The increase in yield was linked to the increased seed-setting rate and 1000-grain weight. LBN did not significantly affect the rice yield under high temperatures. The positive effects of nitrogen fertilizer measures on rice yield were associated with their role in lowering plant temperature and protection against the damage to the chlorophyll fluorescence system. All three nitrogen application measures generally improved rice milling quality and appearance quality under high temperature, with HBN generally showing the greatest impact. Under high temperature, LBN and FN tended to make the texture of cooked rice softer due to the decreased consistency, retrogradation enthalpy and retrogradation percentage, and this was closely associated with the decline in amylose content. In summary, nitrogen supplementation at the heading could efficiently mitigate the adverse impact of high temperature during the early grain-filling period on rice yield and quality.

Identification of reliable QTLs and designed QTL breeding for grain shape and milling quality in the reciprocal introgression lines in rice

Milling quality (MQ) and grain shape (GS) of rice (Oryza sativa L.) are correlated traits, both determine farmers’ final profit. More than one population under multiple environments may provide valuable information for breeding selection on these MQ-GS correlations. However, suitable analytical methods for reciprocal introgression lines with linkage map for this kind of correlation remains unclear. In this study, our major tasks were (1) to provide a set of reciprocal introgression lines (composed of two BC2RIL populations) suitable for mapping by linkage mapping using markers/bins with physical positions; (2) to test the mapping effects of different methods by using MQ-GS correlation dissection as sample case; (3) to perform genetic and breeding simulation on pyramiding favorite alleles of QTLs for representative MQ-GS traits. Finally, with four analysis methods and data collected under five environments, we identified about 28.4 loci on average for MQ-GS traits. Notably, 52.3% of these loci were commonly detected by different methods and eight loci were novel. There were also nine regions harboring loci for different MQ-GS traits which may be underlying the MQ-GS correlations. Background independent (BI) loci were also found for each MQ and GS trait. All these information may provide useful resources for rice molecular breeding.

Relation of Yield and Technological Indicators of Grain and Milled Rice Quality of New Rice Varieties under Competitive Testing

This article presents the results of a studying new rice varieties under competitive testing in the period 2018-2021 on the rice irrigation system of FSBSI “Federal Scientific Rice Centre” (“FSC of Rice”), Belozerny, Krasnodar region. Significant advantages of new rice varieties in terms of a complex of economically valuable traits compared to the standard were revealed: Trio and VNIIR 10289, having maximum grain vitreousity (93.5 and 90.0%), significantly exceed the standard in terms of head rice content of 64.5 and 65.4%; Dialog with the highest yield in the experiment and a mass of 1000 grains of 30.8 g has a total milling yield of 70.3%; VNIIR 10254, despite the low yield of 7.7 t/ha, has a maximum mass of 1000 grains (43.0 g) with a head rice content of 84.1%. In the experiment, a close positive correlation of yield with a mass of 1000 grains was revealed in varieties Trio, Dialog, Vector and VNIIR 10289 (r = 0.76, 0.80, 0.83). A close positive correlation of the total milling yield with the head rice content (according to ISO) was noted in the varieties Trio, Dialog and VNIIR 10289 (r = 0.81, 0.90 and 0.93), which determines their genetic determination at the level of 65, 5, 81.7 and 86.3%.

The effect of alternate partial root-zone drying and deficit irrigation on the yield, quality, and physiochemical parameters of milled rice

While paddy fields produce a high yield, they also require a large amount of water and produce a significant amount of methane. Therefore, the adoption of water-saving irrigation techniques for rice cultivation is critical. Furrowed rice farming may be a viable alternative to paddy rice cultivation. The objective of the present study was to evaluate the impact of alternate partial root-zone drying irrigation on rice yield, milled rice quality, and cooking quality under furrow rice cultivation. A two-year field trial was conducted on a local rice cultivar, Tarom Hashemi, in 2015 and 2016. Seven water regimes, including three levels of regulated deficit irrigation (RDI), three levels of alternate partial root-zone drying irrigation (APRDI), and conventional flooding irrigation (CFI), were used in this study. In RDI and APRDI treatments, plots were irrigated when soil matric potential had reached −0.1 (RDI1 and APRDI1), −0.3 (RDI3 and APRDI3), and −0.6 bar (RDI6 and APRDI6). RDI1 and APRDI1 treatments produced milled rice yield similar to the CFI, while irrigation water productivity (IWP) was significantly higher by 22.9% and 45.7%, respectively. Regardless of the soil water potential, the IWP in APRDI treatments was 16% higher than that of RDI treatments. Severe water stress (RDI6 and APRDI6) caused a marked increase in amylose content and alkali spreading value of milled rice resulting in improved cooking quality. Nitrogen uptake in APRDI treatments was 2% higher than that of RDI treatments. On average, methane emission per milled grain yield declined by 77.9% and 78.7% in RDI and APRDI treatments, respectively. Our data indicate that the expensive and laborious practice of puddling can be avoided to increase water productivity and improve rice quality without sacrificing yield. The results also show that furrow rice cultivation could significantly reduce the methane emission contribution of rice production.

Evaluating Rice Varieties for Suitability in a Rice–Fish Co-Culture System Based on Lodging Resistance and Grain Yield

Rice–fish co-cultures have been practiced for over 2000 years, and they have tremendous potential in terms of increasing food security and economic benefits. However, little research has been conducted into achieving stable yields and high lodging resistance with regard to rice while simultaneously promoting the harmonious and healthy growth of fish in rice–fish co-culture paddy fields. We conducted a field study aimed at selecting suitable rice varieties for rice–fish co-culture systems (encompassing both ratoon and main crop). This selection process was grounded in an evaluation of lodging resistance and grain yield among 33 rice varieties used throughout the studied region. The results revealed a range of lodging indices of the main crop for the second internode, spanning from 62.43 to 138.75, and the annual grain yield (main crop and ratoon crop) ranged from 7.17 to 13.10 t ha−1 within rice–fish co-culture systems. We found that the use of rice–fish co-culture farming could improve the milling quality, nutrient quality, and appearance quality of rice, though the improvement gained through co-culturing varied across rice varieties. Moreover, the lodging index of the three basal internodes of rice plants was significantly and positively correlated with the plant height and the culm fresh weight, but it was negatively correlated with the bending strength of the rice basal internodes. Additionally, the 33 tested rice varieties were clustered in accordance with their lodging resistance (i.e., high resistance with lodging indices 62.43–75.42; medium resistance with lodging indices 80.57–104.62; and low resistance with lodging indices 113.02–138.75) according to the hierarchical cluster analysis. The 33 rice varieties were also clustered in accordance with the annual (main crop and ratoon crop) grain yield (i.e., high yield with 11.17–13.10 t ha−1; medium yield with 10.15–10.83 t ha−1; and low yield with 7.16–9.88 t ha−1). In all, 11 rice varieties were identified by a comprehensive evaluation as suitable varieties for grain production in the rice–fish co-culture system. These varieties displayed favorable traits, including a high annual rice yield, strong lodging resistance, and good grain quality. This is the first study to systematically evaluate rice varieties based on grain yield, lodging resistance, and grain quality in rice–fish co-culture systems.

Consistency assessment of rice milling quality results from USDA‐FGIS official procedures and commercial mills

AbstractBackground and ObjectivesThe milling quality and grade of rice are typically appraised by milling and inspecting samples collected from a rice lot following US Department of Agriculture (USDA) official procedures using a laboratory mill, which should represent milling quality and grade results of rice milled in commercial mills. The objective of this study was to assess whether the official USDA laboratory mill and procedures provide consistent results with those obtained from commercial mills.FindingsThe results showed that the laboratory mill with the official standard procedures had significantly higher (p &lt; .05) total milled rice yield (TRY) (1.6 percentage points) and head rice yield (HRY) (2.6 percentage points), but lower whiteness index (4.4 units) on average than those of commercial mills. The average TRYs of laboratory‐milled rice of long, medium, and short‐grain varieties were 1.8, 1.7, and 1.0 percentage points higher than those from the commercial operations. The milling characteristics of pureline and hybrid rice differed between official standard mills and commercial mills.ConclusionIf the rice samples were milled to the same whiteness as the official standard procedures, the TRYs and HRYs could be close to the results from the commercial mills.Significance and NoveltyThis study provides important information that could be used to improve the consistency and accuracy of rice quality assessment of laboratory mills following the official procedures and assure that milling results are comparable to those of commercial milling processes.

Influence of bran layer on rice milling quality

AbstractBackground and ObjectivesRice milling involves applying forces to remove bran from brown rice to produce milled rice. The physical and chemical properties of a rice kernel may affect both the amount of bran removed during milling and the amount of head rice yield (HRY) produced, which is a determinant of crop value. This study investigated bran thickness and bran chemical composition as factors that influence bran removal and HRY as a result of milling.FindingsThe results showed that brown rice kernels with initial higher surface lipid contents (SLCs) required longer milling times to achieve 0.4% SLC, but the longer milling times did not translate into lower HRYs or higher bran yields. Bran chemical composition had a more significant impact on the milling characteristics than bran thickness. Arabinoxylans had the greatest impact on HRY, followed by lipids and proteins.ConclusionsBran thickness did not have a significant impact on the milling time, bran yield, or HRY. There was significant interaction between arabinoxylans and proteins on HRY and bran yield, which indicates the probability of crosslinking between proteins and arabinoxylans.Significance and NoveltyThis study demonstrates the importance of rice bran chemical components and their interactions in terms of rice milling quality, rather than their physical properties.

Influence mechanism of tempering for storage quality of dried rice based on the evaluation of physicochemical and sensory characteristics and mitochondrial function and structure

Use of tempering has proven to be effective for the improvement of rice milling quality, but few researches focused on its influence mechanism for dried rice storage quality. In this study, influence mechanism of tempering treatments [tempering at 65 °C (DTHT), 50 °C (DTMT) and no tempering (DTNT)] on the storage quality of two varieties rice (“Aolongsimiao” and “Shengtaiyou 018″) was evaluated based on the assessment of physicochemical and sensory quality, and a novel method judging the damage of mitochondrial function and structure in dried rice. During rice drying and storage, compared with DTNT and DTMT samples, DTHT samples showed the slowest increase in fatty acid value (FAV), nonanoic acid (off-flavor compound) content, cooked rice hardness, cross-sectional crack, and ratio of broken rice. DTHT samples suffered less oxidative damage, maintained significantly (p < 0.05) higher mitochondrial antioxidant capacities (MAC) and membrane integrity, and showed a less than 18.18% increase of mitochondrial malondialdehyde (MDA). Mitochondrial super oxide dismutase and MDA were significant correlation (p < 0.01) with moisture content, FAV, appearance, texture, comprehensive score, and stickiness of rice quality. Tempering influence mechanism for rice storage quality might be its maintaining MAC and membrane integrity, and then inhibiting the decrease of dried rice storage quality.

Influence of Oscillatory Motion of a Rice Dehydrator on Energy Consumption and Milling Quality of Rice

This study aimed to evaluate the influence of the oscillatory motion of a rice dehydrator on drying time, drying rate, electrical energy consumption, specific energy consumption, milling quality (broken milled rice, head milled rice and milling recovery) of rice varieties of FARO 62, FARO 15, and FARO 60. The dehydrator was designed to operate either in a stationary or oscillatory motion. The dehydrator motion influences the drying time, drying rate, electrical energy and specific energy consumption and milling quality regardless of the rice variety. The drying time of the rice varieties ranged from 125 to 290 mins, drying rate (2.897 to 6.72 kgH2O/kg solids h), electrical energy consumption (15.43 to 35.46 MJ), specific energy consumption (5.25 to 11.20 MJ/kg), milling recovery (67.58 to 73.97%), head milled rice (60.47 to 69.10%) and broken milled rice (1.62 to 9.46%), respectively. The oscillatory motion of the dehydrator aided a shorter drying time, faster drying rate, less electrical energy consumption and specific energy consumption, and desirable milling quality. The study concluded that the adoption of oscillatory motion during drying would aid in energy conservation and in the production of quality milled rice.

Determining optimal nitrogen management to improve rice yield, quality and nitrogen use efficiency based on multi-index decision analysis method.

Reasonable nitrogen (N) supply is critical for increasing rice yield while improving grain quality and nitrogen use efficiency (NUE). However, the trade-off relationship between yield, quality and NUE of rice under N management has not been well understood enough. In the present study, a 2-year field experiment was conducted to identify optimal N fertilizer management practices that resulted in high-yield, high-quality and high-NUE by using the technique for order preference by similarity to an ideal solution (TOPSIS) with entropy weight (EW) method. All the parameters of rice yield, quality and efficiency were remarkably affected by fertilization treatments. Compared with farmer's fertilization practice (FFP), optimizing N fertilizer treatment (OPT) and substituting 20% of N fertilizer with pig manure based on OPT treatment (OPTM) increased grain yield (2.87-6.62%) by maintaining higher 1000-grain weight and filled grains rate. The agronomic NUE (AE) and N partial factor productivity (PFP) under OPT and OPTM treatment were also remarkably increased by 32.81-43.01% and 28.59-33.28% with respect to the value under FFP treatment, respectively. Meanwhile, OPT and OPTM significantly improved the milling quality of rice by increasing brown rice rate (0.71-1.17%) and head rice rate (1.34-2.31%). OPT and OPTM significantly improved appearance quality by decreasing chalkiness and eating quality by reducing amylose content in 2020. The TOPSIS with EW showed that rice comprehensive evaluation could be maintained at a high level under OPT and OPTM. OPT and OPTM were nutrient management modes of high-yield, high-quality and high-efficiency, and promising practice to improve rice comprehensive productivity. This strategy is also highly-consistent with the United Nations Sustainable Development Goals. © 2023 Society of Chemical Industry.

Effects of Sowing Methods on Paddy Rice Yields and Milled Rice Quality in Rainfed Lowland Rice in Wet Savannah, Togo

Identifying the socio-economic constraints of seeding technologies uptake and analyzing the yields, milled quality and growers’ income under various seeding methods are a strategy for sustainable rainfed lowland rice. A survey and an on-farm experiment were carried out at five locations with a random sample of 50 farmers grouped in five of the fourteen partner cooperatives of ESOP-Pagouda. The survey focused on socio-economic data collection. The experiment, replicated at five locations, involved three treatments: broadcast seeding, direct seeding, and transplanting. The paddy rice yields and milled rice quality were analyzed using R software version 4.1.3, and arithmetic means discriminated at the 5% by the Duncan test. The profitability indicators, such as the Gross Margin (GM) and the Benefit/Cost Ratio (BCR), were calculated. The results showed that 14% of farmers adopted rice transplanting method. The transplanting method increased rice yield (3.3 t/ha) compared to direct seeding (2.8 t/ha) and broadcast seeding (2.2 t/ha). The milled long grain rate (56%) was significantly higher than those under both seeding methods. Additionally, the transplanting method improved the gross margin (1,146 $USD/ha) compared to 663 $USD/ha and 431 $USD/ha for direct and broadcast seeding, respectively. The benefit/cost ratio 1.5 for transplanting was almost double from that of both seeding methods. Despite its high demand for labor and agricultural inputs, the transplanting method provided the highest paddy rice yields and milled rice quality to improve farmers’ income.

Ohmic heating using electrolytes for paddy parboiling: A study on thermal profile, electrical conductivity, milling quality, and nutritional attributes

AbstractOhmic heating (OH), a novel thermal technique could be utilized for paddy parboiling to improve milled rice quality. In this research, two paddy varieties (one traditional and one modern variety) were subjected to OH at different salt concentrations (0%, 0.3%, 0.5%, 0.7%, and 0.9%) and voltage gradients (10, 12, 14, 16, and 18 V/cm) and their influence on thermal profile, electrical conductivity (EC), milled rice quality, and nutritional profile were studied in comparison to the conventional steaming method. A factorial design was used to determine the effect of variety, voltage gradient and holding time on head rice yield (HRY), hardness and color difference of parboiled milled rice. Results indicated the significance of salt and voltage on processing time and HRY. On increasing, both enhanced the EC and heating rate leading to a great reduction in parboiling duration whereas HRY increased on lowering the voltage. High significant effects were observed between the factors for HRY and color. The maximum HRY and hardness were obtained for OH at 0.7% salt and 12 V/cm. This treatment when compared to steaming, consumed less energy, and provided less chalkiness, better HRY and hardness for both varieties to a greater extent. OH also positively impacted the nutritional profile of parboiled rice as it retained more protein and fat than the conventional method. These results reveal the superiority of OH in providing a significant favorable impact on the parboiled milled rice quality and has a great potential to be used for paddy parboiling.Practical applicationsOhmic heating is an emerging thermal technique having the potential for rapid uniform heating. In this study, OH was utilized for paddy parboiling by incorporating electrolytes for replacing the conventional steaming method. Steaming requires a boiler for generating steam, which adds to the processing cost and equipping OH eliminates the need for a boiler. This will save water, energy, space, manpower, and maintenance requirements. OH also reduces the parboiling duration, while improving parboiled rice quality. The ohmic behavior of paddy will also facilitate the design of continuous ohmic systems for paddy parboiling which can be immensely useful in the rice processing industry.

Influence of harvest moisture content and milling duration on microwave‐dried rice physicochemical properties

AbstractBackground and ObjectivesHarvest moisture content (HMC) and milling duration are important factors that influence milled rice quality. The goal of this study is to determine the effect of HMC and milling duration on the physicochemical properties of long grain and medium grain microwave‐dried rice. A long‐grain hybrid rice cultivar (XL753) and a medium‐grain rice cultivar (Titan) with initial HMCs of 16%, 18%, and 20% (wet basis) were sourced from rice farms in Arkansas, USA. The rice samples were dried with the 915 MHz industrial microwave at a specific energy of 525 kJ/[kg‐grain]. The control samples were dried with natural air in an equilibrium moisture content chamber set at 25°C and 56% relative humidity. Following drying, the samples were milled at milling durations of 30, 45, and 60 s, and physicochemical properties were determined.FindingsHMC had significant (p &lt; .05) impacts on head rice yield, crude protein content, and final viscosity of microwave‐dried rice for both cultivars. There were strong positive correlations (Titan: 0.86, XL753: 0.88) between HMC and head rice yield and negative correlations (Titan: −0.85, XL753: −0.62) between HMC and final viscosity of microwave‐dried rice. Milling duration significantly influenced the surface lipid content and whiteness index of microwave‐dried rice for both cultivars. Furthermore, milling duration had significant impacts on the starch damage content and trough viscosity of microwave‐dried rice cultivar XL753 but no significant impact on cultivar Titan. Statistical models predicted HMC of 20% and milling duration of 45 and 42 s for processing microwave‐dried rice cultivars Titan and XL753 respectively, to obtain rice with superior characteristics.ConclusionsHMC and milling duration significantly influenced some physicochemical properties of microwave‐dried rice. We recommend that further studies should be conducted on the cooking, sensory, and storage properties of microwave‐dried rice, to provide information on end‐use and consumer acceptability.Significance and NoveltyThis study provides science‐based information that is vital for optimizing the harvesting and processing conditions of rice dried using the 915 MHz industrial microwave.

The effects of filling level on the milling accuracy of rice in the friction rice mill

The filling levels of rice in friction rice mill is one of the principal factors that determine rice milling quality. Clarifying the influence of filling level on milling accuracy is the key to improve milling quality. In this work, the milling process of particles in mill under different filling levels was examined experimentally and numerically. The effects of filling level on milling degree and milling uniformity were revealed. The results show that with increase of filling level, extra added particles enter originally outer ring afterward mainly inner ring. Particles are subjected to more severe abrasion due to the increase of force and area of milling zone. The tangential dissipated energy of particles increases first then keeps stable. A method which can quantify milling uniformity is established and then applied. Particle rotational kinetic energy directly affects milling uniformity. This study is helpful to provide guidance for parameter selection of similar mills.

An inquiry into the process of upgrading rice milling services: The case of the Mwea Irrigation Scheme in Kenya

Countries in sub-Saharan Africa (SSA) rely heavily on imported rice from Asia that is of superior quality relative to local rice. The objectives of this study are to assess the impacts of the adoption of improved milling technologies and the associated structural transformation of the rice value chain from 2011 to 2019 using the original census of the rice millers in the Mwea Irrigation Scheme in Kenya. Our empirical analysis uses the doubly robust method and the endogenous switching model, which collectively reveal that the adopters of improved milling machines successfully improved the quality of local milled rice to allow it to compete with imported rice, thereby increasing the amount of domestic rice sold to supermarkets as well as to urban traders and consumers. It is also found through probit regression that a few educated, entrepreneurial rice millers operating in rice milling clusters adopted large-scale improved milling machines that included destoning ability, importing them from China around 2010. Later, smaller-sized improved machines were also introduced and more widely adopted in the rice milling clusters. In contrast, the many other millers that did not adopt improved machines were forced to down-size their business or exit the industry. These results imply that adopting improved milling technologies, including destoners, is critical to improving the competitiveness of SSA’s domestic rice against imported rice.

EFFECT OF TWO STAGE DRYING EMPLOYING FLUIDIZED BED DRYING, TEMPERING FOLLOWED BY FIXED BED DRYING ON HEAD RICE YIELD OF BRRI DHAN28 RICE VARIETY IN BANGLADESH

Drying of high moisture paddy to achieve quality milled rice is an important issue in a paddy producing country like Bangladesh. This study has been conducted to investigate the impact of two stage drying technique namely, fluidized bed drying, tempering and followed by fixed bed drying method on quality of BRRI Dhan28 rice variety in terms of head rice yield (HRY). Moist paddy was dried in fluidized bed dryer (FBD) as first stage drying to reduce moisture from 25-27% to 18-19% using three drying temperatures of 120, 130, and 150°C at three bed thicknesses of 8, 10, and 12 cm. The first stage dried samples were immediately tempered for 30 minutes and dried in second stage drying by fixed bed dryer using 40±10C temperature maintaining bed thickness as 30 cm for the further reduction of moisture content to 13-14% (wb). Sun drying method was followed as complete drying of control sample. Control sample was used to compare the milling quality of rice dried in two stage drying technique. In addition, head rice yield was also compared to existing industrial paddy drying complexes. The results revealed that HRY of rice samples obtained from different drying methods was comparable. All the sets of drying parameters in two stage drying yielded better quality HRY than the control and even existing industrial drying method. The highest HRY (53.43%) of milled rice was obtained in the two-stage drying. On the other hand, the samples dried in the sun drying and industrial drying using Louisiana State University (LSU) dryer yielded 49.77% and 48.25% HRY, respectively. Therefore, the two-stage drying technique can be used for drying of high moisture paddy to obtain quality dried rice.

Interactive effects and modeling of some processing parameters on milling, cooking, and sensory properties for Nigerian rice using a one-step rice milling machine

sThis study investigates the interactive effects of processing parameters on the quality of milled rice using a one-step milling machine. Also, predictive models were generated using response surface methodology. The processing parameters were moisture content (10–14 % dry basis), shaft speed of rotation (600–900 rpm), and polishing time (1–3 min). The quality parameters evaluated were milling (head rice yield, percentage broken rice, fine broken rice, and milled rice yield), cooking (optimum cooking time, kernel elongation ratio, and width expansion ratio), and sensory (flavor, aroma, appearance, texture, and overall acceptability) properties. The results showed that the interactive effects of moisture content, shaft speed, and polishing time were significant (P < 0.05) on percentage broken rice, milled rice yield, fine broken rice, optimum cooking time, kernel elongation ratio, width expansion ratio, aroma, and appearance but was not significant on head rice yield, flavor, texture, and overall acceptability. These results were similar to the regression models generated. In conclusion, the interactive effects of these processing parameters affect all the cooking properties but not all milling and sensory properties while using a one-step milling machine.