Head Rice Yield Research Articles

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.

Assessing the Effects of Microwave Treatments on Rice Quality and Mortality of Adult Maize Weevil, Sitophilus zeamais

Highlights The study provides insight to microwave technology and the effects of Sitophilus zeamais mortality on rough rice and brown rice that has been previously dried. The mortality of S. zeamais was highest at 5 kW at 90 s, with 98 and 100% mortality for rough rice and brown rice, respectively. Using a microwave power of 5 kW for 90 s on rough rice did not affect head rice yield (HRY), color, or pasting characteristics. For brown rice, a shorter duration of 34 or 60 s at 5 kW or 3 kW for 90 s is recommended to avoid a reduction in HRY. Abstract. A laboratory study was conducted to determine if an industrial microwave could kill Sitophilus zeamais infesting rough rice and brown rice. The rough rice and brown rice samples were comprised of previously air-dried long-grain hybrid (RT 7521 FP) cultivars at initial moisture contents of 11.3 and 12.7% wet basis (w.b.), respectively. Samples (250 g) were infested with ten S. zeamais adults and heated with a microwave power of 3 and 5 kW for 34, 60, and 90 s. The effects of microwave treatments on moisture, head rice yield (HRY), rice color, and pasting characteristics were evaluated. The mortality of S. zeamais was highest at 5 kW at 90 s, with 98% and 100% mortality for rough rice and brown rice, respectively. Rough rice treated at 5 kW at 90 s did result in significantly lower moisture content than the control; however, HRY, color, and pasting characteristics were not significantly different than the controls. Brown rice treated at 5 kW for 90 s resulted in lower moisture content, and there was a significant decrease in the HRY (28.4%) compared to the control (56.2%). No differences in color and some variations in pasting characteristics were observed when compared to the controls. For brown rice, we recommended a shorter duration of 34 or 60 s at 5 kW or 3 kW for 90 s be used to avoid a reduction in HRY and pasting characteristics. Keywords: Brown rice, Maize weevil, Microwave drying, Rough rice.

High-Power Short Duration Microwave Drying of Rice Versus Fissuring and Milling Yields

Highlights MW specific energy ranging from 422.5 to 507.0 kJ/kg of rice can dry rice to 12.5% moisture content in a single pass. Fissuring percentage was significantly lower for lower drying durations as compared to 3 min drying durations for all power levels. RR dried for one minute with MW at 16-20 kW results in higher head rice yields. Abstract. The utilization of microwave (MW) drying technology to dry rough rice (RR) is considered a promising method for high-moisture RR drying with high throughput. Milling quality is a significant factor in stakeholders adoption of this method. Therefore, experiments were conducted using an industrial MW dryer operating at 915 MHz to examine the effects of different MW power levels and heating durations on RR drying. Single pass drying was performed using 16, 18, and 20 kW power levels and 1, 2, and 3 min heating durations. A control sample was dried in an environmentally controlled chamber at 25°C and 56% relative humidity (RH). The moisture content, surface temperature, fissuring, and head rice yield (HRY) of RR were measured. The initial moisture content of RR was 21.22% w.b. The moisture content of RR after 3 minutes of drying at the studied power levels was close to the recommended rice milling moisture content of 13%, indicating the feasibility of single pass MW drying. The maximum surface temperature of RR at severe (20 kW for 3 min) and least severe (16 kW and 1 min) treatment conditions was 91.9°C and 62.6°C, respectively. Fissuring percentages of 86.2% and 85.3% were observed in RR drying at 20 kW for 3 min after one day and after seven days of fissure examination, respectively. Fissuring percentages of 84.2% and 84.3% were observed at 16 kW for 3 min drying after one day and after seven days, respectively. The HRY at MW drying conditions of 16-20 kW for 1 min was higher than that of RR gently dried at 25°C and 56% RH. MW drying shows promise for reducing drying duration compared to conventional methods. Keywords: Head rice yield, Microwave drying, Moisture content, Rice drying, Rice fissuring.

Fissure Formation in Rice During Conventional and Microwave Drying

Highlights Rice fissuring and breakage have a negative impact on milling quality and market value. Fissure formation during microwave drying may be a combination of different phenomena. The phenomena include the buildup of high internal temperatures and pressures in the kernel and stresses generated from a higher heat flux of liquid at high microwave intensities. Abstract. Rice fissuring and breakage have negative economic impacts on rice processing. Many advances in multi-pass conventional rice drying technologies have not been successful in completely preventing rice fissure formation. Thankfully, novel drying technologies such as the 915 MHz industrial microwave have been shown to have a great potential for rice drying and may reduce rice fissuring (or increase head rice yield) due to the volumetric heating property of microwaves. This review assessed the mechanism of fissure formation in conventionally and microwave-dried grains to provide recommendations for managing fissure formation during the drying of freshly harvested paddy rice. Literature search indicates that fissure formation during microwave drying may be mainly a combination of different phenomena, such as the buildup of high internal temperature and pressure in the kernel, stresses generated from a higher flux of liquid at high microwave intensities, and other mechanisms that are yet to be discovered. Fissure formation in rice during conventional drying of the rice kernels can be explained using the glass transition phenomenon. Keywords: 915 MHz microwave, Fissures, Glass transition Phenomenon, Rice, Volumetric heating.

Impact of Drying Techniques on Physicochemical Properties of Dried Rice and Its Influences on Rice Beer Brewing Process

Highlights Implications of microwave drying on rice brewing performance were tested. Microwave-dried rice is most similar to natural air-dried rice in protein and amylose content. Microwave-dried rice is most similar to natural air-dried rice in brewing utilization. Abstract. Rice is used as an adjunct grain by the beer manufacturing industry. Before utilization, the rice has to be dried to the desired moisture content. The drying process employed may have an impact on the rice’s physicochemical properties, which influence the rice’s performance in the brewing process. This study focused on investigating the impact of microwave drying on rice’s physicochemical properties and utilization in the brewing process. Rough rice samples with an initial moisture content of 19.7% wet basis were exposed to a microwave dryer to deliver specific energy at the rate of 525 kJ/Kg of initial grain mass in a single drying pass. The effects of the single-pass continuous drying on the dried rice amylose content, protein content, and specific gravity (°Plato, fermentable sugar content) of the wort were determined. The results were compared with samples dried using natural air at 25°C and 56% relative humidity (RH) and two-pass hot-air drying at 45°C and 60°C with RH set at 20%. There was a statistical difference in measured rice amylose and protein contents (p= 0.042) between microwave-dried samples and the natural air-dried samples. However, these attributes were significantly different from those of samples dried at a higher temperature of 60°C and an RH of 20%. There was a significant difference (p=0.0197) in the initial gravity content of the all-malt samples and the rice adjunct samples, as expected, but there was no significant difference between the rice adjunct samples. Overall, this study analyzed the effect of microwave drying on rice processing and its subsequent use in the brewing process, but no measurable differences were observed among the wort’s initial and final gravity contents, attenuation levels, and alcohol by volume. Microwave drying was most comparable to natural air drying, but it results in a greater head rice yield, which may benefit rice farmers and processors. Keywords: Amylose content, Brewing process, Microwave drying, Rice drying, Specific gravity.

تأثير عوامل التشغيل على جودة الضرب لألرز طويل الحبة

The current study aimed to test and evaluate sheets’ different perforation shapes, brake angles, and milling durations to improve the quality of long-grain white rice from an abrasive milling machine. The investigated parameters of head rice yield, broken rice percentage, whitening degree, and rice bulk temperature were influenced by five sheets with five perforated shapes (horizontal, vertical, inclined, 1 mm round holes, and 1.5 mm round holes), three brake angles (0, 45, and 90º), and four milling durations (60, 70, 80, and 90 s). The results showed that the horizontal rectangular perforated sheet resulted in the highest value of head rice yield and the lowest value of broken rice. On the other hand, the vertical rectangular perforated sheet resulted in the highest whitening degree, followed by the inclined rectangular perforated sheet. The round holes (1.0 mm and 1.5 mm diameter) are not recommended for the long-grain whitening process because of the resulting high values of broken kernels, rice bulk temperature after the whitening process, and lower values of whitening degree. The brake angle of 90º resulted in the highest value of broken rice for all studied perforated sheets used in this study. This study recommended that the optimum operating conditions were using the horizontal rectangular perforated sheet, zero degree brake angle and milling duration of 80 s.

The effect of rice milling time and feed rate on head rice yield and color properties

This study has been carried out to evaluate the head rice yield, kernel broken and the chance of color depend on milling time and feed rate. In this study, threshed rice kernels by combine-harvester at different cylinder speeds, rice harvesting season in 2018, were used for experiment test. According to results, head rice yield decreased slightly as the cylinder speed increased, with yields varying between 71.40 % and 70.28 %. Processing time was found to have a highly significant effect (p<0.01) on the quantities of unbroken kernel, broken kernel, bran, yield and husk. The highest rate of broken kernel was obtained at a processing time of 25 seconds, and the lowest values were obtained at a processing time of 10 seconds. With a processing time of 10 seconds, the quantities of unbroken kernel, broken kernel, bran, yield and husk were 70.74, 3.260, 0.810, 74.37 and 24.82 %, respectively. When the processing time was 25 seconds, the quantity of broken kernel decreased from 70.74 percent to 62.86 percent, and yield decreased from 74.37 % to 67.58 %. The broken kernel ratio increased from 3.26 percent to 4.633 percent and bran ratio increased from 0.8642 percent to 1.822 percent. Husk ratio, on the other hand, increased from 24.82 % to 30.60 %. In other words, as the processing time increased, so did the bran ratio and husk ratio. The highest whiteness value of 70.92 was obtained at a processing time of 25 seconds; while the lowest whiteness value of 63.81 was obtained at a processing time of 10 seconds. There were declines in a and b values as processing time increased, although the differences were not statistically significant. The highest a and b values were obtained at a processing time of 10 seconds, with -0.690 and 15.01, respectively. In conclusion, when processing paddy to rice, processing time needs to be increased to obtain a whiter rice; to have fewer broken kernels and a higher head rice yield, on the other hand, the processing time needs to be short.

Indigenous storage structures for paddy in North East region

The effect of different indigenous storage methods on the quality of rice during the storage period was studied. Four different varieties of paddy were stored in different storage structures as indigenous types, such as Kot (small bamboo structures), Kei (large size storage structure), wooden structures and metal bins separately, and the total head rice recovery of rice during storage period was studied. The maximum head rice yield was found in the KD cultivar and the minimum in the Huikap cultivar. The different physical dimensions and characteristics of paddy influenced the breakage of paddy, affecting the total head rice recovery during storage. Long, slender grains are more susceptible to breakage, affecting the head yield.

Continuous Monitoring Analysis of Rice Quality in Southern China Based on Random Forest

Rice quality has received more attention, so monitoring and analysis are of great significance to rice quality. General quality indexes of rice in southern China from 2011 to 2020 were determined, including processing quality (brown rice yield, milled rice recovery, head rice yield), appearance quality (grain length, length-width ratio, chalky rice percentage, chalkiness degree, transparency), and cooking quality (alkali spreading value, gel consistency, amylose). Principal component analysis was used to distinguish the regional quality of southern rice. The results showed that amylose and chalkiness were the main contributory quality indexes of rice in South China, the upper reaches of the Yangtze River, and the middle and lower reaches of the Yangtze River. In the past decade, the total high-quality rate of rice in the South has improved. The random forest was used to determine the important influence index of rice quality. The results showed that chalkiness degree, alkali spreading value, and gel consistency were important indexes affecting the quality of southern rice, and random forest could be used as an effective approach for continuous monitoring and analysis of rice quality.

Deep placement of liquid fertilizer at tillering stage influences grain quality, 2-acetyl-1-pyrroline synthesis, and antioxidant response of fragrant rice

In recent years, the deep placement of solid fertilizers has become popular in rice production due to high fertilizer utilization efficiency and productivity. There is limited knowledge about the effect of deep placement of liquid fertilizer at the tillering stage on grain quality and productivity of fragrant rice. Therefore, a two-year field experiment was conducted from 2019 to 2020 with two fragrant rice cultivars Yuxiangyouzhan (YXYZ) and Xiangyaxiangzhan (XYXZ) under four fertilization treatments: no fertilizer application (T1); application of solid fertilizer (150 kg ha −1 NPK; broadcasted 90 kg ha −1 NPK as basal fertilizer and 60 kg ha −1 NPK at the tillering stage, T2); application of liquid fertilizer with 10 % less N (broadcasted 90 kg ha −1 NPK as basal fertilizer and deeply placed 45 kg ha −1 N and 90 kg ha −1 PK at the tillering stage, T3); application of liquid fertilizer with 20 % less N (broadcasted 90 kg ha −1 NPK as basal fertilizer and deeply placed 30 kg ha −1 N and 90 kg ha −1 PK at the tillering stage, T4). The study showed the highest 2-acetyl-1-pyrroline (2AP) content under T3 treatment (2019, 115.35–120.11 μg kg −1 and 112.97–130.30 μg kg −1 , 2020). The proline (PRO) content, proline dehydrogenase (PDH) activity, 1-pyrrolin-5-carboxylic acid (P5C) content, and 1-pyrrolin-5-carboxylic acid synthase (P5CS) activity also improved under T3 and T4 treatments compared with T2 treatment. Besides, the T3 and T4 treatments increased the protein content and decreased the chalkiness degree and chalky rice rate compared with the T2 treatment. Moreover, T3 and T4 treatments improved the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and reduced the malondialdehyde (MDA) content of the leaves compared with the T2 treatment. Further, the structural equation model revealed that POD and CAT and rice appearance quality had significant positive effects on 2AP content, and that POD and CAT indirectly affected 2AP content by showing a significant positive effect on the PRO. The T3 treatment also showed relatively stable and higher head rice yield and net income in the two-year field experiment. Overall, side deep placement of liquid fertilizer improved the 2AP synthesis, and antioxidant response of fragrant rice and under T3 treatment, the head rice yield was stable and the economic income was higher. Therefore, in the future of agricultural production, it is recommended that farmers use liquid fertilizer with 10 % less N (T3) to improve the quality and stress resistance of fragrant rice and obtain stable and more economic benefits. • Deep placement of liquid fertilizer at tillering stage improved 2-acetyl-1-pyrroline and grain quality of fragrant rice. • Deep placement of liquid fertilizer at tillering stage enhanced antioxidant enzyme activities in leaves of fragrant rice. • The relationship among antioxidant response, 2-acetyl-1-pyrroline, and grain quality in fragrant rice were interpreted. • Optimization of deep placement of liquid fertilizer at the tillering stage yield higher economic income.

Registration of a blast‐resistant premium medium‐grain rice germplasm Eclipse

AbstractEclipse (Reg. no. GP‐149, PI 701081) is a blast‐resistant and ‘Calrose’ type medium‐grain‐quality rice (Oryza sativa L.) germplasm that was developed by the USDA‐ARS Dale Bumpers National Rice Research Center, Stuttgart, AR. It was selected from a backcross between a blast‐resistant tropical japonica rice cultivar ‘Katy’ and a temperate japonica medium‐grain rice cultivar ‘M‐202’. Eclipse was evaluated in uniform regional rice nurseries in the southern United States during 2019–2020 and further characterized in Arkansas fields during 2020–2021. Blast resistance was determined under greenhouse and field conditions. Under greenhouse conditions, Eclipse was resistant to races IA45, IB1, IB49, IB54, IC17, IE1, IG1, and IH1, similar to that of Katy. Under naturally infected field conditions in Louisiana and Puerto Rico, Eclipse was resistant to leaf and panicle blast infections, similar to that of Katy. Eclipse has Pi‐ta and Ptr genes and lacks Pi‐b, Pi‐k, and Pi‐z. Eclipse is a semidwarf glabrous type of medium‐grain rice and has a low amylose content, similar to M‐202, and quality of Calrose rice. In the southern United States, Eclipse has an average height of 98.5 cm and yields 6,710 kg grain ha−1. It reaches 50% heading at 84 d after emergence with a lodging incidence of 28.5 and 59% head rice yield. Eclipse is useful for breeding for improving disease resistance and grain quality and can be used directly by rice growers for premium medium‐grain rice production.

Physiological and transcriptomic analysis reveal the regulatory mechanism underlying grain quality improvement induced by rice ratooning.

Ratoon rice cropping has been introduced for increased rice production in southern China and, as a result, has been becoming increasingly popular. However, only a few studies have addressed the regulatory mechanism underlying grain quality improvement induced by rice ratooning. In this study, parameters of rice quality, including head rice yield, chalky grain percentage, grain chalkiness degree, hardness and taste value, were shown to be much improved in the ratooning season rice as compared to its counterparts main and late cropping season rice, indicating that such an improvement was irrespective of seasonal effects. In addition, the nutritional components of grains varied greatly between main-cropping season rice, ratooning season rice and late-cropping season rice and displayed a significant correlation with rice quality. Finally, the regulatory mechanism underlying rice quality improvement revealed that gibberellin-dominated regulation and plant hormone signal transduction jointly contributed to a decrease in formation of chalky grains. This work improves our knowledge on rice quality improvement under rice ratooning, particularly on the regulatory mechanism of plant hormones. © 2022 Society of Chemical Industry.

Optimum total nitrogen application is required to reduce the yield loss of hybrid rice to high temperature

The grain yield and quality of rice (Oryza sativa L.) face great challenges associated with increasing temperatures, thus threatening global food security. The wheat, maize and barley yield loss magnitudes imposed by increasing temperatures reportedly interact with the nitrogen (N) application level under field conditions. However, little is known about the interactive effect between high daytime temperatures and the N supply on the rice grain yield or quality or the influence of this effect on nitrogen use efficiency in the field. In this work, two hybrid rice varieties (Liangyoupeijiu-LYPJ and IIyou602-IIY602) were grown under three N application levels (N75–75 kg ha−1, N150–150 kg ha−1, and N225–225 kg ha−1) in paddy fields in 2019 and 2020 under control and higher-temperature (HT) conditions from the heading stage to maturity. HT exposure significantly decreased the grain yields, grain filling, grain weight, grain-leaf ratio, total biomass at maturity and harvest index (HI) of the two rice varieties at all N levels across both years, while the spikelet m−2 was only affected in 2019. Moreover, the grain yield reduction caused by HT were least at N150 (57.0%) in LYPJ (68.7% and 68.8% in N75 and N225, respectively) and N75 (60.7%) in IIY602(66.0% and 64.5% in N150 and N225, respectively) on average of two years. Grain filling percentage, biomass and HI also had least decreases under N150 in LYPJ and under N75 in IIY602. Regarding the grain quality, HT exposure decreased the head rice yield and grain length, and increased chalkiness in the two varieties in both years while decreasing the amylose content and increasing the protein content in 2019 and 2020, respectively. Relatively optimal N application rates (N75 or N150 for both varieties) improved grain quality indicators such as the brown rice, head rice, grain length, chalkiness degree and amylose content under HT. After HT exposure, nonsignificant changes in N accumulation at maturity and significant reduction in N translocation and N use efficiencies for grain and biomass production were observed in both varieties. Compared to the relatively higher N applications, applying N150 to LYPJ (by 24.3%) and N75 to IIY602 (by 33.7%) induced lower N translocation reductions. Thus, our results suggest that increasing N supply cannot minimize the damage caused by HT in the realistic fields.

Influence of Germinated Brown Rice Production by Water Spraying Method on Its Qualities

This study was aimed to compare the production time (germination and drying process) and quality of germinated brown rice (GBR) obtained from the water spraying-based GBR production (Sprayed-GBR) system and the water soaking-based GBR production (Soaked-GBR) system. The results showed that the Sprayed-GBR, in the germination process, required 2.5 h for spraying in a water spraying step to obtain paddy with the moisture content of 30% (w.b.) and 26 h in an incubation step to obtain the 90% germination percentage. This led to a shorter germination time compared to the Soaked-GBR, which required a germination time of 50 h for a 90% germination percentage. After germination, the moisture content of the Sprayed-GBR was lower than that of the Soaked-GBR. This provided a shorter drying time in the Sprayed-GBR (27 min) drying process compared with the Soaked-GBR (33 min). For GBR qualities, the Sprayed-GBR could decrease the unpleasant odor problem by providing a smaller number of attached microorganisms after germination (Shade drying), leading to a significantly higher score in the odor and the overall acceptability than the Soaked-GBR. This indicated that the Sprayed-GBR got more consumer acceptance. Moreover, the head rice yield value of the Sprayed-GBR was not different from that of the Soaked-GBR. However, the Sprayed-GBR provided a significantly lower GABA content and a significantly higher percentage of fissured kernels than the Soaked-GBR.

Effects of drying approaches combined with variable temperature and tempering on the physicochemical quality of rice

In this study, the effect of drying approaches in conjunction with variable temperature and tempering on the physicochemical quality of rice was investigated. The development of fissures, head rice yield, taste quality, textural properties, and microstructure of rice with different drying approaches were evaluated by employing principal component analysis (PCA). The results showed that increasing the tempering treatment could enhance the physicochemical quality of rice, and that the different drying approaches had a significant influence (P < 0.05) on the development of fissures, head rice yield, taste quality, and textural properties. High temperatures result in partial gelatinization of the starch, destruction of the starch granules, and an increase in fissures, as revealed by the microstructure of rice with different drying approaches. In addition, the drying approaches with a variable temperature of Δ0 (35 °C), Δ5 (45 °C–50 °C), and Δ0 (45 °C) in combination with the tempering treatment exhibited a high overall physicochemical quality. This study offers a point of reference for further research into the changes in the physicochemical quality of rice during drying.

Waxy is an important factor for grain fissure resistance and head rice yield as revealed by a genome-wide association study.

Head rice yield (HRY) is an essential quality trait, and is sensitive to environmental stresses during the grain-filling, harvest, and postharvest stages. It is therefore important for rice production and global food security to select for superior HRY traits; however, the molecular basis of this trait remains unknown. Using diverse rice germplasm material, we performed a genome-wide association study of grain fissure resistance (GFR), the phenotype most associated with HRY, and found that the granule-bound starch synthase I gene Waxy is an important gene controlling GFR. Analysis of near-isogenic lines demonstrated that genetic variations in Waxy conferred different levels of tolerance to fissuring in grains. The null allele wx resulted in the highest GFR, while alleles that increased amylose synthesis reduced GFR. Increases in amylose content led to increases in the ratio of the widths of the amorphous layer to the semi-crystalline layer of the starch granules, and also to increased occurrence of chalkiness. The layer structure determined GFR by affecting the degree of swelling of granules in response to moisture, and chalkiness acted as an accelerator of moisture infiltration to rapidly increase the number of swelling granules. Our study reveals the molecular basis of GFR and HRY, thus opening the door for further understanding of the molecular networks of GFR and HRY.

Response of rice grain quality to elevated atmospheric CO2 concentration: A meta-analysis of 20-year FACE studies

Compared with growth and yield, far less attention has been devoted to the impact of elevated CO2 on rice grain quality. Exposure to elevated CO2 induces numerous physiological changes in plants that can alter the chemical composition and thus the quality of rice grains. This meta-analysis was conducted to synthesize the effect of free air CO2 enrichment (FACE, approximately 550 μmol mol−1) on grain quality of rice grown under open field conditions. Factors that could modify the CO2 effects were also investigated. They included cultivars, nitrogen applications, environmental temperatures and grain types. On average, elevated CO2 decreased head rice percentage by 8%, which led to no increase in head rice yield, despite substantial increases of brown rice yield and white rice yield that were obtained under FACE conditions. Elevated [CO2] increased chalky grain percentage by 26% and chalkiness degree by 30%, which significantly impaired rice appearance. However, the cooking and eating quality was improved by elevated [CO2], as indicated by the changes in starch RVA profiles and the palatability of cooked rice. The nutritional value of FACE rice declined as shown by the 2–9% decreases in the concentrations of nitrogen, phosphorus, magnesium, sulfur, zinc, iron, copper, manganese and amino acids; meanwhile the anti-nutrient phytate and the molar ratio of phytate to zinc were increased. High nitrogen application alleviated negative effects of elevated [CO2] on milling quality and rice appearance but further decreased the bioavailability of essential nutrients. The CO2-induced decreases in element concentrations of white rice were generally higher than those in brown rice. In general, CO2-induced changes on grain quality were seldom modified by rice cultivars, temperatures or experimental locations.

Modelling and experimental analysis of rice drying in new fluidized bed assisted hybrid infrared-microwave dryer

This study aimed to investigate how infrared (1000–2000 W) and microwave power (100–900 W), air velocity (1–5 m/s) and temperature (40–80 °C) affected the specific energy consumption, the moisture removal rate, and the product's quality (whiteness index, head rice yield, water uptake ratio, and elongation ratio) in hybrid dryer. Rising temperature, velocity and microwave power and lower temperatures resulted in improving head rice yield of paddy samples. The experiments proved that the new hybrid system significantly increased the moisture removal rate (from 100 to 700%), head rice yield (from 5 to 40 %) and decreased the specific energy consumption (from 10 to 80%) compared to the single fluidized bed dryer. The water uptake ratio and elongation ratio of the dried samples in the hybrid dryer were higher than the single dryer, however their whiteness index was not significantly different. The best drying conditions are associated with the lowest specific energy consumption and the highest moisture removal ratio and rice quality. Experimental data were fitted into empirical drying models to explain moisture ratio variations during drying. Nomhorm and verma,s model was found to be the best for moisture ratio prediction. Also, the central composite design of response surface methodology was applied to forecast outputs. A modified cubic model was observed in all responses with high R2 values (greater than0.9). The drying parameters were optimized for the specified constraints, resulting in 68 °C temperature, 5 m/s air velocity, 900 w microwave power, and 1479 w infrared power. The experimental values were found to be 0.368607 g/s for the moisture removal rate, 7.16988 MJ/kg water for the specific energy consumption, 90.6% for the head rice yield, 58 for the whiteness index, 3.63 for the water uptake ratio, and 2.28627 for the elongation ratio, at the optimum treatment conditions.

Investigation of rice performance characteristics: A comparative study of LR, ANN, and RSM.

Parboiling is a type of heat pretreatment used in rice processing to reach higher head rice yield and improve the nutrition properties of raw rice. In this research, the goals were prediction and determination of optimum conditions for parboiled rice processing using the response surface method (RSM) as well as modeling the output values by linear regression (LR) and artificial neural networks (ANN). The parameters including steaming time (0, 5, 10, and 15 min), dryer type (solar and continuous dryers), and drying air temperature (35, 40, and 45°C) were employed as input values. In addition, the breakage resistance (BR) and head rice yield (HRY) were selected as output values. The ANN‐based nonlinear regression, the multi‐layer perceptron (MLP), and the radial basis function (RBF) have been developed to model the process parameters, as well as the central composite design (CCD) was conducted for optimization of BR and HRY values. The outputs of RBF network have been successfully applied to predict higher coefficient of determination of BR and HRY as 0.989 and 0.986, respectively, indicating the appropriateness of the model equation in predicting head rice yield and breakage resistance when the three processing variables (steaming time, dryer type, and drying air temperature) are mathematically combined. Also, the lower root mean square error (RMSE) was obtained for each one as 0.043 and 0.041. The optimum values of BR and HRY were obtained as 12.80 N and 67.3%, respectively, at 9.62 min and 36.9°C for a solar dryer with a desirability of 0.941. In addition, the same values were obtained as 14.50 N and 72.1%, respectively, at 8.77 min and 37.0°C for a continuous dryer with a desirability of 0.971.

Appropriate operating condition for golden color parboiled rice production by high temperature fluidized bed drying and tempering

Golden color parboiled rice is practically obtained by a high steaming temperature and a long steaming time. Under this condition, there is a splitting of the rice endosperm, which causes poor head rice and uneven color of parboiled rice grains. In this work, it was therefore proposed to use high temperature fluidized bed drying and tempering for producing golden color parboiled rice. In the experiment, the paddy was soaked in hot water at 70 °C for 5 h, steamed at 103-117 °C for 5-30 min, dried at 110-150 °C to a moisture content of 25% dry basis, and tempered for 30-90 min. The experimental results showed that the degree of starch gelatinization depended on the temperature and the duration of steaming. The gelatinization of rice starch in the steaming step affected the drying rate and effective diffusion coefficient. The head rice yield of the final product ranged from 71-72% and was independent of the drying temperature. The obtained parboiled rice had a golden color, corresponding to the whiteness in the range of 22-24, when the drying temperature was above 130 °C and tempering time was at least 30 min. It was recommended that the soaked paddy should be steamed at 110 °C for 10 min, dried at 150 °C and tempered for 30 min. Under the recommended condition, the parboiled rice was in the “highly parboiled” category, and the total energy consumption was 3.94 MJ/kg wet paddy.