Head Rice Yield Research Articles

PaddyCheck—An Instrument for Rice Quality Determination

Several of the rice quality parameters are nowadays determined manually or partly manually, which leads to subjective results. In order to analyse the rice quality and avoid most of the manual handling, the PaddyCheck instrument was mainly developed to measure the paddy/rough rice kernels. However, the design and technique of the instrument are also suitable for brown rice kernels. The PaddyCheck instrument measures the physical properties of the rice kernels as well as texture properties and translucency. Initial calibrations have been developed to correlate these properties with the Head Rice Yield and Chalkiness, which are two of the most common and important quality parameters for rice.

Variation of Milling and Grain Physical Quality of Dry Season Pathum Thani 1 in Thailand

Pathum Thani 1 (PTT1) is a photoperiod-insensitive, aromatic Thai rice variety that is grown year-round. The rice from some locations is often priced lower than others due to sub-standard grain quality. This study sought to determine the limiting grain quality characteristic(s) in dry season PTT1 and their distribution across Thailand’s irrigated rice regions. To do so, we evaluated the milling and physical quality of milled rice grain of dry season PTT1 from 24 provinces in 5 regions in Thailand. Sixty-seven paddy rice samples were collected and evaluated for head rice yield, chalkiness, whiteness, and translucency. Head rice yield varied by region, with the highest (48.1%) found in samples from the Central region, compared to 34.5-39.7% elsewhere. Head rice chalkiness was the physical quality that varied more widely among the provinces within each region than among regions, with chalkiness at a level that would adversely affect price in more than one-half of the samples. Contrary to the general perception that chalky grain is less resistant in milling, head rice yield actually increased with total chalkiness, expressed as % chalky grain by weight. The total chalkiness correlated negatively with translucency, while the head rice chalkiness correlated positively with whiteness. Grain chalkiness was identified as the grain quality attribute of PTT1 rice that varied with location; this directly affected the price of milled rice grain, as well as indirectly through its relationship with head rice yield and visual appearance of the milled rice grain

GLORIFY: A new forecasting system for rice grain quality in Northern Italy

Abstract A reliable forecast of the pre-harvest grain quality is requested by stakeholders in the rice sector, which is increasingly oriented to the achievement of superior standards to meet the market demand. Despite its economic importance, very few simulation models of the qualitative aspects of rice productions including the effects of weather conditions and farming practices are available. This paper presents GLORIFY, a forecasting system targeting the simulation of head rice yield (HRY), which represents the main determinant of rice market price at global level. A new HRY model was developed using experimental data collected in Northern Italy in 2006–2013 and referred to Loto (japonica) and Gladio (tropical japonica) cultivars, and it was coupled to the WARM rice simulator. Historical simulations were then performed in the period 1994–2013 to reproduce observed HRY variability, with model outputs and weather variables used as independent variables to build multi-regression models. At field level, model performances denoted a good agreement between observed and simulated HRY (R2 and modelling efficiency in the range 0.73–0.93). At province level, best results were obtained for Loto variety, as the regression model was able to explain 78% of the HRY variability, with a root mean square error (RMSE) of 0.77%. The model accuracy slightly decreased when leave-one-out cross-validation was applied (R2 = 0.61, RMSE = 1.04%). The present study lays the basis for a reliable estimation of HRY variability under different management and weather conditions.

Degree of Milling Effect on Cold Water Rice Quality

The aim of this study was to examine the effects of degree of milling on various rice parameters such as proximate composition, and cooking properties using mathematical model. The experiments were performed in the laboratory of Food Research Division, Nepal Agricultural Research Council. The three different medium type rice varieties of Nepal (Lumle-2, Chhomrong and Machhapuchre-3) were exposed to five different degrees of milling (0%, 6%, 8%, 10% and 12%). The degree of milling (DM) level significantly (P≤0.05) affected the milling recovery; head rice yield, nutrient content as well as cooking properties of the rice. Increase in DM resulted in further reduction of protein content, fat content, minerals, milled rice and head rice yield after bran layer was further removed. A positive correlation between DM used in present model, amylose content, kernel elongation and gruel solid loss was observed, however, with an increase in DM; amylose content, kernel elongation and gruel solid loss were found to be increased. Adopting 6 to 8% DM for commercial milling of rice might help to prevent quantitative, qualitative and nutritional loss along with retention of good cooking characteristics.

Effects of drying conditions in hybrid dryer on the GABA rice properties

In this study, pre-germinated rough rice was dried under various conditions using a hybrid dryer that incorporated heat pump dryer with fluidized bed drying (FBD) system in order to compare with the single-stage drying by hot air dryer. The main objective was to investigate the effect of drying conditions on the cooking and physical properties, nutrients and sensorial qualities of GABA rice products. It appeared that the FBD at 100–140 °C led to noticeable increase of head rice yield. The germination process caused the decline of gelatinization enthalpy of brown rice flour, the change of pasting properties, the reduction of cooking time and escalation of the total phenolic content, antioxidant activity and GABA content. The FBD at higher temperature significantly raised the degree of starch gelatinization and caused longer cooking time, higher hardness and adhesiveness of cooked GABA rice. Three-stage drying comprising FBD at 60 °C for 10 min in the first stage followed by FBD at 100 °C in the second stage and then heat pump drying at 45 °C together with tempering step between drying stages was recommended due to its superior GABA rice product quality.

Variations in agronomic and grain quality traits of rice grown under irrigated lowland conditions in West Africa.

Rice breeding in West Africa has been largely skewed toward yield enhancement and stress tolerance. This has led to the variable grain quality of locally produced rice in the region. This study sought to assess variations in the agronomic and grain quality traits of some rice varieties grown in this region, with a view to identifying sources of high grain yield and quality that could serve as potential donors in their breeding programs. Forty‐five varieties were grown under irrigated conditions in Benin and Senegal with two trials in each country. There were wide variations in agronomic and grain quality traits among the varieties across the trials. Cluster analysis using paddy yield, head rice yield, and chalkiness revealed that 68% of the total variation could be explained by five varietal groupings. One group comprising seven varieties (Afrihikari, BG90‐2, IR64, Sahel 108, WAT311‐WAS‐B‐B‐23‐7‐1, WAT339‐TGR‐5‐2, and WITA 10) had high head rice yield and low chalkiness. Of the varieties in this group, Sahel 108 had the highest paddy yield in three of the four trials. IR64 and Afrihikari had intermediate and low amylose content, respectively, with the rest being high‐amylose varieties. Another group of varieties consisting of B6144F‐MR‐6‐0‐0, C74, IR31851‐96‐2‐3‐2‐1, ITA222, Jaya, Sahel 305, WITA 1, and WITA 2 had high paddy yield but poor head rice yield and chalkiness. The use of materials from these two groups of varieties could accelerate breeding for high yielding rice varieties with better grain quality for local production in West Africa.

Effect of Varying Parboiling Conditions on Head Rice Yield for Common Paddy Varieties in Iran

Abstract Various conditions of a parboiling process affect the qualitative parameters of paddy milling. In this study, the effects of drying temperature (45 and 60 °C), moisture content (8, 10 and 12% w.b.), steaming time (10, 20 and 30 min) and paddy varieties (Hashemi and Alikazemi) were investigated on head rice yield (HRY). The samples were husked using a rubber roller husker and whitened by a laboratory abrasive whitener. Results showed that the main effects of all parameters were significant on HRY (P <0.01). The utilization of higher temperature (60 °C), in comparison with non-parboiled rice, without reducing the milling quality was found as one of the advantages of parboiling. Among all experiments, the highest HRY (68.647%) was achieved in the combination of Alikazemi/45 °C/10 min/8%. In the majority of cases, the combinations including Alikazemi variety had higher HRY than Hashemi. For Hashemi variety, the highest HRY (67.297%) was achieved in combination 45 °C/10 min/8%. In terms of HRY, parboiling causes an increase of 25.8% and 43.3% respectively for Hashemi and Alikazemi. Therefore, it is highly recommended in processing of Alikazemi variety.

Physicochemical and nutritional properties of rice as affected by parboiling steaming time at atmospheric pressure and variety.

To elucidate the effect of different parboiling steaming time on the physicochemical and nutritional quality of rice, four varieties, NERICA1, NERICA7, IR841, and WITA4, were soaked at the same initial temperature (85°C) and steamed for 5, 15, 25, 35, and 45 min. NERICA7 steamed for 25 min recorded the highest head rice yield (71.9%). Nonparboiled IR841 recorded the shortest cooking time (17.0 min), while NERICA1 steamed for 35 min recorded the longest cooking time (26.1 min). NERICA1 steamed for 45 min was the hardest (63.2 N), while nonparboiled IR841 was the softest (28.7 N). NERICA7 recorded higher peak and final viscosities across all steaming times compared to the other varieties. NERICA7 steamed for 35 and 45 min recorded the lowest total starch (77.3%) and the highest protein (13.2%) content, respectively. NERICA7 steamed for 25 and 45 min recorded the highest phosphorus (0.166%), magnesium (572 mg/kg), and potassium (2290 mg/kg) content, respectively. We conclude that, depending on desired physicochemical and nutritional properties, specific varieties and steaming times can be selected to achieve those outcomes.

HEAD RICE YIELD OF CROPS HARVESTED BY COMBINE AND HAND AT DIFFERENT RIPENING TIMES IN CAMBODIA

SUMMARYExperiments were conducted across 2 years to determine the effect of harvesting methods – combine harvester and hand harvesting – and harvest time during ripening on milling quality of long grain rice grown in the rainfed lowland ecosystem in Cambodia. Head rice yield (HRY) was highest when rice was harvested 25 days after flowering and decreased with delay in harvesting at 35 and 45 days after flowering. This was accompanied by a general decline in grain moisture content at harvest, although it was still high at 24–25% at 35 days after flowering. The decline in HRY was associated with increases in fissured grain percentage observed immediately after harvest. Hand harvesting produced 2–6% higher HRY than combine harvesting. Fissured grain in hand harvested crops was lower in year 1, but was similar to combine harvested crops in year 2. Both hand and combine harvested crops were sun-dried but rough rice harvested by combine was dried on plastic sheet and this may have contributed to reduction in HRY. Maximum HRY percentage was only about 44% and the factors contributing to this low HRY were discussed. Harvesting time and methods had no significant effect on grain yield, but the field grain loss during the harvesting operation was 2–5% higher in combine than hand harvesting.

Rice grain protein composition influences head rice yield

Background and objectivesThe objective of this study was to determine the extent to which differences in rice grain protein composition are associated with head rice yield (HRY). HRY, the mass of milled unbroken rice grain derived from a defined mass of paddy rice expressed as a percentage, is a commercially important trait targeted by rice breeders. Variation in rice grain protein composition influences rice grain texture, and high grain protein content is associated with high HRY; however, the relationship between rice grain protein composition and HRY is not well understood.FindingsHPLC analysis of protein extracts derived from broken and unbroken milled medium‐ and long‐grain rice suggests that rice grain protein composition differences are associated with HRY. Glutelin, a major class of rice grain storage proteins, displayed the greatest difference between broken and unbroken rice grains but weakest association with HRY. Prolamin and globulin content displayed relatively smaller differences between broken and unbroken medium and long grains, yet both protein fractions were associated with HRY.ConclusionsRice grain protein composition, in addition to other known factors, influences rice HRY.Significance and noveltyProtein composition differences between broken and unbroken rice grains have significant implications for human nutrition and in part explain differences in HRY. Rice breeders face the challenge of balancing the two competing traits of HRY and soft grain texture.

INFLUENCE OF HARVESTING METHODS ON YIELD AND QUALITY OF RICE IN THE REPUBLIC OF MACEDONIA

In this study, the influence of two different paddy harvesting methods (manual harvesting and combine harvesting) on paddy yield, head rice yield and white rice yield was investigated. Field trials were set up in three different locations in the rice producing regions Kocani, Cesinovo-Oblesevo and Stip under the standard production technology, adopted in the entire Macedonian rice production. Two Italian introduced varieties (San Andrea and Onice) were included in the trials. Samples were taken from the treatments with different methods of harvesting (manual and combine harvesting) from which the paddy rice yield data were collected directly. In order to determine the head rice yield, laboratory milling of paddy grains was performed on a paddy quality testing machine (three average samples of 100 g per treatment, duration of milling 1,40 min.). On the base of the data for paddy rice yield and head rice yield, the white rice yield was estimated. According to the results obtained, the highest paddy rice yield (11,925.67 kg ha-1) as well as the highest white rice yield (6,710.57 kg ha-1) were achieved in the treatment with manual harvesting in Kocani region (San Andrea variety). The highest head rice yield (65.80 %) was determined in the treatment with manual harvesting in Stip region (Onice variety), while the lowest head rice yield (43.90 %) was in the treatment with combine harvesting of the variety Onice in Kocani region. In general, the method of manual harvesting resulted in higher values of paddy yield, head rice yield and white rice yield compared to the method of mechanized, combine harvesting in all the examined treatments (two varieties, three locations).

Exploration of Rough Rice Head Yield Subjected to Drying and Retention Durations in a Fluidized Bed System

Abstract.Several researchers have reported that drying freshly harvested rough rice to safe storage moisture content of 14.9% d.b. in fluidized bed dryers resulted in a decrease in head rice yield, as compared with traditional drying methods. This phenomenon was attributed to the high thermal stress that affects rice kernels. The present study hypothesized that drying rough rice in fluidized bed dryers subjected to retention duration would maintain the rice quality as it may reduce the thermal stress. Therefore, the goal of this research was to investigate the effects of heating and retention durations on the dried rice head yield and energy consumption in a fluidized bed dryer. A bench-scale fluidized bed dryer was developed and tested. The effects of drying duration of 10, 20, and 30 min and the retention duration of 0, 15, 30, 45, and 60 min on rough rice moisture content, drying rate, head rice yield, and energy consumption were investigated. During the retention period, paddy released a considerable amount of moisture. This moisture reduction, achieved during retention period, was obtained without any additional heating cost and was a supplement to the overall drying process. The retention period helped with thermal stress management within rice kernels and resulted in maintaining the head rice yield as compared to the rice dried without retention duration. Considering all the studied heating and retention durations, the head rice yield values of rice samples varied from 46.0% to 51.0%. The lowest energy consumption of 3.31MJ/kg waterremoved was achieved at the heating duration of 10 min and the zero retention duration. This value represents 1.44 folds of the theoretical energy required to remove 1 kg of moisture from organic matter. Keywords: Drying, Energy consumption, Head rice yield, Moisture content, Retention duration, Rough rice.

The study of quality attributes of parboiled rice during steaming process with revolved sieve

The steaming process with revolved sieve was studied as a function of steaming time and revolution velocity. The quality of parboiled rice in terms of thermal property, head rice yield and color was investigated and compared to the conventional steaming process such as fixed sieve. The experimental results showed that the steaming process with revolved sieve had advantage over the steaming process with fixed sieve. It led to a steamed sample with higher DG higher head rice yield and lower whiteness value. The required steaming time for a regularity quality by a steaming process with revolved sieve was also shorter. Moreover, the steaming time affected the qualities of parboiled rice. The long steaming time provided the higher DG and head rice yield and lower whiteness value of parboiled rice. Considering revolution velocity, it was found that the revolution velocity did not affect the qualities of parboiled rice. However, the revolution velocity of 5 rpm with steaming time of 5 min provided the difference of quality at each layer.

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

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

EFFECTS OF DIFFERENT PLANTING SYSTEMS ON SOME PRODUCTIVE AND QUALITY TRAITS OF RICE

The traditional planting system of rice in the Republic of Macedonia is wet direct seeding (hand broadcasting of seeds into pre-standing water in the fields). In this paper, the effects of different planting methods of rice (wet seeding as well as dry seeding by using seed drills) on productivity and quality of rice are presented. Field trials were set up at the Experimental Station of the Institute of Agriculture – Skopje, locality Mishjak, Kocani region, with two varieties (San Andrea and Onice) included. The following planting systems were explored: 1. wet direct seeding, with seeding rate of 250 kg seeds per ha (control); 2. dry seeding, 150 kg seeds per ha; 3. dry seeding, 200 kg seeds per ha. During the harvesting, the number of tillers per m2, biological yield, paddy rice yield, head rice yield and white rice yield were analyzed. The highest number of tillers per m2 (San Andrea 383.00 and Onice 731.33) and the highest average paddy yield (San Andrea 11,780.00 kg ha-1 and Onice 10,113.33 kg ha-1) were achieved in the control. The highest biological yield in Onice (21,493.33 kg ha-1) was found in the control, while in San Andrea (20,650.00 kg ha-1) in the treatment dry seeding, 150 kg seeds per ha. For the head rice yield, the highest percentage was determined in the control (San Andrea, 54.57%) and in the treatment dry seeding, 150 kg seeds per ha (Onice, 66.72 %). Both varieties (San Andrea with 6,428.35 kg ha-1 and Onice with 6,143.83 kg ha-1) reached the highest white rice yield in the control. In general, in the treatment dry seeding with 200 kg seeds per ha, the higher values of number of tillers per m2, paddy yield and white rice yield were assessed, compared to the treatment dry seeding with 150 kg seeds per ha, in both varieties.

Effect of parboiling technique on Physico-Chemical and nutritional characteristics of basmati rice

Parboiling method was developed to enhance the milling quality, cooking characteristics and textural properties of Basmati cultivar Pusa Basmati 1121. In order to increase the head rice yield of Basmati rice, three different parboiling methods (traditional parboiling technique, steaming alone and advanced parboiling method) were performed and compared with unparboiled sample. Parboiling method 3 consisting of pre-steaming of paddy at 66.09%. Broken percentage was significantly reduced (p<0.05) to 6.31% while cooking time and water uptake ratio increased to 48.63 minutes and 2.96%, respectively. Hardness, cohesiveness and springiness of parboiled cooked rice increased to 9.52N, 0.16 and 0.23mm whereas adhesiveness was reduced significantly to 0.007Nmm.

Drying of Rough Rice Using Heated Husk for Heat Transfer and Moisture Adsorption

Abstract. Drying of small size samples usually represents a challenge to rice researchers. Using natural air drying to dry these samples exposes them to the fluctuations of ambient air conditions. Therefore, the goal of this research was to evaluate the suitability of drying small size rough rice samples using heated husk as a heat transfer and moisture adsorbent medium. The proposed drying technique could be an attainable process, particularly because it represents conduction heat and moisture transfer rather than natural air drying. The required amounts of rice husk were placed in aluminum containers and kept in an oven overnight to reach the desired temperature. Heated husk samples were mixed with rough rice and maintained for the desired drying duration; following which, the husk and rough rice mixtures were separated pneumatically. The separated rough rice samples were collected to determine moisture content, drying rate, and rice quality. The highest mixture temperature of 34.0°C was achieved at the highest husk to rough rice ratio of 1:2 and the highest husk temperature of 110°C after 4 minutes. A maximum of 6.4% moisture reduction points was achieved by mixing the rice husk to rough rice by 1:2 on a weight basis and employing heated rice husk at 100°C. The highest drying rate of 5.99%/h was achieved during the first hour of drying with the husk-to-rough rice ratio of 1:2 and the husk temperature of 100°C. Milled rice yield ranged between 63.4% and 72.0% while the head rice yield ranged between 39.9% and 67.9%. An empirical correlation was developed to calculate the normalized moisture content as a function of the husk to rough rice ratio, the husk temperature and drying duration with a coefficient of determination of 0.775 under the studied conditions. Keywords: Conduction drying, Heat transfer medium, Moisture absorbent, Rice husk, Rough rice.

Vibratory bed assisted infrared drying of parboiled rice and its rice bran stability

The purposes of this research were divided into two parts: (1) to determine the drying characteristics and quality of parboiled paddy undergoing vibratory bed assisted infrared (VIR) drying, and (2) to study the stability of rice bran from the VIR-dried parboiled paddy. Infrared (IR) drying and hot air (HA) drying were applied for comparison purpose. For the experiment 1, VIR drying of parboiled paddy provided the best drying characteristics with the shortest drying time of 50 min and the maximum drying rate of 0.00146 g water/g dry matter·min. VIR drying also produced the greatest head rice yield of 61.3%. The experiment 2 presented that rice bran from VIR-dried parboiled paddy had the highest oil content of 0.256 ± 0.041 g/g dry matter and the most stable in term of minimum change in free fatty acid (FFA) content. The increase in FFA during storage for 14 days was 0.36%. However, the increases in FFA of rice bran from IR-and HA-dried parboiled rice and normal rice were 0.38, 1.36, and 4.10%, respectively.

Effect of airflow rate on drying air and moisture content profiles inside a cross-flow drying column

ABSTRACTRice at 20.5 and 16.3% initial moisture contents (IMCs) was dried using 57°C/13% RH air at airflow rates (Qs) of 0.36, 0.46, and 0.56 (m3/s)/m2 for 30, 60, and 90 min, respectively, in an experimentally simulated cross-flow drying column. Q significantly affected the drying air and rice moisture content profiles within the drying column; for a particular drying duration, the range of MCs within the column decreased as Q increased. Q also impacted the extents of intra-kernel material state gradients created and thus had potential impacts on kernel fissuring and consequent head rice yield reduction. In addition, the impact of Q on the above-mentioned profiles was dependent on the rice IMC.

Effect of Clearance on Mechanical Damage of Processed Rice

The effect of rubber rolls in husking machine (Yanmar type) on rice cultivars of Tarm Hashemi (TH) and Daillman Mazandarani (DM) were tested during husking at three clearances of 0.4, 0.6 and 0.8 mm between cylinders. The experiments were carried out in a factorial experiment under complete randomized design with three replications. The results showed that the TH cultivar was significantly better than the DM in all studied conditions. The results showed broken rice of 6.239 % and 6.729 %, cracked grain percentage of 3.787 % and 4.671 %, brown rice (husked rice) of 82.049 % and 80.113 %, husking efficiency of 84.719 % and 83.152 % and head rice yield of 70.633 % and 69.202 % for TH and DM, respectively. The clearance of 0.8 mm was significantly superior to the levels of 0.4 and 0.6 mm in all studied conditions.