Parboiling Conditions Research Articles

Influence of parboiling conditions on rice grain quality characters and insect infestation with rice weevil (Sitophilus oryzae. L) of some rice cultivars

Parboiling improves rice grain hardness and reduces susceptibility to Sitophilus oryzae infestation by gelatinizing the starch and enhancing resistance.A newly designed electric machine was used to parboil four Egyptian rice cultivars—Sakha 108, Giza 178, Super 300, and Egyptian Yasmin—at 70, 75, and 80 °C and determine their susceptibility to Sitophilus oryzae L. (Coleoptera: Curculionidae) infestation. Results indicated that heating affected most traits in all four rice cultivars during both study seasons 2021 and 2022. Super 300 rice cultivar exhibited the highest hulling values (81.23 and 81.42%) when heated to 80 °C, while the Yasmin rice cultivar showed the lowest values for hulling (77.66 and 77.45%) at 70 °C. while Giza 178 cultivar showed a significant decrease in broken percentage (90.85 and 94.02%) compared to control when heated to 80 °C. The results also indicated that the Yasmin rice cultivar had the highest values for white belly, hardness, and gel consistency at 80 °C, while the Sakha 108 cultivar showed the lowest values for these traits at 70 °C. Furthermore, the protein, elongation, and water uptake characters significantly responded to the different investigated treatments. Yasmin cultivar at 80 °C showed the highest significant values for protein (9.26 and 9.47%), elongation (65.02 and 65.44%), and water uptake (453.2 and 455.1 ml water/100 g milled grains) in both seasons. Sakha 108 cultivar had the lowest values for these traits at 70 °C. The S. oryzae insects responded differently to the rice cultivars. Using Dobie’s Index of Susceptibility, all cultivars were classified as resistant to S. oryzae infestation. Super 300 was moderately resistant before parboiling but resistant after heat treatment. In conclusion, the study underscores the influence of pre-storage parboiling on rice weevil infestation, suggesting that heat treatment could serve as an effective control measure. These findings emphasize the importance of parboiling conditions in enhancing rice grain quality and bolstering resistance to insect infestation.

Effects of Parboiling on Chemical Properties, Phenolic Content and Antioxidant Capacity in Colored Landrace Rice

Parboiling influences chemical compositions in rice grains. The objectives of this study were to evaluate the change in chemical content, total phenolic content and antioxidant capacity of landrace rice genotypes under parboiling conditions and to identify the genotypes suitable for production of parboiled rice. Landrace rice varieties used in this study consisted of Glam Feang, Glam Tonkeaw, Kawgum, Glam Luem Phua, Medmakham, Deang Sakonnakhon, Sang Yod, Kawniewd-eang, Mali Deang, KDML105 and RD6. Parboiling reduced fiber content, total phenolic content and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity in rice grains. Fiber contents were 1.46% in brown rice (unpolished rice) and 1.40% in parboiled rice (24 h of soaking and 48 h of incubation). Total phenolic contents were 205.67 mg/100 g seed in brown rice and 35.34 mg/100 g seed in parboiled rice. Antioxidant capacity (DPPH) reduced from 68.45% in brown rice to 26.23% in parboiled rice. Ash content and protein content were not significantly affected by the parboiling process. Medmakham cv. had the highest total phenolic content and antioxidant capacity in brown rice and parboiled rice. Gum Leamphea cv. and Medmakham cv. were the best genotypes for ash content, protein content, total phenolic content and antioxidant capacity (DPPH) in brown rice and parboiled rice. Glam Feang cv. had the highest protein contents in brown rice and parboiled rice although it had low total phenolic content and antioxidant capacity. Cluster analysis further showed variation among genotypes, revealing distinct groupings in brown rice and parboiled rice based on chemical properties, phenolic content and antioxidant capacity. This research significantly contributes to a better understanding on how parboiling affects rice compositions and nutritional values. It emphasizes the importance of nuanced comprehension of how different rice varieties respond to parboiling, aiding informed decisions in rice processing and selection to meet specific nutritional needs.

Parboiling process improves phytochemical, chemical, and technological properties of wild rice (Zizania sp.)

Wild rice (Zizania sp.) shows high protein, mineral, fiber, and low lipid contents, which makes this grain a good option for consumption as cooked rice or as an ingredient in food products. However, technological processing can affect the properties of wild rice. The parboiling process can be an alternative to improve the quality of wild rice grains, avoiding the decomposition of the endosperm and reducing nutrient loss during cooking. This study aimed to optimize the parboiling conditions and evaluate the effects on technological, chemical, and phytochemical characteristics. The grains were gelatinized in an autoclave under pressure and time defined by the central composite rotatable design methodology. Ash and lipids levels increased under high pressure and time, while starch digestibility decreased. The parboiling process pressure was the variable that most affected the accumulation of phytochemicals. The highest levels of bioactive compounds were obtained at intermediate pressures (73.54 kPa), while time did not effectively affect the phytochemical profile.

Optimization of soaking conditions (temperature and time) on physicochemical properties of selected parboiled rice varieties grown in Eastern Ethiopia.

This study aimed to optimize soaking temperature and time for better physicochemical properties of parboiled rice varieties grown in Eastern Ethiopia. Two brown rice varieties (NERICA-4 and NERICA-6) were collected from the Somali Regional Agricultural and Pastoral Research Center in Gode. The experiment was designed to aid the design expert software using box-behnken experimental design of response surface methodology to optimize the effects of soaking temperature (60-70°C) and soaking time (4-6h). Relevant physical and chemical composition properties of the parboiled rice varieties were investigated using standard methods. Numerical optimization of the responses was performed using design expert software. The results showed that soaking time and temperature significantly (p < .05) influenced the physicochemical quality of studied brown rice varieties. The optimal soaking temperature and time were 65°C and 6h, respectively, for NERICA-4. Under these conditions, the optimum response variables obtained were 375.37 N, 52 min, 12.3%, 1.24%, 13.86%, 2.17%, 3.2942%, 67.1171%, 343.5kcal/100 g, 274.72 mg/100 g, 318.35 mg/100 g, and 268.31 mg/100 g for hardness, cooking time, moisture, ash, protein, fat, fiber, carbohydrate, energy, magnesium, and potassium and phosphorous content, respectively. However, 65°C and 5h were optimum soaking temperatures and time for NERICA-6, giving hardness, cooking time, moisture, ash, protein, fat, fiber, carbohydrate, energy content, magnesium, potassium, and phosphorous of 375.18 N, 52 min, 12.2%, 1.4%, 11.54%, 2.29%, 2.89%, 69.6%, 345.42 kcal/100 g, 156 mg/100 g, 105.9mg/100 g and 136.9mg/100 g, respectively. The findings showed that rice varieties, in particular NARICA 4, were processed under optimal parboiling conditions in the study setting for better physical properties, proximate composition, and mineral content.

Multi-scale structure characterization and in vivo digestion of parboiled rice

To investigate the multi-scale structural changes and digestibility of parboiled rice, the side chain distribution, helical structure, short/long-range ordered structure, and lamellar structure were systematically characterized and an in vivo postprandial blood glucose test was applied. The results indicate that parboiling has little effect on the side chain distribution, double helix content and helical structure order of parboiled rice. The crystal type of rice starch changed from type A to A + V or B + V after parboiling and the relative crystallinity decreased from 30.45 % to a minimum of 6.87 %. The in vivo study also indicated that parboiling significantly reduces the glycaemic index of rice to medium level. Our work is the first to focus on the parboiling conditions, multi-scale structural changes and in vivo digestibility of parboiled rice, which might provide guidance for the design of less digestible parboiled rice in the future.

Effect of parboiling conditions on zinc and iron retention in biofortified and non-biofortified milled rice.

BACKGROUNDZinc‐biofortified rice could contribute to zinc intake in deficient populations, but processing it into parboiled rice could affect this potential benefit. Zinc and iron true retention (TR) in milled rice produced under conditions resembling household and commercial parboiled methods was evaluated. Zinc and iron TR in milled rice obtained from biofortified and non‐biofortified rice subjected to different soaking temperatures during parboiling was also evaluated.RESULTSConditions resembling commercial parboiling methods resulted in 52.2–59.7% zinc TR and 55.4–79.1% iron TR, whereas those used for household parboiling resulted in 70.7–79.6% zinc TR and 78.2–119.8% iron TR. Zinc TR in milled (8–16% bran removal) biofortified and non‐biofortified parboiled rice was 50.6–66.8% when soaking rough rice at 20 °C and 29.9–56.0% when soaking rough rice at 65 °C; both had lower zinc TR than non‐parboiled rice (58.0–80.6%). Iron TR was generally similar between milled non‐parboiled and parboiled rice (26.2–67.6%) and between parboiled biofortified and non‐biofortified milled rice.CONCLUSIONParboiling conditions used to obtain milled rice targeted for own household consumption resulted in higher zinc and iron TR compared to parboiling conditions used for milled rice targeted for markets. More zinc from the inner endosperm moved towards the outer layers at high soaking temperature, resulting in lower zinc TR for milled parboiled rice soaked in hotter water. Parboiled rice soaked at temperatures used in households could provide more zinc to diets compared to rice soaked in hotter water commonly used in large rice mills, especially when rice is extensively milled. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Modeling the combinatory effects of parboiling and cooking on red paddy rice (Oryza sativa L.) properties

Rice is one of the most consumed cereals in the world. Rice parboiling is usually performed to increase its mechanical and nutritional properties. However, parboiling can cause alterations to the texture when it is cooked for consumption, and texture has a major effect on consumer acceptability. Therefore, quantitatively determining and modeling the relationship between parboiling conditions and postcooking characteristics is meaningful from a process control point of view. Thus, the objective of this research was to study and model the influence of steaming time on the properties of red paddy rice before and after cooking. Rice crystallinity decreases with steaming time, suggesting that starch gelatinization under isothermal conditions follows first-order kinetics. Composition, color, and density showed marginal changes as a result of parboiling, while the cooked texture was significantly affected by final cooking time. Although the samples steamed for extended periods of time presented high mechanical properties, they also demonstrated that they reached the final mechanical properties in less cooking time. A second-order kinetic rate equation best described the evolution of the texture properties during cooking and revealed the complexity of the process.

Processing Parameters for One-Pass Drying of High-Moisture Parboiled Rough Rice with 915 MHz Microwaves

HighlightsThe impact of parboiling process parameters on the feasibility of one-pass microwave drying of high-moisture parboiled rough rice was investigated.Rough rice was parboiled by 3 hours of soaking in water at 71°C, 73°C, or 76°C and then steamed for 5, 10, or 15 min prior to microwave drying at 915 MHz.Moisture content following parboiling at the studied conditions ranged from 42.59% to 48.21% dry basis.Microwave specific energies ranging from 0.04 to 0.29 kWh per kg of parboiled rough rice dry matter (kWh kg-DM-1) were used to dry the parboiled rough rice.Soaking at 73°C and steaming for 10 min followed by one-pass microwave drying at 0.29 kWh kg-DM-1 gave the best results in terms of parboiled rough rice final moisture content and post-drying milling and physiochemical properties.Microwave treatment can provide one-pass drying of parboiled rough rice.Abstract. The volumetric heating phenomenon of microwaves (MW) offers a means to quickly dry high moisture content (MC) parboiled rough rice in one pass. However, to successfully dry parboiled rough rice in one pass using MW while preserving the milled rice yield and quality characteristics, it is vital to investigate the impacts of the pre-drying parboiling conditions on the drying process and the resulting product characteristics. The objectives of this study were to explore the feasibility of using MW at 915 MHz to dry high-MC parboiled rough rice and to determine the implications of the pre-drying soaking and steaming conditions on the parboiled rough rice final moisture content (FMC), milled rice yield (MRY), head rice yield (HRY), and the milled rice physiochemical properties. Freshly harvested, long-grain rough rice of the cultivar Mermentau at MC of 31.58% dry basis (d.b.) was used in this study. The parboiling process involved soaking the rough rice in water at temperatures of 71°C, 73°C, or 76°C and steaming for 5, 10, or 15 min. After parboiling, samples of rough rice for the controlled experiment were gently dried with natural air at 25°C and 65% relative humidity, while samples for MW treatment were dried using a 915 MHz MW dryer, which was set to deliver energy ranging from 0.04 to 0.29 kWh per kg of rough rice dry matter content (kWh kg-DM-1). The MW power applied during treatment ranged from 1 to 8 kW with heating durations of up to 6 min. The rough rice MC immediately increased after the soaking and steaming processes and ranged from 42.59% to 48.21% d.b. Increased soaking temperature led to increased uptake of water after parboiling, decreases in MRY, HRY, protein content, and milled rice surface lipid content (SLC), and increases in total color difference (TCD). Increased steaming duration led to decreased moisture uptake during steaming, decreased MRY, protein content, SLC, and TCD, and increased HRY. Increased MW specific energy led to decreased FMC, HRY, protein content, and SLC and increased TCD. It is recommended that long-grain rough rice should be soaked at 73°C, steamed for 10 min, and then treated at MW specific energy of 0.29 kWh kg-DM-1 in one pass to achieve parboiled rough rice FMC of 18.79% d.b., HRY of 69.33%, and desirable parboiled milled rice physicochemical and sensory properties. At the same parboiling conditions, the control samples had MRY of 74.98% and HRY of 74.07%. MW specific energy greater than 0.29 kWh kg-DM-1 was necessary to dry the parboiled rough rice to MC safe for long-term storage (14.29% to 15.61% d.b.). However, the application of specific energy beyond 0.29 kWh kg-DM-1 caused a reduction of HRY below that of the control samples. Therefore, to preserve HRY, rice processors should use MW specific energy of 0.29 kWh kg-DM-1 to partially dry parboiled rice and then complete the drying to a safe storage MC by using natural or slightly heated air. This study demonstrates the feasibility of using 915 MHz MW heating of high-MC parboiled rough rice to achieve one-pass drying. Keywords: 915 MHz microwaves, Milling yields, One-pass drying, Parboiled rough rice, Physicochemical properties, Rice quality.

Impact of kernel thickness on parboiled rice properties

AbstractBackground and objectiveApproximately 15% of the rice produced in the world is parboiled. Parboiling, a hydrothermal process involving soaking, steaming, and drying, is conventionally utilized to improve milling quality, nutritional value, and shelf life of rice. Because rice is composed of kernels of varying thickness, rice kernel thickness may impact parboiled rice properties. This study investigated the milling and color properties of parboiled rice prepared from two rice cultivars with different kernel thickness distributions and chemical compositions by subjecting them to different soaking temperatures and durations.FindingsRoyJ was composed of a greater proportion of thinner kernels, whereas XL756 was composed of a greater proportion of thicker kernels. The head rice yield (HRY) of the resultant parboiled rice was strongly affected by rice cultivar and thickness fraction, but was not impacted by their chemical compositions. RoyJ had a greater HRY than XL756 for the same thickness fraction under the same soaking conditions. Lightness (L*) and yellowness (b*) appeared to be greatly affected by cultivar with RoyJ displaying greater L* and b* values than XL756 for most conditions.ConclusionKernel thickness and soaking duration were important factors affecting the HRY of parboiled rice for both rice cultivars. Rice cultivars composed of a greater percentage of thinner kernels would be more susceptible to severe parboiling conditions and thus produce more variation in the HRY of parboiled rice.Significance and noveltyThe distribution of kernel thickness is different for different rice cultivars and should be taken into consideration when choosing parboiling conditions to maximize the HRY of parboiled rice.

Optimization of pressure parboiling conditions and pre-conditioned moisture content of brown rice (unpolished rice) for microwave puffing and its comparison with hot sand bed puffing

Brown rice puffing (unpolished rice) gives a more nutritious product compared to traditional puffed polished rice and reduces the cost of the product significantly, even though, the rice bran layer resists expansion during puffing. In the present study, brown rice was puffed in a microwave and hot-sand-bed after its pressure parboiling. Pressure parboiling parameters, steam pressure (196, 294, 392, 490 kPa) and steaming time (5, 10, 15 min), along with pre-conditioned moisture content (8, 10, 12 % wb) were studied and optimized for puffing characteristics (puffing percentage, expansion ratio, whiteness index, bulk density and hardness). All the experiments were carried out using a full factorial design. Statistical analysis showed there was a significant effect of processing variables on puffing characteristics. Optimized steam pressure, steaming time and pre-conditioned moisture content for microwave puffing were found to be 303.6 kPa, 14.25 min and 11.6% (wb) respectively, and for hot-sand-bed puffing to be 260.7 kPa, 15 min and 8% (wb) respectively.

Changes in the zinc content of selected bangladeshi rice varieties through modified parboiling and milling methods

Zinc deficiency is prevalent among women and children in Bangladesh, and methods to increase the zinc content of parboiled rice could contribute to its prevention. We quantified the effect of modified parboiling conditions on zinc content and of the degree of milling on zinc and phytate contents of Bangladeshi rice varieties. Parboiling studies varied the conditions used in the local commercial operations, including pre-steaming and soaking times, change of soaking water, and steaming pressure. Milling studies used 10 Bangladeshi varieties at 0% (brown), 2%, 4%, 6%, 8%, and 10% degree of milling. With ambient soaking water, shorter soaking time was observed with a higher zinc content in brown rice, but not in 10% milled rice, and changing soaking water did not modify zinc content in brown or 10% milled rice. Pre-steaming time and open- vs. closed-system steaming had no significant effect on brown or 10% milled rice zinc content. Reducing the degree of milling from 10% to 6% or 4% resulted in a mean increase in zinc content of 27% and 47%, respectively, and an increase in phytate content of 35% and 72%, respectively. Zinc content in milled rice did not appear to be significantly affected by the parboiling conditions tested. While lower degree of milling resulted in higher zinc content, it is uncertain whether the higher phytate content would fully negate this increase by decreasing the bioavailable fraction of zinc. Human studies of zinc bioavailability from Bangladeshi rice at different degrees of milling are warranted.SAARC J. Agri., 15(2): 31-43 (2017)

Mathematical modeling of starch gelatinization and some quality properties of parboiled rice based on parboiling indicators using RSM

AbstractThe effects of parboiling indicators (soaking temperature and steaming time) on the degree of starch gelatinization (DSG) and several rice quality properties [head rice yield (HRY), color value, lightness, and hardness] of parboiled rice were investigated. A mathematical model was used to predict DSG and rice quality from the parboiling conditions, which were varied as follows: 60, 65, and 70 °C for the soaking temperature and 2, 6, and 10 min for the steaming time (at 96 °C). A central composite design was applied and a total of 13 experimental runs were generated for each step. An ANOVA test showed the all models were significant (p &lt; 0.01) and there was no significant lack of fit in any of the response variables. The most appropriate model for prediction the amount of DSG, HRY, color value, lightness, and hardness of samples was linear (R2 = 0.87), quadratic (R2 = 0.92), quadratic (R2 = 0.97), quadratic (R2 = 0.86), and linear (R2 = 0.94) model, respectively. The DSG and hardness increased with increasing soaking temperature and steaming time, while the HRY and lightness showed a maximum at a steaming time of 6 min. The statistical model was used to predict the optimal parboiling conditions for global optimization of the quality properties.Practical applicationsParboiled rice enjoys high popularity because of its high nutritional content. The most important effect of parboiling is rice gelatinization. The degree of starch gelatinization (DSG) and quality properties (head rice yield, color value, lightness, and hardness) of parboiled rice are determined by the parboiling indicators (PI): soaking temperature and steaming time. These properties can be predicted based on PI using mathematical models. Increasing the parboiling indicators increases the cost of parboiling process. For the parboiling industry, it will help to determine the soaking temperature and steaming time of rice to yield the desired product quality. For this reason, optimizing the parboiling process is economically important for the rice industry.

Impacts of parboiling conditions on quality characteristics of parboiled commingled rice

Commingling of rice cultivars with a wide range of onset gelatinization temperatures (To) could occur during harvesting, drying, storage, and distribution, and consequently impact parboiled rice properties. This study investigated the effects of commingling, soaking temperature and steaming duration on parboiled commingled rice properties. Rough rice of pureline (Taggart and CL151) and hybrid (XL753 and CL XL745) cultivars were mixed at 1:1 weight ratio to obtain 3 commingled rice lots with a difference in To of 1.2, 3.9, and 6 °C. Rough rice was soaked at 65°, 70°, or 75 °C for 3 h, and steamed at 112 °C for 10, 15, or 20 min prior to drying. The effects of soaking temperature and steaming duration were found to vary with commingled rice. Soaking temperature exerted more influence on commingled rice comprising low To cultivars. Commingled rice comprising high To cultivars was less affected by soaking temperature and steaming duration in terms of head rice yield, deformed kernels and pasting viscosities. Both the difference in To among commingled rice cultivars and the To relative to the soaking temperature were important in parboiled commingled rice properties. Commingled rice with a wide range of To tended to result in parboiled rice with less desirable properties.

Optimization of parboiling conditions for enhanced Japonica rice milling

a. It is better to skip the parboiling process than to perform the process improperly. Unfortunately, improper parboiling of rice is a custom in most of the developing countries where there is heavy dependence on rice. b. Variety of rice plays vital role in the degree to which the factors should be combined during the parboiling process. Research should always be carried out on new developed varieties before commercial parboiling commences. c. Parboiling process has impact on rice in diverse ways. It affects the color intensity, lightness, impacts hardness, increase milling yield, etc. d. Different lots of paddy with different initial moisture contents can be mixed safely for parboiling without any loss in quality or quantity. e. Proper parboiling of rice will have significant impact on human health especially in rice consuming nations.

Effect of Soaking Temperature and Steaming Time on the Quality of Parboiled Iranian Paddy Rice

Abstract Iranian paddy (Fajr) is the most popular rice for export and consumption in Iran but it has poor milling yield. To solve this problem, parboiling has been used for improving its milling quality. In this study, the effect of various parboiling conditions (soaking at temperatures of 55–75°C and steaming times for 2–10 min) on some quality properties of Fajr paddy was investigated. After parboiling, the physical properties (degree of milling, head rice yield, lightness and color value) and mechanical properties (rupture force) of parboiled rice were measured. Head rice yield and mean value of rupture force increased significantly (p &lt; 0.05) from 50.10% to 62.11–67.05% and from 108.6 to 128.93–227.30 N, respectively. Also, the color value of parboiled rice increased significantly (p &lt; 0.05) by increasing the length of steaming time. The milling degree of unparboiled rice (17.03%) was significantly (p &lt; 0.05) higher than that of the parboiled rice (15.1–16.9% range). Soaking at 65°C and 4 min steaming time gave the highest values of head rice yield, lightness and rupture force. So, this treatment was found to provide the most desirable quality of Fajr parboiled rice.

Impact of processing conditions on the extractability and molecular weight distribution of proteins in parboiled brown rice

Parboiling, a hydrothermal treatment of paddy or brown rice, impacts the texture and nutritional characteristics of cooked rice. We investigated the impact of parboiling conditions on the extractability and molecular weight (MW) distribution of proteins in brown rice. Brown rice was parboiled using different soaking and steaming conditions. The extractability and MW distribution of proteins extracted with sodium phosphate buffer (50 mmol/L; pH 6.8) containing (i) 2.0% sodium dodecyl sulfate (SDS), (ii) 2.0% SDS/1.0% dithiothreitol (DTT)/6.0 mol/L urea, (iii) 2.0% SDS/1.0% DTT, and (iv) 2.0% SDS/6.0 mol/L urea was examined by size exclusion-high performance liquid chromatography. Depending on the parboiling conditions, protein extractabilities in media (i), (ii), (iii), and (iv) ranged from 14 to 25%, 83 to 100%, 40 to 82%, and 19 to 37%, respectively. Unlike soaking conditions, steaming conditions had pronounced effects on the level of extractable protein. In general, more severe steaming conditions caused greater reductions in protein extractability, indicating a denser protein network. Apparent MW profiles revealed that especially glutelins polymerize upon severe steaming. Albumins, globulins and prolamins either polymerize through disulfide bonds and/or interact with one another through hydrogen bonds or hydrophobic interactions to form a separate protein network or become incorporated in the glutelin network.

Fortification of rice with folic acid using parboiling technique: Effect of parboiling conditions on nutrient uptake and physical characteristics of milled rice

Parboiling was used as a technique for folic acid fortification in brown rice. A range of parboiling conditions (i.e. 70 °C soaking for 1, 2 and 3 h with 0.15, 0.3, 0.6 and 1.2 g folic acid/300 g brown rice and milled for 0, 60 and 120 s) were studied to investigate the uptake of folic acid in the fortified rice. Approximately 20–300 μg folic acid/g was found in the fortified rice and an average of 90% of folic acid was retained in the washed and cooked fortified rice. The quality of the fortified rice was evaluated based on head rice yield (HRY), kernel dimensions and color. No significant change in HRY and grain dimensions were observed between raw and fortified rice, suggesting the economic value of rice will not be compromised with the fortification process and rice uniformity may likely be achieved after mixing with the untreated rice. Despite the inherent yellow color of folic acid, in comparison with parboiled rice, a significant difference in yellowness was exhibited only in rice fortified at 1.2 g folic acid/300 g brown, but not among those fortified at lower fortificant concentrations. The difference in lightness (ΔL∗) (between fortified rice and parboiled rice) was reduced as soaking duration increased.

Effect of parboiling on physical and chemical characteristics and non-enzymatic browning of emmer (Triticum dicoccon Schrank)

Parboiling is a popular technology applied to rice to increase its milling yield, nutritional value and resistance to spoilage by insects and mould. This process was applied to Triticum dicoccon Schrank to induce physical, chemical and organoleptic modifications in order to increase its use and product diversification.Hulled and dehulled emmer samples, subjected to different parboiling conditions, were characterized by analyzing the physical and chemical modifications and the non enzymatic browning.The results showed that although parboiled grains were darker than the untreated reference sample, due to the development of non-enzymatic browning and the diffusion of the pigments contained in the husk and bran, during hydrothermal treatment glumes have a protective action on the caryopsis integrity and against thermal damage.

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

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

Key factors affecting Fe density in Fe-fortified-parboiled rice: Parboiling conditions, storage duration, external Fe-loading rate and genotypic differences

The present study evaluated the key factors affecting the efficiency of iron (Fe) penetration into the endosperm in parboiled rice of different varieties. It also investigated effects of storage time on Fe bio-accessibility, rice colour and Fe retention after rinsing. Rice grains of three varieties were fortified with an increasing range of Fe-fortification rates during the parboiling process, under two typical parboiling conditions, which are ambient soaking temperature for 24 h and 60 °C soaking temperature for 6 h at neutral (6.0–6.5) and acidic pH (3.0–3.5). Soaking of paddy rice, at 60 °C in acidic water for 6 h before steaming, was found to be better for maximising the Fe concentration in white-parboiled rice than the former ambient soaking. Under this parboiling condition, adding 250 mg Fe kg −1 of paddy rice, at soaking, produced the most desirable Fe concentration in white rice, ranging from 17.5 to 25.4 mg kg −1 among the rice varieties tested. The concentrations of Fe in parboiled white rice exhibited an exponential increase with increasing concentrations of Fe in the soaking water in all varieties, which were linearly related to Fe concentration of brown rice ( r = 0.96∗∗, p < 0.01). The colour of the parboiled rice fortified with Fe was initially light yellow, with variation among rice varieties, but it did become slightly darker after 16 weeks of storage, probably because of Fe oxidisation. This may be related to decreasing bio-accessibility after 20 weeks of storage. Storage, however, did not affect the total Fe retention after rinsing, though the retention rate was variety-dependent. Information about parboiling will provide the basis for formulating an optimal industry protocol for producing Fe-fortified-parboiled rice, which can be further refined in pilot studies on the industrial scale.