Cooked rice texture and rice flour pasting properties; impacted by rice temperature during milling

Effects of distribution, structure and interactions of starch, protein and cell walls on textural formation of cooked rice: A review

The constitution and forms of rice determine its processing and cooking properties and further control the cooked rice quality. As the two main components, starch and protein content correlations and their characteristics have been extensively explored. However, rice is mainly consumed as polished kernels, components distribution, cytoplasmic matrix, and cell walls work together, and the properties of extracted components or flour are difficult to reflect the quality of cooked rice accurately. Thus, this review summarizes the multi-scale structure changes of main components during real rice cooking conditions. The dynamic thermal changes and leaching behaviors in rice kernels are compared with pure starch or rice flour. The in situ changes and interactions of starch granules, protein bodies, and cell walls during cooking are reviewed. Based on this, different textural evaluation methods are compared, and the advantages and disadvantages are pointed out. The oral chewing perception and bionic chewing simulation for textual evaluation have gradually become hot. Both rice quality controllers and eating quality evaluators attempt to establish an accurate quality evaluation system with the increased demand for high-quality rice.

Structural changes of starch under different milling degrees affect the cooking and textural properties of rice

A long-term consumption of white rice increases the risk of T2D. Finding an appropriate milling degree (MD) of rice balancing nutrition and palatability benefits public health. This study investigated effects of MD-0 s, 5 s, 60 s on morphological, cooking and textural properties of rice. Texture profile analysis showed that milling decreased hardness, while increased adhesiveness of rice. SEM images showed that milling induced notches and structural damage, which facilitated gelatinization of rice determined by DSC. Leached starch was further analyzed by size exclusion chromatography and chain-length distribution. Pearson correlation analysis revealed that milling induced more leached shot-chain amylose and long-chain amylopectin, which decreased hardness and increased adhesiveness of cooked rice. Collectively, milling-induced changes of starch gelatinization and fine structure of leached starch were decisive factors of rice texture. Moderate processing improved the texture of brown rice and maintained nutrients. This would provide guidance for the health industry of whole grains.

Dry cultivation and cultivar affect starch synthesis and traits to define rice grain quality in various panicle parts

A pot experiment was conducted to explore the effects of high-quality (Huanghuazhan, HH), drought-resistant (IR, IRAT109) and drought-susceptible cultivars (ZS, Zhenshan97) under flooding irrigation and dry cultivation (D) on the starch accumulation and synthesis, physicochemical traits of starch granules and rice grain quality at the upper (U) and lower panicle. Under D treatment, IR and ZS had lower rice quality, especially the appearance and cooking quality. DHH-U had the highest appearance, nutritional and cooking quality among all cultivars under D treatment, which could be ascribed to the synthesis of more short-branch chain amylopectin and correspondingly higher starch granule tightness. DHH-U also maintained ordered carbohydrate structure, crystalline regions, and many hydrophilic and hydrophobic functional groups in starch granules before pasting. It could prevent the polymerization of small molecules to avoid the formation of macromolecules after pasting. Overall, these findings may facilitate the improvement of grain quality in rice dry cultivation.

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

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

Physicochemical and Functional Characteristics of RD43 Rice Flour and Its Food Application

The increased use of a new rice cultivar is the result of increasing consumer demands for healthier choices. In this study, physicochemical, thermal, pasting, and functional properties of flour from RD43 rice, a new rice variety, and its food application were investigated. RD43 rice flour demonstrated an irregular and polyhedral shape with a volume mean diameter of 103 ± 0.15 µm. In addition, the amylose content of RD43 rice and Hom Mali rice flour was 19.04% and 16.38%, respectively. The X-ray diffraction (XRD) and Fourier Transforms Infrared (FTIR) confirmed the presence of a V-type crystalline structure and less crystallinity in RD43 rice flour, which resulted in a significant reduction of the water absorption index (WAI), swelling power (SP), water solubility index (WSI), gelatinization temperature, and pasting properties. Comparing with Hom Mali rice flour, RD43 rice flour had greater ability to disrupt cholesterol micellization and bind bile acid. Furthermore, it had lower starch digestibility, with a lower percentage of rapidly digestible starch (RDS) and higher percentage of undigestible starch than Hom Mali rice flour. Moreover, steamed muffins based on RD43 rice flour had lower starch digestibility than Hom Mali steamed muffins. The sensory analysis showed no significant differences between Hom Mali and RD43 steamed muffins. The findings suggest that RD43 rice flour could be an alternative ingredient for lowering the glycemic index of food products.

Empirical characterization of hydration behavior of Indian paddy varieties by physicochemical characterization and kinetic studies

Temperature is an important factor in the determination of hydration kinetics in paddy, and it varies with variety. To understand this hydration behavior, the current study analyses the hydration kinetics of 12 different paddy varieties of India that were exposed to different soaking temperatures. The protein content of the paddy samples was found to be in the range of 6.13 to 9.19%; whereas, starch content was between 67.79 and 84.88%. The physicochemical composition of paddy varieties as well as variation in time-temperature of hydration was found to be decisive in ascertaining the hydration behavior. An increased hydration rate was observed with increasing hydration temperature as well as with higher amylose content of paddy. Among the varieties studied, the ratio of amylose to amylopectin was between 0.37 and 0.77. For all samples, the gelatinization temperature was in the range of 65.60 to 83.10 °C, which in turn was negatively correlated with amylose content, and influenced the hydration behavior of paddy. The optimum time-temperature condition range for hydration for each paddy variety was between 50 and 60°C for 2 to 3.5 hr, depending upon the variety. The activation energy for the paddy samples in this investigation was found to be in the range of 8.70 to 23.10 kJ/mol. The kinetic modeling of hydration was conducted using Peleg's model, with a good fit. The data indicated that with increment in hydration temperature, the rate of hydration was enhanced in all varieties with a decrease in the Peleg's rate constant (K₁ ) and capacity constant (K₂ ). These constants indicate a direct temperature-dependence of water absorption in paddy. PRACTICAL APPLICATION: The hydration of paddy is an important procedure in paddy processing, and across the world, many industries are working on it. Irrespective of the variety, paddy processing globally has remained tricky. Knowledge about the hydration behavior of paddy would enable food processors to better understand the effect of process parameters and to model their experimental setup to obtain the desired physicochemical attributes, as well as process yield. Customers would benefit from adequately processed paddy with better digestibility for which industry would have to invest less in terms of time and resources, thereby making the hydrated paddy more affordable.

Rice OsLHT1 Functions in Leaf-to-Panicle Nitrogen Allocation for Grain Yield and Quality

Proper allocation of nitrogen (N) from source leaves to grains is essential step for high crop grain yield and N use efficiency. In rice (Oryza sativa) grown in flooding paddy field, amino acids are the major N compounds for N distribution and re-allocation. We have recently identified that Lysine-Histidine-type Transporter 1 (OsLHT1) is the major transporter for root uptake and root-to-shoot allocation of amino acids in rice. In this study, we planted knockout mutant lines of OsLHT1 together wild-type (WT) in paddy field for evaluating OsLHT1 function in N redistribution and grain production. OsLHT1 is expressed in vascular bundles of leaves, rachis, and flowering organs. Oslht1 plants showed lower panicle length and seed setting rate, especially lower grain number per panicle and total grain weight. The concentrations of both total N and free amino acids in the flag leaf were similar at anthesis between Oslht1 lines and WT while significantly higher in the mutants than WT at maturation. The Oslht1 seeds contained higher proteins and most of the essential free amino acids, similar total starch but less amylose with lower paste viscosity than WT seeds. The mutant seeds showed lower germination rate than WT. Knockout of OsLHT1 decreased N uptake efficiency and physiological utilization efficiency (kg-grains/kg-N) by about 55% and 72%, respectively. Taken together, we conclude that OsLHT1 plays critical role in the translocation of amino acids from vegetative to reproductive organs for grain yield and quality of nutrition and functionality.

Utilization of flour from rice brokens in wheat flour chapatti: evaluation of dough rheology, starch digestibility, glycemic index and retrogradation behavior

Broken rice, a byproduct of the rice milling industry was utilized at different levels to evaluate unleavened flat bread (chapatti) making properties of whole wheat flour. Chapattis were prepared by replacing whole wheat flour with broken rice flour up to 50% level. Mixolab studies revealed that incorporation of rice flour lowered dough development time and dough stability of whole wheat flour up to 23.49% and 78.33%, respectively. Lower retrogradation was observed in whole wheat rice flour blends as revealed from soluble starch/amylose. A positive correlation of mixolab retrogradation was observed with soluble starch and soluble amylose. Whole wheat flour chapatti (fresh and retrograded) containing different level of rice flour were also evaluated for glycemic index (GI), rapidly digestible starch (RDS) and slowly digestible starch (SDS). Chapattis containing rice flour demonstrated higher GI and RDS but lower SDS. RDS correlated positively with GI. Chapattis from the whole wheat rice flour blends had good consumer acceptability.

Evaluation of variability and environmental stability of grain quality and agronomic parameters of pigmented rice (O. sativa L.)

Eleven pigmented rice genotypes were evaluated to estimate genetic parameters, heritability and association. The results indicated that, genotypic variation was high among the lines. The distinct seasonal effect on plant performance for antioxidant capacity, anthocyanin, flavonoids, head rice recovery and test weights was also observed. Wet season favoured the crop performance in all genotypes as compared to drought conditions. The differential accumulation of different quality traits such as AOA, anthocyanin content, flavonoids content, etc showed high heritability, which would be transfer to high yeilding popular rice cultivars through conventional or geneticaly modification techniques. The line Mamihunger was chosen as donor of the high-quality rice grain and Annapurna for high yield. Further, Mamihunger are foreseen to be good in nutritional quality and industry use.

Protein and starch characteristics of milled rice from different cultivars affected by transplantation date

The effects of transplantation date on milled rice (physicochemical, amino acids composition and protein profiling) of different cultivars and their starch characteristics (granules size distribution, pasting and thermal) were investigated. Head rice yield increased (2.0-4.1 %) and chalky grains (5-10 %) decreased with delaying the paddy transplantation of different cultivars by 20 days. Delayed transplantation of paddy significantly increased asparagine, glutamine, threonine, cysteine, methionine, tryptophan, lysine and proline content in milled rice. Early transplantation of paddy showed higher accumulation of glutelin and prolamines than that in milled rice from delayed transplantation. The change in amino acid composition of milled rice with delay in transplantation was related to variation in accumulation of glutelin and prolamines. Starch from delayed transplanted paddy showed higher peak viscosity and lower breakdown viscosity than those from early transplanted paddy. These differences were due to higher accumulation of amylose in starch from delayed transplanted paddy than that from early transplanted paddy due to exposure of former to lower night air temperature during starch synthesis.

Effect of low temperature plasma on the functional properties of basmati rice flour

The present study deals with the application of low temperature plasma on basmati rice flour and its effect on functional properties such as gel hydrations properties, flour hydration properties, gelatinization temperatures and antioxidant properties. The water holding capacity and water binding capacity were observed to be increased with increase in plasma power and time of treatment as the air plasma is known to make the surface more hydrophilic. XRD analysis revealed there is no significance difference in the crystalline structure after the plasma treatment. DSC shows a decrease in peak temperatures (Tp) after the treatment. Hot paste viscosities were observed to be decease from 692 to 591 BU was corresponded to decrease in peak temperature. The total polyphenolic content and reducing power was observed to be increased. The effects of plasma treatment on functional groups of polyphenols were observed by changes in absorption intensities using FTIR. This study demonstrates that the low temperature plasma treatmentis capable of improving the functional properties of basmati rice.

Rice: Parboiling and Milling Properties

Parboiling is a hydrothermal processing technique during rice has to pass through many stages which alter the physicochemical properties and nutritional profile of grain. Different parboiling techniques have been developed for preparation and industrialization of rice. During parboiling process, starch granules are gelatinized and retrograded as a result various changes occur in rice kernel, which affects its quality parameters. Parboiling has marked influence on organoleptic properties, improved the strength and nutritional profile of grain. Parboiling treatment principally brings the characteristic change in rice grain such as milling, cooking, storage and eating qualities. Milling is an important unit operation for removing the husk and bran from the rough rice. Milling significantly affects the cooking and nutritional properties of rice. The important parameters focussed during milling are the head rice yield and kernel hardness. Milling technology is therefore geared to obtain maximum outturn of milled rice and to reduce breakage.