Soaking time of rice in semidry flour milling was shortened by increasing the grains cracks

Effects of soaking treatment on water distribution of rice grains, starch characteristics and eating quality of wet rice noodles

Herein, rice was subjected to different soaking processes on water distribution of rice grains, starch characteristics, and eating quality of fresh wet rice noodles. Results demonstrated that, when soaked at temperatures between 10 °C and 40 °C for 120 min, rice grains reached saturation in water absorption, and the hardness gradually stabilized. However, the moisture continued to penetrate the interior of rice grains after 120 min, leading to an increase in moisture content, higher water permeability, and enlarged water migration channels. With extended soaking time periods, the content of damaged starch in rice flour considerably decreased. Although the gelatinization temperature of rice starch decreased after soaking, the enthalpy required for gelatinization increased. The relative crystallinity of rice starch demonstrated an increasing trend, followed by a decreasing trend, and reached its highest value of 18.18 % after 60 min of soaking. To summarize, the texture indices of fresh rice noodles demonstrated an increasing trend, although stretching and cooking quality demonstrated a trend of initially increasing and then decreasing with no considerable changes observed between 120 and 240 min of soaking. In summary, moderate soaking treatment can enhance the edible quality of fresh wet rice noodles.

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.

Superheated steam processing of cereals and cereal products: A review

The concept of superheated steam (SS) was proposed over a century ago and has been widely studied as a drying method. SS processing of cereals and cereal products has been extensively studied in recent years for its advantages of higher drying rates above the inversion temperature, oxygen-free environment, energy conservation, and environmental protection. This review provides a brief introduction to the history, principles, and classification of SS. The applications of SS processing in the drying, enzymatic inactivation, sterilization, mycotoxin degradation, roasting, and cooking of cereals and cereal products are summarized and discussed. Moreover, the effects of SS processing on the physicochemical properties of cereals and the qualities of cereal foods are reviewed and discussed. The applications of SS for cereal processing and its effects on cereal properties have been extensively studied; however, issues such as the browning of cereal foods, thermal damage of starch, protein denaturation, and nutrition loss have not been comprehensively studied. Therefore, further studies are required to better understand the mechanism of the quality changes caused by SS processing and to expand the fields of application of SS in the cereal processing industry. This review enhances the understanding of SS processing and presents theoretical suggestions for promoting SS processing to improve the safety and quality of cereals and cereal products.

The Possibility of Replacing Wet-Milling with Dry-Milling in the Production of Waxy Rice Flour for the Application in Waxy Rice Ball

Due to the large consumption and discharge of water in wet milling, dry-milling is an alternative to produce waxy rice flour. The physical properties and sensory characteristics for preparing waxy rice balls in dry-milled waxy rice flour were compared in this study. The results showed that the damaged starch content increased significantly with the particle size of dry-milled flour, which decreased from 160 to 30 μm. The reduction in particle size increased the pasting viscosity of waxy rice flour, which further improved the stretch ability of dough and increased the viscoelasticity of the rice ball. The increase in damaged starch content directly led to a significant increase in the solubility of dry-milled flour, thereby increasing the freeze cracking rate of the rice ball and reducing its transparency, resulting in a decline in quality. In comparison with wet-milled waxy rice balls, dry-milled waxy rice balls made from rice flour in the range of 40 μm to 60 μm particle size had a similar texture and taste to that of wet-milled ones, moderate freeze cracking rate and better storage stability, as well as a stronger aroma of waxy rice that the consumer favored. GC-MS analysis showed that the content of key aroma compounds, such as grassy and fruity, noted nonanal in dry-milled flour, was 15-30% higher than that in the wet-milled depending on the difference of waxy rice variety. In conclusion, dry-milled waxy rice flour with a particle size in the range of 40 μm to 60 μm could be a candidate to replace wet-milled flour in the preparation of a waxy rice ball.

Ultrasound Treatment Enhanced Semidry-Milled Rice Flour Properties and Gluten-Free Rice Bread Quality

The structural and functional properties of physical modified rice flour, including ultrasound treated rice flour (US), microwave treated rice flour (MW) and hydrothermal treated rice flour (HT) were investigated with wet-milled rice flour (WF) used as a positive control. The results showed the presence of small dents and pores on the rice flour granules of US and MW while more fragments and cracks were showed in HT. XRD and FTIR revealed that moderate ultrasonic treatment promoted the orderly arrangement of starch while hydrothermal treatment destroyed the crystalline structure of rice flour. In addition, the significant decrease of gelatinization enthalpy and the narrowing gelatinization temperature were observed in US. Compared to that of SF, adding physical modified rice flour led to a batter with higher viscoelasticity and lower tan δ. However, the batter added HT exhibited highest G' and G″ values and lowest tan δ, which led to a harder texture of bread. Texture analysis demonstrated that physical modified rice flour (except HT) reduced the hardness, cohesion, and gumminess of rice bread. Especially, the specific volume of bread with US increased by 15.6% and the hardness decreased by 17.6%. This study suggested that ultrasound treatment of rice flour could improve texture properties and appearance of rice bread.

The Impact of Innovative Plant Sources (Cordia myxa L. Fruit (Assyrian Plum) and Phoenix dactylifera L. Biowaste (Date Pit)) on the Physicochemical, Microstructural, Nutritional, and Sensorial Properties of Gluten-Free Biscuits

The gluten-free products available on the markets are deficient in bioactive compounds and high in cost. The present study is designed to develop gluten-free biscuits with enhanced nutritional properties. The gluten-free biscuits are formulated with rice flour (RF) incorporated with Assyrian plum fruit flour (APF) and bio-waste date-pit flour (DPF) according to the following ratios; RF:DPF:APF (100:0:0)/T0, (90:5:5)/T1, (80:10:10)/T2, and (70:15:15)/T3. The results demonstrate that flour blends with different concentrations of APF and DPF incorporated in RF have high contents of protein, damaged starch, crude fiber, ash, phytochemicals, and antioxidants in contrast to 100% RF, which shows the lowest values for all these parameters. The pasting properties of the flour blends reveals that the values of peak, final, breakdown, and setback viscosities reduce from T1 to T3. Similarly, a differential scanning calorimeter reveals that the phase transition temperature of the flour blends decreases with the increasing amylose content. Moreover, the scanning electron microscopy of the biscuit samples shows a positive contribution of APF and DPF for the development of the desired compactness of the structure due to the leaching of amylose content from the starch. The total phenol content (TPC) and total flavonoid content (TFC) increase from 38.43 to 132.20 mg GAE/100 g DW and 18.67 to 87.27 mg CE/100 g DW, respectively. Similarly, the antioxidant activities of biscuits improved. The protein and fiber contents of the biscuits increased from 10.20 to 14.73% and 0.69 to 12.25%, respectively. The biscuits prepared from T3 resulted in a firmer texture with a reduced spread ratio. However, the formulation of T1 and T2 biscuit samples contributed to desirable physical and sensory properties. Therefore, the addition of DPF and APF to RF is a sustainable way to make gluten-free biscuits as they provide adequate amylose, damaged starch, and fiber content to overcome the essential role of gluten in the baked product with nutraceutical properties.

Effects of Different Processing Methods and Internal Components on Physicochemical Properties and Glycemic Index of Adzuki Bean Powder

The estimated glycemic index (eGI) value of adzuki bean powder prepared by steamed cooking (SC), extruded cooking (EC) and roller cooking (RC) was studied comparatively. Results showed that RC had the highest eGI, with 80.1, and both EC and SC resulted in a lower eGI value of 70.0 and 49.7, respectively. Compared with the EC and RC methods, the SC method provided a more intact physical barrier for starch digestion, resulting in a less destroyed cell structure. As the essential components that form the cell wall, the study further investigated the effects of protein and fiber on physicochemical properties, in vitro starch digestibility and the eGI of adzuki bean powder processed with the SC method. Viscozyme and Protamax were used to obtain the deprotein and defiber samples. Results showed that the SC treatment with Viscozyme and Protamax, respectively, had significant effects on in vitro starch digestibility. The eGI of different samples were given as follows: steamed cooking adzuki bean powder (49.7) < deproteined adzuki bean powder (60.5) < defibered adzuki bean powder (83.1), which indicates that fiber may have a greater influence on the eGI than protein.

Effects of milling methods on the properties of glutinous rice flour and sweet dumplings

Glutinous rice flour (GRF) was prepared using three milling process (wet milling, low temperature impact milling (dry milling), and roller milling (dry milling)) to investigate their effects on the physicochemical properties of glutinous rice flour and sweet dumplings prepared with that flour. Results revealed that a method of grinding used in the milling process had a significant (P < 0.05) effect on the properties of GRF and the resulting sweet dumplings. Dry milling (low temperature impact milling and roller milling) resulted in higher damaged starch content and coarser particle size than wet milling. Dry-milled flour exhibited a significantly lower hunter whiter value, apparent viscosity, pasting temperature, enthalpy value, and degree of crystalline compared to the wet-milling method. Dry milling significantly decreased the smoothness of the surface, whiteness value, transmittance of soup, resilience of dumplings, as well as increased the cracking rate and water loss during the fast-freeze. The obtained results could be used as reference for improving sweet dumpling made from dry-milled GRF.

Effects of damaged starch on glutinous rice flour properties and sweet dumpling qualities

This study focused on exploring the effects of damaged starch on glutinous rice flour properties and sweet dumpling qualities. Glutinous rice flours with different damaged starch contents (2-8%) and the same particle size were prepared through sifting and blending of semidry-milled and dry-milled rice flour. The increase of damaged starch content led to an increase in elastic modulus (G'), viscous modulus (G″) and agglomeration of starch granules, and a decrease in peak viscosity, breakdown value and enthalpy change (ΔH). Among all the samples, the rice flour batters with damaged starch content 3% and 4% were more stable and structured, and rice flours with damaged starch content 2% and 3% showed better pasting properties. As for the sweet dumpling qualities, compact structure, weak water mobility, less water loss, slight cracking and desirable cooking and texture properties were observed in the sweet dumplings made from rice flour with damaged starch content of less than 5%. All the results demonstrated that glutinous rice flour with damaged starch content of less than 5% had good flour properties and was suitable for the production of sweet dumplings.

Kinetics of water absorption expansion of rice during soaking at different temperatures and correlation analysis upon the influential factors

Five model equations were used to study the water absorbing expansion kinetics of rice during soaking. The results indicated that the changes of water absorbing expansion in Japonica and Indica rice during soaking at 25, 40, 50, 60 and 70 ℃ can be well simulated (R² > 0.97) by the five model equations. The linear and polynomial equation could fit the changes of model coefficients and all obtained coefficient parameters could be combined in only one equation to predict the water absorbing characteristics of Japonica and Indica rice. The correlation between the basic nutritional components and model coefficients was further analyzed. The results indicated that the water absorbing rate had significant (P < 0.05) negative correlation with protein content, the apparent amylose content had significant (P < 0.05) negative correlation with the maximum expansion ratio, the length and width of rice affect its water absorbing characteristics.

A visualization and quantification method to evaluate the water-absorbing characteristics of rice

A visualization and quantification image analysis method is developed to evaluate the water-absorbing characteristics of rice. A projected image of soaked rice was obtained by a scanner in real time, the expansion ratio of the soaked rice in the projected image was calculated with computer software, and the change in the internal structure was analyzed. The results showed that water absorption had a positive correlation with expansion and the cracks occurred in the internal structure of rice could accelerate the water absorption. The maximum expansion ratio of Japonica rice gradually increased with increased milling time, but that of Japonica glutinous rice was not significantly different (P > 0.05). A high soaking temperature shortened the time to reach the maximum expansion ratio and resulted in a lower expansion ratio in the Indica and Indica glutinous rice but had no significant effect (P > 0.05) in the Japonica and Japonica glutinous rice.

Effect of domestic cooking on rice protein digestibility

The effects of washing, soaking, and common domestic cooking methods (normal cooking, high-pressure cooking, and microwave cooking) on protein content, in vitro protein digestibility, and amino acid composition of japonica and indica rice were investigated. All processes in rice domestic cooking did not affect protein content. However, the gastric and gastrointestinal protein digestibilities decreased significantly after cooking. Protein solubility methods were used to observe the formation of disulfide bonds and hydrophobicity interactions after cooking. Disulfide bonds and hydrophobicity interactions were formed during cooking, and the cooking-induced disulfide bond cross-linking decreased the protein digestibility observably. Moreover, the solubility of 13 kDa prolamin subunit sharply decreased after cooking due to intramolecular disulfide bond cross-linking. Therefore, cooking-induced formation of intramolecular disulfide linkages might stabilize and strengthen the structure of protein body-I, which exhibited strong resistance to proteases, particularly pepsin. Cooking had limited effect on amino acids.

Effects of washing, soaking and domestic cooking on cadmium, arsenic and lead bioaccessibilities in rice

BACKGROUND

The health risk of heavy metals such as cadmium (Cd), arsenic (As) and lead (Pb) in rice can be assessed by their concentration and bioaccessibility. In this work, japonica cultivar Xinfeng 2 and indica cultivar T-You 15 were washed, soaked and cooked using three common domestic cooking methods. The present study investigated the effects of washing, soaking, normal cooking, high-pressure cooking and microwave cooking on the concentration, bioaccessibility and health risk of Cd, As and Pb in rice.

RESULTS

Washing significantly reduced concentrations of Cd, As and Pb, and all three types of cooking reduced bioaccessibilities of these elements. No significant differences in bioaccessibility were observed among rice prepared with different cooking methods. Concentrations and bioaccessibilities of Cd, As and Pb highly affected the values of average daily dose, hazard quotient and lifetime cancer risk. High concentration and bioaccessibility cause As to pose non-carcinogenic and carcinogenic health risks to adults and children. Moreover, compared with adults, children have a high chance of exposure to non-carcinogenic and carcinogenic health risks.

CONCLUSION

Washing and cooking of rice lowered the health risk by reducing Cd, As and Pb concentrations and bioaccessibilities respectively. © 2018 Society of Chemical Industry.

A new SNP in cyOsPPDK gene is associated with floury endosperm in Suweon 542

Pyruvate orthophosphate dikinase (PPDK) is a component of glycolysis to mediate endosperm energy charge by adjusting the ratio of ATP to ADP and AMP that proposed to balance the flow of carbon into starch, protein, fatty acid and amino acid biosynthesis. However, these were inconsistent with the first report of a T-DNA insertional knockout mutant of the rice PPDK gene (flo4) showed that rice with inactivated PPDK gene failed to produce a opaque seeds. Therefore, the PPDK might have multifaceted functions in grain filling stage, which in some ways might depend on the direction of the reversible catalysis. Suweon 542 is a rice (Oryza sativa L.) mutant developed from Oryza sativa ssp. japonica cv. Namil. Suweon 542 has a milky-white floury endosperm suitable for dry filling, with low starch damage, low grain hardness, and fine flour particle size. The mutant locus on chromosome 5 controls the floury endosperm phenotype of Suweon 542. Fine mapping of this locus is required for efficient breeding of rice germplasm suitable for dry milling. In this study, whole genome of Suweon 542 and Milyang 23 were re-sequenced using Illumina HiSeq 2500. Co-segregation analysis of F_3:4 family populations derived from Suweon 542/Milyang 23 was performed using eight CAPS markers and phenotypic evaluation of the endosperm. The target region was mapped to a 33 kb region and identified to encode cytosolic pyruvate orthophosphate dikinase protein (cyOsPPDK). A G→A SNP in exon 8 of cyOsPPDK resulting in a missense mutation from Gly to Asp at amino acid position 404 was responsible for the floury endosperm of Suweon 542. qRT-PCR experiments revealed that FLO4-4 was expressed to a considerably higher level in Suweon 542 than in Namil during the grain filling stage. Overall, fine mapping of FLO4-4 and candidate gene analysis provided further insight into the floury endosperm of rice, and reveal a novel SNP in cyOsPPDK gene can affect the floury endosperm phenotype through active PPDK gene during grain filling stage.

Tailoring rice flour structure by rubbery milling for improved gluten-free baked goods

Ever-growing demand for gluten-free products calls for the development of novel food processing techniques to widen the range of existing baked goods.