Biological Roles of Lipids in Rice

Lipids are organic nonpolar molecules with essential biological and economic importance. While the genetic pathways and regulatory networks of lipid biosynthesis and metabolism have been extensively studied and thoroughly reviewed in oil crops such as soybeans, less attention has been paid to the biological roles of lipids in rice, a staple food for the global population and a model species for plant molecular biology research, leaving a considerable knowledge gap in the biological roles of lipids. In this review, we endeavor to furnish a current overview of the advancements in understanding the genetic foundations and physiological functions of lipids, including triacylglycerol, fatty acids, and very-long-chain fatty acids. We aim to summarize the key genes in lipid biosynthesis, metabolism, and transcriptional regulation underpinning rice's developmental and growth processes, biotic stress responses, abiotic stress responses, fertility, seed longevity, and recent efforts in rice oil genetic improvement.

Improving Rice Quality by Regulating the Heading Dates of Rice Varieties without Yield Penalties

The heading date, a critical trait influencing the rice yield and quality, has always been a hot topic in breeding research. Appropriately delaying the flowering time of excellent northern rice varieties is of great significance for improving yields and enhancing regional adaptability during the process for introducing varieties from north to south. In this study, genes influencing the heading date were identified through genome-wide association studies (GWAS). Using KenDao 12 (K12), an excellent cultivar from northern China, as the material, the specific flowering activator, OsMADS50, was edited using the genome-editing method to regulate the heading date to adapt to the southern planting environment. The results indicated that the osmads50 mutant line of K12 flowered about a week later, with a slight increase in the yield and good adaptability in the southern region in China. Additionally, the expressions of key flowering regulatory genes, such as Hd1, Ghd7, Ehd1, Hd3a, and RFT1, were reduced in the mutant plants, corroborating the delayed flowering phenotype. Yield trait analysis revealed that the primary factor for improved yield was an increase in the number of effective tillers, although there is potential for further enhancements in the seed-setting rate and grain plumpness. Furthermore, there were significant increases in the length-to-width ratio of the rice grains, fat content, and seed transparency, all contributing to an overall improvement in the rice quality. In summary, this study successfully obtained a rice variety with a delayed growth period through OsMADS50 gene editing, effectively implementing the strategy for adapting northern rice varieties to southern climates. This achievement significantly supports efforts to enhance the rice yield and quality as well as to optimize production management practices.

Lipidomic analysis of grain quality variation in high quality aromatic japonica rice

To maintain the purity of the seeds and rice quality of the high-quality rice varieties, five lines with similar field and yield traits were selected from the Nanjing46 population in Liyang and used as study materials, and the original progeny were used as the control material for comparing rice quality and lipid metabolites in this study. The rice quality of the five lines still differed compared to CKN1. The Badh2-E2 gene was detected in all five lines, but its 2-AP content differed. The C11:0 content in CKN1 and VN1 was significantly greater than that in the other four lines. Most of the differentially abundant metabolites were phospholipids, including PA(16:0/18:2), PC(15:0/16:0) and PG(16:0/16:0). These metabolites can be used as potential metabolic markers for identifying quality variation. This study presents a novel methodology and theoretical framework for investigating varietal degradation and ensuring seed purity authentication.

Fumaric acid production by Rhizopus species from acid hydrolysate of oil palm empty fruit bunches

The hemicellulosic fraction of lignocellulosic biomass is a very important material, due to the significant concentration of pentoses present in its composition and that can be used sustainably in biotechnological processes such as the production of fumaric acid. Research efforts are currently being promoted for the proper disposal and valorization of empty fruit bunches (EFB) from oil palm. In this work, seventeen Rhizopus species were evaluated in a fermentation medium with EFB hydrolyzate, without detoxification, as a carbon source for fumaric acid production. Rhizopus circicans 1475 and Rhizopus 3271 achieved productions of 5.65 g.L-1 and 5.25 g.L-1 of fumaric acid at 30 °C, 120 rpm for 96 h, respectively. The percentage of consumed sugars, mainly pentoses, was 24.88% and 34.02% for R. circicans 1475 and R 3271, respectively. Soy peptone and ammonium sulfate were evaluated as nitrogen sources, where soy peptone stimulated the formation of biomass pellets while ammonium sulfate produced mycelia and clamps.

Mechanism of improving anaerobic fermentation performance of kitchen waste pretreated by ionizing irradiation-part 1: rice

Ionizing irradiation, as a new pretreatment method for the anaerobic fermentation of organic pollutants, is featured with fast reaction speed, good treatment effect, no need to add any chemical reagents, and no secondary pollution. This study explores the mechanism of improving anaerobic fermentation performance of rice samples pretreated by cobalt-60 gamma irradiation through the influence on fermentation substrate, acidogenic phase and methanogenic phase. The results reveal that the soluble chemical oxygen demand of the irradiated rice sample at an absorbed dose of 9.6 kGy increases by 12.4 times due to the dissolution of small molecules of fat-soluble organic matter. The yield of biogas in the acidogenic phase increases by 22.2% with a slight increase in hydrogen gas content. The yield of biogas and methane gas content in the methanogenic phase increases by 27.3% and 15%, respectively. Microbial genome analysis, performed with MiSeq high-throughput sequencing and metagenomic methods, suggests the microbial abundance and metabolic functions in the anaerobic fermentation process change significantly as a result of the pretreatment by gamma irradiation.

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.

Extraction, Composition, Functionality, and Utilization of Brewer’s Spent Grain Protein in Food Formulations

In recent years, brewer’s spent grain (BSG) has gained attention as a plant-based protein source because it occurs in large quantities as a by-product of beer brewing. BSG can contribute to future food requirements and support the development of a circular economy. In light of the dynamic developments in this area, this review aims to understand the proteins present in BSG, and the effect of extraction techniques and conditions on the composition, physicochemical, and techno-functional properties of the obtained protein extracts. The water-insoluble hordeins and glutelins form the major protein fractions in BSG. Depending on the beer brewing process, the extraction technique, and conditions, the BSG protein isolates predominantly contain B, C, and ϒ hordeins, and exhibit a broad molecular weight distribution ranging between <5 kDa and >250 kDa. While the BSG isolates obtained through chemical extraction methods seem promising to obtain gelled food products, physical and enzymatic modifications of BSG proteins through ultrasound and proteolytic hydrolysis offer an effective way to produce soluble and functional protein isolates with good emulsifying and foaming capabilities. Specifically tailored protein extracts to suit different applications can thus be obtained from BSG, highlighting that it is a highly valuable protein source.

Evaluation of the Potential of Duckweed as a Human Food, Bioethanol Production Feedstock, and Antileukaemia Drug

This study evaluated the potential of duckweed as a human food, ethanol feedstock, and anticancer drug. First, the nutritional value of wild duckweed was reported for the first time. Its main composition was similar to that of artificially cultivated duckweed, and thus, wild duckweed can serve as a great human food source. In addition, high-starch duckweed induced by nutrient starvation was fermented into bioethanol. A yield of 0.262 g/g, the highest duckweed-ethanol yield reported thus far, was achieved, indicating that duckweed is an excellent feedstock for ethanol production. Finally, the anticancer effects of duckweed flavonoids (DFs) were assessed for the first time using acute myeloid leukaemia (AML) cells as models in vitro and in vivo. The results revealed that DFs possessed antileukaemia activity and were safe and effective for AML therapy. In conclusion, duckweed was demonstrated to be helpful for humans for food security, energy crisis remediation, and tumour treatment.

Generation of new rice germplasms with low amylose content by CRISPR/CAS9-targeted mutagenesis of the FLOURY ENDOSPERM 2 gene

FLOURY ENDOSPERM 2 (FLO2), encoding a tetratricopeptide repeat domain (TPR)-containing protein located in the nucleus, is considered to be a regulatory protein that controls the biosynthesis of seed storage substances. The diversity of flo2 allele is attributable for the variations in grain appearance, amylose content (AC), and physicochemical properties, influencing the eating and cooking quality (ECQ) of rice. In this study, we used CRISPR/Cas9 to introduce loss-of-function mutations into the FLOURY ENDOSPERM 2 gene in Suken118 (SK118), a widely cultivated elite japonica rice variety in Jiangsu, China. Physiochemical analyses of the flo2 mutants were congruent with previous studies, exhibiting lowered AC and viscosity, risen gel consistency (GC) and gelatinization temperature (GT) values, which were all instrumental to the improvement of ECQ. However, the wrinkled opaque appearance and the decrease in grain width, grain thickness and grain weight imply trade-offs in grain yield. Despite the ex-ante estimation for low yielding, the superior ECQ in these novel genotypes generated by using genome editing approach may have the potential for formulating high value specialty food.

Relative Bioavailability of Cadmium in Rice: Assessment, Modeling, and Application for Risk Assessment

Rice consumption is the primary route of cadmium (Cd) exposure to the populations with rice as the staple food. To accurately assess the potential health risks of Cd exposure via rice consumption, determination of Cd relative bioavailability (RBA) in rice is necessary. However, large variations exist in Cd-RBA, hindering the application of source-specific Cd-RBA values to different rice samples. In this study, we collected 14 rice samples from Cd contaminated areas and determined both rice compositions and Cd-RBA using in vivo mouse bioassay. Total Cd concentration varied from 0.19 to 2.54 mg/kg in the 14 rice samples, while Cd-RBA in rice ranged from 42.10% to 76.29%. Cadmium-RBA in rice correlated positively with calcium (Ca) (R = 0.76) and amylose content (R = 0.75) but negatively with the concentrations of sulfur (R = -0.85), phosphorus (R = -0.73), phytic acid (R = -0.68), and crude protein (R = -0.53). Cd-RBA in rice can be predicted by Ca and phytic acid concentrations in a regression model (R² = 0.80). Based on the total and bioavailable Cd concentrations in rice, weekly dietary Cd intake for adults was estimated to be 4.84-64.88 and 2.04-42.29 μg/kg bw/week, respectively. This work demonstrates the possibility of Cd-RBA prediction based on rice compositions and provides valuable suggestions for health risk assessment with consideration of Cd-RBA.

Comparative analysis of rice reveals insights into the mechanism of colored rice via widely targeted metabolomics

Pigmented rice, particularly black rice, has attracted widespread global interest due to its high nutritional value. To obtain a better understanding of differential metabolites between pigmented rice and white rice, we used a widely-targeted metabolomics-based approach to investigate the metabolite profiling of black, red, glutinous, and common white rice. In total, 732 metabolites were identified, of which 281, 305, 241, 267, and 265 differential metabolites were screened by comparing the following group: glutinous/white vs black, glutinous/white vs red, and red vs black. Venn diagram demonstrated that 69 metabolites were shared between pigmented and non-pigmented rice, and 117 between glutinous/white/red vs black. Additionally, metabolic pathways analysis of differential metabolites in glutinous/white/red vs black revealed that the flavonoid biosynthesis, anthocyanin biosynthesis, and flavone and flavonol biosynthesis are differential enrichment metabolic pathways. As such, identifying these different metabolites contribute to a better understanding of the function and nutritional value of various rice strains.

Effect of sodium bicarbonate on the physicochemical properties of fermented rice flour and quality characteristics of fermented semi-dried rice noodles

Considering the effect that fermentation can improve the quality of rice noodles, and given that fermented rice noodles usually have a significantly acidic taste that is not generally acceptable to consumers, this study aimed to neutralize or eliminate the acidic taste of fermented rice noodles by adding sodium bicarbonate, and improve the quality of fermented rice noodles. The physicochemical properties of fermented rice flour and quality characteristics of fermented semi-dried rice noodles were investigated in this study in relation to the addition of sodium bicarbonate (0∼0.5%, w/w). With the increase of sodium bicarbonate addition, the pH value was increased, and lipid and protein content were decreased in rice flour. Meanwhile, thermal properties and farinograph properties showed that the pasting temperature, dough water absorption, dough development time and dough stability time of rice flour increased with the addition of sodium bicarbonate. Pasting properties and rheological properties results showed that a small amount of sodium bicarbonate (0∼0.1%) could increase the pasting viscosity, storage modulus (G'), and loss modulus (G″) of rice flour. Additionally, the hardness and chewiness of semi-dried rice noodles increased with the addition of sodium bicarbonate from 0 to 0.1%. With the addition of a small amount of sodium bicarbonate (0∼0.1%), x-ray diffraction showed that it could increase the crystallinity of semi-dried rice noodles. Low-field nuclear magnetic resonance showed that A₂₁ increased, and A₂₂ and A₂₃ decreased in semi-dried rice noodles. Scanning electron microscope showed that it could enhance the starch-protein interaction and starch-protein formed an ordered and stable network structure. Finally, the principal component analysis showed that the chewiness, texture and eating quality of semi-dried rice noodles were the best with the addition of sodium bicarbonate at 0.1%. This study provides practical value for the application of alkali treatment in rice products and provides a reference for the improvement of related rice noodles products.

From farm to plate: Spatio-temporal characterization revealed compositional changes and reduced retention of γ-oryzanol upon processing in rice

Background

Antioxidants detain the development and proliferation of various non-communicable diseases (NCDs). γ-oryzanol, a group of steryl ferulates and caffeates, is a major antioxidant present in rice grain with proven health benefits. The present study evaluated the distribution and dynamics of γ-oryzanol and its components in spatial and temporal scales and also delineated the effect of processing and cooking on its retention.

Methods

Six rice varieties (four Basmati and two non-Basmati) belonging to indica group were analyzed at spatial scale in four different tissues (leaf blades, leaf sheaths, peduncle and spikelets) and temporal scale at three developmental stages (booting, milky and dough). Additionally, the matured grains were fractioned into husk, embryo, bran, and endosperm to assess differential accumulation in these tissues. Further, milling and cooking of the samples was done to assess the retention upon processing. After extraction of γ-oryzanol by solvent extraction method, individual components were identified by UPLC-QToF-ESI-MS and quantified by RP-HPLC.

Results

The non-seed tissues were significantly different from the seed tissues for composition and quantitative variation of γ-oryzanol. Cycloartenyl caffeate was predominant in all the non-seed tissues during the three developmental stages while it showed significant reduction during the growth progression toward maturity and was totally absent in the matured grains. In contrary, the 24-methylenecycloartanyl ferulate, campesteryl ferulate and β-sitosteryl ferulate showed significant increment toward the growth progression to maturity. Milling caused significant reduction, retaining only an average of 58.77% γ-oryzanol. Cooking of brown rice in excess water showed relatively lower average retention (43.31%) to samples cooked in minimal water (54.42%). Cooked milled rice showed least mean retention of 21.66%.

Conclusion

The results demonstrate prominent compositional variation of γ-oryzanol during different growth stages. For the first time, the study demonstrated that ferulate esters of γ-oryzanol were predominant in the seed tissues while caffeate esters were dominant in non-seed tissues. Basmati cultivars show differential expression of γ-oryzanol and its components compared to non-Basmati cultivars. Cooking in excess water causes maximum degradation of γ-oryzanol. Post-harvest losses due to milling and cooking indicate the necessity of biofortification for γ-oryzanol content in rice grain.

Sri Lankan traditional parboiled rice: A panacea for hyperglycaemia?

The research aimed to scientifically prove that parboiled Sri Lankan traditional rice elicits lower glycaemic responses comparative to raw unpolished or polished rice. Thus the proximate composition and glycaemic indices (GI) of raw, raw polished, and parboiled traditional Sri Lankan rice (Oryza sativa L.) varieties Godaheenati, Batapola el, Dik wee, Dahanala, Unakola samba, and Hangimuththan were studied as comparative data are not available. Cooked parboiled rice contained significantly high moisture (P<0.05) than raw or raw polished. Mineral content was low (<1.5%) regardless of processing. Crude protein was comparatively high (5.8–11.0% DM) with 2.1–5% (DM) fat with raw unpolished and parboiled having higher contents. Digestible starch of raw polished was highest compared to parboiled or raw unpolished (68.8–90.5% DM). Resistant starch was significantly (P<0.05) high in parboiled rice (1.1–7.2%) with the least total dietary fibre in raw polished rice. All varieties of parboiled and raw polished were found to elicit low GI and high GI respectively. High moisture, high resistant starch, and low starch in cooked parboiled rice contributed to low GI compared to raw unpolished or raw polished rice.

qFC6, a major gene for crude fat content and quality in rice

qFC6, a major quantitative trait locus for rice crude fat content, was fine mapped to be identical with Wx. FC6 negatively regulates crude fat content and rice quality. Starch, protein and lipids are the three major components in rice endosperm. The lipids content in rice influences both storage and quality. In this study, we identified a quantitative trait locus (QTL), qFC6, for crude fat (free lipids) content through association analysis and linkage analysis. Gene-based association analysis revealed that LOC_Os06g04200, also known as Wx, was the candidate gene for qFC6. Complementation and knockout transgenic lines revealed that Wx negatively regulates crude fat content. Lipid composition and content analysis by gas chromatography and taste evaluation analysis showed that FC6 positively influenced bound lipids content and negatively affected both free lipids content and taste. Besides, higher free lipids content rice varieties exhibit more lustrous appearance after cooking and by adding extra oil during cooking could improve rice luster and taste score, indicating that higher free lipids content may make rice more lustrous and delicious. Together, we cloned a QTL coordinating rice crude fat content and eating quality and assisted in uncovering the genetic basis of rice lipid content and in the improvement of rice eating quality.

The effects of an innovative pulping technique of synchronously pulping and gelatinizing treatment on raw materials properties, oenological parameters, fermentation process, and flavor characteristics of glutinous rice wine

Liquid-state fermentation has been increasingly applied in the industrial glutinous rice wine (GRW) production. However, products brewed by this emerging technique possess some deficiencies in flavor quality. Therefore, this study firstly developed and optimized an innovative pulping technique by the synchronously pulping and gelatinizing treatment (Process I) to improve GRW flavor quality, and then revealed the influences of Process I on raw materials properties, oenological parameters, fermentation process, and flavor characteristics of GRW. Results show that Process I significantly (p < 0.05) enriched the soluble solid and crude protein content of glutinous rice milk by improving gelatinization degree and pulping efficiency, which consequently enhanced the microbial growth, glycolysis, and protein decomposition during the GRW fermentation process. GC-MS analysis shows that Process I sequentially significantly (p < 0.05) enhanced the esterification and Ehrlich or Harrison pathway during the fermentation process. This contributed to a higher content of key ester and alcohol compounds.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01119-7.

Pasting Properties of Various Waxy Rice Flours: Effect of α-Amylase Activity, Protein, and Amylopectin

Waxy rice has a long history of being cultivated and consumed in China. In this study, the effect of different factors including α-amylase activity, protein, and amylopectin structure on the pasting properties of four waxy rice varieties were investigated. Rice flours were divided into four groups (Vietnam indica (VI), Jiangxi indica (JI), Anhui japonica (AJ), and Dongbei japonica (DJ) group) and treated with AgNO3 solution, DL-dithiothreitol (DTT), or protease (n = 3). Results suggested that both α-amylase activity and protein significantly decrease the pasting viscosity of waxy rice flours. Chain length distribution of amylopectin as measured by high performance ion exchange chromatography (HPAEC-PAD) showed that starch with a higher ratio of short chain leads to a higher pasting viscosity. X-Ray diffractograms showed that the crystal type of all the four varieties of rice starches were characteristic A-type. Relative crystallinity of each rice starch was further calculated, and higher crystallization resulted in a higher viscosity. Our study would provide a fundamental knowledge of the relationship between different factors and waxy starch pasting properties, as well as be a reference for controlling the quality of waxy rice starch-based food products.

Effects of Storage Temperature on Indica-Japonica Hybrid Rice Metabolites, Analyzed Using Liquid Chromatography and Mass Spectrometry

The Yongyou series of indica-japonica hybrid rice has excellent production potential and storage performance. However, little is known about the underlying mechanism of its storage resistance. In this study, Yongyou 1540 rice (Oryza sativa cv. yongyou 1540) was stored at different temperatures, and the storability was validated though measuring nutritional components and apparent change. In addition, a broad-targeted metabolomic approach coupled with liquid chromatography-mass spectrometry was applied to analyze the metabolite changes. The study found that under high temperature storage conditions (35 °C), Yongyou 1540 was not significantly worse in terms of fatty acid value, whiteness value, and changes in electron microscope profile. A total of 19 key differential metabolites were screened, and lipid metabolites related to palmitoleic acid were found to affect the aging of rice. At the same time, two substances, guanosine 3′,5′-cyclophosphate and pipecolic acid, were beneficial to enhance the resistance of rice under harsh storage conditions, thereby delaying the deterioration of its quality and maintaining its quality. Significant regulation of galactose metabolism, alanine, aspartate and glutamate metabolism, butyrate metabolism, and arginine and proline metabolism pathways were probably responsible for the good storage capacity of Yongyou 1540.

A Review of In Vitro Methods for Measuring the Glycemic Index of Single Foods: Understanding the Interaction of Mass Transfer and Reaction Engineering by Dimensional Analysis

The Glycemic Index (GI) has been described by an official method ISO (International Organization for Standardization) 26642:2010 for labeling purposes. The development of in vitro methods for GI measurement has faced significant challenges. Mass transfer and reaction engineering theory may assist in providing a quantitative understanding of in vitro starch digestion and glycemic response from an engineering point of view. We suggest that in vitro GI measurements should consider the mouth and the stomach in terms of fluid mechanics, mass transfer, length scale changes, and food-solvent reactions, and might consider a significant role for the intestine as an absorption system for the glucose that is generated before the intestine. Applying mass transfer and reaction engineering theory may be useful to understand quantitative studies of in vitro GI measurements. The relative importance of reactions and mass-transfer has been estimated from literature measurements through estimating the Damköhler numbers (Da), and the values estimated of this dimensionless group (0.04–2.9) suggest that both mass transfer and chemical reaction are important aspects to consider.

Physicochemical and volatile characteristics present in different grain layers of various rice cultivars

Five rice cultivars were applied for investigating effect of milling degree on rice physicochemical properties. The first layer had the lowest peak viscosity, followed by the second and third layers, indicating the effect of non-starchy components on starch gelatinization behaviors. Consistently, more content of non-starch components in the first layer led to an enhanced gelatinization temperature. Rheological study demonstrated the G' and G" were successively increased as the layer moved inward, indicating a stronger gel network due to the increased amylose content and crystallinity in the corresponding layer. This is the first study to reveal the second layer has the highest digestibility, suggesting both non-starch components and starch structure control starch digestion. Furthermore, analysis of volatile compounds found alcohols and ketones concentrated in the first layer, whilst compounds including (E,E)-2,4-decadienal, 3-octanone and 3-nonen-2-one only existed in the second layer, serving as an indicator for managing the rice quality during milling.

Salt tolerance at vegetative stage is partially associated with changes in grain quality and starch physicochemical properties of rice exposed to salinity stress at reproductive stage

BACKGROUND

Rice yield and grain quality are highly sensitive to soil salinity. Distinct rice genotypes respond to salinity stress differently. To explore the variation in grain yield and grain trait adaptation to moderate, reproductive-stage salinity stress (4 dS/m electrical conductivity), four rice cultivars differing in degrees of vegetative salt tolerance, including Pokkali (salt-tolerant), RD15 (moderately salt-tolerant), KDML105 (moderately salt-susceptible) and IR29 (salt-susceptible), were examined.

RESULTS

Grain fertility and 100-grain weight of RD15, KDML105 and IR29, as well as grain morphology of KDML105 and IR29, were significantly disturbed. Interestingly, grain starch accumulation in RD15 and KDML105 was enhanced under stress. However, only RD15 showed changes in starch physicochemical properties, including increased granule diameter, decreased gelatinization peak temperature (T_p ) and decreased retrogradation onset temperature (T_o ). Notably, Pokkali maintained productivity, grain quality, and starch properties, while the grain quality of IR29 remained unchanged under salinity stress. Multivariate analysis displayed clear separation of productivity, grain morphology, and starch variables of RD15 in the salt-treated group relative to the control group, suggesting that it was the cultivar most impacted by salt stress despite its moderate salt-tolerance at vegetative stage.

CONCLUSION

Our results demonstrate specific salinity responses among the rice genotypes, and suggest discrepancies between degrees of salt tolerance at vegetative stage versus the ability to maintain both grain quality and starch properties in response to salinity stress imposed at reproductive stage. © 2021 Society of Chemical Industry.

Targeted Deletion of the First Intron of the Wxb Allele via CRISPR/Cas9 Significantly Increases Grain Amylose Content in Rice

BACKGROUND

The rice Waxy (Wx) gene plays a major role in seed amylose synthesis and consequently controls grain amylose content. Wx gene expression is highly regulated at the post-transcriptional level. In particular, the GT/TT polymorphism at the 5'splicing site of its 1st intron greatly affects this intron's splicing efficiency and defines two predominant Wx alleles, Wx^a and Wx^b. Wx^a rice often harbours intermediate to high amylose contents, whereas Wx^b rice exhibits low to intermediate amylose contents. By deleting the Wx 1st intron using CRISPR/Cas9 technology, we generate a completely novel Wx allele and further investigate how intron removal affects Wx gene expression and rice grain amylose content.

RESULTS

CRISPR/Cas9-mediated targeted deletion of the Wx 1st intron was performed on 4 rice inbred lines: KY131 (Wx^b), X32 (Wx^b), X35 (Wx^a) and X55 (Wx^lv). Deletion of the 1st intron occurred in 8.6-11.8% of the primary transformants of these 4 inbred lines. Compared to wild-type plants, amylose content was significantly increased from 13.0% to approximately 24.0% in KY131 and X32 mutant lines, which both carried the Wx^b allele. However, no significant difference in amylose content was observed between wild-type plants and X35 and X55 mutant lines, which carried the Wx^a and Wx^lv alleles, respectively. Wx gene expression analysis of wild-type plants and mutants yielded results that were highly consistent with amylose content results. KY131 and X32 mutants accumulated increased levels of steady mRNA transcripts compared with wild-type plants, whereas steady mRNA levels were not altered in X35 and X55 mutants compared with wild-type plants. Grain quality, including appearance quality and eating and cooking quality, which are tightly associated with amylose content, was also assessed in wild-type and mutant plants, and data were presented and analysed.

CONCLUSIONS

This study presents a novel and rapid strategy to increase amylose content in inbred rice carrying a Wx^b allele. Our data strongly suggest that the 1st intron of the Wx gene regulates Wx gene expression mainly at the post-transcriptional level in rice. This finding is in contrast to a previous hypothesis suggesting that it influences Wx gene transcription. In addition, removal of the first intron generates a completely novel Wx allele. Further studies on this new Wx allele will provide invaluable insights into the regulation of Wx gene expression, which will help researchers engineer new Wx alleles to facilitate the breeding of rice cultivars with better eating and cooking quality.

Use of Artificial Neural Network Model for Rice Quality Prediction Based on Grain Physical Parameters

The main goal of this study was to test the ability of an artificial neural network (ANN) for rice quality prediction based on grain physical parameters and to conduct a comparison with multiple linear regression (MLR) using 66 samples in duplicate. The parameters used for rice quality prediction are related to biochemical composition (starch, amylose, ash, fat, and protein concentration) and pasting parameters (peak viscosity, trough, breakdown, final viscosity, and setback). These parameters were estimated based on grain appearance (length, width, length/width ratio, total whiteness, vitreous whiteness, and chalkiness), and milling yield (husked, milled, head) data. The MLR models were characterized by very low coefficient determination (R2 = 0.27-0.96) and a root-mean-square error (RMSE) (0.08-0.56). Meanwhile, the ANN models presented a range for R2 = 0.97-0.99, being characterized for R2 = 0.98 (training), R2 = 0.88 (validation), and R2 = 0.90 (testing). According to these results, the ANN algorithms could be used to obtain robust models to predict both biochemical and pasting profiles parameters in a fast and accurate form, which makes them suitable for application to simultaneous qualitative and quantitative analysis of rice quality. Moreover, the ANN prediction method represents a promising approach to estimate several targeted biochemical and viscosity parameters with a fast and clean approach that is interesting to industry and consumers, leading to better assessment of rice classification for authenticity purposes.

Rice recycling: a simple strategy to improve conidia production in solid-state cultures

Here we studied at a laboratory scale a potential strategy to revalorize the residual rice remaining at the end of a conventional conidia production process in solid-state culture. The conidia production of Trichoderma asperellum Th-T4 (3) and Metarhizium robertsii Xoch-8.1 started with the use of fresh rice (unrecycled rice) as the substrate (cycle one), and continued with the use of recycled rice in successive cycles of conidia production. The rice remaining at the end of the first cycle was reused without any further sterilization or reinoculation. As a result, it was observed that the conidia production and productivity significantly increased in both fungi. Conidia production in T. asperellum Th-T4 (3) increased from 1 × 10⁹ (first cycle) to 2·9 × 10⁹ conidia per gram of initial dry substrate (con⋅gds^-1 ) (second cycle using recycled rice), while in M. robertsii Xoch-8.1, this parameter increased form 5·7 × 10⁸ to 1·4 × 10⁹ con⋅gds^-1 . Both fungi grew faster and conidiated earlier when recycled rice was used as the substrate, therefore, conidia productivity was also significantly improved. Furthermore, the use of recycled rice did not affect conidia viability. This is the first report about a recycling methodology completely free of extra-processing steps, and useful to increase conidia production and productivity.

Comprehensive Evaluation of 17 Qualities of 84 Types of Rice Based on Principal Component Analysis

Rice quality is a complex indicator, and people are paying more and more attention to the quality of rice. Therefore, we used seven rice varieties for twelve nitrogen fertilizer treatments and obtained eighty-four rice types with seventeen qualities. It was found that 17 quality traits had different coefficients of variation. Among them, the coefficient of variation of chalkiness and protein content was the largest, 44.60% and 17.89% respectively. The cluster analysis method was used to define four categories of different rice qualities. The principal component analysis method was used to comprehensively evaluate 17 qualities of 84 rice. It was found that rice quality was better under low nitrogen conditions, Huanghuazhan and Lvyinzhan were easier to obtain better comprehensive rice quality during cultivation. Future rice research should focus on reducing protein content and increasing peak viscosity.

Changes in Physicochemical Properties and Qualities of Red Brown Rice at Different Storage Temperatures

The effects of storage temperature on the physicochemical properties and qualities of red brown rice were investigated in this study. The samples were vacuum-packed in nylon/polyethylene pouches and stored at 15 °C, 25 °C and 35 °C for 12 weeks. The moisture content decreased as storage time was prolonged. Rice stored at 15 °C and 25 °C had a lower falling range of water content compared to the samples stored at 35 °C. Free fatty acid values increased fastest when samples were stored at a high temperature, and the rise can be effectively delayed at low temperatures. The pH of residual cooking water and adhesiveness decreased, while the heating water absorption rate and hardness increased during storage for red and brown rice. Low-field nuclear magnetic resonance results indicate that water molecules migrated, the binding force of H protons became stronger and the bonds between molecules became closer with increased storage duration. Temperature had an obvious correlation with starch granules and protein structure, characterized by a scanning electron microscope and Fourier transform infrared spectroscopy. Low temperatures significantly retarded those changes. The results indicate that storage temperature is a vital factor affecting the physicochemical properties and qualities of red brown rice and provided reference and theoretical basis for the actual storage of red brown rice.

Preclinical Evaluations of Modified Rice Hydrogel for Topical Ophthalmic Drug Delivery of Praziquantel on Avian Philophalmiasis

The present study aims to evaluate the efficacy of a novel drug delivery system of the modified rice hydrogel containing praziquantel (PZQ) against Philophthalmus gralli isolated from ostrich eyes and determine the toxicity of the preparation on chicken eye model. The parasiticidal activity of PZQ (0, 1, 10, and 100 µg/mL) was tested on P. gralli. The ophthalmic antiparasitic hydrogel was formulated with appropriate amount of PZQ and chemically modified rice gel. The parasitic morphology after exposure with the preparation was examined under scanning electron microscope (SEM). The anthelminthic efficacy of the preparation on motility and mortality of parasites was performed by visual inspection and vital dye staining. The ocular irritation of the preparation was evaluated for 21 days using standard avian model followed by OECD 405. The results demonstrated that the parasiticidal activity of PZQ against P. gralli appears to be in a concentration- and time-dependent manner. In addition, the concentration of PZQ 10 µg/mL (Chi squared test, p = 0.003) and exposure time for 24 h (log-rank test, p = 0.0004) is sufficient to kill parasites, when statistically compared to negative control group. Rice hydrogel containing a lethal concentration of 10 µg/mL PZQ was successfully prepared. The preparation illustrated good parasitic killing and motile inhibiting effect on P. gralli compared with PZQ 10 µg/mL and its control (p < 0.05). An appearance under SEM of non-viable parasite after being incubated with the preparation, showing parasitic deformity, was observed comparing with the viable parasite in 0.9% normal saline solution (NSS). Moreover, no irritation of chicken eyes was also observed. Our results contribute to understanding the efficacy and the safety of the rice hydrogel of PZQ which have a predictive value for controlling P. gralli on the animal eyes. However, the pharmacological application needs to be further investigated for the best possible therapeutic approach.

Barley Protein Properties, Extraction and Applications, with a Focus on Brewers' Spent Grain Protein

Barley is the most commonly used grain in the brewing industry for the production of beer-type beverages. This review will explore the extraction and application of proteins from barley, particularly those from brewers’ spent grain, as well as describing the variety of proteins present. As brewers’ spent grain is the most voluminous by-product of the brewing industry, the valorisation and utilisation of spent grain protein is of great interest in terms of sustainability, although at present, BSG is mainly sold cheaply for use in animal feed formulations. There is an ongoing global effort to minimise processing waste and increase up-cycling of processing side-streams. However, sustainability in the brewing industry is complex, with an innate need for a large volume of resources such as water and energy. In addition to this, large volumes of a by-product are produced at nearly every step of the process. The extraction and characterisation of proteins from BSG is of great interest due to the high protein quality and the potential for a wide variety of applications, including foods for human consumption such as bread, biscuits and snack-type products.

Spatial distribution analysis of phospholipids in rice by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry imaging

Phospholipids are one of the main nutrients in rice, which have a positive effect on cancer, coronary heart disease and inflammation. However, phospholipids will become small molecular volatile substances during the aging process of rice, resulting in change the flavor of rice. Therefore, mapping the concentration and the spatial distribution of phospholipids in rice are of tremendous significance in its function research. In this work, we established a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) imaging method for the spatial distribution analysis of phospholipids in rice. A total of 12 phospholipid compounds were found in the range of m/z 500-1000 through a series of conditions optimization. According to the results, lysophosphatidylcholine (LPC) species spread throughout the rice tissue sections and phosphatidylcholine (PC) species distributed in the bran and embryo (particularly in the scutellum). We also compared the signal intensities of phospholipids in different parts of white rice and brown rice by region of interest (ROI) analysis, which showed the relative content of PC species was higher in the embryo and gradually decreased until disappeared with the increase of processing degree during the processing of brown rice to white rice. The PC species on the surface of rice could be used as an important indicator to identify the processing degree of rice. Our work not only establish a MALDI-TOF-MS imaging method for spatial distribution analysis of rice, but also provide the necessary reference for ensuring food security, improving the eating quality of rice and the health benefits of consumers.

Relationship between molecular structure and lamellar and crystalline structure of rice starch

The relationship between molecular structure and crystalline and lamellar structures of fifteen types of rice starches was studied. GPC and HPAEC were used for the molecular chain analysis and WAXS, SAXS, and CP/MAS ¹³C NMR were employed for aggregation structural analysis. The amylopectin content and the average lengths of fb₁-chains (the degree of polymerization (DP) 13-24) were positively correlated with the amount of double helices (r² = 0.92 and 0.57, respectively). In contrast, amylose content was positively correlated with the amounts of amorphous materials in starch (r² = 0.77). The amount of double helices, which constitute a major part of the crystalline matrix, was positively correlated with the lamellar ordering (r² = 0.81), and negatively correlated with the thickness of crystalline lamellae (r² = 0.90) and lamellar repeat distance (r² = 0.84). Conversely, the amount of the amorphous matrix was correlated with these parameters in the opposite way (r² = 0.50, 0.75, and 0.75, respectively).

Grain quality evaluation of japonica rice effected by cultivars, environment, and their interactions based on appearance and processing characteristics

Appearance and processing characteristics of 45 japonica rice samples, collected from different regions in Jiangsu province, were investigated and evaluated in this study. Specifically, the chalkiness degree had been presented significant differences among different cultivars and regions. The average chalkiness degree varied from 6.81% to 15.34% for different regions and from 1.93% to 28.31% for different cultivars. The minimum head rice rate of cultivars from four regions, NJ9108 (HA), was 80.5%. The AC of CNG10, HD5, and PJ surpassed 13.68% and lower than 11.33% for the others. The protein content ranged from 6.1% to 11%, and the taste value was significantly different among cultivars. In addition, the RVA curves of the samples were similar, but the peak viscosities of NG8 and NJ5055 were higher than others, and there were significant differences in RVA traits among regions. Cultivars were the main reasons for the difference in appearance and processing quality of japonica rice, while environmental factors had leaded to the change of rice composition, texture, and gelatinization.

Evaluation of indigenous aromatic rice cultivars from sub-Himalayan Terai region of India for nutritional attributes and blast resistance

Indigenous folk rice cultivars often possess remarkable but unrevealed potential in terms of nutritional attributes and biotic stress tolerance. The unique cooking qualities and blissful aroma of many of these landraces make it an attractive low-cost alternative to high priced Basmati rice. Sub-Himalayan Terai region is bestowed with great agrobiodiversity in traditional heirloom rice cultivars. In the present study, ninety-nine folk rice cultivars from these regions were collected, purified and characterized for morphological and yield traits. Based on traditional importance and presence of aroma, thirty-five genotypes were selected and analyzed for genetic diversity using micro-satellite marker system. The genotypes were found to be genetically distinct and of high nutritive value. The resistant starch content, amylose content, glycemic index and antioxidant potential of these genotypes represented wide variability and 'Kataribhog', 'Sadanunia', 'Chakhao' etc. were identified as promising genotypes in terms of different nutritional attributes. These cultivars were screened further for resistance against blast disease in field trials and cultivars like 'Sadanunia', 'T4M-3-5', 'Chakhao Sampark' were found to be highly resistant to the blast disease whereas 'Kalonunia', 'Gobindabhog', 'Konkanijoha' were found to be highly susceptible. Principal Component analysis divided the genotypes in distinct groups for nutritional potential and blast tolerance. The resistant and susceptible genotypes were screened for the presence of the blast resistant pi genes and association analysis was performed with disease tolerance. Finally, a logistic model based on phenotypic traits for prediction of the blast susceptibility of the genotypes is proposed with more than 80% accuracy.

Identification of a New Giant Emrbryo Allele, and Integrated Transcriptomics and Metabolomics Analysis of Giant Embryo Development in Rice

Rice embryos are rich in high-quality protein, lipid, vitamins and minerals, representing the most important nutritional part of brown rice. However, the molecular mechanism of rice embryo development is poorly understood. In this study, two rice cultivars with contrasting embryo size (the giant embryo cultivar Dapeimi and the normal embryo cultivar 187R) were used to explore excellent genes controlling embryo size, and the developed near-isogenic lines (NILs) (NIL-D, which has the giant embryo phenotype, and its matching line, NIL-X) were used to explore transcript and metabolic properties in the earlier maturation stage of giant embryo development under natural conditions. The map-based cloning results demonstrated that Dapeimi is a novel allelic mutant of the rice GIANT EMBRYO (GE) gene, and the functional mutation site is a single cytosine deletion in the exon1. A total of 285 differentially accumulated metabolites (DAMs) and 677 differentially expressed genes (DEGs) were identified between NIL-D and NIL-X. The analysis of DAMs indicated that plants lacking GE mainly promoted energy metabolism, amino acid metabolism, and lipid metabolism pathways in the rice embryo. Pearson correlation coefficient showed that 300 pairs of gene-metabolites were highly correlated. Among them, OsZS_02G0528500 and OsZS_12G0013700 were considered to be key genes regulating L-Aspartic acid and L-Tryptophan content during rice giant embryo development, which are promising to be good candidate genes to improve rice nutrition. By analyzing rice embryo development through a combination of strategies, this research contributes to a greater understanding of the molecular mechanism of rice embryo development, and provides a theoretical foundation for breeding high-nutrition varieties.

Assessment of arsenic distribution, bioaccessibility and speciation in rice utilizing continuous extraction and in vitro digestion

Rice, a staple food for half the world's population, easily accumulates arsenic (As). Research on As distribution in rice protein and starch and its relationship with rice As bioaccessibility remains limited. This study investigated As distribution, chemical composition, As bioaccessibility and speciation in rice by continuous extraction and in vitro digestion. Of the total As, 87.5-94.5% was in rice protein and 5.0-9.8% in rice starch. The As amount in different protein fractions decreased as follows: glutelin > globulin > albumin > prolamin. As(V), As(III) and DMA in rice were more bioaccessible in the small intestinal phase than the gastric phase, and almost all As(V) dissolved in the small intestinal phase. Bioaccessible As in gastrointestinal digestive solution and As mass in protein fractions (albumin, globulin, and glutelin) were significantly positively correlated (p < 0.05). These results illuminate the bioaccessibility of As to humans consuming As-contaminated rice and avoid overassessment.

Starch gelatinization in the surface layer of rice grains is crucial in reducing the stickiness of parboiled rice

Parboiled rice has high nutritional value but unpleasant palatability. In this study, rice stickiness was significantly reduced by steaming during the parboiling process; however, continuing steaming past certain durations no longer affected rice stickiness. It was also found: (i) the degree of starch gelatinization (DSG) increases and starch crystallinity decreases with increasing steaming time; (ii) the molecular size and chain length distribution (CLD) of leached starch for both white and parboiled rice are significantly different from those of native starch; (iii) the relation between leached amylopectin amount and rice stickiness explains the reduced stickiness by parboiling; and (iv) starch gelatinization in the surface layer of rice grains during parboiling might be critically important in blocking starch leaching, consequently leading to a less sticky texture. This study supplies a way to manage glutinous rice stickiness by parboiling for the production of non-sticky rice foods.

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.

Effect of storage on metabolites of brown rice

BACKGROUND

Storage is an essential part of brown rice circulation. During the storage process, the metabolic activity of brown rice is still ongoing, and long-term storage leads to the deterioration of brown rice. Metabolomics analysis was performed using gas chromatography-mass spectrometry to investigate the changes in metabolites of brown rice after storage at 18 °C for 12 months.

RESULTS

In terms of quantity, sugar, fatty acids, and other metabolites in brown rice decreased after storage, and alcohols, aldehydes, phenols, and amines increased. A total of 34 differential metabolites were screened. In terms of contents, carbohydrates, amino acids, and fatty acids of brown rice decreased after storage, while those of sugar alcohol, amines, and aldehydes increased after storage. Cluster analysis of the samples at zero storage time revealed that the metabolites expressed least became highly expressed after storage and those expressed highly became low after storage. Metabolic pathway analysis showed that storage significantly influenced the lipid metabolism in brown rice. Palmitoleic acid, cholesterol, linoleic acid, and lauric acid are four key metabolites in lipid metabolism during storage of brown rice.

CONCLUSION

Significant changes occurred in quantity and type of brown rice metabolites after storage. Storage has the greatest effect on lipids. Storage caused a 'reverse change' in the metabolites content of brown rice. The results obtained may help in understanding the changes in metabolites profile and delaying of the quality deterioration of brown rice during storage.

Metabolomic Analysis of Germinated Brown Rice at Different Germination Stages

Brown rice (BR) is unpolished rice containing many bioactive compounds in addition to the basic nutrients of the rice grain. Herein, BR was germinated for up to 48 h to prepare germinated brown rice (GBR). The physiological and chemical changes in the GBR during germination were analyzed. GBR samples germinated for 48 h were in the radicle-emergence stage, but root formation was not observed. The change in the GBR metabolite profile during germination was analyzed to determine the effect of germination on the chemical profiles of the GBR samples. Twenty-five metabolites including acidic compounds, amino acids, sugars, lipid metabolites, and secondary metabolites were identified as the components that contributed to the variations in the GBR groups germinated for different time periods. Among the metabolites, the carbohydrates associated with energy production and lipid metabolites changed significantly. Based on the identified metabolites, a metabolomic pathway was proposed. Carbohydrate metabolism, citric acid cycle, and lipid metabolism were the main processes that were affected during germination. Although further studies on the relationship between the metabolite profile and nutritional quality of the GBR are needed, these results are useful for understanding the effect of germination on the physiological and chemical changes in BR.

Untargeted Metabolomics of Fermented Rice Using UHPLC Q-TOF MS/MS Reveals an Abundance of Potential Antihypertensive Compounds

Enzyme treatment and fermentation of cereals are known processes that enhance the release of bound bioactive compounds to make them available for bioactivity. In this study, we tested the angiotensin converting enzyme (ACE) inhibitory ability of destarched rice, Prozyme 2000p treated destarched rice (DP), and fermented DP samples. Prozyme 2000p treatment increased the ACE inhibitory ability from 15 ± 5% to 45 ± 3%. Fermentation of the Prozyme 2000p treated samples with Enterococcus faecium EBD1 significantly increased the ACE inhibitory ability to 75 ± 5%, while captopril showed an ACE inhibition of 92 ± 4%. An untargeted metabolomics approach using Ultra-high-performance liquid tandem chromatography quadrupole time of flight mass spectrometry revealed the abundance of vitamins, phenolic compounds, antioxidant peptides, DPP IV inhibitory peptides, and antihypertensive peptides in the fermented samples which may account for its strong ACE inhibition. Although fermented DP had decreased fatty acid levels, the amount of essential amino acid improved drastically compared to destarched rice. Our results show that fermenting Prozyme-treated destarched rice with Enterococcus faecium EBD1 generates abundant bioactive compounds necessary for developing antihypertensive functional foods.