Determination of contents and antioxidant activity of free and bound phenolics compounds and in vitro digestibility of commercial black and red rice (Oryza sativa L.) varieties

Antioxidant capacities and in vitro anti-microbial activities of rice (Oryza sativa var Bajong) from Borneo

Rice contains antioxidants and phenolic components that exert anti-inflammatory and anticancer properties. Different geographical areas produce rice with various chemical constituents and phytochemicals, in turn these confer differential protective effects including antimicrobial and anticancer properties. Sarawak rice, Oryza sativa var Bajong (Bajong), a fragrant dark purple rice grain harvested from two locations in Sarawak, namely interior Lubok Nibong (LN) and coastal Sri Aman (SA), was assessed for their antioxidant properties and antimicrobial activities. The rice was extracted using methanol solvent and evaluated for total phenolic content (TPC), total flavonoid contents (TFC), as well as their antioxidant and antimicrobial activities based on the Folin-Ciocalteu assay, the aluminium calorimetric method, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity and disk diffusion assay, respectively. Using dual-wavelength measurement, Bajong LN showed 2.16% higher amylose content than Bajong SA. Furthermore, 24-h extract of Bajong LN and 48-h extract of Bajong SA exhibited high antioxidant properties (34-70 µg/mL) and were rich in phenolic (46.54 ± 2.62 mg GAE/g; 25.28 ± 3.91 mg GAE/g) and flavonoid contents (5.53 ± 0.36 mg QCE/g; 7.7 ± 2.19 mg QCE/g) respectively. It is interesting to note that 72-h Bajong extract exhibited the largest zone of inhibition (9-9.3 mm) against Gram-negative Pseudomonas aeruginosa (Ps. aeruginosa), which correlated to the high TPC and TFC despite a reduction of antioxidant activity due to prolonged extraction hours. These significant results conferred added value to a staple, health-promoting Bajong had warranted it to be further investigated as a nutraceutical and pharmaceutical crop.

Exploring a maize-derived dietary fiber-phenolic acid complex with prebiotic effects

The structural, functional, and prebiotic properties of three maize-derived cell wall dietary fiber-phenolic acid complexes (CWDFPC1, CWDFPC2, and CWDFPC3) were investigated. The results showed that all three CWDFPCs had similar proximate composition and XRD pattern (type I). However, there were significant differences in the phytochemical profiles of their phenolic compounds (PC). Although the testa was the primary source of bound PC (BPC) in all three CWDFPCs, CWDFPC2 had the highest BPC content (15.41 mg GAE/g) and exhibited the greatest antioxidant activity in vitro (DPPH and ABTS assays). The water holding capacity of CWDFPC1 (6.53 g/g) and CWDFPC3 (6.86 g/g) was higher than CWDFPC2 (4.84 g/g), and three CWDFPCs had similar nitrite ion adsorption capacity, bile adsorption capacity, and cation-exchange capacity. After 48 h of in vitro fecal fermentation, CWDFPC2 produced more short-chain fatty acids (46.33 mM) compared to CWDFPC1 and CWDFPC3 (40.26 mM and 44.20 mM, respectively).

Ricemilks made from pigmented and aromatic rice varieties: Sensory analysis and physiochemical properties

Along with dairy allergic/intolerant and vegetarian/vegan individuals, flexitarian consumers contribute to the market for plant-based milk alternatives. Niche pigmented (purple and red) and/or aromatic (aromatic brown and white) rice varieties were used to formulate ricemilks, which were compared to a product made from commercial nonaromatic white rice. Descriptive sensory analysis (9 trained panelists) and affective sensory testing (161 consumers) were used to explore perceptions of ricemilks. Additional sample differences were characterized by instrumental color, viscosity, 2-acetyl-1-pyrroline (2-AP), starch quality, total phenolic content (TPC), oxygen radical absorbance capacity (ORAC), and proximate analyses. Compared to nonaromatic white ricemilk, increased bioactive and antioxidant potential was exhibited for pigmented varieties (TPC ranging 56.6-64.5 µg/mL; ORAC ranging 628-753 µM Trolox equivalents). However, the pigments also resulted in decreased acceptability of product color. For red ricemilk, this was overcome after tasting, resulting in the highest grouping of overall liking scores along with aromatic brown and aromatic white ricemilks (5.6-5.7 on a 9-point hedonic scale)-all associated with a desirable "popcorn" aromatic from 2-AP. Highest purchase intent was found for aromatic brown ricemilk (47% overall and 69% among regular dairy and nondairy milk consumers) which was associated with the "dairy" aromatic. Consumers also favored colors and mouthfeel more reminiscent of dairy milk. Ricemilks made from niche pigmented and/or aromatic rices provided unique flavors and outperformed nonaromatic white ricemilk in overall acceptability. Ricemilks made from aromatic whole grain varieties can offer a new health-promoting functional beverage option to consumers, and a new use of niche rice varieties.

Foliar application of iron impacts flavonoid glycosylation and promotes flavonoid metabolism in coloured rice

Coloured rice is known as a healthcare food owing its rich flavonoid content. To better understand the effects of iron on the flavonoid metabolism of coloured rice grains, different concentrations of FeSO4 were foliar sprayed on to red rice Yuhongdao 5815 (RR) and black rice Nanheinuo (BR). The results revealed the association of iron with the increased accumulation of anthocyanins in BR and proanthocyanins in RR along with enhancements in their antioxidant capacities and total flavonoid contents. Metabolomic analysis revealed that the differential metabolites between the iron treated coloured rice and the control primarily occurred because of the O-linked glycosylation of aglycones, which are involved in the flavonoid pathway. RR exhibited a significantly higher number of differential metabolites compared with BR. Thus, foliar FeSO4 application affects the O-linked glycosylation and positively regulates flavonoid metabolism.

Unveiling the distribution of free and bound phenolic acids, flavonoids, anthocyanins, and proanthocyanidins in pigmented and non-pigmented rice genotypes

The total phenolic content, phenolic acid profile, anthocyanins, proanthocyanidins, flavonoids, and antioxidant capacity of the whole-grain and bran portion of sixteen distinct rice genotypes that correspond to three distinct pericarp bran colors-black, red, and non-pigmented (NP)-were examined. Ten free and bound phenolic acids, as well as two flavonoids, were analyzed using HPLC-PDA. The flavonoids included kaempferol and catechin hydrate, and the free phenolic acids included gallic acid, 2,5-dihydroxybenzoic acid, vanillic acid, syringic acid, p-coumaric acid, chlorogenic acid, trans-cinnamic acid, trans-ferulic acid, p-coumaric acid, and sinapic acid. Trans-ferulic acid (207.39 mg/kg), p-hydroxybenzoic acid (94.36 mg/kg), and p-coumaric acid (59.75 mg/kg) were the principal bound phenolic acids in pigmented rice genotypes, whereas in NP genotypes they were trans-ferulic acid (95.61 mg/kg) and p-hydroxybenzoic acid (58.32 mg/kg). The main free phenolic acid was syringic acid (120.43 mg/kg) in all genotypes. 2,5-dihydroxybenzoic acid was also detected in NP genotypes, mainly in the bound form (4.88 mg/kg). NP genotypes Basmati 386 and Punjab Basmati 7 also displayed high content of bran flavonoids (1001 and 1028 mg CE/100 g). The bound form of phenolics had significant DPPH and ABTS + activity. This study found wide diversity in the phenolic acid profile, total phenolic constituents, and antioxidant activity in the bran and whole grain of pigmented and NP rice. The individual phenolic acids in free and bound forms in different fractions of the grain were found to exert their antioxidant activity differently. The results obtained will provide new opportunities to improve the nutritional quality of rice with enhanced levels of phytochemicals in the ongoing breeding programs. Black rice bran contains a high level of phytochemicals and thus has a potent pharmaceutical role. This information would enhance the use of whole-grain and bran of pigmented rice in food product development by food technologists. Further studies may be focused on clinical trials with respect to cancer and diabetes.

Insight into the dynamic molecular mechanism underlying the endogenous polyphenols inhibiting the in vitro starch digestion of highland barley noodles

Highland barley is a type of grain with slow-digesting characteristics. It is worth exploring the impact of non-starch components on starch digestion. In this study, four varieties of highland barley were used to investigate the impacts of endogenous polyphenols (EP) on the relationship between starch structure, physicochemical properties, and the time course digestibility of highland barley noodles. The results showed that EP removal decreased the proportion of long-chain amylopectin and disrupted the crystalline structure, while increasing the short-range ordered structure in the residue. Significant correlations indicated that these structural changes make starch more susceptible to thermal degradation and digestion, causing a 12.60%-52.00% increase in rapidly digestible starch (RDS) and a 12.70%-25.22% decrease in resistant starch (RS). These results revealed the internal factors that affect the slow digestion characteristics of highland barley noodles from the perspective of EP and provide important reference values for a slow digestion diet.

Phenolic Compounds and Antioxidant Capacity Comparison of Wild-Type and Yellow-Leaf gl1 Mutant of Lagerstroemia indica

BACKGROUND

The yellow-leaf gl1 mutant of Lagerstroemia indica exhibits an altered phenylpropanoid metabolism pathway compared to wild-type (WT). However, details on the metabolites associated with leaf color variation, including color-specific metabolites with bioactive constituents, are not fully understood.

METHODS

Chemical and metabolomics approaches were used to compare metabolite composition and antioxidant capacity between the gl1 mutant and WT leaves.

RESULTS

The mutant exhibited an irregular xylem structure with a significantly lower phenolic polymer lignin content and higher soluble phenolic compounds. Untargeted metabolomics analysis identified phenolic compounds, particularly lignans, as key differential metabolites between gl1 and WT, with a significant increase in the mutant. The neolignan derivative balanophonin-4-O-D-glu was identified as a characteristic metabolite in the gl1 mutant. The soluble phenolic compounds of the gl1 mutant exhibited higher FRAP, ABTS, DPPH, and hydroxyl radical scavenging activity than in WT. Correlation analysis showed a positive relationship between antioxidant capacity and phenolic compounds in L. indica.

CONCLUSIONS

Metabolites associated with leaf color variation in the L. indica yellow-leaf gl1 mutant demonstrated high antioxidant capacity, particularly in scavenging hydroxyl radicals.

Evaluation of maceration, microwave, ultrasound-assisted extraction methods on free, esterified and bound phenolic profile and antioxidant activity of black rice

Black rice (Oryza sativa L.) is a rich source of phenolics and anthocyanins. It was aimed to investigate the effect of different extraction methods such as conventional solvent extraction, ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE) on antioxidant activity and phenolic profiling of black rice free, esterified, and bound phenolics fractions. Spectrophotometric methods were used to evaluate antioxidant activity and HPTLC was used for phenolics profiling. The highest content of % yield, total anthocyanin (TAC), total phenolic (TPC), and total flavonoid (TFC) contents were detected in MAE. It was also observed that antioxidant activity based on DPPH, ABTS, superoxide radical-scavenging and ferric reducing antioxidant power (FRAP) assays showed highest activity in MAE. Eight phenolic compounds were identified and quantified by a validated HPTLC method. MAE showed most abundant phenolic compounds. A significant positive correlation was established between % yield, total phenolic content, and total flavonoid content (p < 0.05) where a significant negative correlation was established between % yield, TPC, and TFC with IC50 of antioxidant activity (p < 0.05). Diverse phenolic contents and antioxidant activity were studied with different forms of phenolics with the different extraction methods. It designates that the extraction techniques had effects on the bioactive compounds as well biological properties.

Effect of processing methods and storage on the bioactive compounds of black rice (Oryza sativa L.): a review

Compared to brown and white rice, black rice contains more nutrients and numerous unique bioactive substances, such as essential amino acids, dietary fiber, γ-oryzanols, γ-aminobutyric acid, phenolic compounds, and anthocyanins, which makes it highly valuable for development and use. Whole-grain black rice typically requires a certain amount of processing prior to consumption, with the primary goal of enhancing the taste and texture of whole grains and their products. However, various new processing technologies have been effectively applied to the processing of black rice and the enhancement of its qualitative characteristics, but they also have both positive and negative effects on its nutritional quality. Therefore, evaluation of changes in concentrations of the bioactive substances as natural antioxidants due to processing and storage conditions is critical for establishing dietary guidelines for rice. This review highlights the primary bioactive components of black rice and provides a discussion of the impact of processing methods and storage on the bioactive components of black rice. Furthermore, we summarized the issues that currently exist in the processing and storage of black rice.

Nutritional Profiles of Yoom Noon Rice from Royal Initiative of Southern Thailand: A Comparison of White Rice, Brown Rice, and Germinated Brown Rice

For long-term food sustainability and security, it is crucial to recognize and preserve Indigenous rice varieties and their diversity. Yoom Noon is one of the non-glutinous rice (Oryza sativa L.) varieties being conserved as part of the Phanang Basin Area Development Project, which is administered by the Royal Initiative of Nakhon Si Thammarat in Southern Thailand. The goal of this research was to compare the nutritional profiles of Yoom Noon white rice, brown rice, and germinated brown rice. The results indicated that carbohydrate content was found to be the most plentiful macronutrient in all processed Yoom Noon rice types, accounting for 67.1 to 81.5% of the total. White rice had the highest carbohydrate content (p < 0.05), followed by brown rice and germinated brown rice. Brown rice had more protein and fat than white rice (p < 0.05). The maximum protein, dietary fiber, and ash content were found in germinated brown rice, followed by brown rice and white rice (p < 0.05). White rice had the highest amylose content, around 24% (p < 0.05), followed by brown rice (22%), and germinated brown rice (20%). Mg levels in all white, brown, and germinated brown rice ranged from 6.59 to 10.59 mg/100 g, which was shown to be the highest among the minerals studied (p < 0.05). Zn (4.10-6.18 mg/100 g) was the second most abundant mineral, followed by Fe (3.45-4.92 mg/100 g), K (2.61-3.81 mg/100 g), Mn (1.20-4.48 mg/100 g), Ca (1.14-1.66 mg/100 g), and Cu (0.16-0.23 mg/100 g). Se was not found in any processed Yoom Noon rice. Overall, brown rice had the highest content of macro- and micronutrients (p < 0.05). In all processed rice, thiamin was found in the highest amount (56-85 mg/100 g), followed by pyridoxine (18-44 g/100 g) and nicotinamide (4-45 g/100 g) (p < 0.05). Riboflavin was not identified in any of the three types of processed Yoom Noon rice. Individual vitamin concentrations varied among processed rice, with germinated brown rice having the highest thiamine content by around 1.5 and 1.3 folds compared to white and brown rice, respectively. The GABA level was the highest in germinated rice (585 mg/kg), which was around three times higher than in brown rice (p < 0.05), whereas GABA was not detectable in white rice. The greatest total extractable flavonoid level was found in brown rice (495 mg rutin equivalent (RE)/100 g), followed by germinated brown rice (232 mg RE/100 g), while white rice had no detectable total extractable flavonoid. Brown rice had the highest phytic acid level (11.2 mg/100 g), which was 1.2 times higher than germinated brown rice (p < 0.05). However, phytic acid was not detected in white rice. White rice (10.25 mg/100 g) and brown rice (10.04 mg/100 g) had the highest non-significant rapidly available glucose (RAG) values, while germinated brown rice had the lowest (5.33 mg/100 g). In contrast, germinated brown rice had the highest slowly available glucose (SAG) value (9.19 mg/100 g), followed by brown rice (3.58 mg/100 g) and white rice (1.61 mg/100 g) (p < 0.05).

Development and Optimization of Black Rice (Oryza sativa L.) Sourdough Fermented by Levilactobacillus brevis LUC 247 for Physicochemical Characteristics and Antioxidant Capacity

This study used Levilactobacillus brevis LUC 247 to ferment black rice sourdough, made into Type III black rice sourdough powder to produce black rice sourdough bread. The composition analysis, antioxidant capacity, and storage stability of the black rice sourdough bread with different proportions of black rice powder (0–60%) and fermented for different lengths of time (0–48 h) were discussed. The results showed that the black rice sourdough had the maximum lactic acid bacteria count (9 Log CFU/g) during 12 to 36 h of fermentation. The titratable acid, lactic acid, and acetic acid yields increased with the fermentation time and the proportion of black rice powder. The total anthocyanin content and antioxidant capacity increased with the fermentation time. The hardness and chewiness of the black rice sourdough bread were positively correlated with the black rice sourdough powder content and increased with storage time. In addition, the growth of fungi was significantly slowed as the additional level of black rice sourdough powder increased.

The Addition of Pinto Bean Flour and Margarine in the Development of Red Rice-Based Novel Gluten-Free Cookies to Improve the Technological, Sensory and Physicochemical Properties

This study aimed to understand how the addition of pinto bean flour (PBF) and margarine affected the technological, sensory, and physicochemical properties of red rice-based gluten-free cookies. PBF addition (25-75 g/100 g) and margarine content (13.3-19.3 g/100 g dough) were varied according to a central composite rotatable design. Cookies selection was performed by overlaid contour and principal component analysis (PCA) for technological properties and sensory evaluation, respectively. Chemical composition analyses, bioactive compounds, and microstructure were carried out in the selected formulations. In addition, other physicochemical analyses were carried out during storage time. PBF addition affected the technological properties and increased the nutritional content of proteins (up to 13%), fibers (8.28%), iron (2.13%), zinc (1.54%), and phenolic compounds (139.46 mg gallic acid equivalent/100 g), but it negatively affected sensory acceptance. However, margarine's addition improved all the sensory attributes in all the trials, showing an acceptance greater than 70%. Cookies with 50 g PBF, 50 g red rice flour, and 16.3 g margarine/100 g dough showed better technological, nutritional characteristics, and physicochemical quality up to 60 days of storage. This work contributed to the incorporation of mixtures of red rice and pinto bean for developing more nutritious cookies for celiac patients or even those who wish to consume gluten-free products.

Extraction of phenolic compounds from rice husk via ethanol-water-modified supercritical carbon dioxide

Rice husk, a rice processing byproduct generated in large quantities (∼20% of the grain weight), creates a major disposal problem for the rice industry. However, rice husk contains high-value bioactive compounds that can provide potential health benefits. The objective of this study was to extract high-value phenolic compounds from rice husk using supercritical carbon dioxide (SC-CO2) technology. In this study, the effects of different extraction conditions, namely, temperature (40 and 60 °C), pressure (30 and 40 MPa), and ethanol concentration (15 and 25%, w/w) on the total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity (AA) were investigated. The extraction of phenolic compounds was also studied using different SC-CO2 modifiers, i.e., ethanol and ethanol-water. The highest TPC, TFC, and AA were achieved with 30 MPa, 60 °C, and 25% ethanol-water (50%, v/v) cosolvent mixture as 1.29 mg gallic acid equivalent (GAE)/g, 0.40 mg catechin equivalent (CE)/g, and 0.23 mg Trolox equivalent (TE)/g, respectively. Increasing water content up to 50% (v/v) in the cosolvent significantly improved the extraction yield. p-Coumaric, ferulic, and syringic acids were the predominant phenolic acids in the extracts obtained by cosolvent-modified SC-CO2 and methanol extractions. In addition, ethanol-water-modified SC-CO2 increased rice husk's porosity, which could be a potential pretreatment to enhance cellulose extraction. Thus, ethanol-water-modified SC-CO2 can be utilized to recover polar bioactive compounds from food processing byproducts for developing functional foods while eliminating the use of toxic organic solvents.

Mathematical modeling to predict rice's phenolic and mineral content through multispectral imaging

Over half the world population relies on rice for energy, but being a carbohydrate-based crop, it offers limited nutritional benefits. To achieve nutritional security targets in Asia, we must understand the genetic variation in multi-nutritional properties with therapeutic properties and deploy this knowledge to future rice breeding. High throughput, VideometerLAB spectral imaging data has been effective in estimating total anthocyanin content, particularly bound anthocyanin content, using the high prediction power of partial least square (PLS) regression models. Multi-pronged nutritional properties of phenolic compounds and minerals, together with videometerLAB features, were utilized to develop models to classify a collection of black rice varieties into three distinct nutritional quality ideotypes. These derived models for black rice diversity panels were created utilizing videometerLAB data (L, A, B parameters), selected phenolic types (total phenolics, total anthocyanins, and bound flavonoids), and minerals (Molybdenum and Phosphorous). Random forest and artificial neural network models depicted the multi-nutritional features of black rice with 85.35 and 99.9% accuracy, respectively. These prediction algorithms would help rice breeders strategically breed nutritionally valuable genotypes based on simple, high-through-put videometerLAB readings and a small number of nutritional assays.

Bioactive Compounds and Quality Evaluation of Red-Pigmented Rice Processed by Germination and Roasting

Red-pigmented rice was germinated and processed to develop germinated red rice tea, and the changes in physicochemical, bioactive, and microbial properties due to germination and roasting were investigated. The moisture and crude ash contents of red rice decreased after germination and roasting. Crude protein and crude fat contents increased after germination but slightly decreased after roasting. Total phenolics, flavonoids, and antioxidant activities (DPPH and ABTS radical scavenging activities) increased following germination and heat treatment. However, the increased levels of γ-amino butyric acid after germination significantly decreased during the subsequent roasting step. In addition, total bacteria, yeast, and mold counts increased during the germination process but decreased after heat treatment as compared to those in the original grain; Escherichia coli was not detected. Therefore, germination and subsequent roasting could effectively enhance the contents of the most bioactive compounds and maintain microbial stability in red-pigmented rice.

Antioxidant extract of black rice prevents renal dysfunction and renal fibrosis caused by ethanol-induced toxicity

This study was conducted to evaluate the protective role of extracted natural antioxidants from black rice and their effect on kidney failure and renal cirrhosis caused by ethanol-induced toxicity. Antioxidant activity in terms of total phenol content, flavonoid compounds and anthocyanin, as well as antioxidant capacity, was determined in an extract of black rice. The findings noted that the black rice extract contained high amounts of antioxidant activity and capacity. Total phenolic compounds from black rice extract were fractionated using HPLC and the results showed that ferulic, sinapic, ascorbic, salicylic and coumaric acids were the highest in the extract. Biological experiments were performed on male albino adult rats (40 animals, 10 rats for each group), divided into four groups. After five weeks, kidney functions and protein fractions were assessed. In addition, superoxide dismutase (SOD), glutathione (GSH) and malondialdehyde (MDA) enzyme activities were determined in all groups. The results found that kidney function, total protein, albumin and globulin were affected by renal dysfunction and renal fibrosis in the positive control (PC), whereas groups 3 and 4 noted an improvement in renal function nearly or equal to the healthy rats which were fed on a basal diet. Furthermore, the PC group showed significantly decreased levels of enzymatic antioxidants, namely SOD and GSH with a concomitant elevated MDA level compared with those in the negative rats fed on a basal diet. Groups 3 and 4 also reported improvements in enzyme activity. These results were further supported by histopathological findings which revealed a curative effect in groups 3 and 4, which avoided renal dysfunction and renal fibrosis from ethanol-induced toxicity. From the results, it can be said that the black rice extract with the highest amounts of antioxidants led to improvements in all parameters, especially kidney function, total protein, albumin, and globulin, in addition to enzyme activity. Therefore, black rice can be recommended as a benefit to general health.

Comparative Analysis of Antioxidant Compounds and Antioxidative Properties of Thai Indigenous Rice: Effects of Rice Variety and Processing Condition

Indigenous southern Thai non-glutinous rice varieties Kaab Dum, Khai Mod Rin, Yar Ko, Yoom Noon, and Look Lai made under four different processing conditions, white rice, brown rice, germinated brown rice, and rice grass, were assessed for antioxidant components and in vitro antioxidative activities. According to the findings, rice’s antioxidant components and antioxidant activity were considerably impacted by both variety and processing. High levels of total extractable phenolic compounds (164−314 mg gallic acid equivalent (GAE)/kg, dry weight (dw)) and carotenoid (0.92−8.65 mg/100 g, dw) were found in all rice varieties, especially in rice grass and germinated brown rice, indicating that milling to generate white rice had an adverse effect on those components. Additionally, after germination, a higher γ-oryzanol concentration (9−14 mg/100 g, dw) was found. All rice varieties had higher ascorbic acid, phenolic compound, and carotenoid contents after sprouting. Overall, Yoom Noon rice grass had the highest total extractable phenolic content (p < 0.05). The rice grass from Yoom Noon/Look Lai/Kaab Dum had the highest ascorbic acid content (p < 0.05). The total carotenoid concentration of Look Lai rice grass was the highest, and Yoom Noon’s germinated brown rice had the highest γ-oryzanol content (p < 0.05). All rice varieties’ aqueous extracts had remarkable ABTS free radical scavenging activity, with Khai Mod Rin reaching the highest maximum value of 42.56 mmol Trolox equivalent/kg dw. Other antioxidant mechanisms, however, were quite low. Compared to germinated brown rice, brown rice, and white rice, rice grass often tended to have stronger antioxidant activity. Yar Ko rice grass was found to have the highest DPPH free radical scavenging activity (3.8 mmol Trolox equivalent/kg dw) and ferric reducing antioxidant power (FRAP) (4.6 mmol Trolox equivalent/kg dw) (p < 0.05). Khai Mod Rice grass had the most pronounced metal chelation activity (1.14 mmol EDTA equivalent/kg dw) (p < 0.05). The rice variety and processing conditions, therefore, influenced the antioxidant compounds and antioxidative properties of Thai indigenous rice. The results can be used as a guide to select the optimal rice variety and primary processing in order to satisfy the needs of farmers who want to produce rice as a functional ingredient and to promote the consumption of indigenous rice by health-conscious consumers.

A review on lignin antioxidants: Their sources, isolations, antioxidant activities and various applications

Lignin, a biopolymer obtained from agricultural/forestry residues or paper pulping wastewater, is rich in aromatic structure, which is central to its adoption as a candidate to natural antioxidants. Through insight into its structural features from biomass, different functional groups would influence lignin antioxidant activity, wherein phenolic content is the most important factor, hence massive studies have focused on its improvement via different pretreatments and post-processing methods. Besides, lignin nanoparticles and chemical modifications are also efficient methods to improve antioxidant activity via increasing free content and decreasing bond dissociation enthalpy of phenolic hydroxyl. Lignin samples exhibit comparable radicals scavenging ability to commercial ones, showing their potential as renewable alternatives of synthesized antioxidants. Besides, their applications have also been discussed, which demonstrates lignin potential as an inexpensive antioxidant additive and consequent improvements on multiple functionalities. This review is dedicated to summarize lignin antioxidants extracted from biomass resources, methods to improve their antioxidant activity and their applications, which is beneficial for realizing lignin valorization.

Polyphenol and Anthocyanin Composition and Activity of Highland Barley with Different Colors

In this research, the composition of free phenols, bound phenols, and anthocyanins and their in vitro antioxidant activity and in vitro α-glucosidase inhibiting activity were observed in different barley colors. The outcomes revealed that the contents of total phenols (570.78 mg/100 gDW), total flavonoids (47.08 mg/100 gDW), and anthocyanins (48.07 mg/100 g) were the highest in purple barley. Furthermore, the structure, composition, and concentration of phenolics differed depending on the colors of barley. The types and contents of bound total phenolic acids and flavonoids were greater than those of free total phenolic acids and flavonoids. The main phenolic acids in blue barley were cinnamic acid polyphenols, whereas in black, yellow, and purple barley, benzoic acid polyphenols were the main phenolic acids, and the main types of flavonoids in black and blue barley were chalcones and flavanones, respectively, whereas flavonol was the main type of flavonoid in yellow and purple barley. Moreover, cornflower pigment-3-glucoside was the major anthocyanin in blue, yellow, and purple barley, whereas the main anthocyanin in black barley was delphinidin-3-glucoside. The dark color of barley indicated richness in the anthocyanins. In addition, the free polyphenol fractions had stronger DPPH and ABTS radical scavenging capacity as compared to the bound ones. In vitro α-glucosidase-inhibiting activity was greater in bound polyphenols than in free polyphenols, with differences between different varieties of barley. Purple barley phenolic fractions had the greatest ABTS radical scavenging and iron ion reduction capacities, as well as the highest α-glucosidase-inhibiting activity. The strongest DPPH radical scavenging capacity was found in yellow barley, while the strongest in vitro α-glucosidase-inhibiting activity was found in anthocyanins isolated from black barley. Furthermore, in different colors of barley, there was a strong association between the concentration of specific phenolic compounds and antioxidant and α-glucosidase-inhibiting activities. The outcomes of this study revealed that all colored barley seeds tested were high in phenolic compounds, and had a good antioxidant impact and α-glucosidase-inhibiting activity. As a result, colored barley can serve as an antioxidant and hypoglycemic food. Polyphenols extracted from purple barley and anthocyanins extracted from black barley stand out among them.

Quantification of Amino Acids, Phenolic Compounds Profiling from Nine Rice Varieties and Their Antioxidant Potential

In recent years, the health benefits of the pigmented rice varieties have been reported due to the richness of their bioactive compounds. Therefore, this study evaluated the antioxidant, total flavonoid, total phenolic, anthocyanin content, amino acid and individual phenolic compound quantification of nine Korean-grown rice varieties using spectrophotometric, HPLC-FLD-MS/MS and UHPLC Q-TOF-MS/MS methods. Our research found that the free fractions of DM29 (red rice) had the highest free radical scavenging ability of ABTS and DPPH. In contrast, the highest ferric reducing antioxidant power was observed in the 01708 brown rice variety. The majority of phenolic compounds such as quercetin, ferulic acid, p-coumaric acid, ascorbic acid, caffeic acid and genistein were found in the DM29 sample. The phenolic content of rice varies depending on its color, with DM29 red rice having the highest TPC, TFC and TAC levels. At the same time, the presence of the majority of amino acids was quantified in the 01708 and GR (Gangwon) brown rice varieties. According to this study, colored rice varieties are high in amino acids, phenolic compounds and antioxidants. This research would be beneficial in furthering our understanding of the nutritional value of different colors of rice and their high potential as a natural antioxidant.

Bioactive compounds, biological activity, and starch digestibility of dried soy residues from the soybean oil industry and the effects of hot-air drying

BACKGROUND

Soybean residue is a by-product from the soy industry. It is rich in protein, lipids, carbohydrates, and bioactive compounds but it is still underutilized as a food ingredient. The aim of the present study was to investigate the bioactive components, biological activity, and starch digestibility of soybean residues collected from the soybean oil industry (SOI) and the laboratory (SOL), and the effects of hot-air drying on the treated residues.

RESULTS

The predominant phenolic acids were protocatechuic, chlorogenic, and ferulic acids, and the major flavonoids were rutin, daidzein, and genistein. After hot-air drying, the total phenolic, flavonoid, and isoflavone content of dried SOI and SOL increased significantly, in comparison with untreated whole soybean (WSB), SOI, and SOL. Daidzein of dried SOI and SOL increased from 63 to 510 mg kg-1 dry weight. The 2,2-diphenyl-1-picryldrazyl (DPPH) and ferric reducing antioxidant power (FRAP) values increased almost twofold in comparison with SOI and SOL. The antioxidant compounds in untreated and treated soy-residue extracts were the most efficient in inhibiting α-amylase. The phenolics and flavonoids caused starch digestion to reduce from 6.6% to 2.7%. The correlations, involving phenolic compounds (including phenolics, flavonoids, and isoflavones), demonstrated that the different phenolic extracts showed different antioxidant properties, which played an important role in soy oil-residue phenolic fractions.

CONCLUSIONS

We suggest that soy oil residues could be used as ingredients in functional foods because of their health-promoting attributes. © 2021 Society of Chemical Industry.

Multi-Mechanistic In Vitro Evaluation of Antihyperglycemic, Antioxidant and Antiglycation Activities of Three Phenolic-Rich Indian Red Rice Genotypes and In Silico Evaluation of Their Phenolic Metabolites

The study evaluated the antidiabetic potential of three traditional Indian red rice genotypes/RR (Kattuyanam/KA, Chennangi/CH & Karungkuruvai/KU) using a combination of in vitro, metabolomics (Quadrupole-Time of Flight-Liquid chromatography-Mass spectrometry/Q-TOF-LC-MS/MS), and in silico techniques. In terms of antihyperglycemic potential, KA exhibited the highest inhibitory activity against α-amylase; CH against α-glucosidase; and KU against DPPIV and PTP1B enzymes. KA exhibited the highest antioxidant activity (DPPH, FRAP, and ABTS) and greater inhibition of protein glycation compared to other RR indicating its potential to mitigate diabetic complications. The metabolomic analysis confirmed the presence of 99 phenolics in the sample extracts (KU-71, KA-70, CH-68). Molecular docking studies revealed seven metabolites to be good inhibitors of the four target enzymes and activators of insulin receptor substrate/IRS. The antihyperglycemic and oxidation-glycation reduction composite index revealed KA to have the highest overall antidiabetic potential. Hence, the RR could be utilized in functional foods with a multi-barrelled strategy for diabetes prevention/management.

Phenolic acids and phytosterols in rice grains and wheat flours consumed in five regions of China

Phenolic acids and phytosterols, the main functional compounds in cereals, could promote wellbeing and reduce the risks of diet-related diseases. This study aimed to demonstrate phenolic acid and phytosterol profiles in rice grains and wheat flours, and estimate their intakes in five geographical regions and among different age groups. Phenolic acids and phytosterols mainly existed in bound form, and the whole rice grain had high amount of 161.39 to 368.74 µg/g and 37.50 to 93.31 mg/ 100 g, respectively. In total, nine phenolic acids and six phytosterols were detected with ferulic and p-coumaric acid, and β-sitosterol the most abundant. The dietary intakes of phenolic acids and phytosterols were calculated combined with the dietary foods intake data of Chinese people. The intakes of total phenolic acids and phytosterols from rice grains and wheat flours varied across different regions with Beijing the highest among the five regions. At the age of 2 to 70 years, the average intakes of phenolic acids and phytosterols from rice and wheat flours were 7.74 to 17.52 and 58.02 to 135.61 mg/sp/day, respectively. If 3-ounce of polished rice was replaced by black rice grain, the predicted intakes of total phenolic acids and phytosterols from rice grains and wheat flours would increase by at least 196% and 68%, respectively, especially for free phenolic acids and phytosterols. PRACTICAL APPLICATION: This study would help the consumers know how much phenolic acids and phytosterols they would get from 3 ounces of black rice in a reasonable intake of staple food but shift away other kinds of foods. It could also provide inspirations for food industries to explore the functional cereal foods that are rich in phenolic acids and phytosterols for different regions and different age groups.

Volatile and sensory profiles of different black rice (Oryza sativa L.) cultivars varying in milling degree

In this study, we compared the volatile and sensory profiles of various black rice (Oryza sativa L.) cultivars varying in milling degree. In total, 51 volatiles were identified. 2-Acetyl-1-pyrroline (2-AP) was only detected in aromatic cultivars, and the amount varied depending on the cultivar. Additionally, a nonaromatic black rice cultivar (cv. Sinnongheukchal) contained high amounts of guaiacol. Descriptive analyses revealed significant differences in 13 sensory attributes between aromatic and nonaromatic black rice samples. After milling, the intensities of most volatile compound concentrations and sensory attributes decreased. However, the intensities of the "floral," "sweet aroma," and "sweet taste" sensory attributes increased, regardless of the cultivar. Partial least squares regression analysis showed that 2-AP correlated with the "popcorn" sensory attribute of aromatic black rice cultivars, whereas guaiacol was related to the "smoky" sensory attribute of cooked black rice. This information aids in the selection of black rice cultivars for various purposes in the food industry. For example, Heukhyangchal can be used as sources of food additives due to its smoky and popcorn-like aroma.

Metabolomics of Pigmented Rice Coproducts Applying Conventional or Deep Eutectic Extraction Solvents Reveal a Potential Antioxidant Source for Human Nutrition

Rice bran (RB) corresponds to the outer layers of whole grain rice and contains several phenolic compounds (PCs) that make it an interesting functional food ingredient. PC richness is enhanced in pigmented RB varieties and requires effective ways of extraction of these compounds. Therefore, we investigated conventional and deep eutectic solvents (DES) extraction methods to recover a wide array of PCs from red and black RB. The RB were extracted with ethanol/water (60:40, v/v) and two DES (choline chloride/1.2-propanediol/water, 1:1:1 and choline chloride/lactic acid, 1:10, mole ratios), based on Generally Recognized as Safe (GRAS) components. Besides the quantification of the most typical phenolic acids of cereals, nontargeted metabolomic approaches were applied to PCs profiling in the extracts. Globally, metabolomics revealed 89 PCs belonging to flavonoids (52%), phenolic acids (33%), other polyphenols (8%), lignans (6%) and stilbenes (1%) classes. All extracts, whatever the solvents, were highly concentrated in the main phenolic acids found in cereals (37–66 mg/100 g in black RB extracts vs. 6–20 mg/100 g in red RB extracts). However, the PC profile was highly dependent on the extraction solvent and specific PCs were extracted using the acidic DES. The PC-enriched DES extracts demonstrated interesting DPPH scavenging activity, which makes them candidates for novel antioxidant formulations.

Phenolic profiles and antioxidant activities of free, esterified and bound phenolic compounds in walnut kernel

The free, esterified and bound forms of 37 phenolic compounds (including hydroxybenzoic acid, hydroxycinnamic acids, flavanols, flavonols and flavones) from walnut kernel (Juglans regia L.) were investigated in this study. Results showed that the majority of walnut phenolics were presented in the free form (51.1%-68.1%), followed by bound (21.0%-38.0%) and esterified forms (9.7%-18.7%). Ellagic acid, gallic acid, ferulic acid, sinapic acid and caffeic acid were widely distributed in three forms. Differently, jeuglone, kaempferol, quercetin-7-o-β-d-glucoside and dihydroquercetin were only found in free phenolics. Among the three forms, free phenolics had the highest radical scavenging activity (IC₅₀: DPPH, 15.5 µg/ml; ABTS, 13.6 µg/ml). The correlation coefficients between the antioxidant activities of phenolics and their corresponding contents were 0.82-0.92. More soluble phenolics (free and esterified forms) could be extracted by acetone, while methanol was better at extracting insoluble bound phenolics.

Emotions Evoked by Colors and Health Functionality Information of Colored Rice: A Cross-Cultural Study

This study aimed to examine the emotional responses evoked by cooked colored rice and its health functionality information in both consumers who eat rice as a staple food and consumers who do not eat rice as a staple food. Specifically, Korean and American consumers were exposed to colored rice and its health functionality information and an emotion lexicon was generated and measured based on focus group interviews (FGI) and two online consumer surveys. In test 1, the emotions evoked by presentation of stimuli to Koreans (N = 10) and Americans (N = 10) were extracted through FGIs and the first online consumer survey (Koreans = 69; Americans = 68) and an emotion lexicon was generated. As a result, a total of 34 terms were confirmed. Test 2 was conducted during the second online consumer survey (capturing data from a total of 208 Koreans and 208 Americans), utilizing the terms generated in test 1. In this test, only the colors (CO) of colored rice were presented to one group, while colors and health functionality information (CO&H) were presented to the other group. The overall liking for stimuli in both countries was highly correlated with familiarity. Koreans showed significantly more familiarity and liking for CO of white and black CO rice, while Americans showed significantly more familiarity and liking for CO of white and yellow rice. Hierarchical cluster analysis was performed to categorize the emotion terms, and the emotion terms were sorted into the three clusters, “Positive”, “Negative”, and “New”, for both countries. Under informed conditions, the emotions became more positive, and emotions in the “New” cluster were evoked in both countries. The current study employed a cross-cultural approach to assess consumers’ emotional responses to colored rice and health functionality information. Our findings suggest that providing foods with preferred colors for each culture and providing sufficient information on the said foods will help to promote unfamiliar foods.

Effects of food hydrocolloids on quality attributes of extruded red Jasmine rice noodle

The aim of this study was to examine the quality characteristics of extruded red Jasmine rice flour (RJF) noodle that had been prepared with hydrocolloids, namely guar gum (GG), carboxymethyl cellulose (CMC), and xanthan gum (XG) at the concentrations of 0.0 (control sample), 0.2, and 0.4% (w/w), respectively. The use of hydrocolloids had no effect on total phenolic contents, antioxidant properties (DPPH, ABTS, and FRAP), color, and X-ray diffraction patterns (p > 0.05). In contrast, the hydrocolloids tended to increase the expansion ration of the noodle. GG and CMC improved cooking, textural, and sensory properties. Ultimately, 0.2%-GG showed the lowest cooking loss (5.07%) when compared with others. Moreover, it also provided the noodle with better textural properties such as tensile strength, extensibility, hardness, cohesiveness, and chewiness (p < 0.05). For these reasons, the highest acceptability (6.75) for the noodle was achieved with GG02. XG resulted in lower overall acceptability (5.05), particularly the 0.4%-XG recipe (p < 0.05). Thus, usage of 0.2%-GG was the best option for improving the qualities of extruded RJF noodle. XG was deemed ineffective for improving the noodle.

The phenolic compounds profile, quantitative analysis and antioxidant activity of four naked barley grains with different color

In the present study, the profile of phenolic compounds in colored (white, yellow, black and blue) naked barley was detected and their content and antioxidant abilities were investigated. The results showed that there were 156 phenolic substances identified, including monophenol, phenolic acids, flavonoids and other polyphenols. The black sample had the most types of phenolic. The content of phenolic varies depending on color of naked barley and the highest values of total phenolic acid and total flavonoids were observed in black and white samples. Furthermore, the strongest ferric reducing antioxidant power and the free radical scavenging ability of DPPH, ABTS, and superoxide anion showed in white, white, yellow and black naked barley. While white and yellow samples had the strongest scavenging ability of hydroxyl radical. There was significant correlation between phenolic components and anti-oxidation. This study suggests that colored naked barley grains are rich in phenolic compounds with antioxidant capacity.

Bio-properties of Saba banana (Musa 'saba', ABB Group): Influence of maturity and changes during simulated in vitro gastrointestinal digestion

Saba banana, a popular fruit crop grown in Southeast Asia, is an economical source of a variety of beneficial agents. This study examined the variations in total phenolic, flavonoid, and antioxidant activities of five maturity stages of Saba banana, and their changes during simulated in vitro gastrointestinal digestion as affected by varying structural compositions. Antioxidant activities were evaluated using ferric reducing antioxidant power (FRAP), metal ion chelating (MIC) activity, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. Results of DPPH and ABTS were compared in terms of TEAC (Trolox Equivalent Antioxidant Capacity) and VCEAC (Vitamin C Equivalent Antioxidant Capacity) values. Bio-properties were found to be highest in mature green stage with values slightly decreased as ripening proceeded. Simulated digestion showed a continuous increase in total phenolic with comparatively faster release in structure-less state (slurry) than samples with intact structure (cut). The trend of antioxidant activities was increased in the gastric phase and then decreased at the onset of intestinal phase, except for MIC which showed a reverse effect. Our study indicated that the bio-properties of Saba banana were affected by maturity and modifications in its physical structure and composition could influence the release behaviors of food components during simulated digestion.

Chemical and physical evaluation, antioxidant and digestibility profiles of white and pigmented rice from different areas of Indonesia

Abstract Black rice and red rice are often claimed to have more health benefits than white rice. They have been reported to have greater antioxidant activity and lower digestibility than white rice, functional properties which are important to prevent the metabolic disorders related to diseases such as diabetes. However, rice grown in different areas or subjected to different processing has shown different physical, chemical and functional properties. Thus the objectives of this study were to determine the physical properties (hardness, colour and gelatinization profile), chemical properties (proximate composition, total phenolic and flavonoid contents, antioxidant capacity), and the in vitro digestibility of Solok black rice (SBR), Solok red rice (SRR), Tangerang black rice (TBR), Cianjur red rice (CRR) and Cianjur white rice (CWR) cultivated in different areas in Indonesia. The results revealed that rice cultivated in different areas showed different physical characteristics and chemical compositions. The In vitro analysis of the digestibility of the starch with α-amylase showed that pigmented rice was less digestible (56.10% to 83.43%) than white rice (87.35%). A normal cooking method commonly used in society was found to significantly reduce the total phenolic content, flavonoids and antioxidant capacity of the rice.