The influence of starch structure and anthocyanin content on the digestibility of Thai pigmented rice

Incorporating ions during thermal processing tailors the microstructure and practical features of rice starch/anthocyanin binary system

Understanding the interplay among salt ions, anthocyanin and starch within food matrices under thermal conditions is important for the development of starch-based foods with demanded quality attributes. However, how salt ions presence influences the microstructure and properties of starch/anthocyanin binary system remains largely unclear. Herein, indica rice starch (IRS) and rice anthocyanin (RA) were used to construct an IRS-RA binary system, with thermal treatment under different concentrations of Na+ (10-40 mM) and types of salt ions (Na+ and Ca2+). The incorporation of salt ions induced the formation of a porous gel matrix, and destroyed the hydrogen bond between starch and anthocyanin through electrostatic interactions, reducing the storage modulus and radius of gyration of the binary system, and increasing the relative crystallinity (from 1.08 % to 1.51 % (20 mM Na+) and 1.69 % (20 mM Ca+)) of the IRS-RA binary system at 90 °C. Also, the DPPH radical scavenging ability of the binary system at 90 °C was enhanced upon incorporating salt ions (0.93 for Na+ condition and 0.94 for Ca2+ condition at 20 mM ion concentration). It is noteworthy that Ca2+ inclusion had more significant effects than the case for Na+ presence, presumably due to the increased charge density.

Polyphenols in Cereals: State of the Art of Available Information and Its Potential Use in Epidemiological Studies

Cereals are the basis of much of the world's daily diet. Recently, there has been considerable interest in the beneficial properties of wholegrains due to their content of phytochemicals, particularly polyphenols. Despite this, the existing data on polyphenolic composition of cereal-based foods reported in the most comprehensive databases are still not updated. Many cereal-based foods and phenolic compounds are missing, including pigmented ones. Observational epidemiological studies reporting the intake of polyphenols from cereals are limited and inconsistent, although experimental studies suggest a protective role for dietary polyphenols against cardiovascular disease, diabetes, and cancer. Estimating polyphenol intake is complex because of the large number of compounds present in foods and the many factors that affect their levels, such as plant variety, harvest season, food processing and cooking, making it difficult matching consumption data with data on food composition. Further, it should be taken into account that food composition tables and consumed foods are categorized in different ways. The present work provides an overview of the available data on polyphenols content reported in several existing databases, in terms of presence, missing and no data, and discusses the strengths and weaknesses of methods for assessing cereal polyphenol consumption. Furthermore, this review suggests a greater need for the inclusion of most up-to-date cereal food composition data and for the harmonization of standardized procedures in collecting cereal-based food data and adequate assessment tools for dietary intake.

Analysis of volatile compounds, betaine, and antioxidant effect in goji berry (Lycium barbarum L.) powder extracted by various drying methods and extraction solvents

Goji berry (Lycium barbarum L.), a deciduous solanaceous shrub, were subjected to extraction using five solvents (water, 50% and 70% ethanol, and 50% and 70% methanol) and dried using two methods: freeze drying (FD) and spray drying (SD). To investigate the chemical properties of these various goji berry powders, an examination was conducted on the content of volatile compounds, betaine, antioxidant effect, total phenolic content (TPC), and total flavonoid compounds (TFC) (p < 0.05). The total volatile compound content was highest in SD powder with 50% ethanol extract, showing a 66.7% increase over the control. The betaine content was in the range of 9.25-31.9 mg/g dry weight, and it exhibited a significant increase with higher water concentration in the extraction solvent. Betaine, total phenolic compounds and total flavonoid compounds showed a significant increase in the sequence of SD followed by FD (p < 0.05). Overall, the SD sample showed superior benefits when evaluating volatile compounds, betaine, and antioxidant effect. SD was more suitable for drying goji berry, as it retains its appearance and biological activity.

Advancements in understanding low starch hydrolysis in pigmented rice: A comprehensive overview of mechanisms

This review explores the health-promoting properties of pigmented rice, focusing on its unique ability to promote slow starch digestion and improve blood sugar regulation. While the impact of slow starch digestibility is widely acknowledged, our current understanding of the underlying mechanisms remains insufficient. Therefore, this review aims to bridge the gap by examining the intricate factors and mechanisms that contribute to the low starch hydrolysis of pigmented rice to better understand how it promotes slower starch digestion and improves blood sugar regulation. This paves the way for future advancements in utilizing pigmented rice by enhancing our understanding of the mechanisms behind low starch hydrolysis. These may include the development of food products aimed at mitigating hyperglycemic symptoms and reducing the risk of diabetes. This research broadens our understanding of pigmented rice and facilitates the development of strategies to promote health outcomes by incorporating pigmented rice into our diets.

Insight into the nutritional, physicochemical, functional, antioxidative properties and in vitro gastrointestinal digestibility of selected Thai rice: Comparative and multivariate studies

Nutritional, physicochemical, functional, antioxidative and digestion properties of brown and white rice flours from four Thai rice varieties (Luangpatue, upland rice, RD43, and Hommali) were investigated and compared. Due to differences in grain color, the color parameters of flours varied significantly. Protein, fat, ash, carbohydrate, and moisture content, total dietary fiber, and calories of these rice flours were 6.94-10.21%, 1.68-3.16%. 0.554-1.442%, 71.20-79.68%, 9.79-10.53%, 1.07-3.64%, and 350.82-362.73 kcal/100g, respectively. RD43 brown rice (18.4%) and Luangpatue white rice (26.5%) respectively exhibited the lowest and highest amylose content. Luangpatue rice flours also showed higher swelling power, setback value, final viscosity, and thermal properties than other varieties. The variations in hydration properties and oil absorption index were noticeable among these rice flours. In addition, the highest level of total phenolic content and antioxidant activity led to the lowest estimated glycemic index (eGI = 62.92) found in upland brown rice. It was confirmed by the multivariate analysis results. This study reported the diverse physicochemical properties and composition-property relationships of two kinds of flours from four rice varieties collected from Thailand for the first time. It exhibited possible capabilities for the development of various rice-based products that promote health based on their characteristics on industrial scale.

Characterization of starch film incorporating Hom Nil rice extract for food packaging purposes

Poor water resistance, mechanical properties and stability limit the food packaging applications of starch films. Since the properties of starch films are improved by incorporating phenolic compounds and anthocyanins from natural plant extracts, Hom Nil rice (HN) extract was incorporated into cassava starch solution to produce a starch-based packaging film. We evaluated the extraction condition to optimize the total phenolic and anthocyanin contents of the HN extract. The optimal ratio of ethanol solution:Hom Nil rice powder was 5:1 v/w% and the optimal extraction time was 60 min. The influence of HN extract on the viscosity of the film solution and the properties of the obtained films were investigated. The results showed that the HN extract increased the viscosity of the starch solution. A film containing 8 wt% of HN extract produced the highest water contact angle and tensile strength, and hindered the retrogradation process. Therefore, cassava starch film modified with the proposed HN extract has the potential to be used as a food packaging material.

Structure and physicochemical properties of a new variety of purple rice (Oryza sativa L. indica) starch

The investigation of the structure and physicochemical properties of starch extracted from a new variety of purple rice was the aim of this study. Starch extracted from a new variety of purple rice named Tianzi No. 1 (PRS) is different in structure and physicochemical properties compared with waxy rice starch (WRS), japonica rice starch (JRS), and indica rice starch (IRS). PRS granules were diversified in shape, and the birefringence of starch particles were clearly observed. Fourier-transform infrared (FT-IR) spectroscopy exhibited the degree of double helix and low short-range order structure of PRS differed from IRS, JRS and WRS. X-ray diffraction analysis shows that PRS presented a typical A-type XRD pattern and possessed lower crystallinity. Based on rheological experiment results, PRS had the highest apparent viscosity, storage modulus (G') and loss modulus (G″). According to textural experiments, PRS gels had higher textural paraments before and after retrogradation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01205-w.

Evaluation of vegetable sauerkraut quality during storage based on convolution neural network

Vegetable sauerkraut is a traditional fermented food. Due to oxidation reactions that occur during storage, the quality and flavor in different periods will change. In this study, the quality evaluation and flavor characteristics of 13 groups of vegetable sauerkraut samples with different storage time were analyzed by using physical and chemical parameters combined with electronic nose. Photographs of samples of various periods were collected, and a convolutional neural network (CNN) framework was established. The relationship between total phenol oxidative decomposition and flavor compounds was linearly negatively correlated. The vegetable sauerkraut during storage can be divided into three categories (full acceptance period, acceptance period and unacceptance period) by principal component analysis and Fisher discriminant analysis. The CNN parameters were fine-tuned based on the classification results, and its output results can reflect the quality changes and flavor characteristics of the samples, and have better fitting, prediction capabilities. After 50 epochs of the model, the accuracy of three sets of data namely training set, validation set and test set recorded 94%, 85% and 93%, respectively. In addition, the accuracy of CNN in identifying different quality sauerkraut was 95.30%. It is proved that the convolutional neural network has excellent performance in predicting the quality of Szechuan Sauerkraut with high reliability.

Effects of Far-Infrared Radiation Drying on Starch Digestibility and the Content of Bioactive Compounds in Differently Pigmented Rice Varieties

Far infrared radiation (FIR) was applied to six rice varieties with different coloring of the pericarp (purple, red or non-pigment). Changes were determined in amylose content, in gelatinization parameters, in the content of bioactive compounds, in antioxidant activity and in the in vitro digestibility of pigmented rice as affected by FIR. The highest contents of amylose, total phenolic (TPC), total flavonoid (TFC) and total anthocyanins (TAC) were found in the purple and red varieties. Overall, FIR increased TPC, TFC and TAC, including antioxidant capacity. Quercetin and apigenin contents were increased while rutin and myricetin decreased significantly (p < 0.05) in all FIR-dried samples. Dephinidin, cyanidin-3-glucosides and pelargonidin increased after FIR treatment. Mostly, FIR-treated samples were found to have greater gelatinization enthalpy, compared with unheated rice samples. FIR-dried rice showed lower starch digestibility (25−40%) than unheated rice. This research suggested that the specific genotype of rice had the greatest influence on amylose content in pigmented rice, while FIR drying had no further effect. Our results suggest that FIR could enhance the content of the bioactive compounds capable of inhibiting α-amylase, thereby lowering starch digestibility. Hence, FIR may be considered as an appropriate drying method for pigmented rice regarding health benefits.

Transcriptome and Metabolome Analyses Reveals the Pathway and Metabolites of Grain Quality Under Phytochrome B in Rice (Oryza sativa L.)

BACKGROUND

Grain size and chalkiness is a critical agronomic trait affecting rice yield and quality. The application of transcriptomics to rice has widened the understanding of complex molecular responsive mechanisms, differential gene expression, and regulatory pathways under varying conditions. Similarly, metabolomics has also contributed drastically for rice trait improvements. As master regulators of plant growth and development, phys influence seed germination, vegetative growth, photoperiodic flowering, shade avoidance responses. OsPHYB can regulate a variety of plant growth and development processes, but little is known about the roles of rice gene OsPHYB in modulating grain development.

RESULTS

In this study, rice phytochrome B (OsPHYB) was edited using CRISPR/Cas9 technology. We found that OsPHYB knockout increased rice grain size and chalkiness, and increased the contents of amylose, free fatty acids and soluble sugar, while the gel consistency and contents of proteins were reduced in mutant grains. Furthermore, OsPHYB is involved in the regulation of grain size and chalk formation by controlling cell division and complex starch grain morphology. Transcriptomic analysis revealed that loss of OsPHYB function affects multiple metabolic pathways, especially enhancement of glycolysis, fatty acid, oxidative phosphorylation, and antioxidant pathways, as well as differential expression of starch and phytohormone pathways. An analysis of grain metabolites showed an increase in the free fatty acids and lysophosphatidylcholine, whereas the amounts of sugars, alcohols, amino acids and derivatives, organic acids, phenolic acids, alkaloids, nucleotides and derivatives, and flavonoids decreased, which were significantly associated with grain size and chalk formation.

CONCLUSIONS

Our study reveals that, OsPHYB plays an important regulatory role in the growth and development of rice grains, especially grain size and chalkiness. Furthermore, OsPHYB regulates grain size and chalkiness formation by affecting gene metabolism interaction network. Thus, this study not only revealed that OsPHYB plays a vital role in regulating grain size and chalkiness of rice but reveal new functions and highlighted the importance and value of OsPHYB in rice grain development and provide a new strategy for yield and quality improvement in rice breeding.

A review on application of molecular simulation technology in food molecules interaction

Molecular simulation is a new technology to analyze the interaction between molecules. This review mainly summarizes the application of molecular simulation technology in the food industry. This technology has been employed to assess structural changes of biomolecules, the interaction between components, and the mechanism of physical and chemical property alterations. These conclusions provide a deeper understanding of the molecular interaction mechanism in foods, break through the limitations of scientific experiments and avoid blind and time-consuming scientific research. In this paper, the advantages and development trends of molecular simulation technology in the food research field are described. This methodology can be used to contribute to further studies of the mechanism of molecular interactions in food, confirm experimental results and provide new ideas for research in the field of food sciences.

Application of Two-Stage Variable Temperature Drying in Hot Air-Drying of Paddy Rice

The aim of this study was to investigate the effect of two-stage variable temperature drying (VTD) on the quality and drying efficiency of paddy rice in the hot air-drying process. A constant temperature of 50 °C (CTD) was used as a control group. VTD and CTD methods were applied in a 15 ton batch type recirculating grain dryer. Three aspects (appearance quality, physical and chemical properties, taste quality) of the paddy rice samples from the dryer were measured and compared. It was observed that paddy rice with an initial moisture content of 25.3% (wet basis) was dried to 14% (wet basis). Compared to CTD, the VTD method could reduce the drying time and fissuring rate by 0.7 h and 42%, respectively. It had a head rice yield (HRY) of 78.45%, compared to 76.45% by CTD. The fatty acid content of the VTD samples was 2.28% lower than those of CTD, and it exhibited a 34% decrease in amylose content. These results show that two-stage VTD is an advanced hot air-drying method that can be used to improve the quality of dried paddy rice, maintain efficiency, and reduce the cost of the drying process by minimizing the rate of energy consumption.

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.

Drying Characteristics and Quality Attributes Affected by a Fluidized-Bed Drying Assisted with Swirling Compressed-Air for Preparing Instant Red Jasmine Rice

A new process for the production of instant red jasmine rice was investigated using fluidized bed drying with the aid of swirling compressed air. Drying characteristics were evaluated using the operating parameters of fluidizing air temperature (90–120 °C) and pressure of swirling compressed air (4–6 bar). Appropriate air pressure was determined based on the highest value of model parameters from the semi-empirical Page equation and effective diffusivity. Influences of supply time of swirling compressed air (2–10 min) and drying temperature of 90–120 °C were investigated and optimized based on the quality attributes using response surface methodology. Drying at 120 °C and compressed air pressure of 6 bar gave the highest rate constant and effective diffusion coefficient. Drying at 120 °C combined with injecting swirling air for 2 min was the most suitable approach, while drying at 90 °C and supplying compressed air for 10 min was the best choice to preserve antioxidant properties. Air temperature of 98.5 °C with 2 min supply of swirling compressed air suitably provided high physical and rehydration properties and retained high health benefits of antioxidant compounds. Finally, after rehydration in warm water at 70 °C for 10 min, the textural properties of the rehydrated rice sample were comparable to conventionally cooked rice.

Non-Traditional Muesli Mixtures Supplemented by Edible Flowers: Analysis of Nutritional Composition, Phenolic acids, Flavonoids and Anthocyanins

In this study, the effect of using medicinal plants on nutrition composition and biologically active substances in cereal mixtures were investigated. In order to develop new type of non-traditional muesli mixtures supplemented with edible flowers, eight muesli mixtures were prepared applying the mixing ratio of 60‒70% of non-traditional flakes and 30‒40% of lyophilized fruits and edible flowers. This study examines nutritional composition, digestibility, fibres and phenolics of nutraceutical muesli mixtures using enzymatic-gravimetric and chromatographic methods. It shows that the mixture of kamut, einkorn, red and black quinoa or rice flakes together with hibiscus, mallow, rose, fruits has increased the fibre content (11.9‒21.2%) and in vitro digestibility (87.8‒93.8%). The greatest concentrations of individual phenolic contents were determined in free and soluble bound fractions of the mixtures. Cyanidin-3-glucoside (up to 116 mg/kg) and delphinidin-3-glucoside (up to 76.9 mg/kg) were established as major anthocyanins. Considering the individual phenolic fractions, sinapic and protocatechuic acids were the most abundant phenolic acids and quercetin and epigallocatechin represented the most frequent flavonoids. These results indicate that non-traditional muesli with edible flowers containing a high amount of nutrients and bioactive substances have the potential to enhance a nutritionally balanced diet.

The Potential of High-Anthocyanin Purple Rice as a Functional Ingredient in Human Health

Purple rice is recognized as a source of natural anthocyanin compounds among health-conscious consumers who employ rice as their staple food. Anthocyanin is one of the major antioxidant compounds that protect against the reactive oxygen species (ROS) that cause cellular damage in plants and animals, including humans. The physiological role of anthocyanin in plants is not fully understood, but the benefits to human health are apparent against both chronic and non-chronic diseases. This review focuses on anthocyanin synthesis and accumulation in the whole plant of purple rice, from cultivation to the processed end products. The anthocyanin content in purple rice varies due to many factors, including genotype, cultivation, and management as well as post-harvest processing. The cultivation method strongly influences anthocyanin content in rice plants; water conditions, light quantity and quality, and available nutrients in the soil are important factors, while the low stability of anthocyanins means that they can be dramatically degraded under high-temperature conditions. The application of purple rice anthocyanins has been developed in both functional food and other purposes. To maximize the benefits of purple rice to human health, understanding the factors influencing anthocyanin synthesis and accumulation during the entire process from cultivation to product development can be a path for success.

Structural changes of rice starch and activity inhibition of starch digestive enzymes by anthocyanins retarded starch digestibility

The effects of anthocyanins on in vitro and in vivo digestibility of rice starch were evaluated in this study. Then, the effects of anthocyanins on physicochemical properties of rice starch and on starch digestive enzymes (α-amylase and α-glucosidase) were investigated to understand the mechanism of the effects of anthocyanins on starch digestibility. Characterization of physicochemical properties of rice starch indicates a structural change due to the presence of anthocyanins, hindering its access to starch digestive enzymes. Besides, anthocyanins inhibited the activities of starch digestive enzymes by binding to their active sites, competing with the substrates and changing the secondary structure of the enzymes. The above stated changes of rice starch and starch digestive enzymes due to the presence of anthocyanins both contributed to retarding the digestibility of rice starch. This study could offer some theoretical guidance to the development of new type rice-based food with low glycemic index.

In Vitro Glycemic Response of Indigenous Pigmented Rice Cultivars from South India and Influence of Different Carbohydrate Components

Staple diet patterns such as white rice consumption play an important part in the occurrence of chronic lifestyle-related disease like diabetes. This study intended to identify pigmented rice cultivars from India as an alternative to white rice. Nine carbohydrate components were quantified in six red and two black pigmented rice varieties. In vitro starch digestibility was also analyzed and the predicted glycemic index (pGI) was estimated. The relationship between the carbohydrate components and the pGI of the rice varieties was analyzed. The rice varieties, Kattuyanam and Chennangi exhibited high levels of insoluble dietary fibre, total dietary fibre and amylose. High soluble dietary fibre contents were observed in Poonghar and Aruvadam kuruvai. The levels of resistant starch and slowly digestible starch were found to be the highest in Karupakavuni. The results indicated Kattuyanam, Chennangi, Karungkuruvai, and Poonghar to be low pGI rice varieties (< 55). The three varieties, Kesari, Karupakavuni, and Aruvadam kuruvai were categorized under the medium pGI category (56-69). Mapillai samba had a high pGI of 70 which could be due to processing (partially milled and parboiled), but had significantly lower pGI than the white rice, Sona masuri (GI – 76). The dietary fibre components, resistant starch, slowly digestible starch, and the amylose content were negatively correlated with the pGI. Among these components, the insoluble dietary fibre, total dietary fibre, and resistant starch with significantly high (p ≤0.01) correlation were found to be the major determining factors of pGI in the studied pigmented rice cultivars. The inclusion of the identified pigmented rice varieties with low to medium glycemic response in the diet could become a key role in the dietary management of diabetes, especially among the rice-eating population.

Breathing New Life to Ancient Crops: Promoting the Ancient Philippine Grain "Kabog Millet" as an Alternative to Rice

Consumption of underutilised ancient crops has huge benefits for our society. It improves food security by diversifying our staple foods and makes our agriculture more adaptable to climate change. The Philippines has a rich biodiversity and many plant species used as staple foods are native to the Philippines. An example of ancient Philippine crops is the kabog millet, an ecotype of Panicum miliaceum. There is a dearth of information about its uses and properties; hence, in this study, the nutritional quality of kabog millet was evaluated. The total starch, % amylose, ash, dietary fibre, proteins, essential amino acid profile, phenolic acids, carotenoids, tocopherols, and the antioxidant properties of its total phenolic acid extracts were compared to four types of rice (white, brown, red, and black) and a reference millet, purchased from local Swiss supermarkets. Our analyses showed that kabog millet has higher total dietary fibre, total protein, total phenolic acids, tocopherols, and carotenoids content than white rice. It also performed well in antioxidant assays. Our results indicate that kabog millet is a good alternative to rice. It is hoped that the results of this study will encourage consumers and farmers to diversify their food palette and address food insecurity.

Changes in curcuminoids and chemical components of turmeric (Curcuma longa L.) under freeze-drying and low-temperature drying methods

We investigated how various drying methods affect the chemical components and microstructure of turmeric. We used freeze drying (FD), hot-air drying (HD) at 50 °C and sun drying (SD). Compared to all dried samples, fresh turmeric had greater amounts of chemical components (curcuminoids, phenolic acids, flavonoids and amino acids) andgreater antioxidantactivity (DPPH and FRAP) except for ABTS^.+ values. SD caused a severe decline of three major curcuminoids, resulting from UV and light degradation. Curcumin was decreased the most by SD (72%), followed by HD (61%) and FD (55%), respectively. Curcumin degradation to ferulic acid and vanillin was explored by FTIR analysis. The amino acids were decreased by all drying methods. FD was considered to be most suitable for drying turmeric. Microstructure changes were least after freeze drying, but were still evident compared with fresh turmeric.