Resistant starch-enriched brown rice exhibits prebiotic properties and enhances gut health in obese mice.

Resistant starch serves as a prebiotic in the large intestine, aiding in the maintenance of a healthy intestinal environment and mitigating associated chronic illnesses. This study aimed to investigate the impact of resistant starch-enriched brown rice (RBR) on intestinal health and functionality. We assessed changes in resistant starch concentration, structural alterations, and branch chain length distribution throughout the digestion process using an in vitro model. The efficacy of RBR in the intestinal environment was evaluated through analyses of its prebiotic potential, effects on intestinal microbiota, and intestinal function-related proteins in obese animals fed a high-fat diet. RBR exhibited a higher yield of insoluble fraction in both the small and large intestines compared to white and brown rice. The total digestible starch content decreased, while the resistant starch content significantly increased during in vitro digestion. Furthermore, RBR notably enhanced the growth of four probiotic strains compared to white and brown rice, displaying higher proliferation activity than the positive control, FOS. Notably, consumption of RBR by high-fat diet-induced obese mice suppressed colon shortening, increased Bifidobacteria growth, and improved intestinal permeability. These findings underscore the potential prebiotic and gut health-promoting attributes of RBR, offering insights for the development of functional foods aimed at preventing gastrointestinal diseases.

Structural characteristics of resistant starch-enriched rice during digestion and its effects on gut barrier function in high-fat induced obese mice.

Dietary supplementation with indigestible carbohydrates is known to improve the gut environment and prevent obesity and inflammatory diseases by modulating the gut microbiota. In previous work, we established a method for the production of resistant starch (RS)-enriched high-amylose rice (R-HAR) using citric acid. The present study aimed to evaluate changes in structural characteristics during digestion of R-HAR and its effects on the gut health. A three-step in vitro digestion and fermentation model was used, then, RS content, scanning electron microscopy, and branch chain length distribution were analyzed during in vitro digestion. During the digestion of R-HAR, the RS content increased, and the structure was predicted to have a greater impact on the gut microbiota and gut environment. To study the intestinal health effects of R-HAR, its anti-inflammatory and gut barrier integrity activities were assayed in HFD-induced mice. Intake of R-HAR suppressed colonic shortening and inflammatory responses induced by HFD. Furthermore, R-HAR exhibited gut barrier protective activity with an increase in tight junction protein levels. We determined that R-HAR may be a potentially beneficial intestinal environment improver, which may have various implications in the food industry as rice.

Comparison of rheological properties between Mixolab-driven dough and bread-making dough under various salt levels.

The properties of wheat dough according to salt level and type of mixer were investigated, and parameters derived from each analysis were comprehensively compared. Mixolab analysis showed that water absorption decreased with salt level while the dough strength increased. In the Mixolab C2 stage, related with thermal strength, C2 temperature and time had stronger correlation with other dough strength parameters than C2 torque. Thickness increase of gluten strand was dominant in the doughs prepared by vertical mixer (VMD) than in those prepared by Mixolab device (MLD), for the same salt level. In large deformation, increase in resistance to extension by salt level was much greater in VMD than in MLD. In small deformation, relationships of salt level with G', G'' and power-law exponent (n) were linear and non-linear in MLD and VMD, respectively. Since MLD could not perfectly reflect VMD, properties of dough should be considered in multiple ways for its comprehensive understanding.

Impact of chemical modification by immersion with malic acid on the physicochemical properties and resistant starch formation in rice.

The effects of immersion time on the physicochemical properties and resistant starch (RS) formation of malic acid-treated rice were investigated. Malic acid treatment decreased the frequency of cracks within the rice kernel. The color (lightness) was significantly affected by the immersion time, reflecting the browning of rice. The degree of substitution gradually increased with the immersion time and reached a plateau after 12 h, and the intensity of the C=O bond peak detected in the Fourier-transform infrared spectroscopy showed a similar trend. However, the crystallinity of rice decreased as the immersion time increased, which was confirmed by the X-ray diffraction and thermal transition properties. A gradual increase in RS was observed as the immersion time and DS increased, ranging from 44.5% to 73.3%, reaching a maximum after 12 h of immersion. Therefore, 12 h was determined to be the optimal immersion time for maximizing RS content. This information about the structural characteristics and heat-stable properties of malic acid-treated rice in starch digestion can be used to develop a low-digestible food ingredient and lead to further application of the study. PRACTICAL APPLICATION: This study reported the preparation and physicochemical properties of malic acid-treated resistant starch with different immersion times. This information could contribute to the structural characterization of resistant starch and the development of low-calorie processed rice products.

Development of Freeze-Thaw Stable Starch through Enzymatic Modification.

The use of unmodified starch in frozen foods can cause extremely undesirable textural changes after the freeze-thaw process. In this study, using cyclodextrin glucanotransferase (CGTase) and branching enzymes, an amylopectin cluster with high freeze-thaw stability was produced, and was named CBAC. It was found to have a water solubility seven times higher, and a molecular weight 77 times lower, than corn starch. According to the results of a differential scanning calorimetry (DSC) analysis, dough containing 5% CBAC lost 19% less water than a control dough after three freeze-thaw cycles. During storage for 7 days at 4 °C, bread produced using CBAC-treated dough exhibited a 14% smaller retrogradation peak and 37% less hardness than a control dough, suggesting that CBAC could be a potential candidate for clean label starch, providing high-level food stability under repeated freeze-thaw conditions.

Effects of Citrus Peel Hydrolysates on Retrogradation of Wheat Starch.

Retrogradation is the principal cause for bread staling and, therefore, it has attracted a lot of interest from the food industry. In this study, the inhibitory effect of citrus peel hydrolysates (CPH) on retrogradation of wheat starch (WS) in the presence of sucrose was investigated. The pasting properties showed that further addition of CPH caused a lower setback value than the addition of sucrose alone. Hardness of the gel, retrograded at 4 °C for five days, showed a similar tendency, which was reduced more in CPH addition than WS itself or sucrose addition alone. The low retrogradation enthalpy of the CPH including starch gel also indicated the positive effect of CPH on retarding retrogradation. These results suggested that incorporation of CPH in starch-based foods would be effective for inhibiting retrogradation, preventing the deterioration of the quality of food products.

Clean Label Meat Technology: Pre-Converted Nitrite as a Natural Curing.

Clean labeling is emerging as an important issue in the food industry, particularly for meat products that contain many food additives. Among synthetic additives, nitrite is the most important additive in the meat processing industry and is related to the development of cured color and flavor, inhibition of oxidation, and control of microbial growth in processed meat products. As an alternative to synthetic nitrite, pre-converted nitrite from natural microorganisms has been investigated, and the applications of pre-converted nitrite have been reported. Natural nitrate sources mainly include fruits and vegetables with high nitrate content. Celery juice or powder form have been used widely in various studies. Many types of commercial starter cultures have been developed. S. carnosus is used as a critical nitrate reducing microorganism and lactic acid bacteria or other Staphylococcus species also were used. Pre-converted nitrite has also been compared with synthetic nitrite and studies have been aimed at improving utilization by exploiting the strengths (positive consumer attitude and decreased residual nitrite content) and limiting the weaknesses (remained carcinogenic risk) of pre-converted nitrite. Moreover, as concerns regarding the use of synthetic nitrites increased, research was conducted to meet consumer demands for the use of natural nitrite from raw materials. In this report, we review and discuss various studies in which synthetic nitrite was replaced with natural materials and evaluate pre-converted nitrite technology as a natural curing approach from a clean label perspective in the manufacturing of processed meat products.

Impact of starch granule-associated channel protein on characteristic of and λ-carrageenan entrapment within wheat starch granules.

This study investigated the physicochemical characteristics of protease-treated wheat starch (PT-WST) to understand the role of starch granule-associated proteins (SGAPs) and the potential capability of PT-WST to provide a nutrient delivery system (NDS). Protease treatment was conducted at 4 °C and 37 °C (PT04 and PT37), respectively. A model delivery system was assessed with PT37 granules infiltrated by λ-carrageenan (λC) under variations of molecular size (λC hydrolysates produced from 0, 2.5, 100, and 500 mM HCl solution), agitation time, and temperature. Protein-specific (3-(4-carboxybenzyl)quioline-2-carboxaldehyde) or non-reactive (methanolic merbromin) fluorescent dye staining revealed that removal of SGAPs on surfaces and channels were more effective for PT37 than for PT04. Consistent amylose content, swelling, and gelatinization temperature before and after protease treatment suggested minimal impact on the starch structure. PT37 presented higher solubility and pasting viscosity than PT04. This resulted from excessive SGAP removal, which enhanced entrapment capacity. λC molecular size and agitation temperature showed a negative correlation with the content of λC entrapped within PT37, and this content depended on the interplay between the agitation time and λC molecular size. As λC molecular size decreased, the λC distribution became uniform throughout the granules, which confirmed the potential of PT-WST as a carrier for NDS.

Fabrication of citric acid-modified starch nanoparticles to improve their thermal stability and hydrophobicity.

Starch nanoparticles (SNPs) were reacted at 130 °C for 1.5 h in the presence of citric acid (30 %) to enhance their thermal stability and hydrophobicity. Citric acid content in SNP was controlled by washing with different concentrations of ethanol (95 %, 70 % and 60 %) for 2, 5 and 10 min and then subjected to heat treatment at 130 °C. After the modification, the peak at 1732 cm-1 representing ester bond was observed via FT-IR, and the intensity of the peak was decreased with a lower ethanol content in washing medium. For the 60 % ethanol condition, the granular structure was promptly fragmented into particles less than 50 nm in the aqueous solution. The modification enhanced the thermal stability and hydrophobicity of the SNPs. The modified SNPs was used as a nano-vehicle wall material for encapsulating beta-carotene as a model hydrophobic material. Approximately 80 % beta-carotene was encapsulated in the modified SNPs.

Starch Retrogradation in Rice Cake: Influences of Sucrose Stearate and Glycerol.

Retrogradation properties and kinetics of rice cakes with the addition of glycerol (GLY) and sucrose fatty acid ester (SE) were investigated. In hardness, both rice cakes with glycerol (RGLY) and rice cakes with sucrose fatty acid ester (RSE) showed lower initial hardening compared with the control for up to 5 days. X-ray diffraction (XRD) pattern of RSE showed a B+V-type pattern, and the relative crystallinity showed that GLY and SE lowered the initial and final crystallization of rice cake. Both GLY and SE affected the retrogradation enthalpy, glass transition temperature, and ice melting enthalpy in differential scanning calorimeter (DSC). However, 1H NMR relaxation time (T2) of rice cake decreased regardless of additives. From these results, the addition of glycerol and sucrose stearate inhibits the retrogradation process of rice cakes, which will solve industrial problems. Applying the Avrami equation for retrogradation kinetics of rice cake was suitable in XRD and DSC with high coefficient of determination (0.9 < R2). Meanwhile, the other retrogradation index improved the R2 when the exponential rise to maximum equation was used. This suggests that there is an alternative of Avrami equation to predict the retrogradation.

Characteristics of wheat starch-pectin hydrolysate complexes by dry heat treatment.

The objective of this study was to characterize dry heat-induced wheat starch-pectin hydrolysate (WST/PH) complexes to develop the retrogradation-retarded starch. Native (N-) and protease-treated (P-) WST were used as starch sources. Pectin hydrolysates were mixed independently with N-WST and P-WST to a mixing ratio of 49:1 (based on total solid contents), followed by drying below 10% moisture and dry heat treatment at 130 °C for 4 h. The molar degrees of substitution (MS) was higher for WST/PH complexes than its mixtures, and apparent amylose contents decreased with their MS. Relative to WST/PH mixtures, solubilities were higher for WST/PH complexes, while swelling powers didn't differ. WST/PH complexes showed the lower degree of retrogradation, setback viscosities, slowly gelling tendency, and syneresis. These phenomena were more pronounced in WST/PH mixtures and complexes prepared with P-WST. Overall results suggest that dry heat-induced WST/PH complexes could be a potential retrogradation-retarded starch to replace chemically-modified starches.

Impact of starch granule-associated surface and channel proteins on physicochemical properties of corn and rice starches.

The objective of this study was to investigate the impact of removing starch granule-associated proteins (SGAPs), especially starch granule-associated surface and channel proteins, on the overall characteristics of corn and rice starches. Protease treatment predominantly removed SGAPs on surfaces and in channels of the starches without significant damage, as evidenced by confocal laser scanning microscopy coupled with protein-specific and non-reactive fluorescent dye staining. Compared to untreated starches, protease-treated (PT) starches showed higher solubility and lower swelling power. However, there were no changes in their gelatinization and melting temperatures, despite their higher relative crystallinity. The stability of swollen starch granules during shearing was reduced following SGAP removal, reducing their peak, final and setback viscosities of the paste. Taken together these results indicate that SGAP removal predominantly affects the rheological properties of starch. Furthermore, the lower setback in PT-starch pastes suggests short-term retrogradation may be retarded by protease treatment of starch.

Starch nanoparticles produced via acidic dry heat treatment as a stabilizer for a Pickering emulsion: Influence of the physical properties of particles.

To evaluate the effect of the starch particle size on the stability of a Pickering emulsion, starch particles with various mean diameters were prepared using dry heat treatment under mildly acidic conditions. As addition level of acid increased, mean diameter of starch particles decreased from 23,100 to 15.7 nm, and contact angle of water droplet on the starch film increased from12 to 42.7°. Confocal microscopy revealed that a cohesive layer of starch particles with diameter of 28.6 nm surrounded the oil droplets, which may stabilize the emulsion. For starch particles smaller than 33.5 nm, the emulsion stability index increased up to approximately 95 % when starch content was higher than 9.1 %. For 16.7 % starch content, starch particles (< 33.5 nm) could form a stable emulsion with oil content of up to 61 %. For the emulsion stabilized by starch with 28.6 nm, it was stable when subjected to heating and freeze-thawing treatment.

Amylosucrase-modified waxy potato starches recrystallized with amylose: The role of amylopectin chain length in formation of low-digestible fractions.

This study examined the contribution of amylose to the organization of each starch fraction in recrystallized starch. Amylosucrase (AS)-modified waxy potato starches with different branch chain lengths were completely solubilized with amylose (3:1 ratio) and recrystallized at 4 °C for 48 h. The content of rapidly digestible starch and resistant starch (RS) showed linear change with degree of AS modification, while slowly digestible starch (SDS) did not. The changes in structural characteristics were tracked according to serial removal of each fraction. Results from iodine binding property, branch chain length, X-ray diffraction, and thermal property analysis indicated that branch chain length of amylopectin determined the length of the amylose-amylopectin double helix and the mobility of amylose and that formation of SDS or RS could be induced by controlling the length of amylopectin chains. These findings could be used for production of customized starches with specific digestive properties for health benefits.

Physicochemical and retrogradation properties of modified chestnut starches.

Physicochemical properties of acetylated (AC), cross-linked (CL), and hydroxypropylated (HP) chestnut starches were investigated. Modified chestnut starch showed low RS and amylose contents. AC revealed the highest solubility and HP showed the highest swelling power at 60 °C. CL showed the lowest solubility and swelling power at both 60 and 90 °C. AC and HP showed a lower pasting temperature and higher peak viscosity than native chestnut starch (NC). Modified chestnut starch formed gels at higher solid content than NC. CL had the lowest freeze-thaw stability, and AC and HP showed the strongest tolerance to freeze-thaw cycles. Amylopectin melting enthalpy of NC dramatically increased over the first 2 days and continued increasing gradually until day 24. On the other hand, all the modified chestnut starches showed a slight increase in amylopectin melting enthalpy, indicating retarded retrogradation. CL showed the lowest degree of retrogradation, followed by HP, AC, and NC.

Physicochemical properties of partially α-glucan-coated normal corn starch formed by amylosucrase from Neisseria polysaccharea.

Amylosucrase (AS) is a glycosyltransferase that produces linear α-1,4 glucans using sucrose as the sole substrate. In this study, for various applications, α-glucan-coated starch (α-GCS) was produced by AS (20 U/Lreactant) from Neisseria polysaccharea to improve the physicochemical properties of raw normal corn starch (NCS) by applying different reaction conditions (i.e., varying the substrate concentration, pH, and temperature). Field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) showed that raw NCS was successfully coated by α-glucan. Differential scanning calorimetry (DSC) and rapid viscosity analyses (RVA) of the α-GCS confirmed that the α-glucan coating decreased the degree of retrogradation. Notably, compared to raw NCS as a control, starch retrogradation was significantly (p < 0.05) decreased by 13.7% after five weeks. Therefore, the novel α-GCS can be applied as a functional material for controlled retrogradation in the starch-based food industry for shelf-life extension.

Antioxidant properties of a sulfated polysaccharide isolated from an enzymatic digest of Sargassum thunbergii.

The protective effect of sulfated polysaccharides (PS-4) isolated from Sargassum thunbergii against oxidative stress in cells and zebrafish was investigated. To begin, a variety of enzymatic extraction methods were used, including five carbohydrases and four proteases. Among the enzymatic extracts, the S. thunbergii Celluclast-assisted extract (STC) demonstrated the strongest scavenging activities against hydrogen peroxide (H2O2). Five polysaccharide fraction (PS-1 to 5) were isolated from STC and purified using ion exchange column chromatography. The antioxidant activity of these fractions was then assessed. PS-4 demonstrated the most promising free radical scavenging and antioxidant activity. PS-4 had a higher content of sulfated polysaccharide than STC. Thus, increasing the proportion of sulfated polysaccharides may be attributed to protection against H2O2-mediated cell damage and oxidative stress in cell lines and in zebrafish. These results suggest that PS-4 could be a potent antioxidant agent in functional foods and cosmetics.

A study of the quality characteristics of frozen Korean rice cake by using different thawing methods.

The characteristics of frozen rice cakes after thawing them using different methods, such as standing at room temperature (NT), running water (RWT), pan-grill (PT), steam (ST), microwave (MWT), and superheated steam thawing (SHST), were compared. Frozen rice cakes treated by MWT or SHST showed the shortest thawing time of 3 min. The MWT treatment showed the largest thawing loss, while the ST treatment showed the highest moisture content. The ST, RWT, and MWT treatments showed the highest water activity values. The NT treatment exhibited the highest hardness values, whereas the ST treatment showed the lowest values, possibly due to the adverse effects of high temperature on them. Sensory evaluation showed differences in appearance, moistness, and tenderness according to the thawing method, but there was no significant difference in overall acceptability. This study suggests that the qualities of frozen rice cakes varied depending on the different thawing methods.

Enzymatic Synthesis of Structured Monogalactosyldiacylglycerols Enriched in Pinolenic Acid.

We enzymatically prepared structured monogalactosydiacylglycerols (MGDGs) enriched in pinolenic acid (PLA). PLA-enriched free fatty acids (FFAs) containing ∼86 mol % PLA were produced from an FFA fraction obtained from pine nut oil (PLA content, ∼13 mol %) by urea crystallization. Commercial MGDGs (5 mg) were acidolyzed with PLA-enriched FFAs using four commercial immobilized lipases as biocatalysts. The reaction was performed in acetone (4 mL) in a stirred-batch reactor. Lipozyme RM IM (immobilized Rhizomucor miehei lipase) was the most effective biocatalyst for the reaction. Structured MGDGs containing 42.1 mol % PLA were obtained under optimal reaction conditions: temperature, 25 °C; substrate molar ratio, 1:30 (MGDGs/PLA-enriched FFAs); enzyme loading, 20 wt % of total substrates; and reaction time, 36 h. The structured MGDGs were separated from the reaction products at a purity of 96.6 wt % using silica column chromatography. The structured MGDGs could be possibly used as emulsifiers with appetite-suppression effects.

Immunomodulatory effects of polysaccharide fraction isolated from Fagopyrum esculentum on innate immune system.

The present study investigates the immunomodulatory activities of buckwheat polysaccharide fraction (BPF) from the seed of Fagopyrum esculentum on RAW 264.7 macrophage cell line and Cyclophosphamide-induced immunosuppressed conditions in mice models. The results of in vitro showed that treatment with 0.5-10 µg/mL of BPF can modulate immune responses. MTT assay and nitric oxide production and immune-related cytokine levels were conducted. Treatment with BPF at a dose of 10 µg/mL of BPF increased immune responses on macrophages. Moreover, natural killer (NK) cell cytotoxicity was conducted. The apoptosis of YAC-1 cells increased as the co-culture ratio between spleen cells and YAC-1 cells increased approximately 4- fold compared to the control group from 12.5:1 to 50.0:1. The in-vivo immunomodulatory effects of BPF were evaluated by cyclophosphamide-induced mice model. The immune response of BPF was determined against cyclophosphamide (100 mg/kg) immunosuppressed mice at doses of 50 mg/kg and 100 mg/kg of BPF as compared to control. The results of this study showed that BPF administration increased spleen and thymus indices as well as the leukocytes count in the blood of immunosuppressed mice. All of results suggested that BPF are potentially acts as immunomodulator for activation of immune responses.