Development of polysaccharide-complexed nano-sized rice protein dispersion.

The objective of this study was to improve water solubility of the rice protein (RP) by forming complexes with anionic polysaccharides, such as sodium alginate (SA) and xanthan gum (XG). In addition, utilization of the RP complexes as an emulsifier was evaluated. The prepared RP-SA or RP-XG complexes were analyzed by measuring their particle size, ζ-potential, and water solubility as well as by confocal laser scanning microscopy. The formation of a complex between RP-SA and RP-XG improved the water solubility and dispersibility of RP over a wide range of pH values (3, 5, 7, and 9). Confocal fluorescence images showed that the aggregation of RP molecules was prevented by the formation of complexes between RP and polysaccharides. When soybean oil-in-water emulsions were prepared with complexes, RP-SA (ratio 4:1) and RP-XG(ratio 4:1) complex-stabilized emulsions were stable for 4 weeks of storage.

Retarding Oxidative and Enzymatic Degradation of Phenolic Compounds Using Large-Ring Cycloamylose.

The phenolic compounds (PCs) abundant in fruits and vegetables are easily browned by oxygen and browning enzymes, with subsequent destruction of nutrients during food processing and storage. Therefore, natural anti-browning additives are required to control these reactions. The aim of the present study was to investigate the feasibility of cycloamylose (CA) complexation as a way to improve stability of PCs against oxidation and browning enzymes. The complex was prepared by reacting enzymatically produced CA with a degree of polymerization of 23-45 with PCs in aqueous solution. No significant differences were observed between the PCs and their CA complexes in 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging experiments. However, the reduction rate of their antioxidant activity was clearly reduced in the presence of CA for as long as 4 weeks. At the studied concentrations, the activity of polyphenol oxidase on all of the tested PC species was inhibited in the presence of CA, although this effect was less evident as the substrate concentration increased. The higher the CA concentration added to apple juice, the lower the variation in the total color difference (ΔE*) during storage, confirming that CA could be used as an effective natural anti-browning agent. Our study is the first to study the potential of CA as a natural material for browning control. The results obtained will provide useful information for active food applications requiring oxidative stability in fruit products.

Influences of added surfactants on the water solubility and antibacterial activity of rosemary extract.

Rosemary extract (RE) has significant antioxidant and antibacterial properties; however, the application of RE to areas with an aqueous solution is limited due to its poor solubility. There is a need for research focused on finding a method to improve water solubility for incorporating RE into aqueous systems, such as food and cosmetic. Therefore, in this study, the micellar solubilization of RE is conducted using four types of surfactants (Tween 20, polyglyceryl-10-laurate, polyglyceryl-10-myristate, and polyglyceryl-10-monooleate) to increase the water solubility of RE and the effects of various surfactant types and concentration on solubility were investigated. Antibacterial activities of the mixture solutions containing RE and surfactants were also examined. The water solubility of RE significantly improved when surfactants were added into the RE solution and especially in polyglyceryl-10-monooleate, with the longest tail, was the most effective for increasing solubility. In terms of the antibacterial effect on Bacillus subtilis, it was observed that a relatively lower concentration of surfactants was effective. The results of this study provide useful information for the development of a new RE-loaded delivery system for food and cosmetic application.

Methods to improve rice protein dispersal at moderate pH.

Dispersion of rice protein (RP) at a neutral pH is highly important for its application in the food industry. We analyzed the solubility of RP at different pH conditions and found higher solubility at pH < 3 and pH > 8 than at a neutral pH. Furthermore, at pH 2, the RP solubility improved from 30 to 63% with sonication; however, the samples precipitated when the pH was increased from 2 to 7. To circumvent this, anionic pectin and sodium alginate were added to the RP solution at pH 2. Pectin formed a complex with RP at pH 2, showing a shift in the zeta-potential from 17.3 mV (RP only) to - 1.0 mV (RP plus 1% pectin). Interestingly, the formation of this RP-pectin complex allowed RP to remain dispersed when the pH was increased to 7. Moreover, a stable emulsion could be prepared using the RP-pectin complex as an emulsifier.

Preparation of functional rice cake by using ß-carotene-loaded emulsion powder.

The purpose of this study was to apply a powdered ß-carotene-loaded emulsion to a real food product, Korean traditional rice cakes (Garaedduk). ß-Carotene was incorporated into the oil phase of a sodium caseinate-stabilized emulsion. Emulsion powder containing ß-carotene was prepared using freeze-drying, and maltodextrin and gum arabic were used as wall materials. Oil/protein/maltodextrin weight ratios of 3:1:2 and 3:1:5 (core-to-wall ratios of 1:1 and 1:2) were used, and gum arabic was added by replacing the amount of maltodextrin for 0.1%, 0.2%, and 0.5% w/w. Manufactured emulsion powders prepared with wall material at a core-to-wall ratio of 1:2 remained stable after reconstitution in terms of particle diameter and ζ-potential. The encapsulation efficiency of the emulsion powder increased by 90% in the presence of maltodextrin at a core-to-wall ratio of 1:2. Garaedduk containing the emulsion powder was then manufactured and it was confirmed that ß-carotene was not degraded during the manufacturing process of Garaedduk by using HPLC. The results from this study may be useful for rational designing of functional foods with lipophilic bioactive materials.

Properties and Digestibility of Octenyl Succinic Anhydride-Modified Japonica-Type Waxy and Non-Waxy Rice Starches.

Waxy and non-waxy rice starches from japonica type Korean rice varieties were esterified with different levels of octenyl succinic anhydride (OSA), and the molecular structure of amylopectin (AP), digestibility, and emulsion stability were investigated. As OSA levels increased, the degree of substitution, granule size, peak and final viscosities, emulsion stability, and short chain of AP increased. However, the gelatinization temperature and enthalpy, and digestibility decreased. All OSA esterified starches showed a new band at 1723 cm-1, but maintained A-type crystallinity. The DP6-12 of AP in waxy rice starch (WRS) was higher than that in non-waxy rice starch (NRS) with increasing OSA levels. Because the amylose and long chain of AP accessed easily with OSA groups, the digestibility of NRS was lower than that of WRS. The emulsion stability was higher in WRS than in NRS. From the above results, it is suggested that amylose should have a higher affinity with OSA esterification than AP and that the emulsion stability should increase in WRS, but the digestibility should decrease in NRS after OSA modification.

UV and storage stability of retinol contained in oil-in-water nanoemulsions.

This study was performed to examine the stability of retinol contained within oil-in-water (O/W) emulsions under UV and during storage at different temperatures. O/W emulsions were prepared using different emulsifiers and oil concentrations. The stability of the retinol contained in the O/W emulsions was investigated by measuring the percentage of residual retinol in the samples after UV exposure and storage at different temperatures (4, 25, and 40 °C). The oil concentration of the emulsion had a greater impact on UV stability than the type of emulsifier used, whereas the storage stability at different temperatures was affected by both the choice of emulsifier and the oil concentration. The storage stability of the retinol contained in the O/W emulsions may be related to the lipid oxidation properties of the emulsions rather than the latter's physical stability. Experiments with EDTA and different oil types were performed to confirm this theory.

Molecular structures of rice starch to investigate the differences in the processing quality of rice flours.

The molecular structures of non-waxy rice starches purified from three Korean rice cultivars, Dongjin1, Hopyeong, and Ilmi, were investigated to determine the main reasons why it is difficult to make manju with Dongjin1 flour compared to other rice flours with similar processing qualities. The molecular structural characteristics of the three rice starches were analyzed by high-performance size-exclusion chromatography and high-performance anion-exchange chromatography. The Dongjin1 starch had lower molecular weight (MW) amylose, a smaller proportion of short a chains, and higher average amylopectin branch chain length than the other two starches. These properties of Dongjin1 starch resulted in a lower water binding capacity, lower swelling power at 80 °C, and lower peak viscosity than those of the other two starches. It is suggested that the MW of amylose and degree of polymerization of amylopectin are important factors to make gluten-free bakery products using non-waxy rice flours.

Effect of xanthan gum on lipid digestion and bioaccessibility of ß-carotene-loaded rice starch-based filled hydrogels.

The aim of this study was to examine the effects of xanthan gum on the lipid digestibility, rheological properties, and ß-carotene bioaccessibility of rice starch-based filled hydrogels. ß-Carotene was solubilized within lipid droplets of emulsion that were then entrapped within rice starch hydrogels fabricated with different concentrations of xanthan gum. At a low concentration of xanthan gum (<0.5wt%), the viscous characteristics of the filled starch hydrogels increased. Furthermore, these hydrogels had a slower rate of lipid digestion than the ß-carotene-loaded emulsion. As the concentration of xanthan gum was increased (to 1.0wt% and 2.0wt%), the filled starch hydrogels became more elastic gel-like than those without xanthan gum, and also had the fastest rate and highest final extent of lipid digestion. The addition of xanthan gum to the filled starch hydrogel lowered the bioaccessibility of ß-carotene to varying degrees, depending on the xanthan gum concentration. The results obtained from this study can be useful in designing gel-like food products fortified with lipophilic nutraceuticals.

Physicochemical interactions of cycloamylose with phenolic compounds.

The complex formation capability of cycloamylose (CA), having a degree of polymerization of 23-45, with phenolic compounds (PCs) was investigated using various physicochemical techniques. The fluorescence intensity of PCs increased and then reached a plateau at 10-20mM cyclodextrin, while it continued to increase at up to 60mM CA. Thermodynamic data of CA complexes with PCs revealed that the binding process was primarily enthalpy-driven and spontaneous. CA favored to form the most stable complex with chlorogenic acid (CHA) among all PCs. Chemical shift changes for the protons in interior and exterior of CA, as well as in PCs suggested a possible formation of both inclusion and extramolecular interactions between CA and PCs. The ROESY spectrum confirmed that the aromatic moieties of CHA were partially interacted with CA molecules through relatively weak binding. XRD, DSC, and SEM results also supported the complex formation by intermolecular interaction between CA and CHA.

Fluorescence imaging of spatial location of lipids and proteins during digestion of protein-stabilized oil-in-water emulsions: A simulated gastrointestinal tract study.

A whey protein isolate-rhodamine B conjugate (WPI-RB) was synthesized to visualize changes in the location of a protein emulsifier in oil-in-water emulsions during digestion. An oil-soluble dye (Nile Red) was used to visualize changes in the lipid phase during digestion. Protein-labeled and lipid-labeled emulsions were passed through a simulated gastrointestinal tract consisting of mouth, stomach, and intestinal phases, and changes in protein and lipid location and morphology were monitored using confocal laser scanning microscopy. The proteins remained attached to the lipid droplet surfaces in the mouth and stomach, but formed large aggregates in the small intestine. The lipid droplets were highly flocculated in the mouth, highly coalesced in the stomach, and fully digested in the small intestine. Our results show that conjugation of fluorescence dyes to protein emulsifiers is useful for direct visualization of their location, as well as for understanding the behavior of food emulsions within the gastrointestinal tract.

Novel formulation of low-fat spread using rice starch modified by 4-α-glucanotransferase.

Low-fat spreads were developed using a thermoreversible gelling agent, the 4-α-glucanotransferase (4αGT)-modified rice starch. The low-fat spreads consisted of the modified starch paste (or rice starch or maltodextrin), olive oil (0-30% w/w), egg yolk, salt, xanthan gum, and butter flavor, and were produced by homogenization, ultrasonic processing at 50% amplitude for 2min, and cold-gel setting at 4°C for 24h. Formulations with 15% and 20% of the modified starch paste resulted in highly stable oil-in-water low-fat spreads having varied textural properties and acceptable spreadability, whereas formulations with rice starch and maltodextrin did not yield enough stability and consistency. Moreover, the modified starch-based low-fat spreads showed high thermoreversibility. These results indicated that 4αGT-modified starch could be used in the preparation of low-fat spreads, allowing the formulation of functional products for healthy diets.

Influence of methylcellulose on attributes of ß-carotene fortified starch-based filled hydrogels: Optical, rheological, structural, digestibility, and bioaccessibility properties.

There is considerable interest in controlling the gastrointestinal fate of nutraceuticals to improve their efficacy. In this study, the influence of methylcellulose (an indigestible polysaccharide) on lipid digestion and ß-carotene bioaccessibility was determined. The carotenoids were encapsulated within lipid droplets that were then loaded into rice starch hydrogels containing different methylcellulose levels. Incorporation of 0 to 0.2% of methylcellulose had little impact on the dynamic shear rheology of the starch hydrogels, which may be important for formulating functional foods with desirable textural attributes. The microstructure, lipid digestion, and ß-carotene bioaccessibility of the filled hydrogels were measured as the samples were passed through simulated oral, gastric, and small intestinal phases. The lipid digestion rate and carotenoid bioaccessibility decreased with increasing methylcellulose. This effect was attributed to the ability of the methylcellulose to inhibit molecular diffusion, promote droplet flocculation, or bind gastrointestinal components thereby inhibiting triacylglycerol hydrolysis at the lipid droplet surfaces. This information may be useful for rationally designing functional foods with improved nutritional benefits.

Control of ß-carotene bioaccessibility using starch-based filled hydrogels.

ß-Carotene was incorporated into three types of delivery system: (i) "emulsions": protein-coated fat droplets dispersed in water; (ii) "hydrogels": rice starch gels; and (iii) "filled hydrogels": protein-coated fat droplets dispersed in rice starch gels. Fat droplets in filled hydrogels were stable in simulated mouth and stomach conditions, but aggregated under small intestinal conditions. Fat droplets in emulsions aggregated under oral, gastric, and intestinal conditions. ß-Carotene bioaccessibility was higher when encapsulated in filled hydrogels than in emulsions or hydrogels, which was attributed to increased aggregation stability of the fat droplets leading to a larger exposed lipid surface area. ß-Carotene bioaccessibility in starch hydrogels containing no fat was very low (≈1%) due to its crystalline nature and lack of mixed micelles to solubilise it. The information presented may be useful for the design of rice-starch based gel products fortified with lipophilic nutraceuticals.

Release properties of gel-type W/O/W encapsulation system prepared using enzymatically-modified starch.

A gel-based encapsulation system was developed by incorporating W/O/W emulsions and 4-α-glucanotransferase (4αGTase) treated starch capable of thermoreversible gel formation, and its physical and release characteristics were investigated as functions of preparation conditions and temperature. Release properties of the W/O/W gels were affected by stability and encapsulation efficiency (EE) of W/O/W emulsions embedded within. Lower EE caused by longer sonication time increased fast release dye portion, which resulted in higher dye release rate, even though emulsion stability improved at longer sonication time. Lower dye release rate of W/O/W gels prepared with relatively higher W/O volume fractions slightly increased as temperature increased from room temperature to 90 °C. However, samples prepared with relatively lower W/O volume fractions showed higher dye release rate and a larger increase at 90 °C. The 4αGTase-treated starch gel improved W/O/W emulsion stability and thus retarded dye release even at 90 °C.

Indocyanine green-loaded perfluorocarbon nanoemulsions for bimodal (19)F-magnetic resonance/nearinfrared fluorescence imaging and subsequent phototherapy.

We have developed an indocyanine green-loaded perfluorocarbon (ICG/PFCE) nanoemulsion as a multifunctional theranostic nanomedicine which enables not only (19)F magnetic resonance (MR)/near-infrared fluorescence (NIRF) bimodal imaging but also subsequent photodynamic/photothermal dual therapy of cancer. The hydrodynamic size of ICG/PFCE nanoemulsions was 164.2 nm. The stability of indocyanine green (ICG) in aqueous solution was significantly improved when loaded on perfluorocarbon nanoemulsions. In addition, ICG/PFCE nanoemulsions showed good dispersion stability in aqueous media containing 10% fetal bovine serum, for at least 14 days. (19)F-MRI of ICG/PFCE nanoemulsions showed that the signal intensity increased with increasing nanoemulsion concentration with no signal observed from the surrounding background. Using NIRF imaging with perfluorocarbon nanoemulsion alone, without ICG, did not produce NIRF, while clear and bright fluorescent images were obtained with ICG/PFCE nanoemulsions at 10-µM ICG equivalent. The capacity of ICG-loaded nanoemulsions to generate heat following light irradiation by using an 810-nm laser was comparable to that of free ICG, while singlet oxygen generation of ICG-loaded nanoemulsions was significantly better than that of free ICG. In vitro cytotoxicity tests and fluorescence microscopy confirmed biocompatibility of the nanoemulsion. Upon light irradiation, U87MG glioblastoma cells incubated with ICG/PFCE nanoemulsions underwent necrotic cell death. The therapeutic mechanism during light illumination appears to be mainly due to the photodynamic effect at lower ICG concentrations, whilst the photothermal effect became more obvious at increased ICG concentrations, enabling combined photodynamic/photothermal therapy of cancer cells.

Physicochemical functionality of 4-α-glucanotransferase-treated rice flour in food application.

The physicochemical properties of 4-α-glucanotransferase (4αGTase)-modified rice flours were examined by measuring the molecular weight distribution, moisture sorption isotherm, and melting enthalpy of ice crystals. The results obtained by measuring the moisture sorption isotherm and melting enthalpy of ice crystals revealed that 4αGTase-modified rice flours had high water binding capacity than that of control rice flour. When the textural properties of noodles containing 4αGTase-treated rice flours after freeze-thaw cycling were measured by texture profile analysis, the textural properties of control noodle deteriorated. However, those of noodle with 4αGTase-modified rice flours were retained. For the melting enthalpy of ice crystals formed within cooked noodles, 4αGTase-treated rice flour showed similar effect to sucrose for reducing the melting enthalpy of ice crystals, however, the texture and taste of noodle with sucrose was undesirable for consuming. 4αGTase-treated rice flour appeared to have good potential as a non-sweet cryoprotectant of frozen product.

Influence of environmental stresses on the stability of W/O/W emulsions containing enzymatically modified starch.

The present study was performed to investigate the stability of W/O/W emulsions containing 4-α-glucanotransferase (4αGTase)-treated starch against environmental stresses such as heating, shearing, and repeated freeze-thawing. W/O/W emulsions were subjected to thermal processing at different temperatures ranging from 30 to 90 °C for 30 min, constant shear for 0-7 min, and freeze-thaw cycling between -20 °C and 30 °C, respectively, and followed by encapsulation efficiency (EE) measurement. As for the case of thermal stress, it was clearly shown that addition of 4αGTase-treated starch in the internal aqueous phase of emulsions helped to maintain higher EE during thermal processing. However, at lower PGPR level (2%), the addition of 4αGTase-treated starch dramatically reduced EE at temperatures higher than 70 °C, which was probably related to the melting of 4αGTase-treated starch gel. The incorporation of 4αGTase-treated starch improved the stability of emulsions during shearing process, but could not prevent W/O/W emulsions from creaming and destabilizing during freeze-thaw cycling.

Photosensitizer-conjugated polymeric nanoparticles for redox-responsive fluorescence imaging and photodynamic therapy.

Photosensitizers conjugated with hyaluronic acid via disulfide linkers were developed for biologically activatable near-infrared fluorescence imaging and photodynamic therapy. The nanoparticles prepared from the conjugate are nonfluorescent and nonphototoxic in their native state, but become highly fluorescent and phototoxic in response to reductive agents inside cancer cells.

Hypocholesterolemic and hypoglycemic effects of enzymatically modified carbohydrates from rice in high-fat-fed C57BL/6J mice.

SCOPE: Enzymatically modified rice starch (ERS) synthesized with 4-α-glucanotransferase has a longer structure than rice starch, which could delay digestion, similar to dietary fiber. We investigated the effects of ERS on glucose and lipid metabolism with mice fed a high-fat diet containing ERS (HFD-ERS). METHOD AND RESULTS: Four weeks of ERS feeding showed hypoglycemic effects with a significant reduction in fasting glucose (46%), insulin (57%), and leptin (83%) levels; improved glucose tolerance (20% in AUC of oral glucose tolerance test); and increased adiponectin concentrations (+27%) compared to the HFD group. Notably, phosphorylation of AMP kinase (AMPK) was markedly induced in the HFD-ERS livers compared to HFD livers. Additionally, ERS significantly reduced total cholesterol concentrations with induction of fecal bile acid excretion (+21%, P<0.05) in the HFD-ERS group compared to the HFD group. The mRNA and protein expressions of hepatic LDL receptors were significantly induced. However, cholesterol 7 alpha-hydroxylase (CYP7A1) expression was downregulated possibly due to induction of intestinal farnesoid X receptor (FXR; +2.4-fold, p<0.05) and fibroblast growth factor-15 (FGF-15; +2.2-fold, p<0.01). CONCLUSION: Our data suggest that ERS feeding may have hypoglycemic and hypocholesterolemic effects via a mechanism similar to that of dietary fiber.