Rice Bran Protein Isolate Research Articles

Effect of Rice Bran Protein Isolate (RBPI) Addition on the Sponge Cake Qualitative and Bioactive Properties

The current study investigated the effect of rice bran protein isolate (RBPI), in the amounts of 0, 1, 2, and 3% of wheat flour, which are mentioned in abbreviate as C, RBPI1, RBPI2, and RBPI3, respectively, on qualitative and bioactive properties of sponge cake. The results indicated that RBPI contains 57.58% protein with high pepsin digestibility (87.95%). RBPI addition increased the consistency (Bostwick number) and specific gravity (SG) of the prepared batter samples from 7.62 cm and 1.08 for the control to 6.50 cm and 1.14 for RBPI3, respectively. The protein content of sponge cake increased significantly from 6.31% (C) to 6.95% (RBPI3), but the cake volume and baking loss decreased significantly ( p < 0.05 ) with increasing the amount of RBPI. The crust color of the cake samples was changed ( L ∗ and b ∗ were decreased, and a ∗ was increased) by RBPI addition. The texture profile analysis (TPA) and sensory evaluation demonstrated that up to 2% of wheat flour can be replaced by RBPI without negatively affecting the characteristics of these. Total phenol content (TPC) and DPPH scavenging activity of RBPI2 were also improved. According to the results obtained from all the evaluations, the addition of RBPI to up to 2% of wheat flour is recommended to improve the qualitative and bioactive properties of the prepared functional sponge cake.

Effect of Steam Flash-Explosion on Physicochemical Properties and Structure of High-Temperature Denatured Defatted Rice Bran Protein Isolate.

The effects of Steam Flash-Explosion (SFE) on the physicochemical properties and molecular structure of high-temperature denatured defatted rice bran protein isolate (RBPI) were investigated. The mechanism of SFE treatment on high-temperature denatured defatted RBPI was revealed. The analysis of the physical and chemical properties of RBPI showed that the surface hydrophobicity, characteristic viscosity, and thermal stability of rice bran protein isolate were significantly affected by the pressure of saturated steam and pressure holding time. Under the conditions of 2.1 MPa and 210 s, the surface hydrophobicity index decreased significantly from 137.5 to 17.5, and the characteristic viscosity increased significantly. The peak temperature of denaturation decreases from 114.2 to 106.7 °C, and the enthalpy of denaturation decreases from 356.3 to 231.4 J/g. The higher structure (circular dichroic spectrum and endogenous fluorescence spectrum) of rice bran protein isolate was analyzed by volume rejection chromatography (SEC). The results showed that steam flash treatment could depolymerize and aggregate RBPI, and the relative molecular weight distribution changed greatly. The decrease in small molecules with poor solubility was accompanied by the increase in macromolecules (>550 kDa) soluble aggregates, which were the products of a Maillard reaction. The contents of free sulfhydryl and disulfide bonds in high-temperature rice bran meal protein isolate were significantly increased, which resulted in the increase in soluble aggregates containing disulfide bonds. Circular dichroism (CD) analysis showed that the α-helix content of the isolated protein was significantly decreased, the random curl content was increased, and the secondary structure of the isolated protein changed from order to disorder. The results of endogenous fluorescence spectroscopy showed that the high-temperature rice bran meal protein isolate was more extended, tryptophan was in a more hydrophilic microenvironment, the fluorescence intensity was reduced, and the tertiary structure was changed. In addition, the mean particle size and net surface charge of protein isolate increased in the aqueous solution, which was conducive to the development of the functional properties of the protein.

Comparison of Different Protein Emulsifiers on Physicochemical Properties of β-Carotene-Loaded Nanoemulsion: Effect on Formation, Stability, and In Vitro Digestion.

In this study, β-carotene-loaded nanoemulsions are emulsified using four biomacromolecular proteins—peanut protein isolate (PPI), soy protein isolate (SPI), rice bran protein isolate (RBPI), and whey protein isolate (WPI)—in order to explore their emulsion stability and in vitro digestion characteristics. All four nanoemulsions attained high encapsulation levels (over 90%). During the three-stage in vitro digestion model (including oral, gastric, and small intestine digestion phases), the PPI-emulsified nanoemulsion showed the highest lipolysis rates (117.39%) and bioaccessibility (37.39%) among the four nanoemulsions. Moreover, the PPI-emulsified nanoemulsion (with the smallest droplet size) also demonstrated the highest stability during storage and centrifugation, while those for the RBPI-emulsified nanoemulsion (with the largest droplet size) were the lowest. In addition, all four nanoemulsions showed superior oxidation stability when compared with the blank control of corn oil. The oxidation rates of the PPI- and WPI-stabilized groups were slower than the other two groups.

The Improvement of Nanoemulsion Stability and Antioxidation via Protein-Chlorogenic Acid-Dextran Conjugates as Emulsifiers.

In this experiment, the peanut protein isolate (PPI), soybean protein isolate (SPI), rice bran protein isolate (RBPI), and whey protein isolate (WPI) were modified by linking chlorogenic acid covalently and linking dextran by Maillard reaction to prepare protein-chlorogenic acid-dextran (PCD) conjugates. As for structures, conformational changes of conjugates were determined by Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE), Fourier transform infrared (FT-IR), and fluorescence measurements. The molecular weights of PCD conjugates became larger, the structure became disorder, and the amino acid residues inside the protein were exposed to the polar environment when compared to protein-chlorogenic acid (PC) and native proteins (NPs). As for properties, the interfacial tension reduced and antioxidant activity of PCD conjugates enhanced in varying degrees. Based on this, PCD conjugates were used as emulsifiers in order to investigate the properties of nanoemulsions and compared with PC conjugates and NPs. The mean droplet diameters (MDD) results showed that the nanoemulsions that were stabilized by PCD conjugates had the smallest particle sizes and exhibited uniformly dispersed spherical shapes. The storage and oxidative stabilities of PCD conjugates were also significantly improved. In comparison, nanoemulsion that was stabilized by PPI-chlorogenic acid-dextran conjugate had the smallest particle size and optimal stability among four protein stabilized nanoemulsions.

Changes in the antioxidant properties of rice bran protein isolate upon simulated gastrointestinal digestion

This study aimed to evaluate changes in the antioxidant properties of rice bran protein isolate (RBPI) upon simulated gastrointestinal digestion. A two-stage in vitro digestion system (pepsin treatment followed by pancreatin treatment) was used to generate GI-digested RBPI. Antioxidant activities were evaluated using various oxidative systems: measurement of oxygen radical antioxidant capacity (ORAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS+) assay, and reducing power assay. After gastrointestinal digestion, the protein solubility and free phenolic compounds increased from 24.6% to 94.5% and from 2.1 to 17.6 mg/g, respectively. The ORAC value of the GI-digested RBPI was significantly higher (p < 0.05) than that of the intact RBPI (473.5 vs. 44.2 μmol Trolox equivalents/g); furthermore, the GI-digested RBPI also showed significantly higher DPPH & ABTS radical-scavenging activities and reducing power than intact RBPI (p < 0.05). This study provides novel quantitative insights into the antioxidant properties of GI-digested RBPI in various oxidation systems and indicates that simulated gastrointestinal digestion is potentially applicable for producing bioactive components with higher antioxidant potentials than those of RBPI.

Effect of radio frequency treatment on functional, structural and thermal behaviors of protein isolates in rice bran

To investigate the influence of radio frequency (RF) stabilization treatment on rice bran protein isolate (RBPI) properties, functional, structural and thermal behaviors of RBPI obtained from RF treated RB were evaluated under various temperatures between 80 and 120 °C holding for 5 min. The results showed that RF heating had negative impact on the yield, purity, foaming properties and solubility of RBPI when the treatment temperature was higher than 100 °C, while the absorption and emulsifying properties were improved. No significant changes were observed in primary structure of RF treated samples, but the second structure changed with an increase in random coil and a decrease in β-sheet, α-helix and β-turn. The decreased tryptophan fluorescence and increased surface hydrophobicity suggested alterations in tertiary structure. RF treatment also caused noticeable decrease in denaturation temperature and enthalpy of RBPI. The results would provide basic information for food applications of proteins isolated from RF stabilized RB.

Physicochemical Properties and Storage Stability of Food Protein-Stabilized Nanoemulsions.

This study investigated the preparation and properties of corn oil nanoemulsions stabilized by peanut protein isolate (PPI), rice bran protein isolate (RBPI), soybean protein isolate (SPI), and whey protein isolate (WPI). The mean droplet diameter of four protein-stabilized nanoemulsions prepared via ultrasound method was less than 245 nm. PPI-stabilized nanoemulsions showed better stability for 4 weeks, while the mean droplet diameter of RBPI-stabilized nanoemulsions had exceeded 1000 nm during the third week of storage. Fourier transform infrared and interfacial tension (IT) analysis showed that the higher level of disordered structure and lower IT of proteins made the stability of nanoemulsions better. Moreover, bivariate correlation analysis discovered that α-helix (p < 0.01) and β-turn (p < 0.05) of proteins were related to the mean droplet diameter of nanoemulsions, the random coil (p < 0.05) was related to the zeta potential of nanoemulsions. This study provided new idea for the relationship between the structure of protein and properties of protein-stabilized nanoemulsions.

Effect of dry heat stabilisation on the functional properties of rice bran proteins

SummaryRice bran was stabilised by dry heat method at 120 °C for 10–60 min, and then, protein was extracted from stabilised rice bran using weak alkali method. The storage characteristics of stabilised rice bran and the influences of dry heat pretreatment on the physicochemical properties of rice bran protein isolate were also evaluated. The results indicated that dry heat pretreatment could not only prevent rancidity of rice bran effectively, but also improve some functional properties of rice bran proteins, such as emulsifying properties, oil holding capacity, and water holding capacity. However, foaming properties and protein solubility were slightly destroyed because of heating. Rice bran was pretreated at 120 °C for 10 or 20 min and then extracted at pH 9.5, and the protein yields were 50.09% and 46.98%, respectively. Therefore, the dry heat treatment at 120 °C for 10 or 20 min was a suitable alternative process in stabilisation of rice bran.

Binding of tea catechins to rice bran protein isolate: Interaction and protective effect during in vitro digestion

Rice bran protein isolate (RBPI) was prepared from defatted rice bran and used to deliver tea catechins. RBPI had the high adsorption selectivity for tea catechins over caffeine. The adsorption characteristics of tea catechins onto RBPI were determined over a range of time (0–300min), concentration (0.25–3.5gL−1) and temperatures (5°C, 20°C and 35°C). The adsorption kinetic data of EGCg and total catechins (TC) onto RBPI showed excellent fitness with the pseudo-second-order model, indicating that chemisorption is the dominating process. Langmuir and Freundlich models adequately described the isothermal adsorption of tea catechins onto RBPI, and the maximum adsorption of EGCg and TC were achieved at 5°C. SDS-PAGE profiles indicated that globulin and albumin were the major soluble proteins in RBPI to bind tea catechins. Fourier transforms infrared spectroscopy analysis showed that the protein secondary structures of RBPI were altered upon interaction with catechins, with a great increase in random coil and β-antiparallel, a minor increase in α-helix and a reduction in large loop and turn. Binding tea catechins to RBPI respectively increased the recovery% of EGCg and TC from 10.5% and 17.7% to 29.5% and 31.6% after in vitro intestinal digestion. Thus, RBPI is a promising food matrix for delivering tea catechins to gastrointestinal tract.

Preparation and characterization of protein from heat-stabilized rice bran using hydrothermal cooking combined with amylase pretreatment

Hydrothermal cooking (HTC) combined with amylase pretreatment (AP) was used to improve protein extraction from heat-stabilized rice bran. The physicochemical and emulsifying properties of rice bran protein isolate (RPI) were evaluated. Depending on HTC temperature (120 and 150 °C), HTC alone significantly increased extraction yield, while protein purity was decreased. In contrast, HTC combined with AP significantly improved both extraction yield and protein purity (about 45–50% and 72–74%, respectively). The AP avoided the co-precipitation of gelatinized starch during the acidic precipitation. Electrophoresis and size exclusion chromatography profiles indicated that HTC led to the dissociation of insoluble protein aggregates in rice bran, with subsequent increase of soluble aggregates in RPI, linked by non-covalent (e.g., hydrophobic interaction) and covalent bonds (disulfide bond). This result was evidenced by the increased disulfide bond contents and surface hydrophobicity of RPI. In addition, HTC-prepared RPI exhibited excellent emulsifying property.

EFFECT EXTRACTION METHODS OF RICE BRAN PROTEIN ON THEIR FUNCTIONAL PROPERTIES

This investigation was carried out to study the functional properties and amino acids compositions of rice bran protein isolate (RBPI) and rice bran protein concentrate (RBPC). The results indicate that (RBPI) had better water binding capacity, protein content and yield as compared to (RBPC), while oil binding capacity lower in (RBPI) than (RBPC). Nitrogen solubilities of (RBPI) were 52.3, 8.4, 63.5, 79.1, 83.7 and 81.5% at pH 2, 4, 6, 8, 10 and 12, respectively. RBPI had better foaming and emulsifying properties than (RBPC). While, RBPI had similar foaming properties in comparison to egg white, but emulsifying properties of RBPI were lower than those of bovine serum albumin. The results of amino acid analysis showed that the relative content of cystine and methionine in RBPC were lower than that of RBPI and RBP, while leucine and phenylalanine were higher in RBPC .The computed protein efficiency ratio(C-PER) and biological value (B V) of RPBI were higher than those of RBPC and value of all samples were lower than that of standard casein protein. Obtained results indicate that the RBPC and RBPI have high qualities of both nutritional and functional properties and could be competitive proteins ingredients in food products.

Preparation and Characterisation of Protein Hydrolysates from Indian Defatted Rice Bran Meal

Rice bran meal is a very good source of protein along with other micronutrients. Rice bran meal has been utilized to produce protein isolates and respective protein hydrolysates for potential application in various food products. De-oiled rice bran meal, available from Indian rice bran oil extraction plants, was initially screened by passing through an 80-mesh sieve (yield about 70%). A fraction (yield-30%) rich in fibre and silica was initially discarded from the meal. The protein content of the through fraction increased from 20.8% to 24.1% whereas silica content reduced from 3.1% to 0.4%. Rice bran protein isolate (RPI) was prepared by alkaline extraction followed by acidic precipitation at isoelectric point. This protein isolate was hydrolysed by papain at pH 8.0 and at 37 degrees C for 10, 20, 30, 45 and 60 minutes. The peptides produced by partial hydrolysis had been evaluated by determining protein solubility, emulsion activity index (EAI), emulsion stability index (ESI), foam capacity and foam stability (FS). All protein hydrolysates showed better functional properties than the original protein isolate. These improved functional properties of rice bran protein hydrolysates would make it useful for various application especially in food, pharmaceutical and related industries.

Preparation and functional properties of rice bran protein isolate.

Rice bran protein isolate (RBPI) containing approximately 92.0% protein was prepared from unstabilized and defatted rice bran using phytase and xylanase. The yield of RBPI increased from 34% to 74.6% through the use of the enzymatic treatment. Nitrogen solubilities of RBPI were 53, 8, 62, 78, 82, and 80% at pHs 2.0, 4.0, 6.0, 8.0, 10.0, and 12.0, respectively. Differential scanning calorimetry showed that RBPI had denaturation temperature of 83.4 degrees C with low endotherm (0.96 J/g of protein). RBPI had similar foaming properties in comparison to egg white. But emulsifying properties of RBPI were significantly lower than those of bovine serum albumin. The result of amino acid analysis showed that RBPI had a similar profile of essential amino acid requirements for 2-5-year-old children in comparison to that of casein and soy protein isolate.