作者机构：
[Wu, W; Li, Fang; Wu, Xiaojuan; Wu, Wei; Li, Helin; Lin, Qinlu; Wu, XJ; Zhao, Mengmeng] Cent South Univ Forestry & Technol, Fac Food Sci & Engn, Changsha 410004, Hunan, Peoples R China.;[Zhou, Xiaoling] Chen Keming Food Mfg Co Ltd, Changsha 414000, Hunan, Peoples R China.
通讯机构：
[Wu, W ; Wu, XJ] C;Cent South Univ Forestry & Technol, Fac Food Sci & Engn, Changsha 410004, Hunan, Peoples R China.
关键词：
High internal phase Pickering emulsions;Interfacial adsorption properties;Protein oxidation;Rice bran protein fibril aggregates
摘要：
The effects of rice bran rancidity-induced protein oxidation and heating time on the stability of rice bran protein fibril aggregates (RBPFA)-high internal phase Pickering emulsions (HIPPEs) were investigated. The optimal conditions for RBPFA-HIPPEs were 8 mg/mL RBPFA with an oil phase volume fraction of 75 %. Moderate oxidation (rice bran stored for 3 d) and moderate heating (8 h) enhanced the wettability, flexibility, diffusion rate, and adsorption rate of RBPFA, meanwhile, the rheological properties of RBPFA-HIPPEs increased. RBPFAHIPPEs could be stably stored for 50 d at 25 degree celsius. Moderate oxidized and moderate heated RBPFA-stabilized HIPPEs could remain stable after heat treatment and could be re-prepared after freeze-thaw (3 cycles). Additionally, the stability of RBPFA-HIPPEs was significantly related to the structural characteristics and interfacial properties of RBPFA. Overall, moderate oxidation and moderate heating enhanced the storage, thermal, and freeze-thaw stability of RBPFA-HIPPEs by improving the interfacial properties of RBPFA.
通讯机构：
[Wu, W ; Wu, XJ] C;Cent South Univ Forestry & Technol, Fac Food Sci & Engn, Changsha 410004, Hunan, Peoples R China.
关键词：
Alkaline pH-shifting;Emulsion stability;Epigallocatechin-3-gallate;Rice bran protein;Soybean protein isolate
摘要：
For improving the emulsion stability of rice bran protein (RBP), RBP was modified by different concentrations of epigallocatechin-3-gallate (EGCG) in the presence of soybean protein isolate (SPI), and RBP-EGCG-SPI conjugate was prepared by alkaline pH-shifting. The results showed that the addition of EGCG led to an increase in the bound phenol content and the flexibility of the secondary structure, a decrease in the free sulfhydryl and disulfide bond content of the RBP-EGCG-SPI conjugate. EGCG covalently bound to RBP and SPI through non-disulfide bonds. When the concentration of EGCG was 10% (w/v), the emulsifying activity index and emulsion stability index of conjugate reached the maximum value (36.61m(2)/g and 255.61min, respectively), and the conjugate had the best emulsion stability. However, an EGCG concentration above 10% (w/v) negatively affected the emulsion stability, with increasing particle size due to protein aggregation. Summarily, the modification of EGCG improved the emulsion stability of conjugate by regulating the spatial structure of RBP-EGCG-SPI conjugate. The work provided an important guide to further improve the emulsion stability of RBP.
作者机构：
[Wu, W; Li, Fang; Wu, Xiaojuan; Wu, Wei; Li, Helin; Zhao, Mengmeng] Cent South Univ Forestry & Technol, Fac Food Sci & Engn, Changsha 410004, Hunan, Peoples R China.;[Li, Fang; Wu, Xiaojuan; Wu, Wei; Li, Helin; Zhao, Mengmeng] Natl Engn Res Ctr Rice & Byprod Deep Proc, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Wu, W ] C;Cent South Univ Forestry & Technol, Fac Food Sci & Engn, Changsha 410004, Hunan, Peoples R China.
关键词：
Protein oxidation;Rheological properties;Rice bran protein fibril aggregates;Rice bran rancidity;Structural characteristics
摘要：
Rice bran protein (RBP) was isolated from rice bran (RB) with different storage time and rice bran protein fibril aggregates (RBPFAs) were prepared by heating (90 degrees C) under acidic condition (pH 2.0) to investigate the effects of RB rancidity on the structural characteristics and rheological properties of RBPFAs. The results showed that the optimal RBP concentration for the preparation of RBPFAs was 40 mg/mL. As the heating time increased, the thioflavin T intensity, 8-sheet content, average particle size, & zeta;-potential, and surface hydrophobicity of RBPFAs firstly significantly increased and then decreased (P < 0.05). When the heating time remained constant, the thioflavin T intensity, 8-sheet content, & zeta;-potential, and surface hydrophobicity of RBPFAs significantly decreased with increasing the RB storage days from 0 to 10 d, while the average particle size significantly increased (P < 0.05). When heated for 8 h, the thioflavin T intensity of RBPFAs decreased from 1027.86 to 521.06 with increasing RB storage time, while the average particle size increased from 976.55 nm to 1285.50 nm. The viscosity, storage modulus (G & PRIME;) and loss modulus (G") of RBPFAs gradually increased with the increase of RBP oxidation degree and heating time. Furthermore, the average particle size of RBPFAs was significantly correlated with their rheological properties (P < 0.05). Overall, RBP oxidative aggregation induced by RB rancidity inhibited the formation of RBPFAs, but enhanced their rheological properties. This study was instructive for the development and application of RBPFAs.
作者机构：
[Guo, Weidan; Zhan, Miao; Wu, Wei; Fu, Xiangjin; Liu, Hui] Cent South Univ Forestry & Technol, Coll Food Sci & Engn, Changsha 410004, Peoples R China.;[Fu, Xiangjin] Hunan Prov Key Lab Processed Food Special Med Purp, Changsha 410004, Peoples R China.;[Fu, Xiangjin] Hunan Prov Engn Technol Res Ctr Seasonings Green M, Changsha 410004, Peoples R China.
通讯机构：
[Xiangjin Fu] H;Hunan Provincial Key Laboratory of Processed Food for Special Medical Purpose, Changsha 410004, China<&wdkj&>College of Food Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, China<&wdkj&>Hunan Provincial Engineering Technology Research Center of Seasonings Green Manufacturing, Changsha 410004, China<&wdkj&>Author to whom correspondence should be addressed.
摘要：
Silver carp (Hypophthalmichthys molitrix) is a potential source for making surimi products. However, it has the disadvantages of bony structures, high level of cathepsines and muddy off-odor which is mainly caused by geosmin (GEO) and 2-methylisoborneol (MIB). These disadvantages make the conventional water washing process of surimi inefficient (low protein recovery rate, and high residual muddy off-odor). Thus, the effect of the pH-shifting process (acid-isolating process and alkali-isolating process) on the cathepsins activity, GEO content, MIB content, and gelling properties of the isolated proteins (IPs) was investigated, comparing it with surimi obtained through the conventional cold water washing process (WM). The alkali-isolating process greatly boosted the protein recovery rate from 28.8% to 40.9% (p < 0.05). In addition, it removed 84% GEO and 90% MIB. The acid-isolating process removed about 77% GEO and 83% MIB. The acid-isolated protein (AC) displayed the lowest elastic modulus (G '), the highest TCA-peptide content (90.89 +/- 4.65 mg/g) and the highest cathepsin L activity (65.43 +/- 4.91 U/g). The AC modori (60 degrees C for 30 min) gel also demonstrated the lowest breaking force (226.2 +/- 19.5 g) and breaking deformation (8.3 +/- 0.4 mm), indicating that proteolysis caused by the cathepsin deteriorated the gel quality of AC. The setting (40 degrees C for 30 min) considerably increased the breaking force (386.4 +/- 15.7 g) and breaking deformation (11.6 +/- 0.2 mm) of the gel made from the alkali-isolated protein (AK) (p < 0.05). In AC and AK gel, a clearly visible cross-linking protein band with a molecular weight greater than MHC was seen, demonstrating the presence of endogenous trans-glutaminase (TGase) activity, that improved the gel quality of AK. In conclusion, the alkali-isolating process was an effective alternative method for making water-washed surimi from silver carp.
作者机构：
[Wu, W; Wu, Xiaojuan; Yu, Xinyi; Wu, Wei; Li, Helin] Cent South Univ Forestry & Technol, Fac Food Sci & Engn, Changsha 410004, Hunan, Peoples R China.;[Wu, Xiaojuan; Yu, Xinyi; Wu, Wei; Li, Helin] Natl Engn Res Ctr Rice & Byprod Deep Proc, 498 South Shaoshan Rd, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Wu, W ] C;Cent South Univ Forestry & Technol, Fac Food Sci & Engn, Changsha 410004, Hunan, Peoples R China.
关键词：
Rice bran protein;Protein structure;Endogenous phenolics;Total phenolics;Degree of dephenolization
摘要：
The structure of rice bran protein obtained from defatted rice bran at various dephenolization times (0, 1, 2, 4, and 6) was examined to determine the impact of the degree of rice bran dephenolization upon rice bran protein structure. The total phenolics content in defatted rice bran and rice bran protein gradually decreased as dephenolization times increased, ranging from 390.12 to 131.16 mg GAE/100 g DW and from 30.80 to 17.85 mg/g, respectively, and the free sulfhydryl content of rice bran protein increased from 16.45 to 28.24 nmol/mg, accompanied by a decrease in surface hydrophobicity and the content of high molecular weight subunits. Furthermore, the maximum intrinsic fluorescence intensity and the flexibility of the secondary and spatial structure of rice bran protein initially increased and subsequently declined, reaching the highest level after two dephenolization cycles, while the absolute value of Zeta potential and particle size initially reduced and subsequently increased, reaching the lowest value after two dephenolization cycles. This study showed that the degree of removal of endogenous phenolics from defatted rice bran had an important effect on the structure of rice bran protein, which provided a more theoretical reference for regulating the structural characteristics of rice bran protein.
摘要：
The effects of storage time of fresh rice bran on the structure and antioxidant properties of rice bran soluble dietary fiber (RBSDF) were investigated. As the storage time of rice bran prolonged, a significant increase of acid value of rice bran crude oil was accompanied by a significant decrease of RBSDF yield (P < 0.05). The antioxidant properties of RBSDF first increased, and then decreased, which was accompanied by the formation of oxidized aggregates of RBSDF. The results of FT-IR and monosaccharide composition implied that hydroxyl oxidation was accompanied by changes in monosaccharide composition of RBSDF during storage of rice bran. As the storage time of rice bran increased, the content of free phenolics gradually increased, the content of bound and total phenolics first increased, and then decreased. The results of correlation analysis showed that among the factors affecting the antioxidant properties of RBSDF, the content of phenolics and soluble aggregates was more significant than monosaccharide composition. Overall, the structure and antioxidant properties of RBSDF were related to the degree of rice bran rancidity, suggesting that the degree of rice bran rancidity could be one of the potential means to regulate the antioxidant properties of RBSDF.
通讯机构：
National Engineering Laboratory for Rice and By-product Deep Processing, School of Food Science and Engineering, Central South University of Forestry and Technology, Changsha, China
作者机构：
[Zhou, Qi; Li, Fang; Wu, Xiaojuan; Wu, Wei; Li, Helin; Zhang, Benpeng] Cent South Univ Forestry & Technol, Fac Food Sci & Engn, Changsha 410004, Hunan, Peoples R China.;[Zhou, Qi; Li, Fang; Wu, Xiaojuan; Wu, Wei; Li, Helin; Zhang, Benpeng] Natl Engn Res Ctr Rice & Byproduct Deep Proc, 498 South Shaoshan Rd, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Wei Wu] F;Faculty of Food Science and Engineering, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China<&wdkj&>National Engineering Research Center of Rice and Byproduct Deep Processing, 498 South Shaoshan Road, Changsha, Hunan, 410004, PR China
摘要：
To explore the effects of rice bran endogenous phenolics on rice bran protein under rice bran rancidity-induced oxidation, the structure of non-dephenolized and dephenolized rice bran protein with different degrees of rice bran rancidity (rice bran was stored for 0, 1, 3, 5, and 10 d) were investigated. During rice bran storage, dephenolization increased the carbonyl (from 5.32-24.59 to 6.11-26.52 mu mol/g) and free sulfhydryl (from 24.41-32.33 to 32.64-45.04 mu mol/g) contents of rice bran protein, and decreased disulfide bonds content (from 24.26-26.61 to 21.78-25.42 mu mol/g). Meanwhile, endogenous phenolics improved rice bran protein secondary structural flexibility. Moderate oxidation (rice bran was stored for 0 and 1 d) induced by rice bran rancidity unfolded rice bran protein. The increase of maximum fluorescence emission wavelength red shift and the improvement of surface hydrophobicity induced by endogenous phenolics under moderate oxidation indicated rice bran endogenous phenolics further promoted the unfolding of rice bran protein. Excessive oxidation (rice bran was stored for 3, 5, and 10 d) caused protein aggregation. This work demonstrated that endogenous phenolics significantly affected rice bran protein structure under oxidation, especially the synergistic effect of endogenous phenolics and moderate oxidation on protein unfolding state.
作者机构：
[Li, Fang; Wu, Xiaojuan; Wu, Wei] Cent South Univ Forestry & Technol, Coll Food Sci & Engn, 498 Southern Shaoshan Rd, Changsha 410004, Hunan, Peoples R China.;[Li, Fang; Wu, Xiaojuan; Wu, Wei] Natl Engn Res Ctr Rice & Byprod Deep Proc, 498 South Shaoshan Rd, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Wei Wu] C;College of Food Science and Engineering, Central South University of Forestry and Technology, 498 Southern Shaoshan Road, Changsha, Hunan 410004, P. R. China<&wdkj&>National Engineering Research Center of Rice and Byproduct Deep Processing, 498 South Shaoshan Road, Changsha, Hunan 410004, P. R. China
作者机构：
[Li, Fang; Wu, Xiaojuan; Wu, Wei; Li, Helin] Cent South Univ Forestry & Technol, Fac Food Sci & Engn, Changsha 410004, Hunan, Peoples R China.;[Li, Fang; Wu, Xiaojuan; Wu, Wei; Li, Helin] Natl Engn Lab Rice & By Prod Deep Proc, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Wei Wu] F;Faculty of Food Science and Engineering, Central South University of Forestry and Technology, Changsha, Hunan, 410004, China<&wdkj&>National Engineering Laboratory for Rice and By-product Deep Processing, Changsha, Hunan, 410004, China
关键词：
Rice bran rancidity;Rice bran protein;Protein oxidation;Emulsion stability;Interface protein
摘要：
Rice bran protein (RBP) was prepared from rice bran (RB) under different storage periods (0, 1, 5, 7, 10 d), and isolated RBP was used to prepare protein emulsion. The RB crude oil acid value, the RBP oxidation degree, the RBP emulsion stability, and the interface-adsorbed protein and interface-unabsorbed protein structure of RBP emulsion were evaluated. With the RB storage time prolonged, the acid value of RB crude oil and the RBP carbonyl content gradually increased, indicated the occurrence of RB rancidity and RBP oxidation. Furthermore, RBP oxidation led to significant changes in the RBP emulsion stability. Moderate oxidation (RB stored for 1 d) could increase the stability of RBP emulsion, while excessive oxidation (RB stored for 5–10 d) could weaken the emulsion stability. In addition, the increasing RB storage time changed the flexibility and aggregation degree of the adsorbed protein and unabsorbed protein on the emulsion interface. The correlation analysis showed that the stability of the protein emulsion was highly correlated (P < 0.01) with the flexibility of interface-adsorbed protein, but showed little correlation with the flexibility of the unabsorbed protein at the interface. By regulating the oxidation degree of RPB to improve the emulsion stability, this research can provide a theoretical reference for promoting the stability of protein emulsions, and enlarging their applications in food systems.
摘要：
Rice bran globulin was prepared by rice bran with different storage periods and evaluated for its oxidation degree, structural characteristics and interfacial properties. As storage time of rice bran extended, protein carbonyl content gradually increased from 1.68 to 11.20 nmol/mg, and sulfhydryl content decreased from 21.10 to 6.40 nmol/mg, indicating rice bran rancidity caused rice bran globulin oxidation. Other structural indexes showed rice bran globulin oxidation caused significant changes in secondary structure of rice bran globulin, and strengthening disulfide bonds induced rice bran globulin further aggregation and cross-link. Besides, increasing storage time of rice bran led to the loss of foaming capacity, foam stability, emulsifying activity and emulsion stability of rice bran globulin. Correlation analysis between interfacial properties and oxidation extent along with structural characteristics of rice bran globulin revealed that protein oxidation extent, surface hydrophobicity, protein solubility and zeta potential were highly related with the interfacial properties of rice bran globulin.
摘要：
As a secondary oxidation product derived during rice bran oxidative rancidity, malondialdehyde (MDA) was selected to study the impact of oxidative rancidity on the digestion properties of rice bran protein. MDA modification promoted the content of protein carbonyl groups and disulfide bonds from 2.0 to 10.34 nmol/mg, 12.04-16.51 nmol/mg, respectively. The results of FT-IR, intrinsic fluorescence spectra, surface hydrophobicity, molecular weight distribution and protein electrophoresis implied that MDA changed the secondary structure of rice bran protein, and promoted protein aggregation and cross-link through non-disulfide covalent bonds. Besides, increasing concentration of MDA caused the loss of degradation potential of protein, which accompanied by the loss of pepsin and trypsin digestibility from 33.86 to 24.29%, 70.10 to 47.05%, respectively. Furthermore, MDA treatment led to the decrease in antioxidant activities of digestion products, which might be attributed to the less formation of digestion products with molecular weight of 500-1500 Da. Correlation analysis between parameters of rice bran protein oxidation and protein digestion revealed that rice bran protein oxidation was significantly related to the reduction of digestion parameters. Overall, incubation with MDA altered the structure of rice bran protein, which had a significant correlation with the deterioration of digestion properties.
