Research Progress on Extraction, Functional Properties and Modification Approach of Quinoa Protein

Quinoa is considered as a pseudo-cereal and recommended by FAO as the most suitable "whole food" for human consumption. With the rapid development of the health industry, the demand for quinoa products is increasing. According to the FAO standards, quinoa protein has a balanced amino acid composition, containing nine essential amino acids. It is also rich in lysine and methionine compared with other grains and legumes. Therefore, more and more studies have focused on the nutritional value and functional properties of quinoa protein. In this study, the composition, nutritional value and extraction methods of quinoa protein are reviewed, and the research progress in the functional properties such as emulsification, foaming, gelation and digestion properties of quinoa protein are also discussed. In addition, due to the enhanced functional properties of quinoa protein after modification, the effects of physical and biological modification on the functional properties of quinoa protein are also summarized in this paper. Quinoa protein, as a high-quality protein, can be deeply explored and applied in the processing of plant proteins, promoting the industrialization of quinoa protein

Studies on Alkaline Extraction and Acid Precipitation Process of Polyphenols from Longan Seeds and Identification of the Extracts

为了更合理有效的开发利用龙眼核多酚资源，本文尝试采用碱提酸沉工艺提取龙眼核多酚，初步鉴定了龙眼核多酚提取物的主要成分，对其抗氧化和自由基清除能力进行了评价。 选择低成本，浸取效果较好的磷酸钠缓冲液为浸取溶剂，确定了龙眼核前处理的最优干燥条件为50℃下干燥30h，利用响应面法对浸取工艺进行优化：磷酸钠缓冲液pH=11、浓度10mM，浸取温度70℃，料液比1:40，浸取时间25min。在此工艺条件下龙眼核多酚的浸出率为46.86±0.43mg/g，达到理论预测值的103.67%，同时达到水/乙醇浸提工艺的98.17%。 对龙眼核多酚的酸法沉淀分离工艺进行了优化，得到了最优的工艺条件为：将过滤后...A process of alkaline extraction and acid precipitation was adopted in this paper in an attempt to extract polyphenols from longan seeds. The process was optimized and the components were preliminarily identified. The antioxidant activity and free radical scavenging capacity of longan seeds polyphenols were evalued finally. Sodium phosphate buffer, as a low-cost solvent with better extraction c...学位：工学硕士院系专业：化学化工学院_化学工程学号：2062010115144

Enzymatic Preparation of Quinoa Protein Peptides and Its Lipid-lowering and Uric Acid-Lowering Activity in Vitro

To study the optimal enzymatic hydrolysis conditions and uric acid-lowering activity of lipid-lowering peptides from quinoa protein, this study used quinoa as raw material to extract protein, and used pancreatic lipase inhibition rate as the activity index. The enzymatic hydrolysis process of lipid-lowering peptides was optimized by single factor experiment and response surface analysis. The pancreatic lipase inhibitory activity, sodium taurocholate binding activity, cholesterol esterase inhibitory activity, xanthine oxidase inhibitory activity and amino acid composition of quinoa protein peptides were analyzed and characterized. The results showed that the optimal enzymatic hydrolysis conditions of lipid-lowering peptides from quinoa were as follows: pH1.6, enzymatic hydrolysis temperature 42.9 ℃, substrate concentration 3.03%, enzymatic hydrolysis time 1 h and enzyme to substrate ratio 0.2%. The theoretical value of inhibition rate of pancreatic lipase was 90.43%, and the actual value was 90.93%±0.10%. The optimal enzymatic hydrolysates showed excellent effect of lowering lipid in vitro. The IC50 of pancreatic lipase inhibition rate and cholesterol esterase inhibition rate were 7.49 μg/mL and 4.73 mg/mL, respectively. Meanwhile, the EC50 of taurocholic sodium binding rate was 0.53 mg/mL. In addition, the optimal enzymatic hydrolysates showed good xanthine oxidase inhibition effect (IC50=5.97 mg/mL), indicating that it had the uric acid-lowering effect in vitro. Amino acid analysis showed that quinoa protein peptides were rich in essential amino acids (34.23%), and the percentage of hydrophobic amino acid and acidic amino acid were 34.11% and 31.66%, respectively. The quinoa protein peptides had high lipid-lowering and uric acid-lowering activities in vitro, which provided a theoretical basis for the high-value application of quinoa protein peptides

Optimization of Enzymatic Hydrolysis and Decolorization Process of Walnut Protein

This paper aimed at the high-value utilization of walnut cake, a by-product of oil processing industry. The walnut protein (WP) was extracted by alkali extraction-acid precipitation method from cold-pressed walnut cake, then trypsin hydrolysis process was optimized by single factor experiment and orthogonal design, with degree of hydrolysis (DH) as the indicator. Subsequently, the decolorization process of WP hydrolysate was optimized with protein recovery rate and decolorization rate as the indicators. The results showed that the extracted walnut protein was of high purity and could be used for further enzymatic hydrolysis and decolorization tests. After optimization, the DH of WP could be increased to 21.08% under the following conditions: the substrate concentration of 3%, the hydrolysis temperature of 55 ℃, the enzyme addition of 6 250 U/g protein, and the enzymatic hydrolysis time of 5 h. The optimal process of decolorization of walnut protease hydrolysate was obtained at an activated carbon addition of 1.2% (W/V), a pH of 4.5, a adsorption temperature of 45 ℃, and a decolorization time of 90 min. Under these conditions, the decolorization rate of walnut protease hydrolysate was 78.05%, protein recovery rate was 82.16%, and the combined weighted mean score was 80.11. The optimization process of trypsin hydrolysis and decolorization could provide some references for the development and utilization of walnut cake

Structural Characterization and Antioxidant Activity of Walnut Peptides

This study prepared and structurally characterized peptides with different molecular masses from walnut meal protein by enzymatic hydrolysis with a mixture of two proteases followed by ultrafiltration, and it also explored the antioxidant activities of walnut peptides and their protective effects on oxidative damage in HepG2 cells. The results showed that the antioxidant activity of walnut protein hydrolysate (WPH) with molecular mass < 1 kDa was the strongest, with half-maximal inhibitory concentration (IC50) of 11.47, 35.67 and 49.72 mg/mL for hydroxyl radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging capacity, respectively. Moreover, the < 1 kDa walnut peptide fraction could reduce the reactive oxygen species (ROS) content and increase the superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GSH-Rx) and glutathione peroxidase (GSH-Px) activity in HepG2 cells. The walnut peptide was irregular in shape and had a smooth surface and dense structure with numerous rough patterns and pores. The walnut peptide had a maximum absorption peak at 225 nm wavelength. The most abundant secondary structures of the walnut peptide were random coil (36.5%) and β-sheet (36.6%). These results indicate that the < 1 kDa walnut peptide has a protective effect against oxidative damage in HepG2 cells

Preventive Effect of Volvariella volvacea Fruit Body Polypeptides on Acute Alcoholic Liver Injury in Mice and Its Influence on Intestinal Microflora

To investigate the preventive effect of Volvariella volvacea fruit body polypeptides (VVFP) on acute alcoholic liver injury in mice and its influence on the intestinal microbiota, VVFP (1–3 kDa molecular mass) which had been previously obtained by our laboratory was given by gavage to mice. The mice were randomly divided into six groups: blank control, model, positive control, low-dose VVFP, moderate-dose VVFP and high-dose VVFP. Serum indexes, liver indexes and histopathological sections were compared among these groups, and 16S rDNA gene high-throughput sequencing was used to analyze the diversity of the intestinal microflora and the relative abundance at the phyla and genus levels in each sample. Results showed that VVFP significantly reduced the levels of triglycerides (TG), total cholesterol (TC), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity in the serum and malondialdehyde (MDA) in the liver, and decreased the levels of the inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and significantly increased the activities of alcohol dehydrogenase (ADH), total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-PX) in the liver. The 16S rRNA sequencing showed that VVFP significantly reduced the α-diversity indices Chao1 and observed species, increased the Shannon index, and regulated the abundance of Bacteroides, Firmicutes, Streptomyces, Lactobacillus and Vibrio, thereby reducing liver damage. In conclusion, VVFP can reduce alcoholic liver injury, which will provide a theoretical basis for the application of VVFP in the field of functional foods

Effect of Protamex Hydrolysis on Foaming Properties and Structural Properties of Corn Glutelin

The effects of different durations of hydrolysis with Protemex on the foaming properties, surface tension, physicochemical properties and static rheological properties of corn glutelin were determined. The results showed that the solubility and foaming properties of corn glutelin were significantly improved by Protamex hydrolysis. The foaming capacity of the 120 min hydrolysate was highest, which was 2.8 times higher than that of corn glutelin, and its foam stability was also good. The hydrolysate had the lowest surface tension and the highest apparent viscosity. The microscopic morphology of the foam formed was fine and uniform, with a thick protein film. With the prolongation of hydrolysis time, the average particle size of corn glutelin hydrolysates decreased continuously, the endogenous fluorescence intensity and surface hydrophobicity increased gradually, while the surface net charge decreased first and then increased. The results of Raman spectroscopy showed that after appropriate hydrolysis, the α-helix content decreased, and the random coil and β-angle contents increased; the peak intensity ratio of tyrosine residues (I850/I830) increased, and the peak intensity of tryptophan residues (I760) decreased. Nevertheless, the β-folding content changed little. Long-time hydrolysis significantly increased the content of random coil and decreased the peak intensity ratio of tyrosine residues (I850/I830). Therefore, restricted hydrolysis can change the structure and interface properties of corn glutelin, improve its foam properties, and consequently increase the potential utilization rate of corn gluten meal in the food field

Extraction of Pleurotus ostreatus Protein by the Aqueous Two-phase System and Its Characterization

To achieve green and efficient extraction of Pleurotus ostreatus protein (PP), the phase diagram of the PEG-(NH4)2SO4 aqueous two-phase system (ATPS) was constructed using the cloud point method. Protein extraction concentration was utilized as evaluation indicator to investigate the effects of ATPS factors such as the molecular weight and mass fraction of PEG, mass fraction of (NH4)2SO4, and proportion of added crude PP extraction. Furthermore, the basic components of PP including emulsification characteristics, foaming properties, and water and oil holding capacities were explored. The optimal process conditions for PP extraction were determined using response surface methodology, with PEG2000 mass fraction set at 19.5%, (NH4)2SO4 mass fraction at 22.6%, and protein crude extract mass fraction at 26%. Under these conditions, the extraction rate of protein reached 93.16%, with a protein content of 1.71 mg/mL. Analysis of the physical and chemical properties revealed uniform protein composition with an average particle size of approximately 220.2 nm. The total amino acid content was measured at 221.46 mg/g, with the highest aspartic acid (Asp) content at 25.06 mg/g. Moreover, PP exhibited exceptional emulsification stability 65.22%, foaming properties 79.87%, and water holding capacity 2.61±0.18 g/g. Compared with similar food proteins, PP protein had higher emulsifying stability, foaming ability, and water holding capacity. This study used a green, environmentally friendly, and low toxicity aqueous two-phase method to extract PP protein, providing a new approach for the green and sustainable development of protein extraction in the food industry, and a research foundation for the development of functional foods based on PP protein

火麻仁蛋白制备、性能表征及超声改性研究

火麻(Cannabis sativa L)又称大麻，桑科大麻属植物，其栽培和利用已有上千年历史。火麻仁为火麻的种子仁，收录于2015年版《中国药典》，属于药食同源物质。四氢大麻酚含量低于0.3%的火麻称之为工业大麻，随着大麻二酚(CBD)开发持续火爆，工业大麻种植面积持续攀升，火麻籽产量剧增，迫切需要进行髙值化综合利用。蛋白质是火麻仁的主要成分，其提取分离通常采用碱提酸沉技术，产品颜色重、蛋白含量低限制了火麻仁蛋白的深度利用。针对上述问题，本文研究改进盐溶盐析法提取蛋白质，在理化性质和功能特性等方面与碱提酸沉制备的蛋白质进行了比较，并探索了超声改性火麻仁蛋白，以期为火麻仁蛋白深度开发利用提供依据。取得的主要研究结果如下：1.火麻仁蛋白制备研究。火麻仁蛋白通过两种方法制备，分别是碱提酸沉法和经过实验室改进的盐溶盐析法。采用正交试验优化这两种工艺，结果表明：碱提酸沉最佳工艺为提取温度50℃、碱液pH值9.5、料液比1:20，蛋白提取率83.43%，蛋白含量85.9%，外观颜色浅黄色。盐溶盐析最佳工艺为提取温度50℃、氯化钠质量分数5%、料液比1:20, 蛋白提取率69.09%，蛋白含量94.8%，外观颜色乳白色。2.火麻仁蛋白性能表征。构建了高效液相色谱检测氨基酸组成的方法，用于探究火麻仁蛋白中17种氨基酸的组成。火麻仁蛋白氨基酸组成丰富，包含人体所需的8种必需氨基酸，且含量高于30%；同时发现精氨酸含量高，其中HPI-SE精氨酸含量可达15.09%。SDS-PAGE表明，两种方法制备的火麻仁蛋白主要成分均为麻仁球蛋白，它由六个分子量为55 kDa的亚基组成，每个亚基由一个分子量34 kDa的酸性基团和一个分子量为18或19 kDa的碱性基团通过二硫键连接组成。不同pH条件下，两种火麻仁蛋白的溶解性曲线均呈U型，但是在相同pH条件下，二者的溶解性存在较大差异。溶液pH值小于5时，HPI-SE溶解性更高，当溶液pH值大于9.0时，HPI-AE溶解性更高。火麻仁蛋白的起泡性、持水力同蛋白质的溶解性呈现正相关；当pH值远离等电点时，同种电荷的静电斥力提高了蛋白质的溶解性，改善了蛋白质的起泡性、持水力等功能特性。3.火麻仁蛋白超声改性研究。以盐溶盐析法制备的火麻仁蛋白为原料，在超声功率400 w时，超声时间的延长可显著影响火麻仁蛋白的溶解性、起泡性。超声处理未对蛋白质的氨基酸组成、肽链分子量分布产生影响，但使火麻仁蛋白的表面结构变得疏松，覆盖的球形颗粒粒径减小，部分活性位点暴露出来，进而强化了蛋白质-水的相互作用，改善了火麻仁蛋白的溶解性、起泡性。;Hemp (Cannabis sativa L) has strong adaptability and wide distribution. Its cultivation and utilization have thousand year history. Hemp seed is included in Chinese Pharmacopoeia (2015 Edition), which is medicinal and edible substance. Hemp with tetrahydrocannabinol (THC) content less than 0.3% is called industrial hemp. With the popularity of research on cannabidiol (CBD), the planting area of hemp continues to rise, and the output of hemp seed increases dramatically, so it is urgent to carry out high-value comprehensive utilization. Protein is the main component of hemp seed, and the traditional technology of alkali extraction/acid precipitation is still used in the extraction of hemp seed protein. The heavy color, low protein content of the product limit the utilization of hemp seed protein. In view of the above problems, this paper studied the method of salt extraction/salt precipitation to extracted protein, and compared it with the protein obtained by alkali extraction/acid precipitation in the aspects of and functional properties, and explored the ultrasonic modification of hemp seed protein. The main research results are as follows:1. The preparation of hemp seed protein isolate. Hemp seed protein isolates (HPIs) from defatted hemp seed meal (HPM) were prepared using two methods, one was the traditional extraction method of alkaline extraction/acid precipitation (HPI-AE), the other was a laboratory improved extraction method of salt extraction/salt precipitation (HPI-SE). The orthogonal experiment was used to optimize the extraction process of hemp seed protein. The results showed that the best extraction process of alkali extraction/acid precipitation was extraction temperature 50 ℃, pH value 9.5, and solid-to-solvent ratio 1:20 (g/mL). And the best extraction process of salt extraction/salt precipitation was extraction temperature 50 ℃, mass fraction of sodium chloride 5%, and solid-to-solvent ratio 1:20 (g/mL). The protein content of HPI-SE 94.8% was higher than that of HPI-AE 85.9%, but the protein extraction rate of HPI-SE 69.09% was lower than that of HPI-AE 83.43%, the appearance color of HPI-SE was white, while that of HPI-AE was light yellow.2. The characterization of hemp seed protein. A HPLC method was constructed to study the composition of 17 amino acids in hemp seed protein. It was found that the content of essential amino acids in HPIs was higher than 30%, the content of arginine in HPIs was high, and the content of arginine in HPI-SE was as high as 15.09%. SDS-PAGE showed that the main component of HPIs was hemp seed globulin, which was composed of six subunits with molecular weight of 55 kDa, each of which was composed of an acid subunit with molecular weight of 34 kDa and an alkaline subunit with molecular weight of 18 or 19 kDa connected by a disulfide bond. Under different pH conditions, the solubility curves of HPIs were U-shaped, but under the same pH conditions, the solubility of HPIs were different: The solubility of HPI-SE was higher than HPI-AE when the pH value was less than 5; the solubility of HPI-AE was higher than HPI-SE when the pH value was greater than 9.0. The foaming and water holding capacity of HPIs were positively related to the solubility of protein. When the pH value was far away from the isoelectric point, the electrostatic repulsion of the same charge improved the solubility, foaming capacity and water holding capacity.3. The ultrasonic modification of hemp seed protein. The effect of ultrasonic treatment on the functional properties of HPI-SE and its mechanism were studied. It was found that the solubility and foaming capacity of HPI-SE were significantly affected by the prolongation of ultrasound time when the ultrasonic power was 400 w. The results showed that the ultrasonic treatment had no effect on the amino acid composition and the molecular weight distribution of peptide chain; the surface structure of hemp seed protein became loose, the size of covered spherical particles decreased, and the content of sulfhydryl group increased. The results showed that the three-dimensional structure of hemp seed protein became loose and some active sites were exposed, which enhanced the interaction between protein and water, thus improving the solubility and foaming capacity of hemp seed protein.&nbsp;</p