Interaction and Functionality of Mixed Myofibrillar and Enzyme-hydrolyzed Soy Proteins

ABSTRACT Native and briefly heated (85 °C for 3 min) soy protein isolates (SPI) were partially hydrolyzed (4% DH) by Alcalase® and Flavourzyme™ before incorporation into a pork myofibril isolate (MPI) system. The hydrolysis of soy protein enhanced its interaction with MPI, leading to a decreased thermal stability of both soy and muscle proteins. Alcalase SPI hydrolysates, when compared with nonhydrolyzed SPI, improved viscoelastic properties and hardness of MPI gels, while Flavourzyme SPI hydrolysates had an adverse effect. Hydrolyzed SPI augmented emulsifying properties of MPI; the specific efficacy depended upon the type of enzymes used, the SPI:MPI ratio, and whether SPI was heated before hydrolysis.     

Antioxidant Activity of Soy Protein Hydrolysates in a Liposomal System

ABSTRACT: Native and heated soy protein isolate was hydrolyzed with 3 purified (pepsin, papain, and chymotrypsin) and 3 crude (Alcalase®, Protamex^TM, and Flavourzyme^TM) proteases. The hydrolysates were incubated (37 °C, 1 h) with a liposome-oxidizing system (50 μM FeCl₃/0.1 mM ascorbate, pH 7.0) to test antioxidant activities by determining the concentrations of TBARS. Degree of hydrolysis of SPI hydrolysates ranged from 1.7 to 20.6%. Both hydrolyzed and nonhydrolyzed SPI decreased TBARS (by 28 to 65%), except for papain-hydrolyzed samples. Samples of chymotrypsin- and Flavourzyme-hydrolyzed (0.5 h) preheated SPI had the greatest inhibitory effect on lipid oxidation.     

乳清分离蛋白水解物对猪肉糜抗氧化作用的研究

研究乳清分离蛋白(WPI)的碱性蛋白酶(alcalase)水解物的抗氧化能力,并将其应用于生肉糜中研究其抗氧化效果。实验分为6组,第1组为对照组,第2组加入2.0%的WPI未水解物,第3～5组中分别加入1.0%、1.5%、2.0%的水解物冻干粉(5h),第6组中加入0.02%的BHA,在冷藏过程中测定肉糜的红度值(a*)、硫代巴比妥酸值(TBARS)值、pH值、高铁肌红蛋白(MetMb)含量,并对产品的感官指标进行评定。结果表明,在贮藏7d内,与对照组相比,添加WPI水解物处理组能够显著抑制生肉糜脂肪的氧化(P<0.05),其中2%WPI水解物处理组效果最明显,能显著降低TBARS值、增加肉糜的红度值(a*)(P<0.05),且其高铁肌红蛋白(MetMb)含量仅为对照组的79%,与添加BHA处理组的水平相当。同时,WPI水解物处理组抑制脂肪的氧化效果比WPI未水解组好。因此,WPI水解物可以有效的抑制食物中脂肪氧化,且其抗氧化效果与水解物的使用量相关。     

Amino Acid Absorption in Portal Blood After Duodenal Infusions of a Soy Protein Hydrolysate Prepared by a Novel Soybean Protease D3

ABSTRACT:  The intestinal absorption of amino acids from decapeptide was investigated in rats under unrestrained conditions. The soy protein hydrolysate utilized in the experiment was produced by a novel soybean protease D3. The enzymatic features of protease D3 showed high homology with cathepsin L and cathepsin K and the average molecular weight of D3 hydrolysate is approximately 1200. We compared the intestinal absorption of D3 hydrolysate in portal blood with that of an amino acids mixture and soy protein with the same amino acid composition by determining the concentration of individual amino acids after a single administration of a nitrogen source. The absorptive velocity and intensity of each amino acid were calculated from its rate of elevation in the portal blood. And in most cases, these were higher in the D3 hydrolysate than in amino acids mixture and protein. The proportion of the amount of each amino acid absorbed in portal blood from D3 hydrolysate was much more like the composition of the administrated amino acids than like that from the amino acids mixture. The result of in vitro digestion assay indicated that D3 hydrolysate was hydrolyzed easier than the hydrolysates produced by microbial proteases. This is the first report to demonstrate that the D3 hydrolysate, which contains decapeptide as a dominant fraction, was more rapidly utilized than the amino acids mixture and protein as is the case with di-, tripeptides. This suggested that this hydrolysate could be available for nutraceutical use as well as use in nutritious foods for athletes and patients.     

Soy Protein Hydrolysate Debittering by Lysine-Acetylation

To reduce bitterness of soy protein hydrolyates, chemical modification of lysine was investigated. Isolated soy protein (ISP) was treated with N-acetylimidazole for acetylation of lysine and tyrosine. 0-acetyI tyrosine was deacetylated at pH 11. The lysine-acetylated soy protein and control protein were hydrolyzed by bromelain to the same degree of hydrolysis (10%), and then bitterness of each protein hydrolysate was evaluated. Sensory analyses indicated that bitterness of hydrolysates of lysine-acetylated ISP decreased in comparison with hydrolysates of control ISP (p<0.005). Surface hydrophobicity of hydrolysates of lysine-acetylated ISP slightly increased, and they had fewer lysine residues at the C-terminal region than hydrolysates of control ISP.     

茴香种子蛋白质水解物和肽的抗氧化和蛋白质保护潜力

茴香种子是一种可食用的香料,经常用于增进各种烹饪的香气和味道,并且因其药用价值而在不同文化中被珍藏。之前的研究报告提及了与茴香种子相关的各种生物活性。然而,对于来自茴香种子的水解蛋白质知之甚少。在本文中,作者从茴香种子中分离出总蛋白质,然后使用四种不同的蛋白酶进行酶水解。本文中也报道了水解度,pH和温度曲线。在ABTS自由基清除测定的指引下,作者使用离心过滤,C18反相和强阳离子交换(SCX)来进一步分离碱性蛋白酶消化的蛋白质水解物。与粗水解物相比,纯化水解物的自由基清除潜力增强了4.5倍。通过肽测序进一步分析纯化的SCX级分,本文也鉴定出两个肽序列,其范围为6～8个氨基酸。紧接着,文中也报道了使用白蛋白变性抑制试验来测试茴香肽的蛋白质保护潜力,其中一种茴香肽(EDVDFR)更被测出与纯谷胱甘肽(GSH)相当的EC50值。总要言之,茴香种子衍生的蛋白质水解物和茴香肽有潜力被进一步开发成促进健康的补充剂或作为食品添加剂用于保存富含蛋白质的食物。     

棉粕蛋白及其枯草蛋白酶酶解产物的组分分析

通过常规测定、凝胶层析、高效液相色谱等3种方法，测定和分析了棉粕蛋白及其枯草蛋白酶酶解产物的组份，并进行比较研究。结果表明，棉粕经过枯草杆菌蛋白酶酶解之后，可溶性蛋白比例比原来增加了1倍，游离氨基酸的含量增加了2.9倍；棉粕原料和酶解后的蛋白质产物经过SephadexG-50凝胶层析分离后均得到2个主要蛋白峰，并且它们相对分子质量分别为16300u和7950u左右，而酶解物2个峰的蛋白质含量比棉粕原料中的少；通过高效液相色谱分析，棉粕蛋白含有较多大分子蛋白，酶解之后大分子蛋白含量下降了7.71％，小分子肽的种类与含量明显增加，含量由16.36％增加至63.27％，游离氨基酸的含量由4.9％增加至19.4％。     

胃蛋白酶水解大豆分离蛋白的研究

采用胃蛋白酶对大豆分离蛋白进行酶法水解,随着酶解时间的延长,蛋白质的水解度逐渐增大,水解6h,DH为7.90%。采用分子筛凝胶过滤色谱(SE-HPLC)和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)对不同的酶解时间下大豆分离蛋白酶解物的分子结构进行表征,结果表明,胃蛋白酶选择性地酶解大豆11 S球蛋白。大豆分离蛋白经胃蛋白酶水解6 h后,分子量大于10 ku的部分占21.34%,其中主要是7 S球蛋白;分子量小于5 ku的部分所占比例为68.30%。对酶解物中的游离巯基和二硫键含量测定结果表明,随着酶解的进行,游离巯基的含量呈现先增大后减小的趋势,二硫键的含量总体变化不大。该研究旨在更好地了解胃蛋白酶水解大豆分离蛋白的机理,并为开发大豆分离蛋白酶解物产品提供理论依据。     

Physical and chemical modification of SPI as a potential means to enhance small peptide contents and antioxidant activity found in hydrolysates

The hydrolytic behaviour of the thermal and chemical modified soy protein isolate (SPI) and the antioxidant activity of the resultant hydrolysates have been evaluated in the present study. Thermal treatment, especially in combination with the addition of sodium sulfite, increased the susceptibility of protein hydrolysis due to the unfolding of proteins and the cleavage of disulfide bonds. Succinylation and acylation resulted in significant decrease in amino acids content than that of phosphorylation due to steric hindrance effect as a result of introduction of longer and bulky side chains. Thermal and chemical modification resulted in a significant increase in small peptide content found in hydrolysates, which in turn enhanced significantly the 2,2-Diphenyl-1-picryhydrazyl (DPPH) radical scavenging activity of the hydrolysates, indicating that modification of proteins before hydrolysis could be an efficient way to enhance the small peptide content with desired antioxidant activity.Industrial relevanceEnzymatic hydrolysis of SPI using selected protease has been intensively studied, however, reports on optimization of the substrate by thermal and chemical modifications before hydrolysis to obtain desired hydrolysates are still limited. In this work, SPI was thermally treated or chemical modified and then hydrolyzed by Alcalase. The results indicated that physical and chemical modification of SPI could change the levels of formaldehyde nitrogen and small peptide nitrogen, and consequently enhanced significantly the DPPH radical scavenging activity of the hydrolysates. This work was helpful to provide a feasible and economic way to enhance the contents of small peptides with desired antioxidant properties.     

Influence of Protein Source, Type, and Concentration, and Product Form on the Protein Quality of Commercial Enteral Formulas

ABSTRACT: The total, protein, and nonprotein nitrogen, 3 amino acids (lysine, histidine, and tyrosine), available lysine, and in vitro protein digestibility in enteral formulas were determined. Available lysine and protein digestibility were lower in the liquid formulas tested than in the powdered formulas. The protein quality of the formula made from soy protein isolate (soy) was lower than that of the formulas made from casein, and the protein quality of a low-protein formula was lower than that of the standard formulas. There was a statistically significant correlation between the available lysine content and protein digestibility in the polymeric formulas. New methods are required for assessing the protein quality of formulas containing hydrolyzed proteins.     

Rice Dreg Protein as an Alternative to Soy Protein Isolate: Comparison of Nutritional Properties

Rice dreg protein could be a valuable source of plant-based proteins, as an alternative to soy proteins in some food products. Here, nutritional properties of rice dreg protein were compared with those of soy protein isolate. The protein content of rice dreg protein was approximately 62.6 g/100 g sample, with large amounts of fat, carbohydrate, and ash. The denaturation temperatures of rice protein isolate from rice dreg protein were 47.4 and 97.2°C, respectively. This indicated that these proteins could be denatured during rice syrup processing to form aggregates, but were relatively more stable than rice endosperm protein and soy protein isolate. The main amino acids in rice dreg protein and rice protein isolate were Glu, Pro, Arg, Asp, and Leu, with Lys as the lowest content. Most of essential amino acids and nutritional parameters of rice protein isolate and rice dreg protein met the suggested nutritional requirements for a child according to FAO/WHO, and were relatively higher than those of soy protein isolate. In addition, rice protein isolate showed better digestibility than soy protein isolate during four hours sequential pepsin and pancreatin digestions. The final digestibility value was 96.66% for rice protein isolate compared to 91.41% for soy protein isolate. Thus rice dreg protein could potentially replace soy proteins as a good source of value-added protein for human nutrition in response to the increasing demand for plant proteins.     

Enzymatic hydrolysis of soybean protein using lactic acid bacteria

The proteolytic activity of 12 lactic acid bacteria (LAB) strains, assayed on soy protein extract at a temperature of 37 °C for 6 h, was evaluated by SDS–PAGE, reverse-phase HPLC and free-amino acid analyses. The results indicated that α- and α′-subunits of β-conglycinin were the preferred substrates for the majority of the LAB. Only a few strains exerted some action against the basic polypeptides of glycinin, this fraction was the least degraded of all soy protein fractions. Whole-cell suspensions of LAB used in this study generated hydrophilic and hydrophobic peptides from mainly soy protein fractions. RP-HPLC analyses indicated differences in the profiles of the hydrolysates, with several peaks decreasing in size and new peaks being formed. Three of the selected strains assayed increased the level of total free amino acids in the soy protein extract (SPE) and hydrolyzed principally essential amino acids and flavour precursor amino acids.     

Preparation and Functional Properties of Enzymatically Deamidated Soy Proteins

Heat-denatured soy protein was hydrolyzed by Alcalase to 2.0% or 4.0% degree of hydrolysis (DH), heated again at 100°C and deamidated with B. circulans peptidoglutaminase. The extent of deamidation was 6.0% and 8.2% for 2.0 DH hydrolysates and 12.8% and 16.0% for 4.0 DH hydrolysates heated for 15 and 30 min, respectively. Deamidation increased protein solubility and substantially enhanced emulsifying activity under mildly acidic (pH 4–6) as well as alkaline conditions. Deamidation improved emulsion stability and foaming power of heat-denatured hydrolysed soy proteins. Enzymatically deamidated soy protein hydrolysates had improved functional properties compared to nondeamidated hydrolysates and the native soy protein.     

Enzymatic hydrolysis of soy proteins and the hydrolysates utilisation

Soy proteins are very important protein source for human being and livestock. Enzymatic hydrolysis of soy protein can enhance or reduce its functional properties and improve its nutritious value. Soy protein hydrolysates were primarily used as functional food ingredients, flavour and nutritious enhancers, protein substitute, and clinical products. Conditions for hydrolysis were usually mild, whereas recently high pressure treatment attracted more interest. Degree of hydrolysis (DH) was usually between 1% and 39.5%. The main problem associated with proteolytic hydrolysis of soy protein was production of bitter taste, hydrolysates coagulation and high cost of enzymes. Bitterness reduction can be achieved by control of DH, selective separation of bitter peptides from hydrolysates, treatment of hydrolysates with exo‐peptidases, addition of various components [adenosine monophosphate (AMP), some amino acids, monosodium glutamate (MSG), etc.] to block or mask the bitter taste, and modification of taste signalling. Hydrolysates coagulation can be resolved by selecting appropriate enzymes and by applying immobilisation technology the production cost can be reduced. Enzymatic hydrolysis also enhances bioactivity of soy proteins through conversion of glycosides to aglycones, increasing antioxidant and immunoregulatory properties. Finally, future works have been discussed.     

Whey protein-derived exosomes increase protein synthesis and hypertrophy in C2­C12 myotubes

We sought to examine potential amino acid independent mechanisms whereby hydrolyzed whey protein (WP) affects muscle protein synthesis (MPS) and anabolism in vitro. Specifically, we tested (1) whether 3-h and 6-h treatments of WP, essential amino acids, or l-leucine (Leu) affected MPS, and whether 6-h treatments with low-, medium-, or high doses of WP versus Leu affected MPS; (2) whether knockdown of the primary Leu transporter affected WP- and Leu-mediated changes in MPS, mammalian target of rapamycin (mTOR) signaling responses, or both, following 6-h treatments; (3) whether exosomes isolated from WP (WP-EXO) affected MPS, mTOR signaling responses, or both, compared with untreated (control) myotubes, following 6-h, 12-h, and 24-h treatments, and whether they affected myotube diameter following 24-h and 48-h treatments. For all treatments, 7-d post-differentiated C₂C₁₂ myotubes were examined. In experiment 1, 6-h WP treatments increased MPS compared with control (+46%), Leu (+24%), and essential amino acids (+25%). Moreover, the 6-h low-, medium-, and high WP treatments increased MPS by approximately 40 to 50% more than corresponding Leu treatments. In experiment 2 (LAT short hairpin RNA-transfected myotubes), 6-h WP treatments increased MPS compared with control (+18%) and Leu (+19%). In experiment 3, WP-EXO treatments increased MPS over controls at 12 h (+18%) and 24 h (+45%), and myotube diameters increased with 24-h (+24%) and 48-h (+40%) WP-EXO treatments compared with controls. The WP-EXO treatments did not appear to operate through mTOR signaling; instead, they increased mRNA and protein levels o eukaryotic initiation factor 4A. Bovine-specific microRNA following 24-h WP-EXO treatments were enriched in myotubes (chiefly miR-149-3p, miR-2881), but were not related to hypertrophic gene targets. To summarize, hydrolyzed WP-EXO increased skeletal MPS and anabolism in vitro, and this may be related to an unknown mechanism that increases translation initiation factors rather than enhancing mTOR signaling or the involvement of bovine-specific microRNA.     

黄鲫(Setipinna taty)蛋白酶解液的抑菌活性及稳定性研究

以黄鲫为原料测定其氨基酸组成,比较风味蛋白酶、胰蛋白酶、胃蛋白酶、碱性蛋白酶和木瓜蛋白酶水解黄鲫蛋白所得酶解液对大肠杆菌的抑菌作用,并对抑菌效果最强的蛋白酶酶解液进行抑菌稳定性研究。结果表明：黄鲫蛋白必需氨基酸含量丰富,其中胃蛋白酶的水解液对大肠杆菌抑菌作用强,相对分子质量主要分布在3000～1000;黄鲫胃蛋白酶酶解液对热稳定,酸性低pH值可增强其抑菌效果,可耐受胰蛋白酶和β-内酰胺酶处理,该酶解液有作为天然抗菌剂应用的前景。     

Antioxidant Peptide Fractions Isolated from Wheat Germ Protein with Subcritical Water Extraction and Its Transport Across Caco‐2 Cells

Wheat germ protein (WGP) was extracted with subcritical water and then hydrolyzed with Alcalase 2.4 L to obtain antioxidant hydrolysates. Wheat germ peptides (WG‐P, Mw < 1 kDa) were purified by using Sephadex G‐15 column chromatography. The results showed that WG‐P‐4 possessed the strongest DPPH radical scavenging activity in comparison with other peptides fractions. In addition, free amino acids and LC‐MS/MS analysis showed that Gly‐Pro‐Phe, Gly‐Pro‐Glu, and Phe‐Gly‐Glu were the major peptides of WG‐P‐4. Interestingly, the WG‐P‐4 fractions had good absorption characteristic. Moreover, the ratio of P_app both sides of apical compartment (AP) and basolateral compartment (BL) were between 0.5 and 1.0 on Caco‐2 cell model, which indicated that transmembrane transportation was mainly passive transport. Therefore, WG‐P could exert an effective antioxidant action by across the intestinal epithelium.     

常见大豆制品中蛋白质的体外消化特性

本研究以常见大豆制品（大豆分离蛋白（soy protein isolate,SPI）、微波大豆、水煮大豆、豆浆、氯化钙豆腐和氯化镁豆腐）为研究对象,采用标准的静态体外消化模型——INFOGEST 2.0,测定不同时间点胃肠消化产物的完整蛋白、分子质量分布、游离氨基浓度和粒径大小,以探究大豆蛋白的消化特性。结果表明,不同加工方式均能促进大豆蛋白的消化。经过胃消化阶段后,几种大豆制品中部分蛋白被消化。而肠消化后,大豆蛋白均被彻底消化为短肽。相较于SPI,大豆经微波和水煮处理后,大豆蛋白的游离氨基浓度明显增加,但微波加热后大豆蛋白消化得更彻底;豆浆中大豆蛋白的消化程度低于氯化钙豆腐和氯化镁豆腐,两种豆腐中大豆蛋白的消化程度没有明显差异。总之,不同加工方式处理大豆均能不同程度地促进大豆蛋白的消化。本研究有助于更好地了解不同加工方式得到的大豆制品中大豆蛋白的消化特性,为人们摄取植物蛋白提供参考。     

大豆蛋白水解物促酸奶乳酸菌增殖及生长动力学

由于乳酸菌缺乏一些生物代谢途径,不能合成生长必需的氨基酸、维生素等物质,营养要求十分苛刻,必需依赖生长环境提供必需氨基酸、维生素等生长因子才能获得高密度生长。应用化学限定培养基进行大豆蛋白水解物、全价氨基酸和生长基本氨基酸3种氮源条件下乳酸菌的生长动力学研究,结果表明:保加利亚乳杆菌和嗜热链球菌在分子量小于5 ku的大豆蛋白水解物培养基中的最大生长速率μmax分别为0.215/h和0.262/h,约为全价氨基酸的2倍,细胞密度增加到5倍。20种全价氨基酸氮源培养基对两种乳酸菌的生长效能很低,保加利亚乳杆菌和嗜热链球菌的最大生长速率分别为0.10/h和0.12/h,pH值只达到pH4.5～5.0。基本氨基酸氮源只能满足乳酸菌生长的最低要求。分子量小于5 ku的大豆蛋白水解物比全价氨基酸对乳酸菌生长具有显著的促进作用,表明乳酸菌生长的最佳氮源是寡肽而不是氨基酸,大豆蛋白水解物可以用作乳酸菌高密度培养添加物。     

天然大豆蛋白的选择性酶解

研究了几种微生物蛋白酶水解天然大豆蛋白的选择性。用SDS-聚丙烯酰胺凝胶电泳分析酶解过程中大豆蛋白各组分的变化,电泳结果显示-βconglycinin比glycinin容易被蛋白酶水解,-βconglycinin的α’亚基比α亚基更容易水解,-βconglycinin的β亚基比α’亚基和α亚基更难水解;glycinin的酸性亚基比其碱性亚基更容易被水解。