鸭蛋清蛋白多肽体外抗氧化活性的研究

对经"蛋清水解专用蛋白酶-碱性蛋白酶"和"碱性蛋白酶-胰蛋白酶"双酶分步酶解鸭蛋清蛋白得到的多肽的抗氧化活性进行了研究。结果表明,当"蛋清水解专用蛋白酶-碱性蛋白酶"酶解蛋清蛋白的水解度为21%时,多肽的抗氧化活性最高,其对二苯代苦味酰基自由基(DPPH·)、羟基自由基(·OH)、超氧阴离子(O2-·)的清除率和对大豆卵磷脂过氧化作用的抑制率分别为75.76%、84.17%、72.73%和47.59%;当"碱性蛋白酶-胰蛋白酶"酶解蛋清蛋白的水解度为15%时,多肽的抗氧化活性最高,其对DPPH·、·OH、O2-·的清除率和对大豆卵磷脂过氧化作用的抑制率分别为75.15%、93.84%、58%和40.51%。产物肽的分子量均分布在小于5300D的范围内。     

Influence of degree of hydrolysis on functional properties,antioxidant activity and ACE inhibitory activity of peanut protein hydrolysate

Functional properties, antioxidant and Angiotensin-converting enzyme (ACE) inhibitory activities of peanut protein isolate (PPI) and peanut protein hydrolysate (PPH) prepared using Alcalase, at different (10%, 20%, 30% and 40%) degrees of hydrolysis, (DH) were investigated. Hydrolysis (at DH > 10%) significantly (p < 0.05) improved the solubility (>80%) of PPI, especially in the pH range of 4–6. However, PPI showed better emulsifying and foaming properties than PPH (p < 0.05). As DH increased, ferrous ion chelating activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and ACE inhibitory activity of PPH increased, while reducing power decreased (p < 0.05). Bleaching of beta-carotene by linoleic acid was suppressed better by PPI and PPH at 10% DH than of PPH at higher DH. Thus, the results reveal that DH affects functional properties, antioxidant and ACE inhibitory activities of peanut protein.     

Effect of thermal treatment on the antioxidant activity of egg white hydrolysate and the preparation of novel antioxidant peptides

Heat treatment will affect the nutritional properties and potential bioactivity of food materials. The aim of this work was to evaluate the effect of different thermal treatment (4, 56, 65 and 100 ℃) and in vitro gastrointestinal digestion on the antioxidant activity of egg white hydrolysate. The results demonstrated that egg white hydrolysate treated at 65 ℃ exhibited the highest antioxidant. Remarkably, the simulated digestion significantly increased antioxidant activity of egg white hydrolysate. Furthermore, we identified twenty-four potential antioxidant peptides by performing mass spectrometry and bioinformatic analysis. Six peptides were selected based on the activity prediction score of the online tool. The results showed that P6 (ACPECPK) possessed the most outstanding antioxidant properties and had low cytotoxicity and allergenicity. Bioinformatics technology combined with biochemical assays may offer a way for discovering novel antioxidant peptides from different kinds of food under various heat treatment conditions.     

酶解对蛋清蛋白液起泡性能和乳化性能的影响

利用碱性蛋白酶水解蛋清蛋白,主要研究了酶用量、底物浓度和酶解时间对蛋清蛋白液起泡性能和乳化性能的影响。实验结果表明,酶解条件对蛋清蛋白液的起泡性能和乳化性能有一定程度的影响,当碱性蛋白酶酶解温度为45~50℃,pH6~8.5时,其最佳酶解条件为酶用量4%,底物浓度3%,酶解时间6h。在此最佳酶解条件下获得的蛋清蛋白酶解液起泡性为27.65%,发泡能力178.26,泡沫稳定性60.33%,乳化容量37.86%,乳化稳定性127.23,乳化活性指数134.53,乳状液稳定指数1.83。      

Enzymatic hydrolysis of fish gelatin under high pressure treatment

The effect of high pressure treatment on the hydrolysis of fish skin gelatin and the antioxidant properties of the hydrolysates was evaluated. Hydrolysis was performed by Alcalase, collagenase, trypsin and pepsin both at atmospheric pressure and under high pressure (100 MPa/15 and 30 min, 200 MPa/15 and 30 min, 300 MPa/15 min). The degree of hydrolysis (DH) was determined according to the base consumption via pH‐stat as well as the percentage of soluble nitrogen in trichloroacetic acid (TCA). About 16% of nitrogen in the gelatin was still soluble in 10% TCA, indicative of a significant amount of low molecular weight components. The high pressure treatment increased the DH with all the enzymes used between 5% and 10%. However, in comparison with the hydrolysates obtained at atmospheric pressure after 3 h of digestion under controlled conditions (using a pH‐stat), the radical scavenging capacity of the pressured hydrolysates was only significantly enhanced when Alcalase or collagenase were used. High pressure may be a useful tool for the quick obtaining of gelatin hydrolysates with antioxidant capacity.     

Evaluation of plasma,high‐pressure and ultrasound processing on the stability of fructooligosaccharides

Fructooligosaccharides (FOS) are among the main carbohydrates with prebiotic activity, and they are the most applied functional carbohydrate ingredient in the food industry. FOS are known to hydrolyse when subjected to thermal processing, thus partially losing its functional properties. In this study, we evaluate whether three nonthermal technologies are suitable for processing FOS regarding its stability after processing. FOS were subjected to ultrasound, high‐pressure processing (HPP) and atmospheric cold plasma (ACP). The FOS solution, 70 g L^?1, was set at a concentration recommended for human intake. The treatments were carried out at operating conditions usually used for microbial inactivation in foods (HPP at 450 MPa for 5 min; US at 600–1200 W L^?1 for 5 min; ACP at 70 kV for 15–60 s). NMR and HPLC analysis of the FOS components showed that ACP, ultrasound and HPP have not induced any significant change on FOS concentration (<2.0%) nor on the degree of polymerisation of the FOS (<3.3%). Contrarily to what is reported for thermal treatments, these nonthermal technologies were considered suitable for FOS processing.     

Biochemical properties and antioxidant activity of myofibrillar protein hydrolysates obtained from patin (Pangasius sutchi)

Antioxidant activities of myofibrillar protein hydrolysates (MPH) prepared from patin (Pangasius sutchi) using papain and Alcalase^® 2.4 L with different degrees of hydrolysis (DH) were investigated. With a DH of 65.83%, the hydrolysate prepared with papain exhibited the maximum of 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging activity (71.14%) with a reducing power of 0.310. At a concentration of 1 mg mL^?1, the papain‐MPH exhibited a Trolox equivalent antioxidant capacity (TEAC) of 70.50 ± 1.22 μmol g^?1 protein. With a DH of 83.6%, the Alcalase‐MPH had the highest metal‐chelating activity. Low molecular weight peptides showed higher antioxidant activities than high molecular weight peptides. Both papain‐MPH and Alcalase‐MPH contained high amounts of the essential amino acids (48.71% and 48.10%, respectively) with glutamic acid, aspartic acid and lysine as the dominant amino acids. These results suggest that the protein hydrolysates derived from patin may be used as an antioxidative ingredient in both functional food and nutraceutical applications.     

Effect of technological practices on individual betalains and antioxidant activity of Columbian betalain‐rich raw materials

The effect of different technological practices on ulluco (ullucus tuberosus) and Opuntia dillenii has been scrutinised. Their stability at different pHs and temperatures of storage or processing over time was monitored. Our aim was focused on the determination of individual betalains and antioxidant activity, not previously conducted in conjunction with these raw materials. On the basis of the results, it could be asserted that the ullucus tuberosus and Opuntia dillenii were more suitable for being added to low‐acidic foods (pH 5 and 6), in the light of the higher values of betalains and antioxidant capacity (1.3‐fold higher compared with pH 4). With regard to the temperature, cold storage conditions (4 °C) were optimal to increase or maintain as possible the initial content of betalains and antioxidant capacity. After cooking (80 °C), the identified betalains completely disappeared, but the low‐acidic conditions (pH 6) favoured the greater antioxidant activity when kept at that temperature.     

Effect of NaCl on thermal aggregation of egg white proteins from duck egg

Thermal aggregation of duck egg white solution (1 mg protein/ml, pH 7) was monitored in the presence of different NaCl concentrations (0–6%, w/w) across the temperature range of 20–90 °C. Duck egg white solution exhibited higher turbidity with coincidental increases in surface hydrophobicity and decreases in sulfhydryl group content as temperatures increased from 70 to 90 °C (p < 0.05). As NaCl concentration increased, the negative charge decreased, with coincidental increases in particle size of aggregate after heating to 90 °C. As visualised by confocal laser scanning microscopy, larger clusters of protein aggregates were observed with increasing NaCl concentrations. Major duck egg white protein with molecular mass of 45 kDa disappeared in the presence of 2–6% NaCl after heating above 80 °C, regardless of concentrations. Therefore, NaCl, especially at high concentrations, could induce thermal aggregation of duck egg white protein, which could determine the characteristics of salted egg white after heating.     

Compositions and antioxidant properties of protein hydrolysates from the skins of four carp species

Compositions and antioxidant properties of protein hydrolysates prepared from four carp skins: black carp, grass carp, silver carp and bighead carp, using pepsin, with a degree of hydrolysis (DH) of 6–15%, were investigated. The yield of freeze‐dried hydrolysates was in the range of 54–62 g/100 g (dry skin). The content of protein and ash in four freeze‐dried hydrolysates was 72–81% and 8–17%, respectively. All hydrolysates contained high amount of hydrophobic amino acid residues (389–480 residues/1000 residues). Meanwhile, their antioxidant properties were evaluated by in vitro assays. The results revealed that all hydrolysates possessed potent antioxidant activities and showed dose dependency as the activity increased with sample concentration, capable of scavenging 72–88% of DPPH and 61–69% of hydroxyl radicals, respectively, at the highest tested concentration. The hydrolysates exhibited high reducing power and β‐carotene–linoleic acid oxidation inhibition. Among the four hydrolysates, the hydrolysate derived from bighead carp skin was superior to others in terms of yield, DH and antioxidant activities.     

超声波对蛋清蛋白-果糖美拉德反应体系的影响

以蛋清蛋白-果糖体系（EW-F）为对象,研究超声波对反应体系pH、自由氨基、1,1-二苯基-2-三硝基苯肼（DPPH）自由基清除能力、还原力和亚硝酸根离子清除能力的影响。结果表明:超声波能促使反应体系pH和自由氨基含量降低,促进美拉德反应进程,提高美拉德反应体系的抗氧化能力。      

不同酶水解对鸡蛋清蛋白降解和潜在致敏性的影响

酶水解是降低食物过敏原致敏性的一种常用手段,本文分别利用胃蛋白酶、木瓜蛋白酶、中性蛋白酶和碱性蛋白酶水解鸡蛋清蛋白,通过三羟甲基氨基甘氨酸-十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（Tricine-SDS-PAGE）,并结合水解度（邻苯二甲醛法）分析监测蛋清蛋白的酶解过程,进一步利用制备的兔抗蛋清蛋白多克隆抗体血清和鸡蛋过敏患者血清池评估酶解产物的抗原性和致敏性。结果表明:木瓜蛋白酶和碱性蛋白酶能够有效的水解蛋清蛋白,并且所得酶解产物的抗原性和致敏性较低,其中,木瓜蛋白酶水解蛋清蛋白后产物的抗原性降低了59.23%,致敏性降低了4.91%;碱性蛋白酶水解蛋清蛋白后产物的抗原性降低了57.61%,致敏性降低了4.55%。因此,木瓜蛋白酶和碱性蛋白酶对鸡蛋清蛋白降解及致敏性降低方面均有显著影响。      

Improving antioxidant activities of whey protein hydrolysates obtained by thermal preheat treatment of pepsin,trypsin, alcalase and flavourzyme

Antioxidant activity of whey protein concentrate (WPC) hydrolysates was evaluated. Hydrolysates were obtained by pepsin, trypsin, alcalase and flavourzyme enzymatic reaction and preheat treatment of 95 °C for 5 or 10 min. The degree of hydrolysis (DH) was determined by 2,4,6‐trinitrobenzene sulphonic acid method, and antioxidant properties were determined by three spectrophotometric methods: ferricyanide method, ferric reducing/antioxidant power assay and diphenyl‐picryl hydrazinyl radical‐scavenging activity. For all the enzymes, briefly preheat treatment (95 °C/5 min) increased DH of WPC. Alcalase hydrolysates showed the highest antioxidant activity by three methods. The changes in antioxidant activity was coincidental with the changes in DH (R² = 0.988). Hydrolysates analysed by polyacrylamide gel electrophoresis and high performance liquid chromatography indicated that the α‐La was hydrolysed completely by pepsin, trypsin and alcalase and was resistant to flavourzyme to some extent; β‐lactoglobulin was only completely hydrolysed by trypsin and alcalase. Results indicated that antioxidant activity of hydrolysates was greatly related to the exposure of amino acid residues.     

水解度对螺旋藻肽乳化性、起泡性及抗氧化性的影响

研究了水解度对螺旋藻肽乳化性、起泡性以及抗氧化能力的影响。结果表明,随着水解时间的延长,螺旋藻肽的水解度逐渐增大。水解过程中,螺旋藻肽的起泡性、DPPH自由基清除能力以及还原力均随着水解度的增加先增大后减小,羟基自由基清除能力随着水解的进行先减小后增大,达到最大后再减小。而泡沫稳定性、乳化性、乳化稳定性则随着水解度的增大逐渐减小。这说明,在螺旋藻肽的生产过程中,并不是水解度越大越好,而应根据对产品物化性质与抗氧化能力的要求,确认最佳水解度。      

Effects of high‐pressure processing and enzymatic dephosphorylation on phosvitin properties

BACKGROUND: Egg phosvitin could be a good source of functional peptides. Enzymatic dephosphorylation and high‐pressure processing combined with thermal treatment applied before proteolysis could produce phosvitin hydrolysates with different properties compared to its native form. RESULTS: Phosvitin structure was maintained overall during high‐pressure treatment of 600 MPa applied at an initial temperature of 65 °C regardless of the pH and duration of treatment, confirming the high structural stability of this phosphoprotein. Treatment of phosvitin with phosphatase increased the degree of dephosphorylation from 24% to 63%, after 2 and 18 h, respectively. Moderate dephosphorylation of phosvitin prior to proteolytic digestion improved its hydrolysis, allowing formation of peptides with a molecular weight lower than 17,000 kDa as determined by size exclusion chromatography. Angiotensin‐converting enzyme (ACE) inhibition and antioxidant activity of dephosphorylated and protease‐treated phosvitin was increased by 52% and 39%, respectively, as compared to protease‐digested native phosvitin. CONCLUSION: Enzymatic dephosphorylation before proteolysis mimicking in vivo gut conditions improved ACE inhibition and antioxidant activity of phosvitin hydrolysates. Copyright © 2012 Society of Chemical Industry     

Effect of high‐pressure processing on myofibrillar protein structure

Modification of myofibrillar proteins induced by high‐pressure processing has been investigated at pressures ranging from 50 to 600 MPa for 10 min at 20 °C. Analysis by spectroscopic methods and circular dichroism of myofibrillar proteins in phosphate buffer pH 6.0 containing 0.6 M KCl showed no changes in the secondary structure of proteins. However, study of protein conformation by quasielastic light scattering and gel filtration chromatography proved the emergence of aggregation after treatment at pressures higher than 300 MPa. This aggregation was accompanied by enhanced binding of anilino‐1‐naphthalene‐8‐sulphonic acid, which indicated an increase in hydrophobic bonding of myofibrillar proteins. Modification of the tertiary and quaternary structures of proteins may induce a molten globule state. Copyright © 2003 Society of Chemical Industry