In vitro haem solubility of red cell fraction of porcine blood under various treatments

An in vitro peptic digestion at gastric pH 2.0 was used to assess the haem solubility of red cell fraction (RCF) of porcine blood derived samples. The in vitro haem solubility of the RCF decreased greatly in the denaturated form of haemoglobin. However, the native haemoglobin was susceptible to be hydrolysed by enzyme mixture of Flavourzyme and Alcalase. The in vitro digestion of the hydrolysates showed that the highest haem solubility was reached at degree of hydrolysis between 8.75% and 12.33%. The in vitro haem solubility was positively correlated with content of the highly soluble peptides with molecular weights ranged from 7.5 kDa to 1 kDa, but negatively with peptides fractions >7.5 kDa and <1 kDa, mostly due to the precipitation of the highly molecular weight fraction (>7.5 kDa) and part of small peptides (<1 kDa) with higher haem/peptide ratio, which was confirmed by gel filtration chromatograms and by the analysis of the precipitate at pH 2.0.     

碱性蛋白酶限制性水解对高温菜籽粕蛋白功能性质的影响

为改善高温菜籽粕蛋白质的功能性质,用碱性蛋白酶对其进行限制性水解,并研究不同水解度(DH)高温菜籽粕蛋白功能性质及相对分子质量分布。结果表明：碱性蛋白酶限制性水解高温菜籽粕蛋白的溶解度、乳化性和吸油性均有所改善,其中溶解度随水解度增加而增加,pH7.0 时DH为10% 的高温菜籽粕蛋白的溶解度达63.82%,是原蛋白溶解度的2.1 倍;DH 为2.0% 的水解蛋白乳化性最好,pH6.0 和pH8.0 时乳化指数分别为0.43 和0.49,比原蛋白乳化指数分别高0.13 和0.11;DH 为8% 的水解蛋白吸油性最好,为4.39g/g。水解后高温菜籽粕蛋白的某些功能性质与其相对分子质量分布有一定的关系,需控制高温菜籽粕蛋白水解度以获得某种良好的功能性质。     

复合酶制备鱼蒸煮液水解肽及其抗氧化活性研究

目的:研究鳀鱼蒸煮液的最佳酶解工艺条件,并分析所制备水解肽的分子量分布和抗氧化特性。方法:以三氯乙酸氮溶解指数(Trichloroacetic acid-nitrogen soluble index,TCA-NSI)为酶解效率的评价指标,在单因素实验基础上,运用中心组合设计法优化水解肽的制备工艺,并对酶解产物的分子量分布及抗氧化活性进行分析。结果:鳀鱼蒸煮液的最佳酶解条件为酶解时间45 min、酶解温度54.5 ℃、酶解pH8.2、碱性蛋白酶与中性蛋白酶比例1:1,在此条件下TCA-NSI可达76.51%。所制备的水解肽中分子量低于1500 Da的多肽含量可达81.941%。水解肽对DPPH自由基、羟自由基和超氧阴离子自由基清除率的IC₅₀分别为2.45、1.37和3.45 mg/mL,表明其具有较强的抗氧化活性。结论:采用复合酶法可高效酶解鳀鱼蒸煮液,并获得具有较强抗氧化活性的水解肽,可为鳀鱼蒸煮液高值化利用及活性肽产品开发提供理论依据。     

正交试验优化哈蟆油蛋白双酶法水解工艺

目的：考察双酶法制备哈蟆油蛋白的最佳工艺。方法：以哈蟆油为原料,采用柠檬酸浸提和水煎煮的方法提取哈蟆油蛋白,先后加入胃蛋白酶和碱性蛋白酶进行酶解,根据酶解后哈蟆油蛋白相对分子质量分布,应用单因素和正交试验确定哈蟆油蛋白酶解的最佳条件。结果：最佳酶解条件为胃蛋白酶与底物比（m/m）1∶2 000、酶解时间2 h、碱性蛋白酶与底物比（m/m）1∶100、酶解时间6 h,酶解后哈蟆油蛋白相对分子质量小于5 000所占的比例为94.85%,哈蟆油蛋白中蛋白质含量为49.85%。结论：胃蛋白酶与碱性蛋白酶结合使用可以有效地降低哈蟆油蛋白的相对分子质量,利于人体吸收。     

Iron-binding peptides from whey protein hydrolysates: Evaluation,isolation and sequencing by LC–MS/MS

Iron–peptide complexes have been considered a promising source of more bioavailable iron, with reduced side effects as compared to iron salts. Whey protein isolate (WPI) hydrolyzed by alcalase, pancreatin or flavourzyme was ultrafiltered (cut off 5 kDa) and their fractions – retentates and filtrates – were evaluated for iron-binding capacity. The Fe–hydrolysate complexation reaction resulted in a dramatic increase in iron solubility at pH 7.0, from 0% to almost 100%. This result was obtained regardless of the molecular mass profile or the enzyme used to obtain the samples. Fractions from hydrolysate obtained with pancreatin (HP) were chosen to continue the study. The complexes formed with both fractions from HP were stable under simulated gastric digestion (50.8–89.4%). To identify the peptides with iron-binding capacity, the HP fractions were isolated by IMAC-Fe^3 +, and the retentate showed higher relative concentrations of iron-binding peptides than the filtrate. Iron-binding peptide sequencing, accomplished by LC–MS/MS, showed Glu and/or Asp in all the sequences, and their carboxylic groups were amongst the main iron-binding sites. WPI hydrolysis with pancreatin yields peptides that can form iron complexes with the potential to increase iron bioavailability and reduce its pro-oxidant effect.     

Continuous production of wheat gluten peptide with foaming properties using immobilized enzymes

Gluten peptides are prepared using limited hydrolysis of wheat gluten, resulting in improved solubility and physico-chemical properties. In general, the hydrolysis is performed using a batch-wise process. In this study, we developed a bioreactor system that can continuously produce gluten peptides with foaming properties. Two kinds of acid protease, pepsin and rapidase, were immobilized on porous chitosan beads. The partial deamidation of gluten in advance increased initial velocity of hydrolysis by immobilizing protease and also worked to enhance foaming properties. A packed-bed reactor filled with immobilized protease was designed, and operating parameters were optimized. The optimized conditions were as follows: pH, 3.0; temperature, 40 °C; substrate concentration, 40 mg/ml; and space velocity, 2.0 h^–1. Based on these results, a bench-scale reactor was manufactured to determine the stability of continuous operation. The half-life of the reactor was approximately 45 days, and both productivity and quality were stable and excellent.     

Physicochemical characteristics and shelf life estimation of maize/soybean extrudates added with bovine haemoglobin

Maize/soybean (88:12) extrudates fortified with bovine haemoglobin as a source of iron with the addition of iron absorption enhancers were developed. The aims were to evaluate physicochemical characteristics and to predict shelf life by sensory analysis. Extrudates were made using a Brabender 20 DN single‐screw extruder. Specific mechanical energy consumption (SMEC), expansion ratio, specific volume, water solubility and water absorption were measured. Extrudates were stored at three temperatures (12.5, 30 and 45 °C) for 50 days. Colour, crispness and rancid flavour were evaluated by a trained panel. Both addition of haemoglobin and enhancers did not produce significant differences for SMEC, expansion and specific volume. Flavour was the attribute with the greatest degree of damage during storage, thus was used for predicting shelf life. The expanded product added with haemoglobin, and Na₂EDTA could be kept for 15 months at 15 °C or 10 months at 22 °C without rancid flavour development.     

Alcalase蛋白酶酶解高温豆粕制备水溶性大豆多肽

以氮溶指数为指标,应用Alcalase蛋白酶酶促降解高温豆粕,以获得高得率的水溶性大豆肽。酶促降解的优化实验结果表明:在加酶量1750U/g、底物浓度4%（w/w）、温度60℃、pH9.0的条件下酶促降解3h所得到的水解产物其氮溶指数达到了62.97%,比水解前提高了47.87%;酶解前后大豆蛋白的SDS-PAGE图谱表明:Alcalase蛋白酶可以催化大豆蛋白迅速地降解,水解1h后,7S蛋白的α-亚基,α’-亚基,β-亚基以及11S的酸性亚基已经完全消失,水解3h后,11S的碱性亚基也基本消失,且大多数的肽类分子量在20ku以下;与以大豆分离蛋白为原料制备的多肽相比,以高温豆粕为原料制备的多肽苦味值较低。      

Effects of pH and salt concentration on functional properties of rambutan (Nephelium lappaceum L.) seed albumin concentrate

Searching new protein sources is essential due to an increase in protein demand. In this study, rambutan seed albumin concentrate (RSAC) with the protein content of 80.8% was isolated from defatted rambutan seed meal. The effects of pH and sodium chloride concentration on solubility and functional properties of RSAC were investigated. RSAC had minimum solubility at pH 4. Water absorption capacity at pH 7 and oil absorption capacity of RSAC were 0.79 and 6.13 mL g^?1, respectively. Both foaming and emulsifying capacities achieved maximal levels at pH 12. In sodium chloride solution, foaming capacity and stability achieved maximal levels at the concentration of 0.6 mol L^?1, while the highest emulsifying capacity and stability were noted at the concentration of 0.2 mol L^?1. The least gelation concentration of RSAC was 100 g L^?1 and this value decreased by five times as salt concentration in the protein solution was 0.6 mol L^?1. RSAC was a potential functional ingredient in food processing.     

响应面法优化南极磷虾蛋白酶解物溶解性工艺

以南极磷虾蛋白酶解物的溶解性为指标,在单因素实验的基础上,采用响应面优化实验分析了南极磷虾蛋白酶解过程中酶与底物比、时间、温度、pH等因素对南极磷虾蛋白酶解物溶解性的影响,建立了南极磷虾蛋白酶解物溶解度与各因素的最佳工艺的回归模型并进行了验证。实验从4种酶中优筛选出木瓜蛋白酶作为酶解用酶,在此基础上,结合实际生产情况确定木瓜蛋白酶酶解南极磷虾蛋白的最适工艺为:酶与底物比0.25%(w/w)、酶解时间30 min、酶解温度55 ℃、酶解pH6.0,此时南极磷虾蛋白酶解产物的溶解度为12.06%±0.21%。因此,酶解改性能够改变南极磷虾蛋白的溶解性。     

响应面法优化秋刀鱼酶解制备抗氧化活性肽的工艺

采用酶解法从秋刀鱼肌肉中提取抗氧化活性肽,以水解度(DH)、TCA-可溶性肽含量、DPPH自由基清除率、Fe3+还原力、·OH清除率以及O2?·清除率为指标,从六种商业用酶中(中性蛋白酶、碱性蛋白酶、风味蛋白酶、木瓜蛋白酶、菠萝蛋白酶、胰蛋白酶)筛选出最适蛋白酶.以料液比、酶添加量、酶解时间、温度、pH五个因素进行单因...     

Grass carp peptides hydrolysed by the combination of Alcalase and Neutrase: Angiotensin‐I converting enzyme (ACE) inhibitory activity,antioxidant activities and physicochemical profiles

In this study, grass carp peptides were prepared by enzymatic hydrolysis of grass carp protein using the combination of Alcalase and Neutrase, and angiotensin‐I converting enzyme (ACE) inhibitory activity in vitro, antihypertensive activity in vivo, antioxidant activities, and physicochemical properties of peptides achieved from grass carp protein were characterised after ultrafiltration and desalted processes using mixed ion exchange resins. The purified peptides exhibited strong ACE inhibitory activity (IC₅₀ = 105 μg mL^?1), antihypertensive activity with the maximal drop for systolic blood pressure (SBP) of 43 mmHg at a dosage of 100 mg per kg body weight in spontaneously hypertensive rat (SHR), and antioxidant activities indicated by thiobarbituric acid‐reactive substance values in a liposome‐oxidising system, radical‐scavenging activity and chelation of metal ions (Fe²⁺). The molecular weight of peptides was <1000 Da. Compared to grass carp protein, the peptides separated from enzymatic hydrolysates possessed similar amino acid compositions, but contained higher concentrations of essential amino acids. Moreover, the peptides exhibited excellent solubility at a wide range of pH values from 2 to 10, and lower apparent viscosity than the protein. The peptides separated from enzymatic hydrolysates might be used as a promising ingredient in antihypertensive functional foods and nutraceuticals.     

蛤蜊肽的制备工艺优化及其增强免疫活性

目的:以菲律宾蛤仔(Ruditapes philippinarum)为原料,研究蛋白肽制备工艺及其增强免疫活性。方法:以蛋白水解度为评价指标,筛选最适蛋白酶,采用单因素实验和响应面试验确定最佳酶解条件;氨基酸分析仪分析蛤蜊肽氨基酸组成;通过小鼠器官/体重比值、小鼠脾淋巴细胞转化实验、血清溶血素实验、小鼠腹腔巨噬细胞吞噬鸡红细胞实验、NK细胞活性实验评价蛤蜊肽的增强免疫活性。结果:菲律宾蛤仔蛋白肽制备的最适蛋白酶为胰蛋白酶,最佳酶解条件为温度48.4℃,pH8.0,加酶量3795 U/g,料液比1:2,水解时间4 h,该工艺下蛋白水解度达到15.33%,蛋白肽重均分子量为418 Da;其氨基酸组成合理,必需氨基酸占比达到41.48%;经口给予小鼠不同剂量的蛤蜊肽30 d,与空白对照组比较,小鼠的脏器比值无显著影响(P>0.05),低剂量(700 mg/(kg·d))与高剂量(2800 mg/(kg·d))下能显著提高血清溶血素水平(P<0.05),低剂量(700 mg/(kg·d))与中剂量(1400 mg/(kg·d))下能显著提高小鼠腹腔巨噬细胞吞噬鸡红细胞吞噬率(P&l...     

Physicochemical,thermal, and rheological properties of acid-hydrolyzed sago (Metroxylon sagu) starch

The effects of acid hydrolysis on physicochemical and rheological properties of sago starch were investigated. Sago starch was hydrolyzed in hydrochloric acid at 50 °C for 6, 12, 18, and 24 h. The molecular weight distribution, physicochemical, thermal, and rheological properties of acid-hydrolyzed sago starch (AHS) were determined. After 24 h of hydrolysis, molecular weight of amylopectin and amylose were decreased to 3.57 × 10⁵ and 6.5 × 10⁴ g/mol, respectively. Differential scanning calorimetry studies showed that the gelatinization temperature and enthalpy of AHS increased with increasing degree of hydrolysis. Hydrolyzed sago starch containing low molecular weight fractions exhibited cold water solubility up to 100%. Setting temperature of AHS decreased with increasing hydrolysis time but amylose content and gel strength increased in the first 12 h of acid hydrolysis but decreased with extended hydrolysis time. Hydrolyzed sago starch in concentrations lower than 8 g starch per 100 g water was cold water soluble and could be used to modify properties of starch for specific applications such as yogurt and concentrated milk processing.     

Antioxidant activities and functional properties of soy protein isolate hydrolysates obtained using microbial proteases

Soy protein isolate (SPI) hydrolysates were prepared using microbial proteases to produce peptides with antioxidant activity. The process parameters (substrate and enzyme concentrations), hydrolysis time, functional properties and the effects of ultrafiltration were further investigated. The results showed that the soy protein isolate exhibited a 7.0‐fold increase in antioxidant activity after hydrolysis. The hydrolysis parameters, defined by the experimental design, were a substrate concentration of 90 mg mL^?1 and the addition of 70.0 U of protease per mL of reaction. The maximum antioxidant activities were observed between 120 and 180 min of hydrolysis, where the degree of hydrolysis was approximately 20.0%. The hydrolysis increased solubility of the soy protein isolate; however, the hydrolysates exhibited a tendency to decrease in the interfacial activities and the heat stability. The SPI hydrolysates fractions obtained by ultrafiltration showed that the enzymatic hydrolysis resulted in samples with homogenous size and strong antioxidant activity.     

酶水解制备具有潜在免调节活性大豆肽的研究

由于已有的一些研究报道初步表明带正电荷的小分子肽具有免疫调节作用,本研究分别应用Alcalase、Flavourzyme、Protease A和Peptidase R四种商业酶,单独使用或将它们进行组合,分别以大豆分离蛋白（SPI）、可溶性大豆蛋白（SSP）和不溶性大豆蛋白（InSP）为底物,在不同的酶-底物比、底物浓度、pH和温度条件下进行水解大豆蛋白,测定了水解度、水解产物的分子量分布和带正电荷肽的相对含量.结果表明,Alcalase在相同条件下可以获得较高的水解度和较大的水解蛋白平均分子量;以InSP作为底物的水解产物中带正电荷肽的相对含量最高.水解条件对水解度有较明显的影响,但是平均分子量和正电荷肽相对含量的影响较弱。     

Study of the fermentation conditions and the antiproliferative activity of rapeseed peptides by bacterial and enzymatic cooperation

Based on previously determined preparation conditions of rapeseed peptides by mixed solid‐state fermentation, the optimisation of the fermentation conditions of rapeseed meal to obtain rapeseed peptides using the cooperation of mixed bacteria and a neutral protease was studied. The appropriate parameters of synergistic fermentation using mixed bacteria and a neutral protease were as follows: initial fermentation pH of 6.5, fermentation temperature of 35 °C, fermentation time of 2 day and the added amount of neutral protease of 200 U g^?1 weight of dry rapeseed meal. Furthermore, Tricine‐SDS‐PAGE analysis of the rapeseed peptide extracts was performed, and the amino acid composition of the rapeseed meal before and after fermentation was evaluated. Then, the analysis of cytotoxicity and antiproliferative activity of the extracts on human HepG2 liver cancer cells, human MCF‐7 breast cancer cells and human HeLa cervical cancer cells indicated that the extracts had an antiproliferative effect on the cancer cells.     

酶解菜籽粕制备多肽的研究

本试验以菜籽粕为原料,从四种蛋白酶中挑选出中性蛋白酶和碱性蛋白酶对菜籽粕进行同步复合酶解。分别考察了不同的加酶量、酶比、料液比和时间对多肽得率的影响,并利用响应面分析法对混合蛋白酶水解菜籽粕的条件进行了优化。结果表明,在加酶量固定为4500 U/g,温度50℃,pH为8.0,料液比1:8及碱性蛋白酶:中性蛋白酶为3:1条件下酶解6.5 h,可使多肽得率达到54.89%。     

Enzymatic hydrolysis of rice dreg protein: Effects of enzyme type on the functional properties and antioxidant activities of recovered proteins

The effects of various proteases on the formation and characteristics of rice dreg protein hydrolysates (RDPHs) were investigated. Enzymatic hydrolysis of often under-utilised rice dreg protein (RDP) with different enzymes studied here was found to significantly improve protein content and solubility. RDPHs prepared by alkaline protease showed better protein recovery, producing higher protein content with much smaller peptides, while hydrolysates generated by Protamex showed the highest antioxidant activities with more than 80% solubility over a wide pH range. The results indicated that the type of protease greatly influenced the molecular weight and amino acid residue composition of RDPH. The enzyme type also determined the functional properties and antioxidant activity of the recovered proteins. It was found that an optimum allocation of alkaline protease in addition to the Neutrase enzyme could be an appropriate strategy to produce RDPH with desirable functionalities, antioxidant properties, and low salt content.     

The role of non-haem proteins in meat haemoprotein digestion

The influence of additional protein on the in vitro digestion of haem compounds was investigated. When either (59)Fe-labelled haemoglobin in blood or unlabelled purified haemoglobin were digested in vitro, the formation of low molecular weight (< 10,000), dialysable, iron degradation products was very limited (<18% of the total iron) and consisted mostly of haematin compounds. The presence of additional protein, in the form of bovine serum albumen or gelatin, greatly increased the formation of low molecular weight (<10,000) degradation products; the increase being proportional to the concentration and type of added protein. In these systems approximately two-thirds of the low molecular weight iron compounds were non-haematin in character. However, the digestion of aqueous muscle extracts resulted in the greatest formation of low molecular weight (<10,000) iron degradation products (>70% of the total iron), nearly all of which were non-haematin compounds. A hypothesis is presented explaining how haemoprotein degradation occurs in meat and related systems during normal physiological digestion.