Functional Properties of Hydrolysates from Proteolysis of Heat-denatured Whey Protein Isolate

Heat-denatured whey protein isolate was hydrolyzed with trypsin, α-chymotrypsin, Alcalase or Neutrase to 2.8, 4.3, 6.0 or 8.0% degree of hydrolysis. Hydrolysates were fractionated by ultrafiltration and freeze-dried. Protein content of retentates showed little variation but permeates differed with enzyme. Surface hydrophobicity increased with hydrolysis but was not linear except for α-chymotrypsin. Ultrafiltration increased solubility and the permeates and retentates had better solubility than hydrolysates. Retentates had higher emulsifying activity index than hydrolysates while permeates did not form stable emulsions. Permeates formed stable foams but hydrolysates and retentates showed poor foaming characteristics. Specificity of the enzyme, and degree of hydrolysis influenced the functional properties of the peptides. Fractions generated by trypsin, at all levels of hydrolysis generally had higher solubility, emulsifying properties and foaming properties. Permeates from Alcalase hydrolysis had the best foam capacity but low foam stability.     

超高压对风味蛋白酶酶解大豆分离蛋白中P34免疫活性的影响

研究超高压对风味蛋白酶处理大豆分离蛋白（soybean protein isolate,SPI）中致敏原P34免疫活性的影响。并对脱敏后的SPI功能特性进行了研究。结果表明：超高压处理对风味蛋白酶消除SPI中致敏原P34具有促进作用,将消除P34致敏性的酶解时间由120 min缩短到了60 min。超高压联合风味蛋白酶酶解脱敏的SPI溶解性、黏度、保水性、吸油性、乳化性和乳化稳定性、起泡性和泡沫稳定性都比单纯酶酶解的SPI明显提高。     

Effects of limited enzymatic hydrolysis with pepsin and high-pressure homogenization on the functional properties of soybean protein isolate

Effects of limited enzymatic hydrolysis with pepsin and/or high-pressure homogenization in acid condition on the functional properties and structure characteristic of soybean protein isolate (SPI) were investigated. Functional properties, including protein solubility, surface hydrophobicity, particle size distribution, the ability of resisting freezing/thawing, foaming properties and dynamic surface properties were evaluated. Result showed that, single acid treatment could improve functional properties of SPI, but was not as effective as single or combined pepsin hydrolysis and high-pressure homogenization in acid condition. Emulsibility, the ability of resisting freezing/thawing and foaming capacity of soybean proteins were remarkably improved by the combination treatment, but no improvement of foaming stability was detected. Changes of structures were detected by surface hydrophobicity, and hydrodynamic diameter. It was found that aggregates existed in all treated samples. Besides, more flexible and soluble aggregates were observed in samples treated by limited pepsin proteolysis, high-pressure homogenization and the combination treatments, which might contribute to their functional properties.     

高固形物浓度对大豆分离蛋白酸性蛋白酶酶解产物功能特性的影响

本文系统研究了提高固形物浓度对酸性蛋白酶酶法改性大豆分离蛋白分子量分布、氮溶解指数、分散稳定性、持水力、乳化性、起泡性和泡沫稳定性的影响。结果表明:大豆分离蛋白经过酸性蛋白酶控制酶解制备的改性大豆分离蛋白,其产物氮溶解指数、起泡性均有明显提高,分散稳定性略有提高;但持水力、乳化性、泡沫稳定性有所降低。在相同水解度下,随着酶解体系中固形物浓度的提高,改性大豆分离蛋白的分散稳定性、持水力、乳化活性均呈上升趋势,酶解产物中分子量小于10 kDa的肽段以及氮溶解指数呈下降趋势。当水解度小于8%时,低浓度酶解产物起泡性高于高浓度酶解产物,而水解度超过8%时,高浓度酶解产物起泡性大体高于低浓度酶解产物。     

Antioxidant and antiinflammatory properties of germinated and hydrolysed Brazilian soybean flours

The effect of germination in combination with Alcalase hydrolysis of Brazilian soybean cultivar BRS 133 on the production of soybean flours with bioactive peptides as modulators of oxidative stress and markers of inflammation was monitored. The electrophoretic profile showed a weak protein breakdown during germination. However, a strong breakdown of the proteins can be observed after the first hour of hydrolysis with Alcalase. MALDI-TOF-MS analysis of the protein extracts showed differences in the intensity and profile of peptide mass fingerprint due to germination and hydrolysis. Germinated flour showed higher soluble protein concentration and antioxidant capacity. All soybean protein extracts and protein hydrolysates produced (G0, G18 and G72) showed a significant (p < 0.05) inhibition on inflammatory markers such as nitric oxide (20.5–69.3%), iNOS (22.8–93.6%), PGE₂ (64.0–88.3%), COX-2 (36.2–76.7%), and TNF-α (93.9–99.5%) in LPS-induced RAW 264.7 macrophages. However, protein extracts of flours with 18 h of germination were more potent in inhibiting pro-inflammatory responses when compared to 72 h. It can be concluded that a combination of 72 h of soybean BRS 133 germination and 1 h Alcalase hydrolysis resulted in the formation of bioactive compounds with more potent antioxidant activity, and improvement in the reduction of some of the markers of inflammation.     

Egg yolk protein modification by controlled enzymatic hydrolysis for improved functionalities

Delipidated egg yolk protein (EYP) is produced as a co-product of egg yolk lecithin extraction. This EYP is expected to have poor functionality because of protein denaturation caused by ethanol treatment during lecithin extraction. Two food grade endo-proteases were used to produce EYP hydrolysates (EYPh) with two degrees of hydrolysis (DH), 3% and 6%. Protein solubility was improved as DH increased. Solubility profiles for both EYP and EYPh were relatively less pH-dependent compared with soy protein. Except for foaming capacity, EYPh showed improvement in foam stability, foaming speed, and foam density. Emulsion stability was improved for all EYPhs. Treatments at DH of 6% showed significant increase in emulsification capacity. We have shown quantitatively how controlled enzymatic hydrolysis can be applied to ethanol-treated lipid-free EYP to increase protein solubility, and thus to improve foaming and emulsification properties.     

超声波处理对蜂王浆蛋白功能和结构的影响

探讨不同功率的超声波处理(20 kHz,200、400、600 W)对蜂王浆蛋白溶解性、乳化性、起泡性、水解度以及表面疏水性的影响。同时,通过对王浆蛋白二级结构、三级结构和微观结构的分析,探讨超声波处理改善蜂王浆蛋白功能特性的机制。结果表明,与未处理组相比较,蜂王浆蛋白经过400 W处理后,其溶解度增加10.90%,乳化活性增加67.18%,乳化稳定性增加15.87%,起泡性增加60.00%,起泡稳定性增加118.75%,水解度增加83.33%,表面疏水性增加18.65%。蛋白质的二、三级结构分析显示,该处理条件可以诱导蛋白质发生去折叠化。微观结构分析显示,蛋白质经400 W处理后,其表面较为粗糙,碎片化程度增加。这些结果表明,超声波处理所诱导的蛋白质构象的变化,是其功能特性得以改善的主要原因。     

苦杏仁蛋白的功能特性

采用稀盐溶液浸提及等电点盐析相结合的方法提取制备苦杏仁蛋白,研究pH值、NaCl浓度、蛋白质量浓度和温度等因素对苦杏仁蛋白功能特性(溶解性、持水性、吸油性、乳化性及乳化稳定性、起泡性及起泡稳定性)的影响。结果表明：在等电点pI附近时,苦杏仁蛋白的溶解性、持水性、乳化性及乳化稳定性、起泡性最差;在较低NaCl浓度范围内(0～0.8mol/L)提高NaCl浓度可促进蛋白溶解性、乳化性及乳化稳定性、起泡性及起泡稳定性的提高,而较高的NaCl浓度对蛋白功能特性提高具有抑制作用;当蛋白质量浓度达到一定水平时(3～4g/100mL),蛋白功能特性(乳化性及乳化稳定性、起泡性及起泡稳定性)提高趋于平缓;在适宜的温度范围内,提高温度可有效提高苦杏仁蛋白各项功能特性,但当温度继续上升,各项功能特性持续降低。     

两种酶水解鲢鱼蛋白产物功能性质研究

采用Alcalase 2.4L和Flavourzyme 500L蛋白酶对鲢鱼肉进行水解,研究了水解产物的水解度与体系的pH值对其功能性质的影响。水解产物的溶解度在pH4时最低,碱性时具有较高的溶解度;浊度随pH值变化趋势与溶解度相反,浊度越大,溶解度越小。随水解度的增加,水解产物的乳化活性指数、乳化稳定性、起泡性和泡沫稳定性减小(p<0.05);在水解度相同情况下,水解产物的功能性质取决于所用酶的种类。结果表明,鲢鱼肉蛋白水解产物的功能性质受其水解度和所用酶种类的影响。     

限制性酶解乳清蛋白功能性质研究

探究乳清蛋白在碱性蛋白酶限制性水解下功能性质变化。以乳清蛋白的溶解性,乳化性、乳化稳定性,起泡性、起泡稳定性为考察指标,确定乳清蛋白的等电点及分析不同水解度下乳清蛋白功能性质在p H调控下的变化。结果表明:乳清蛋白的等电点为4.8。乳清蛋白进行限制性酶解后功能性质有了很大提高,其中溶解性在DH14、p H10下达到最大值,较原蛋白提高了14.55%;起泡性在DH14、p H4下达到最大值,较原蛋白提高了107.5%;起泡稳定性在DH4、p H4下达到最大值,比原蛋白提高了8.66%;乳化性在DH14、p H12下达到最大值,比原蛋白提高了56.1%;乳化稳定性DH4、p H12下达到最大值,比原蛋白提高了50.42%。      

金带细鲹鱼肉蛋白酶解物水解度与其抗氧化性和功能特性间的相互关系

采用胰蛋白酶水解金带细鲹鱼肉蛋白制备不同水解度(10.8%、14.9%、19.0%和21.7%)的酶解产物,研究水解度与酶解产物抗氧化性和功能特性的关系。抗氧化性分析表明,低水解度处理显著增大了酶解物清除羟基自由基的能力、清除DPPH自由基的能力和螯合亚铁离子的能力(p<0.05),而高水解度处理则增强了酶解产物的金属还原力(p<0.05)。功能特性结果表明:随着水解度的增大,酶解产物的溶解度逐渐增大,而乳化活性和乳化稳定性逐渐降低,起泡性和泡沫稳定性也降低。同时,随着p H的增加,酶解物的溶解性和乳化稳定性呈先下降后上升的趋势,而起泡性和泡沫稳定性则随着p H的增加而降低。上述分析表明,适当的酶解处理对改善金带细鲹鱼肉蛋白的功能特性及抗氧化活性具有一定的作用。      

Functional properties of protein hydrolysates from pea (Pisum sativum,L) seeds

The aim of this study was to investigate the effects of partial enzymatic hydrolysis on functional properties of two different pea protein isolates obtained from two pea genotypes, Maja and L1. Papain and commercial protease (Streptomyces griseus protease) were used for protein modification. Solubility, emulsifying and foaming properties were estimated at four different pH values (3.0, 5.0, 7.0 and 8.0). Papain increased solubility of L1 pea protein isolate at pH 3.0, 5.0 and 8.0, emulsifying properties and foaming capacity at all pH values. Otherwise, papain increased solubility of Maja pea protein isolate only at pH 8.0. This pea protein isolate modified with both enzymes formed emulsions with improved stability at lower pH (3.0, 5.0). The commercial protease‐prepared pea protein isolates showed generally low solubility and different emulsifying and foaming properties. Proper selection of enzyme, conditions of hydrolysis and genotypes could result in production of pea protein isolates with desirable functional properties.     

鸡蛋清蛋白水解物的物化及功能性质的研究

蛋清蛋白质溶解性欠佳且容易起泡,使其应用受限。本文利用Alcalase酶解鸡蛋蛋清蛋白制取水解度为5~15%的酶解物并对酶解物的理化性质和功能性质进行了表征。测定性质包括乳化性、起泡性及稳定性以及溶解性、表面疏水性。所有酶解产物具有较低的表面疏水性,水解大大提高了溶解度,当水解度15%时最大值为89%,但乳化性有所降低,起泡性及稳定性也大约下降了40%。     

三相卧螺法生产小麦淀粉工艺中轻相液蛋白质的营养学评价

将小麦面粉和谷朊粉中蛋白质的营养进行比较,评价了三相卧螺法生产小麦淀粉过程中的副产物轻相液中蛋白质的营养价值。结果表明：轻相液中蛋白质的氨基酸评分和化学评分均高于小麦面粉和谷朊粉,其中必需氨基酸指数（EAAI）、生物价（BV）、氨基酸比值系数分（SRCAA）、体外蛋白质消化率（IVPD）、蛋白质的效率比（PER）以及蛋白质消化率校正的氨基酸评分（PDCASS）分别为0.95、92.06、73.73、85.4%、1.89和0.43。同时,利用模糊识别法计算得到轻相液中蛋白质的贴近度为0.85,高于小麦面粉和谷朊粉。因此,轻相液中的蛋白质优于小麦面粉和谷朊粉中的蛋白质。     

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.     

豆酱自然发酵过程中蛋白质和氨基酸的变化规律

为研究豆酱在自然发酵过程中蛋白质、氨基酸组成及含量的变化规律,以按照东北豆酱传统方法制作的自然发酵豆酱为研究对象,在检测蛋白质含量、氨基氮含量、氨基酸含量、非蛋白氮含量和水解指数等指标变化的基础上,对豆酱的氨基酸评分(amino acid score,AAS)、化学评分(chemical score,CS)、必需氨基酸指数(essential amino acid index,EAAI)进行分析。结果表明,豆酱蛋白质含量、非蛋白氮含量、蛋白水解指数先上升后下降;氨基氮含量则先不断增加后减少至稳定。自然发酵豆酱中共含有17种氨基酸,但不同发酵时期豆酱中氨基酸含量差异较大,成品豆酱中氨基酸总量维持在41.00 mg/g左右,明显高于生豆粉(11.42 mg/g)和熟豆粉(11.06 mg/g)中氨基酸总量。不同发酵时期豆酱中必需氨基酸与非必需氨基酸的比值在0.48~0.77之间,提示豆酱中的蛋白质为优质蛋白。分析不同发酵时期豆酱的AAS、CS和EAAI可知,发酵20 d时EAAI最高达29.41,发酵50~75 d豆酱的EAAI保持在16.16~17.40之间。通过比较4种呈味氨基酸的含量可知,甜味氨基酸苦味氨基酸鲜味氨基酸无味氨基酸。     

鳙鱼鱼肉蛋白的酶解及其对功能性质的影响

为了改善鳙鱼鱼肉蛋白(BCMP)的功能性质以扩大其在食品工业中的应用,以鳙鱼为原料制备了鳙鱼鱼肉蛋白,并利用碱性蛋白酶Alcalase2.4L对其进行水解,得到了3种不同水解度(DH4.5%、DH9.0%、DH13.5%)的酶解物。研究了BCMP及其酶解物的功能性质,包括溶解性、持水性、持油性、乳化性、起泡性。结果表明,与原鳙鱼鱼肉蛋白相比,酶解物的功能性质除持油性以外均有不同程度的提高。此外,DH4.5%的酶解物乳化性和起泡性最高,过度水解(DH9.0%、DH13.5%)反而造成乳化性和起泡性下降。     

鲤鱼鱼肉蛋白酶水解物抗氧化性及功能特性

采用碱性蛋白酶对鲤鱼鱼肉蛋白进行酶解,制备不同水解度的水解物。测定水解物的抗氧化活性以及不同pH值条件下水解物的功能特性。结果表明:随着水解度的逐渐升高,水解物的抑制脂质氧化能力、D PP H自由基清除能力、还原能力以及金属离子(Cu2+和Fe2+)螯合能力逐渐增加(P<0.05);同时,水解物的溶解性、乳化性和起泡性都在pH值为4.0(等电点)时达到最低,而后溶解性和乳化性随着pH值升高而增大(P<0.05),而起泡性随着pH值的升高先上升后又下降。因此,鲤鱼鱼肉蛋白碱性蛋白酶水解物可以提高蛋白质的抗氧化活性和溶解性,但是较高的水解度会在一定程度上降低其乳化性和起泡性。     

Functional and electrophoretic characteristics of faba bean (Vicia faba) flour proteins as affected by germination

Faba beans (Vicia faba) were germinated at room temperature for 3 and 6 days respectively. The effect of germination on the protein fractions, protein solubility index, PAGE pattern and some functional properties i.e. emulsification capacity (EC), foaming capacity (FC), foam stability (FS), water and fat absorption capacities of the flour was studied. Germination decreased albumins, globulins and prolamins at different levels but non protein nitrogen and glutelins were increased. The protein solubility index was high at both extreme pH values with an isoelectric point (IP) at pH of 4.4-4.5. The solubility of the protein slightly increased due to germination at all the pH values. PAGE pattern revealed on obvious dissociation and utilization for both fast and slow moving protein fractions during germination. Emulsification and foaming properties vs pH profile were similar to the pattern of solubility vs pH. Both properties were high at acidic and alkaline pH's and the minimum values were at pH 4 to 5. Germination process improved EC, FC and FS of the flour in comparison with that of dry bean flour. Water absorption of faba bean flours was improved during germination but the fat absorption markedly decreased.     

Enzymatic and extrusion pretreatments of defatted rice bran to improve functional properties of protein concentrates

This study evaluated effects of enzymatic, extrusion and combined pretreatments on functional and thermal properties of protein concentrates from defatted rice bran to improve their applicability to food formulations. After the pretreatments, protein concentrates were recovered by alkaline solubilisation and isoelectric point precipitation. Water absorption capacity, oil absorption capacity, emulsifying and foaming properties, and thermal stability were determined in protein concentrates. Yields of each pretreatment were above 62% protein. Enzymatic hydrolysis increased all functional properties studied, mainly for emulsifying activity index (an increase of 71.1%) and foaming capacity (an increase of 60.3%). The extrusion affected positively the oil absorption capacity, emulsifying activity index and foaming capacity. The combined process was able to raise the functional properties. The principal component analysis confirmed that 95.5% improvement in functional properties of concentrates had a strong positive correlation with the pretreatments. However, the pretreatments affected thermal stability and the enthalpy of denaturation negatively.