水相酶解法菜籽蛋白提取液超滤工艺研究

对水相酶解法提取菜籽油与菜籽蛋白所得菜籽蛋白液进行超滤处理，研究超滤条件对超滤膜透过速率的影响，得出操作压力、温度、料液的pH、料液蛋白质浓度影响较大。试验结果表明，控制操作压力O．20-O．30MPa，温度50℃，料液pH9-10时效果较好。采用超滤工艺，所得菜籽蛋白不含毒素、纯度及回收率在90％以上，功能特性优于酸沉法。     

酵母抽提物提取海藻糖超滤特性研究

采用聚醚砜超滤膜对酵母味素溶液进行超滤试验，并对超滤特性及影响特性的操作因素进行研究，结果表明：在整个超滤过程，通量衰减变化很大，蛋白质主体浓度的对数和渗透通量呈线性关系；随料液浓度增加，膜通量下降，蛋白截留率和海藻糖透过率增加；料液pH和操作压力均影响通量、蛋白截留率和海藻糖透过率。经提取后的海藻糖浓度为25．7％，整个过程海藻糖总提取率达89．8％。     

超滤浓缩微生物胞外多糖PS-9415发酵液的研究

本文采用了截留分子量为70，000的平板超滤膜对微生物胞外多糖PS－9415的发酵液进行了超滤浓缩的研究。膜的透过通量受料液浓度，搅拌速度，操作压力等因素的影响。其中，降低料液浓度，增加搅拌，提高压差可以增加膜的透过通量。0．5％的多糖在室温,0.15MPa下超滤108min可浓缩2倍。     

低聚木糖的超滤纯化生产工艺优化

以纯化分离秸秆酶解液中低聚木糖为目的,以蛋白、木质素去除率和低聚木糖的透过率为评价指标,采用工业化超滤膜分离装置,考察料液浓度、操作压力、温度、pH值对超滤除杂的影响。单因素实验确定初步的工艺条件后,Box-Behnken模型优化得最佳超滤纯化工艺条件为:料液浓度2.24°Bx,操作压力0.18 MPa,温度25℃,pH 7.0。在此条件下,低聚木糖的透过率为92.1%,蛋白去除率67.9%,木质素去除率67.8%,透过液澄清透亮。响应面法分析各因素对超滤提纯效果的影响,其强弱性依次为:料液浓度、pH值、操作压力、操作温度。     

中空纤维膜分离酵母提取液中活性成分的初步研究

以啤酒废酵母为原料,研究了中空纤维膜(微滤和超滤)分离酵母提取液中活性成分的工艺.基于超滤机理分析了操作压力、温度、pH值和料液浓度对膜通量的影响,得到超滤工艺最佳条件:压力为0.105MPa,温度、pH值和料液浓度分别为24℃、6.0、3.0%.在此条件下,膜通量为18.42 L/m2·h,海藻糖透过率为96.36%,蛋白质截留率为94.50%.经高效液相色谱(HPLC)验证,实现了酵母提取液中活性成分的分离.     

南瓜籽蛋白酶解液的超滤分离及其抗氧化活性研究

采用超滤技术分离南瓜籽蛋白酶解液,通过研究操作压力、料液浓度、pH和时间四个因素对膜通量和膜效能的影响,依次得到截留分子量分别为10、4ku两次超滤的最佳工艺条件,并比较超滤前后酶解液的抗氧化活性。结果表明,截留分子量为10ku的超滤膜的操作压力为0.25MPa、料液浓度为3.0%、料液pH为7,操作时间为60min;截留分子量为4ku的超滤膜的操作压力为0.20MPa、料液浓度为2.0%、料液pH为7,操作时间为60min。经过超滤以后分子量小于4ku的组分具有更强的清除自由基的能力,其中清除50%DPPH自由基所需的多肽浓度即半抑制浓度IC50值为2.76mg/mL、清除羟基自由基(·OH)的IC50值为2.91mg/mL、清除超氧阴离子自由基(O2-·)的IC50值为23.58mg/mL,同时对铁离子还具有显著的还原能力,吸光度为0.5时所需的多肽浓度为9.43mg/mL。     

中空纤维超滤膜浓缩胞外参糖PS-9415发酵液的研究

采用了截留分子量为50,000的内压式中空纤维超滤器对微生物胞外多糖PS-9415发酵液进行浓缩分离的研究.研究表明,膜的透过通量受温度、料液浓度、操作压力等操作参数的影响,其中高温、低浓度的料液在较高的操作压力下有较高的透过通量.经过稀释、离心除菌的发酵液比不经过处理的发酵液透过通量高,衰减慢.0.05MPa下对3%的料液3L超滤浓缩,可得到5.8%的浓缩液,多糖回收率为82 7%;0.1MPa下0 5%的料液可浓缩至2.95%,浓度提高了4.9倍.     

中空纤维超滤膜浓缩胞外多糖PS-9415发酵液的研究

采用了截留分子量为50,000的内压式中空纤维超滤器对微生物胞外多糖PS-9415发酵液进行浓缩分离的研究。研究表明,膜的透过通量受温度、料液浓度、操作压力等操作参数的影响,其中高温、低浓度的料液在较高的操作压力下有较高的透过通量。经过稀释、离心除菌的发酵液比不经过处理的发酵液透过通量高,衰减慢。0.05MPa下对3%的料液3L超滤浓缩,可得到5.8%的浓缩液,多糖回收率为82.7%;0.1MPa下0.5%的料液可浓缩至2.95%,浓度提高了4.9倍。     

食醋超滤澄清研究

对食醋进行了超滤澄清研究,考察了不同膜、搅拌速率、透过液通量、料液温度等对食醋超滤过程的影响,并对其中膜污染阻力进行了分级研究.结果表明,截留分子量为100kDa的PVDF超滤膜适合食醋超滤澄清,且效果显著,可使浊度从175 NTU降至0.2 NTU以下,总酸度损失率<6%、葡萄糖和乳酸则基本没有损失;随着搅拌速率的增加、透过液通量的降低以及料液温度的升高,食醋超滤澄清过程的跨膜压力随之降低,而总酸度损失率亦同样有降低趋势;膜污染阻力的分级测定显示,膜表面浓差极化层与滤饼层分别占总膜阻的38.15%和28.95%,而膜内部污染阻力几乎可以忽略;采用浓度为0.05mol/L的NaOH溶液浸泡24h,可有效清除膜污染,清洗后膜阻为新膜膜阻的98%.     

菜籽蛋白超滤液反冲对超滤膜污染的控制研究

超滤是制备植物油料蛋白的先进工艺技术，但膜的污染问题严重影响超滤技术的推广应用。本文在研究了菜籽蛋白水溶液在中空纤维超滤装置中的超滤行为之后，研究了膜面透过液反冲对膜污染的控制作用。实验结果表明：菜籽蛋白水溶液的超滤浓缩速率随时间延长而下降；对工作中的超滤膜进行定期间歇反冲（反冲时间20s、反冲频率为1次／15min、反冲压差为0．2MPa），是控制膜污染程度的有效措施，这样可以使超滤膜的透水速率恢复90％以上。     

Influence of pH and salt concentration on the emulsifying properties of native wheat gliadins and of their chymotryptic hydrolysates

Chymotryptic hydrolysates with degrees of hydrolysis around 1% were prepared from purified β- and γ-gliadins of wheat. Some functional properties were studied at pH 4.0 and 6.5 in the absence or in the presence of 1% and 2% NaCl. The hydrolysates were highly soluble in all the conditions of pH and salt concentration tested, whereas the solubility of native gliadins did not exceed 20%, except at pH 4.0, 0% NaCl. The differences in emulsifying properties between hydrolysates and native proteins were great in the presence of salt. Phase separation was almost complete immediately after emulsification with the native gliadins, but creaming was slowed down and limited with the hydrolysates. Furthermore, emulsions stabilized with hydrolysates showed a very strong resistance to coalescence. Although some differences were observed between hydrolysates of β- and γ-gliadins, the peptides adsorbed at the alcane/water interface were in both cases the more hydrophobic and charged, corresponding to the non-repetitive domain of the gliadin sequences.     

Recovery of protein hydrolysates from brewer’s spent grain using enzyme and ultrasonication

The aim of this study was to develop a green ultrasound-assisted enzymatic process to separate protein from brewer’s spent grain (BSG) to produce protein hydrolysates and determine the physicochemical properties of produced protein hydrolysates. When the enzyme (Alcalase) loading increased from 1 to 20 μL g⁻¹ BSG, the protein separation efficiency increased from 34.0% to 61.6%. The application of ultrasound pretreatment further increased protein separation efficiency to 69.8%. More promisingly, the ultrasound pretreatment was able to reduce enzyme loading by 73% and decrease enzyme incubation time by 56%. The produced protein hydrolysates had molecular weights lower than 15 kDa and high protein solubilities at the pH of 1.0–11.0. The ultrasound pretreatment improved the protein solubility to above 90%. Glutamic acid and proline were the most abundant amino acids in produced protein hydrolysates. This study demonstrated that enzymatic hydrolysis along with ultrasound pretreatment is an effective way to separate protein from BSG.     

酶解-膜分离组合制备ACE抑制肽

测试了膜分离操作压力、温度、pH值、料液体积浓度等操作参数对酶活力、血管紧张素转换酶(ACE)抑制肽分离的影响,并建立分段酶解、分级膜分离组合模式实现从扇贝裙边酶解产物中分离ACE抑制肽.结果表明:膜分离操作操作参数对酶活力、ACE抑制肽分离均有较大影响;二段酶解-二级膜分离组合模式制备及分离ACE抑制肽的得率最高,为5.73%,其IC50为0.088mg/ml;一段酶解-二级膜分离组合模式制备及分离ACE抑制肽的得率为3.19%,其IC50为0.081mg/ml;一段酶解-单级膜分离组合模式制备及分离ACE抑制肽的得率只有2.31%,其IC50为0.078mg/ml.     

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.     

Antibody binding and functional properties of whey protein hydrolysates obtained under high pressure

This paper examines the potential of high hydrostatic pressure to produce whey protein hydrolysates that combine low immunoglobulin (Ig)G- and IgE-binding with acceptable functional properties, with the aim to produce milk-based ingredients with reduced potential allergenicity that could be used in hypoallergenic foods. Treatment with pepsin and chymotrypsin under high pressure produced, in minutes, hydrolysates in which α-lactalbumin and β-lactoglobulin were totally proteolysed, giving rise to large and hydrophobic peptides. Such hydrolysates presented reduced antigenicity and human IgE-binding properties. The hydrolysates obtained with pepsin at 400 MPa showed improved heat stability, particularly at a pH, close to the isoelectric point of the whey proteins, and their emulsion activity indexes at pH 7.0 were superior to those of the untreated whey proteins. These results suggest that the peptides present retained low antigenicity together with sufficient capacity to form emulsions.     

Foaming properties of barley protein isolates and hydrolysates

Foaming properties of the barley protein isolates (BPI) and barley protein hydrolysates (BPH) were investigated by using gas sparging method. BPIs were produced from hulled (BPI-1) and hull-less (BPI-2) barley flours by extracting with 70% (v/v) ethyl alcohol. BPI-2 was hydrolyzed with Subtilisin enzyme using pH-stat technique in order to produce hydrolysates at 3% (BPH-1) and 6% (BPH-2) degree of hydrolysis. Barley flour, BPI-1 and the pellets and supernatants obtained from centrifugation of BPI-1 were examined by SDS-PAGE. The foaming properties of BPIs and BPHs were determined as a function of pH and protein concentration. The results showed that foaming properties were affected by the changes in pH of the medium in isolates and hydrolysates. Foaming properties of isolates were improved below and above the isoelectric pH. The lowest values were observed at pH 6, which is close to the isoelectric pH of BPIs. The protein hydrolysates displayed improved foam stability at basic pH values, while stability was very low at acidic pH values. Generally, at all pH values in both isolates, the highest foam volumes and stability were observed for 1% (w/v) protein concentrations.     

阴离子交换树脂分离酪蛋白糖巨肽工艺条件优化

采用离子交换树脂从乳清粉中分离酪蛋白糖巨肽(casein glycomacropeptide,CGMP),筛选适于分离CGMP的离子交换树脂并考察静态吸附过程中吸附pH值、吸附时间、缓冲液浓度等因素对CGMP分离效果的影响。乳清粉溶液在pH5.1时离心除杂后与201×4树脂混合,吸附条件为吸附pH3.9、吸附时间1h、缓冲液浓度0.02mol/L、洗脱液为0.5mol/L pH4.0的氯化钠溶液、洗脱时间4h;100g乳清粉利用此工艺条件可得1.45g唾液酸含量10.4%(以蛋白质计)的CGMP。该工艺方法分离过程简单、纯化效果好、唾液酸含量高,适用于工业化生产。     

Response surface methodology for autolysis parameters optimization of shrimp head and amino acids released during autolysis

Protein hydrolysates were prepared from the head waste of Penaens vannamei, a China seawater major shrimp by autolysis method. Autolysis conditions (viz., temperature, pH and substrate concentration) for preparing protein hydrolysates from the head waste proteins were optimized by response surface methodology (RSM) using a central composite design. Model equation was proposed with regard to the effect of temperature, pH and substrate concentration. Substrate concentration at 23% (w/v), pH at 7.85 and temperature at 50 °C were found to be the optimal conditions to obtain a higher degree of hydrolysis close to 45%. The autolysis reaction was nearly finished in the initial 3 h. The amino acid compositions of the autolysis hydrolysates prepared using the optimized conditions in different time revealed that the hydrolysates can be used as a functional food ingredient or flavor enhancer. Endogenous enzymes in the shrimp heads had a strong autolysis capacity (AC) for releasing threonine, serine, valine, isoleucine, tyrosine, histidine and tryptophan. Endogenous enzymes had a relatively lower AC for releasing cystine and glycine.     

底物浓度对碱性蛋白酶水解面筋流变特性的影响

本文较系统地研究了Alcalase碱性蛋白酶催化不同浓度小麦面筋蛋白水解过程中酶解产物的表观现象、表观粘度、剪切应力和流变特性。研究结果表明:酶解体系中小麦面筋的浓度越高,p H值下降幅度越少,在反应刚开始的6 h内是p H值变化最明显的区间,固形物浓度越高的样品,越早进入变化平稳的阶段。随着固形物浓度的提升和酶解时间的延长,酶解液的水分活度有下降的趋势,且固形物浓度越大,水分活度下降幅度越大,下降速度越快。在整个反应过程中,各固形物浓度酶解物的表观粘度和剪切应力均会随着酶解时间的延长而不断下降;固形物浓度越大下降趋势越明显,且不同固形物浓度酶解液的表观粘度和剪切应力的大小始终保持40%32%24%16%8%。此外,研究发现Ostwald-dewaele模型可以很好的拟合碱性蛋白酶催化不同固形物浓度小麦面筋蛋白酶解液的流变特性。     

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。