Enhancement of Peptidoglutaminase Deamidation of Soy Protein by Heat Treatment and/or Proteolysis

The limited deamidating ability of B. circulans peptidoglutaminase towards soy protein was increased 27-fold by protein hydrolysis and altering soy protein conformation by moist heat. Adding disulfide bond reducing agents such as cysteine or sodium sulfite or salts such as NaCl or KC1 to the reaction mixture had little or no effect on deamidation. However, heat treatment at 100°C for 15 min, both before and after Alcalase proteolysis, rendered soy protein very susceptible to amide hydrolysis by peptidoglutaminase.     

Deamidation of Soy Peptides and Proteins by Bacillus circulans Peptidoglutaminase

The ability of Bacillus circulans peptidoglutaminase to deamidate soy proteins was investigated. Peptidoglutaminase readily hydrolyzed the γ-amide of glutamine residues in soy peptides, but its activity toward soy proteins was low (0.4–1.3% deamidation). Molecular size and conformation of soy protein may be critical to enzymatic deamidation. Gel adsorption was used to partially purify the enzyme. Gel eluates exhibited higher acitivty than the cell extract toward soy peptides and all soy proteins but US globulin. The specific activity of the gel eluate toward 7S globulin and a water extract of soy flakes was doubled over the original cell extract.     

Recovery of Native Potato Protein Comparing Expanded Bed Adsorption and Ultrafiltration

Obtaining native protein from potato fruit water (PFW) acceptable for food consumption was attempted by comparing expanded bed adsorption (EBA) and ultrafiltration (UF).The methods were assessed on their process performance and the product quality. Extractable tuber proteins were recovered from lab-prepared PFW either by adsorption to an EBA column using a mixed mode resin (0.31 L) or by batch concentration in an UF (10 kDa MWCO, 0.093 m²) unit and then freeze dried. The yields on protein and esterase activity were higher (p < 0.05 and p < 0.01; Mann–Whitney U-test) in UF (3.2 g l⁻¹ PFW and 3.17 kU l⁻¹ PFW) than in EBA (1.8 and 1.21). The performance difference was also reflected in process productivity for esterase activity which was fivefold better (p < 0.01) in UF (4.30 kU h⁻¹) than with EBA (0.84) due to the higher enzyme retention; protein productivities were the same. The content of solanidine glycoalkaloids was depleted to moderate levels but came out unaffected by the processing method: EBA 286 ppm, UF 213 ppm. The low levels of chlorogenic acid in all EBA preparations were negatively correlated to high brightness score (L* = 73.8%), a favorable attribute in food-quality proteins. Both methodologies produced native preparations of comparable protein content (75%). EBA processing, however, increased the fraction of the patatin protein which may offer advantages in food applications.     

大豆蛋白酸法去酰胺改性及对蛋白溶解性的影响

对大豆蛋白酸法去酰胺改性的反应条件进行了研究,确定了最佳反应条件:盐酸浓度0.5 mol/L,大豆蛋白含量3%,反应温度90℃,反应时间2h,此条件下的去酰胺度为63.9%.并且研究了去酰胺度与溶解性的关系,结果发现,去酰胺度在23.1%～69.6%之间,大豆蛋白的溶解性随着去酰胺度的增加而增加,并具有线性相关性.通过对改性前后大豆蛋白的溶解性进行比较,发现在整个pH范围内溶解性均有提高.     

玉米蛋白去酰胺改性的研究

酸法去酰胺作用能改变玉米蛋白的结构和乳化性能,考察了反应时间,盐酸浓度以及反应温度对反应的影响.结果表明:反应时间8 h,温度60℃,盐酸浓度0.05～0.1 mol/L为较好的反应条件,在此条件下能有效的抑制蛋白水解,去酰胺度达到28.6%,对应改性蛋白的乳化活性和乳化稳定性从原始蛋白的8.2 m2/g和32%提高到26.7 m2/g和74.5%.随去酰胺程度的增大,玉米蛋白的表面疏水性和分子柔性先增加后趋于平衡,但去酰胺作用并未造成玉米蛋白二硫键的断裂或形成.     

Deamidation During Treatment of Soy Protein with Protease

When soy protein was treated with protease in phosphate buffer, ammonia was generated in addition to the occurrence of peptide bond hydrolysis. The source of the ammonia was likely the nonenzymatic deamidation of glutamine in the hydrolysate because free glutamine was found to deamidate in phosphate buffer with or without protease. Both the glutamine deamidation and the deamidation during enzymatic proteolysis of soy protein were catalyzed by certain anions. Of the anions investigated, phosphate and bicarbonate were by far the most effective in that regard, borate only slightly effective, and acetate not effective at all.     

Effect of Anions on the Deamidation of Soy Protein

Anions from common salts were investigated for their effects on the deamidation of soy protein isolate. Phosphate and bicarbonate anions were most effective for enhancing deamidation. Borate anions were much less effective while acetate, sulfate and chloride anions were totally ineffective. Significant deamidation (>30%) was normally accompanied by significant peptide bond hydrolysis (> 3%). Deamidated soy protein isolate with up to 4.5% peptide bond hydrolysis had greatly improved solubility, foam activity and ability to emulsify oil.     

大米蛋白改性及对功能性质的影响

对大米蛋白酸法脱酰胺改性的工艺进行了研究,确定了最佳工艺条件:大米蛋白溶液质量浓度25 g/L、加入的盐酸浓度0.19 mol/L、反应时间3.18 h、反应温度92℃,此条件下脱酰胺度为48.9%,并且研究了此脱酰胺条件下大米蛋白溶解性、乳化性、起泡性、持水、持油性,结果发现,随着脱酰胺程度的增加,溶解性、乳化性、起泡性都有所增加,而持水、持油性能变化不大.     

酶法脱酰胺对米谷蛋白分子微观结构的影响

大米蛋白经酶法脱酰胺后功能性质的显著改善与其分子微观结构的变化有关。通过扫描电镜(SEM)分析、二硫键含量测定和差示扫描量热分析(DSC)研究脱酰胺后米谷蛋白分子超微结构、分子间作用力和聚合度的变化。结果表明：米谷蛋白颗粒超微结构随着脱酰胺度的增加逐渐松散;脱酰胺后分子内部分二硫键被迅速还原,但酶法脱酰胺不会影响到其肽链内二硫键;DSC图谱分析表明脱酰胺后蛋白质热稳定性和聚合度均有降低。     

Effect of Enzymatic Protein Deamidation on Protein Solubility and Flavor Binding Properties of Soymilk

Abstract: The effect of enzymatic deamidation by protein‐glutaminase (PG) on protein solubility and flavor binding potential of soymilk was studied. Treatment of soymilk with PG for 2 h (temperature of 44 °C and enzyme:substrate ratio (E/S) of 40 U/g protein) resulted in high degree of protein deamidation (66.4% DD) and relatively low degree of protein hydrolysis (4.25% DH). Deamidated (DSM) and control soymilks (CSM) did not differ with respect to aroma, but differed in taste characteristics by sensory evaluation. Protein solubility in DSM was enhanced at weakly acidic conditions (pH 5.0), but did not differ from non‐deamidated soymilk at pH values of 3.0 and 7.0. Odor detection thresholds for the flavor compounds vanillin and maltol were approximately 5 and 3 fold lower, respectively, in DSM than in CSM. Dose‐response curves (Fechner's law plots and n exponents from Stevens's power law) further demonstrated that DSM had a lower flavor binding potential than CSM. PG deamidation has the potential to reduce flavor binding problems encountered in high protein‐containing foods and beverages. Practical Application: The findings of this study can help lead to the development of technology to produce protein‐containing foods with improved functional properties, especially protein solubility, and potentially decreased flavor fade problems associated with flavor‐protein interactions, especially with carbonyl containing flavor compounds.     

Deamidation of Protein in a Soy Extract by Ion Exchange Resin Catalysis

Proteins in a soy extract were partially deamidated in dilute HCl (0.05N) with and without the use of Dowex 50 resin as a catalyst. In the presence of Dowex 50 resin, soy protein underwent about 1.5 to 3.0 times as much deamidation, depending on temperature, as did protein in the absence of resin. Increasing the temperature from 58° to 85°C increased both deamidation and peptide bond hydrolysis. The ratio of deamidation to total hydrolysis (the sum of deamidation and peptide bond hydrolysis) decreased as temperature increased. This ratio was higher for the catalyzed reaction. The deamidated protein showed improvement in various functional properties including solubility, water-binding, whippability, and the ability to emulsify oil.     

大米浓缩蛋白脱酰胺研究(I) 酸法脱酰胺与酶法脱酰胺工艺比较与参数优化

通过测定大米浓缩蛋白的脱酰胺度与水解度,比较了酸法与酶法两种脱酰胺工艺对大米浓缩蛋白脱酰胺作用的优劣,并对酸法脱酰胺工艺的参数进行优化。实验表明酸法脱酰胺优于酶法脱酰胺。温度是影响大米浓缩蛋白脱酰胺作用最重要的因素,在本试验条件范围内,酸法脱酰胺度最高且水解度最低时的工艺条件组合为盐酸浓度0.2N,大米蛋白含量5%,反应时间4h,反应温度85℃。     

大米浓缩蛋白脱酰胺研究(Ⅰ)酸法脱酰胺与酶法脱酰胺工艺比较与参数优化

通过测定大米浓缩蛋白的脱酰胺度与水解度，比较了酸法与酶法两种脱酰胺工艺对大米浓缩蛋白脱酰胺作用的优劣，并对酸法脱酰胺工艺的参数进行优化。实验表明酸法脱酰胺优于酶法脱酰胺。温度是影响大米浓缩蛋白脱酰胺作用最重要的因素，在本试验条件范围内，酸法脱酰胺度最高且水解度最低时的工艺条件组合为盐酸浓度0．2N，大米蛋白含量5％，反应时间4h，反应温度85℃。     

超滤技术在大豆分离蛋白生产中的应用研究

利用平板超滤装置对加工大豆分离蛋白进行了应用研究。重点探讨了料液ｐＨ值、温度、浓度和操作压力,流量对超滤膜通量及大豆分离蛋白品质的影响。通过实验得到了最佳工艺参数。     

超滤法浓缩乳清蛋白前处理研究

为了提高乳清在进行超滤的通透性,从而提高超滤的效率,对利用CaCl2絮凝沉淀乳清的工艺条件进行研究,通过单因素和正交试验优化,综合考虑蛋白含量、脂肪含量和透光率3个指标,确定最佳的絮凝工艺条件为pH7.5、1mol/L CaCl2溶液添加量12mL/L、在60℃水浴缓慢搅拌絮凝15min。在最佳絮凝工艺条件下进行验证,结果表明：经过预处理后的乳清蛋白损失率只有13.6%,脂肪去除率达到86%以上,透光率也有显著提高。     

超滤和反渗透双膜工艺在印染废水回用中的应用

由于印染废水成分复杂且不稳定,盐度高,可生化性差,使用常规生化处理方法难以达到最佳回用效果。文章研制了一种新型抗污染超滤膜,结合反渗透技术成功处理印染废水。实践表明,该系统运行稳定,对COD、C1的去除效率均可达97％以上;对悬浮物、色度的去除率达到100％。系统出水符合印染车间生产回用水的要求。     

水洗机废水的回收利用

介绍了淮北印染集团公司水洗机产生的废水经简单处理后,回收利用到部分设备和清洁卫生用水．节约了水资源,减少了污水排放量,取得了明显的经济效益和环境效益。     

超滤法纯化苦荞麦蛋白液的数学模型

超滤是根据物质相对分子质量大小进行分离的方法,其分离效果好、运行成本低,广泛应用于食品、生物及制药行业.在苦荞麦蛋白液的生产过程中,盐分的加入使蛋白液需要进一步的纯化去除.研究了超滤过程中膜温度、蛋白液浓度、膜压力、膜操作时间等对膜通量的影响,建立了超滤法除去苦荞麦蛋白液中盐分的数学模型,并对模型进行探讨.     

Fractionation of Soy Protein Hydrolysates using Ultrafiltration Membranes

The effect of membrane pore size on the molecular weight distribution and selected functional properties of a protein hydrolysate produced from soy isolate and Pronase was examined. Molecular weight distributions were similar for permeates from 5000, 10,000 and 50,000 molecular weight cut-off (MWCO) membranes: two large fractions at 2300 and 1000 daltons. The 100,000 MWCO membrane resulted in three fractions of 25,000, 13,000 and 2300 daltons. Solubility of the hydrolysate increased with decrease in MWCO, while foam stability decreased.