大豆乳清蛋白特性及回收利用研究进展

大豆分离蛋白加工过程中产生大量乳清废水,直接排放会造成环境污染和资源浪费。大豆乳清废水中含有大豆乳清蛋白(Soybean Whey Proteins, SWP)、大豆异黄酮、大豆低聚糖等多种营养成分,其中大豆乳清蛋白应用价值极高,富含胰蛋白酶抑制剂、β-淀粉酶、大豆血球凝集素、脂肪氧合酶等多种功能因子。基于此,本文针对大豆乳清蛋白的回收利用,归纳总结了大豆乳清蛋白中的主要组成成分,并对各组分的研究利用以及其功能特性进行总结与分析,同时对大豆乳清蛋白的回收方法及利用进行了梳理,以期为工业生产实践中高值化利用提供理论和技术上的参考。     

大豆乳清蛋白功能特性的研究

对经过膜分离技术提取的大豆乳清蛋白的功能特性进行研究。主要研究了pH对大豆乳清蛋白的溶解特性、起泡性能及乳化性能的影响,并对大豆乳清蛋白的组成成分进行了电泳分析。结果表明,大豆乳清蛋白具有较好的溶解性及起泡性,但泡沫稳定性及乳化性不如大豆分离蛋白。大豆乳清蛋白主要包含6种成分。     

双蛋白纳米颗粒Pickering乳液的构建及稳定性研究

为获得稳定性较好的蛋白基Pickering乳液,实验采用pH循环法以绿豆蛋白和乳清蛋白为原料制备双蛋白纳米颗粒并进行表征,进一步以此为基质制备Pickering乳液,并对Pickering乳液微观结构、粒径及流变学等进行表征,同时探讨了乳液的加工稳定性。结果：获得了粒径为100~250 nm的蛋白纳米颗粒;其制备的Pickering乳液为水包油型,且具有良好稳定性;与单一蛋白纳米颗粒乳液比较,双蛋白纳米颗粒乳液的乳化特性及其本身的稳定性有所提高。乳液的流变学说明乳液出现了剪切稀化现象,形成了凝胶网络结构。随着双蛋白中乳清蛋白比例的增加,乳液粒径减小,稳定性增加。因此,双蛋白制备的纳米颗粒Pickering乳液理化性质得到改善。研究结果可为混合蛋白构建稳定的乳液体系及活性成分的递送提供参考。     

Production and functional properties of beef lung protein concentrates

This work investigated the production and the properties of meat protein concentrates from beef lungs (BLPC) at pilot scale. Protein recovery and functional properties were compared to those of BLPC obtained using membrane technology in a previous work (Selmane, D., Vial, C., & Djelveh, G. (2008). Extraction of proteins from slaughterhouse by-products: Influence of operating conditions on functional properties. Meat Science, 79, 640–647). An alkaline solubilisation method was applied for protein extraction, followed by pI precipitation for concentration. The physicochemical properties of BLPC such as molecular mass, solubility, surface hydrophobicity, surface tension and interfacial tension, as well as technofunctional emulsifying and foaming properties were determined. These were compared to those of commercial protein ingredients, such as sodium caseinates, whey protein isolates, egg white proteins and soy protein isolates. Results showed that proteins from BLPC included a low-molecular-weight fraction and exhibited good solubility and high hydrophobicity with small surface and interfacial tensions. This explained their excellent emulsifying activity, better than sodium caseinates, and their good foaming properties.     

Functional and Biological Properties of Peptides Obtained by Enzymatic Hydrolysis of Whey Proteins

The study of peptides released by enzymatic hydrolysis of whey proteins has been initially focusing on improving their functional properties in food model systems. Our first study showed that peptides 41 to 60 and 21 to 40 from β-lactoglobulin (β-LG) were responsible for improved emulsifying properties of a tryptic hydrolysate of whey protein concentrate (WPC). Further work showed that adding negatively charged peptides from tryptic hydrolysates of WPC could prevent phase separation of dairy-based concentrated liquid infant formula, as a replacement for carrageenan. Hydrolysis of whey proteins using a bacterial enzyme was also successful in improving heat stability of whey proteins in an acidic beverage. Some tryptic peptides demonstrated improvement in the heat stability and in modifying thermal aggregation of whey proteins. Recent research has shown that whey peptides could trigger some physiological functions. Within the scope of this research our work has led to the development of a whey protein enzymatic hydrolysate that has demonstrated antihypertensive properties when orally administered to spontaneously hypertensive rats and human subjects. Our work then focused on the fractionation of hydrolysates by nanofiltration to prepare specific peptidic fractions; however, peptide/peptide and peptide/protein interactions impaired membrane selectivity. The study of those interactions has lead to the demonstration of the occurrence of interactions between β-LG and its hydrophobic fragment 102–105 (opioid peptide), which probably binds in the central cavity of the protein. This latest result suggests that β-LG could be used as a carrier for the protection of bioactive peptides from gastric digestion. Our work therefore has shown that the enzymatic hydrolysis of whey proteins is not only improving their functional properties, but it is also providing powerful technology in the exploitation of their biological properties for functional foods and nutraceutical applications.     

Dairy and Vegetable Protein Blends by Co-Extraction and Co-Ultrafiltration

A process was developed for the manufacture of blends of dairy and vegetable proteins by co-extraction and co-ultrafiltration. Defatted soy flour proteins were extracted using either acid or sweet whey as the solvent. The whey/soy slurry was separated in a two stage extraction process using a centrifugal desludger. The proportion of whey protein in the blend was determined by the number of extractions and the total amount of whey used. The combined extracts were processed by ultrafiltration to increase the protein content of the blends. Solubility characteristics of the blends indicate potentially good functional properties.     

Investigation of physical stability of Pickering emulsion based on soy protein/β-glucan/coumarin ternary complexes under subcritical water condition

The binding of proteins and polysaccharides/polyphenols can modify the interfacial properties of proteins. Therefore, this study aimed to explore the feasibility of soy protein-glucan-coumarin complex (S-G-C) fabricated by subcritical water treatment as novel emulsifiers with decent physicochemical stability. The addition of β-glucan and coumarin (CM) led to partial unfolding of soy proteins, the corresponding particles decreased and structure became tighter, and thereby the ternary complexes, which were formed mainly through hydrogen bonding and hydrophobic interaction exhibited more suitable three-phase contact angles (92.6°) compared with soy protein alone and binary complexes. CM might increase hydrophobic effect while β-glucan attached to the outer layer might provide steric repulsion, which effectively improve physical stability of Pickering emulsion against environmental stresses and retard droplet aggregation and creaming during the 28 days storage. This study provides a reference for the preparation of novel emulsifier with improved physicochemical and functional performance.     

大豆蛋白用作啤酒泡沫稳定剂的研究

本研究以脱脂大豆蛋白粉为原料,碱溶酸沉法制备大豆分离蛋白(SPI)和大豆乳清蛋白(WSP),根据大豆分离蛋白酶解过程中溶解性及泡沫稳定性的变化情况,确定大豆分离蛋白的酶解程度。再通过对酶解大豆分离蛋白(ESPI)及大豆乳清蛋白(WSP)的性能实验及应用实验进一步考察大豆蛋白用作啤酒泡沫稳定剂的可行性。结果表明,酶解30min后,ESPI溶解性和泡沫稳定性均有所增强;ESPI和WSP不仅能改善低度熟啤酒的泡持性,而且可以明显改善纯生啤酒货架期内的泡持性;大豆蛋白的添加不会影响啤酒的非生物稳定性。     

Composition, Physicochemical and Functional Properties of Reference Whey Protein Concentrates

Four reference whey protein concentrates (WPCs) were prepared from pasteurized and nonpasteurized acid casein whey and Cheddar cheese whey using ultrafiltration/diafiltration and spray drying processes. The WPCs exhibited comparable composition, protein solubility and PAGE and reverse phase HPLC properties. Major differences were observed in the viscosity and foaming properties of the reference WPCs as a function of pH. The WPCs generally produced higher foam expansion but lower viscosity and stability values than for liquid egg white protein. The findings were discussed in terms of the need for additional, fundamental knowledge of the physicochemical structure and reactivity of whey proteins to understand the reasons for their poor functional performance.     

Model studies on reactions of plant phenols with whey proteins

Whey proteins were modified by reaction with selected phenolic compounds (ferulic-, chlorogenic-, caffeic- and gallic acid) and related substances (quinic acid and p-quinone) as well as with extracts from coffee, tea, potato and pear at pH 9. The derivatives formed were characterized in terms of their physicochemical and digestion properties. The derivatization was accompanied by a reaction at the lysine and tryptophan side chains, whereby their content was decreased in comparison to that in the control whey proteins. Moreover, the solubility of the derivatives decreased over a broad pH range and the derivatization influenced the hydrophobe-hydrophile character of the whey proteins. The isoelectric points were shifted to lower pH values in the order of reactivity as follows: gallic acid > p-quinone > caffeic acid > chlorogenic acid. The other derivatives showed no or few changes compared to the control whey proteins. The formation of high molecular fractions was documented with SDS-PAGE. Especially the derivatives of chlorogenic-, caffeic-, gallic acid and p-quinone showed an increase in molecular weight of beta-lactoglobulin fraction from 18,300 to 20,000 Da. A dimer formation in molecular range 40,000 was also registered. MALDI-TOF-MS was applied to characterize the binding of the individual phenolic compounds or their oxidation products to the whey protein fractions, alpha-lactalbumin and beta-lactoglobulin. In vitro experiments showed that the digestion of the derivatized whey proteins with the enzymes of the gastrointestinal tract (trypsin, chymotrypsin, pepsin and pancreatin) was adversely effected. Similar results with regard to physicochemical characterization and digestion properties of the whey proteins treated with the applied extracts from plant beverages, fruit and vegetable were also documented. Coffee and tee were comparatively the most reactive extracts.     

Functional properties of single cell protein produced by kefir microflora

Single cell protein (SCP) was produced by aerobic fermentation of cheese whey by kefir microorganisms. A feed-batch system was developed on a bioreactor of 4 1. The experiments were conducted under controlled pH (5.5) and temperature (30 °C) conditions. The biomass was analyzed for protein, lipids, carbohydrates and ash and its functional properties (emulsification, foaming, gelation) were studied. Single cell protein (53.9% protein) exhibited emulsifying properties similar to those of defatted soy flour, while its Ibaming activity and foam liquid stability were much higher. Finally, texture profile analysis of gels, formed by heating water dispersions of SCP, showed that the structures produced were stronger compared with those of gels made with soy flour.     

Functional properties and Angiotensin-I converting enzyme inhibitory activity of soy–whey proteins and fractions

Soy proteins when prepared to high purity can confer good functional properties and the whey by-product is a potential source for bioactivity. In this study, we determined the protein, moisture, fiber, solubility, foaming, emulsion properties, as well as Angiotensin-I converting enzyme (ACE-I) inhibitory activity of prepared soy–whey proteins and its fractions. The soy–whey proteins were fractionated into < 5, > 5, > 10, and > 50 kDa using ultrafiltration. The expanded AACC methods were used to determine protein, moisture, and fiber analyses of the whey and its fractions. Solubility method was conducted to determine the protein solubility profile of the soy–whey and its fractions at varying pHs. Turbidimetric method was used to evaluate emulsifying activity (EA) and emulsion stability (ES). There were significant differences observed in moisture, protein and salt contents between unfractionated, > 50 kDa and smaller sized fractions. No significant differences were observed with phytic acid and total dietary fiber contents among all samples. The unfractionated whey protein and > 50 kDa fraction showed better solubility than other fractions. Unfractionated whey protein had the highest foam capacity (42.7 mL) while the fraction > 5 kDa showed the greatest foaming stability (46 min). The highest emulsion activity (0.33 ± 0.1) and stability (825.1 ± 45.1) was obtained with the > 50 kDa fraction while the unfractionated whey protein had the highest ACE-I inhibition activity. The findings indicate that soy–whey protein fraction (> 50 kDa) had good solubility, emulsion activity and stability, while the unfractionated whey protein exhibited the strongest ACE-I inhibition percentage (19%).     

Effect of Whey Pretreatment on Composition and Functional Properties of Whey Protein Concentrate

The effect of pretreatment upon the composition and physicochemical and functional properties of whey, ultrafiltration (UF) retentate and freeze-dried and spray-dried whey protein concentrates (WPC) was investigated. Pretreatment was by cooling cheese whey to 0-5°C, adding calcium chloride, adjusting to pH 7.3, warming to 50°C, and removing the insoluble precipitate that formed by centrifugation or decantation. UF permeation flux rate of pretreated whey was about double that for control whey. Pretreated whey was essentially turbidity free, contained 85% less milkfat, 37% more calcium and 40% less phosphorus than whey. Pretreated whey WPC proteins were slightly more soluble at pH 3, but less functional for emulsification than whey WPC proteins. Neither whey WPC proteins nor pretreated whey WPC proteins was functional for foaming at 6% protein concentration.     

Improving surface functional properties of tofu whey-derived peptides by chemical modification with fatty acids

Effect of acylation with saturated fatty acids on surface functional properties of tofu whey-derived peptides was investigated. Tofu whey (TW) and soy proteins (7S, 11S, and acid-precipitated soy protein [APP]) were hydrolyzed by Protease M 'Amano' G, and resulting peptide mixtures were acylated with esterified fatty acids of different chain length (6C to 18C) to form a covalent linkage between the carboxyl group of fatty acid and the free amino groups of peptide. Acylation significantly (P < 0.05) increased emulsifying properties of 7S, 11S, and APP peptides independent of fatty acid chain length. Acylation decreased water binding capacity although oil binding capacity of acylated tofu whey ultra filtered fraction (UFTW < 3 kDa), 7S- and 11S-peptides were improved compared to native peptides. 7S peptides acylated with long chain fatty acids had shown significant higher surface hydrophobicity as in contrast with acylated UFTW < 3 kDa and APP peptides. Fluorescence spectra studies revealed structural conformation of acylated soy peptides as compared to native peptides. This study shows that chemical modification with fatty acids can further affect functional properties of soy proteins.     

Evaluation of proteolytic and ACE-inhibitory activity of Lactobacillus acidophilus in soy whey growth medium via response surface methodology

Soy whey is a rich by-product of tofu-manufacturing industries. We have previously optimized the growth of Lactobacillus acidophilus FTCC 0291 in soy whey upon supplementation of meat extract, vegetable extract and peptone using response surface methodology (RSM). The present study evaluated the proteolytic and angiotensin-I converting enzyme (ACE)-inhibitory activities of L. acidophilus FTCC 0291 in the optimized soy whey medium. The probiotic-fermented soy whey exhibited growth-associated proteolysis and ACE-inhibitory activity. Proteolysis was highly correlated with ACE-inhibitory activity, indicating that peptides liberated via fermentation may have exerted in vitro antihypertensive properties. Of the three nitrogen sources studied, peptone was found to have the highest influence on growth performance and ACE-inhibitory activity. Our results strongly indicated that probiotic-fermented soy whey produced in vitro antihypertensive bioactivity, and hence could be further developed into a carrier for probiotics with enhanced functional properties.     

Comparative Study on Heat Stability and Functionality of Camel and Bovine Milk Whey Proteins

Heat stability, emulsifying, and foaming properties of camel whey have been investigated and compared with that of bovine whey. Camel whey is similar to bovine whey in composition, but is deficient in β-lactoglubulin (β-LG), a major component of bovine whey. Whether the deficiency in β-LG will affect stability and functional properties is not yet known. Substantial information on the functional properties of bovine milk whey proteins is available; however, there is little research done on functional properties of camel whey proteins. Therefore, the objective of this study was to investigate the heat stability, emulsifying, and foaming characteristics of camel whey proteins. Calorimetric studies showed no significant difference in heat stability between bovine and camel whey proteins in liquid form. Upon drying, thermograms indicated that the 2 proteins are different in composition and thermal stability. The difference is represented in the absence of β-LG and the occurrence of protein denaturation peak at a lesser temperature in camel whey. The first marginal thermal transition in bovine whey appeared at 81°C, followed by 2 other transitions at 146 and 198°C. For camel whey, the transitions appeared at 139, 180, and 207°C respectively. The first marginal denaturation peak in bovine whey is due to β-LG, which is essentially absent in camel whey, while the second peak is due to the mixture of α-lactalbumin, serum albumin, and possibly part of the partially stabilized β-LG structure during the denaturation process. Because camel whey is deficient in β-LG, the denaturation peak at 139 must be due to the mixture of α-lactalbumin and camel serum albumin. In both proteins, the highest thermal transition is due to sugars such as lactose. The solubility study has shown that camel whey is more sensitive to pH than bovine milk whey and that heat stability is lowest near the isoelectric point of the proteins at pH 4.5. The sensitivity to pH resulted in partial denaturation and increased tendency to aggregate, which caused poor and unstable emulsion at pH 5. Both bovine and camel whey proteins have demonstrated good foaming properties; however, the magnitudes of these properties were considerably greater in bovine milk for all of the conditions studied.     

蛋白质-卵磷脂复合体系功能特性的研究进展

蛋白质与卵磷脂间发生的相互作用可以增强蛋白质功能特性,且二者形成的复合体系不仅能够作为递送系统传递生物活性物质、药物等以达到在胃肠道中的缓释效果,提高包埋物质的装载率及体外释放度,还能够实际应用于食品工业中提高我国传统蛋白基产品的质量及拓宽种类,如蛋白粉、婴儿配方乳以及运动营养食品等。本文综述了玉米醇溶蛋白、大豆蛋白、卵磷脂的理化性质和功能特性,蛋白-卵磷脂二者间的相互作用对蛋白的改善,蛋白-卵磷脂复合纳米颗粒、乳液及凝胶的特性,以及复合体系在食品工业、医药等领域作为递送系统和提高食品质量的应用,为改善单一蛋白体系的稳定性及提高其应用价值提供参考价值依据,对促进我国蛋白基食品产业高质量发展具有重要意义。