A comparative study of the functional properties of amaranth and soybean globulin isolates

The functional properties of the amaranth globulin isolate were determined and compared to those of the well studied soybean globulin isolate. Functional properties investigated included protein solubility, heat coagulation, foaming and emulsifying activity and stabilities, as well as fat binding. Overall, the amaranth globulin isolate was found to have significantly higher solubility (p ⪇ 0.05) i.e., 9 times higher, and higher heat stability (p ⪇ 0.05) in the vicinity of its isoelectric point, pH 5–6, than the corresponding soybean globulin isolate. Between pH 3–9 the amaranth globulin isolate was found to have significantly higher (p ⪇ 0.05) foaming capacities and stabilities than the soybean isolate. Maximum foaming capacity for the amaranth globulin was determined to occur around its isoelectric point. The emulsifying activity of the amaranth globulin isolate was found to be significantly higher (p ⪇ 0.05) between pH 3–9 than the corresponding soybean globulin isolate. The most substantial difference between the two isolates was that the amaranth isolate showed maximal emulsifying activity and stability at pH 7.0. Little difference was observed in the fat absorption capacities between the two prepared isolates. Nutritionally, the amaranth globulin isolate was found to be of superior quality compared to the soybean globulin isolate due to its higher content of essential amino acids. Overall, the functional properties of the amaranth globulin isolate were much better than the soybean isolate especially in the vicinity of its isoelectric point, suggesting a potential advantage if used in various thermally processed food formulations that fall within this pH range; a range where more common isolates perform very poorly.     

Relationship between physicochemical and functional properties of amaranth (Amaranthus hypochondriacus) protein isolates

Protein isolates from six amaranth lines/cultivars (APIs) were evaluated to study their physicochemical (hunter colour, protein content and zeta potential), structural (thermal and conformational) and functional (emulsification, foaming, water and fat absorption) properties. APIs had protein content, whiteness index and gel temperature in range of 79.4–85.4%, 41.17–54.26 and 87.8–91.8 °C, respectively. The Fourier‐transform infrared spectra of APIs revealed α‐helix, β‐sheets and random coil conformations in the secondary structure. APIs with higher relative proportion of β‐sheets had higher Differential Scanning Calorimeter denaturation temperature and gel temperature. Minimum protein solubility (PS) was observed at pH 5.0, indicating isoelectric point (pI) of amaranth proteins. The PS, emulsifying activity index (EAI), emulsifying stability index (ESI), foaming capacity (FC) and foam stability (FS) of APIs at neutral pH were related to their zeta potential (ζ). The emulsifying and foaming properties were also determined at different pHs (between 2.0 and 9.0). The EAI‐pH profile of APIs confirmed close relationship between the emulsifying ability and PS.     

Peanut protein concentrate: Production and functional properties as affected by processing

Peanut protein concentrate (PPC) was isolated from fermented and unfermented defatted peanut flour by isoelectric precipitation and physical separation procedures. PPC was dried by spray or vacuum drying. PPC powders from each drying technique were evaluated for proximate composition and functional properties (protein solubility, water/oil binding capacity, emulsifying capacity, foaming capacity and viscosity) along with defatted peanut flour and soy protein isolate as references. PPC contained over 85% protein versus 50% protein in the defatted peanut flour used as raw material for PPC production. PPC had a solubility profile similar to that of peanut flour, with minimum solubility observed at pH 3.5–4.5 and maximum solubility at pH 10 and higher. Roasting of peanut reduced all functional properties of defatted peanut flour while fermentation had the reverse effect. The type of drying significantly affected the functional properties of PPC. Spray dried PPCs exhibited better functional properties, particularly emulsifying capacity and foaming capacity, than vacuum oven dried PPC. Spray dried PPCs also showed comparable oil binding and foaming capacity to commercially available soy protein isolate (SPC). At equivalent concentrations and room temperature, PPC suspension exhibited lower viscosity than soy protein isolate (SPI) suspensions. However, upon heating to 90 °C for 30 min, the viscosity of PPC suspension increased sharply. Results obtained from this study suggest that the PPC could be used in food formulations requiring high emulsifying capacity, but would not be suitable for applications requiring high water retention and foaming capacity. PPC could be a good source of protein fortification for a variety of food products for protein deficient consumers in developing countries as well as a functional ingredient for the peanut industry. The production of PPC could also add value to defatted peanut flour, a low value by-product of peanut oil production.     

Selected functional properties of detoxified rapeseed protein preparations effected by phytic acid

Detoxified rapeseed protein preparations with high protein content (>90 %) produced by extraction, ultra-and diafiltration, have a very good solubility and excellent foaming properties (better than egg white). The emulsifying properties (emulsifying activity and emulsion stability) are moderate. The N-solubility profile of these preparations (albumin and globulin mixing) has been influenced by phytic acid (PA). It is possible to observe a shift of the isoelectric range to lower pH-values and parallel a decrease of solubility if the amount of PA (3, 5, 10 %) is increased. The foaming properties have also been dependent on the PA content. A higher concentration of PA (3, 5, 10 %) causes a decrease in the foaming activity. The results have been discussed concerning the interactions between PA and proteins.     

桃仁清蛋白与大豆分离蛋白功能特性比较研究

为提高桃仁清蛋白(PKA)在食品工业中的应用,将其与大豆分离蛋白(SPI)对照,研究了PKA的溶解性、持水性、持油性、起泡性及泡沫稳定性、乳化性及乳化稳定性和凝胶性等功能特性.结果表明:与SPI相比,PKA具有很好的溶解性、泡沫稳定性、乳化稳定性及较低的凝胶质量浓度,持油性略高于SPI,但起泡性、乳化性及持水性较差;PKA溶解性受溶解条件影响较小.PKA具有良好的功能性质,适合作为食品添加剂或配料.     

热水蒸煮大豆蛋白产品的功能性研究

研究了热水蒸煮时间对脱脂大豆粉、醇洗大豆浓缩蛋白、大豆分离蛋白的影响。热水蒸煮提高了浓缩蛋白和分离蛋白的起泡性和乳化性，对脱脂大豆粉的乳化性有所提高，但不能提高其起泡性。破坏胰岛素抑制剂和微生物的热水蒸煮对蛋白质的加工具有重要的意义。     

Functional properties of isolated porcine blood proteins

The isolated proteins contained in the blood from slaughterhouses could be recovered and used to improve the functional and nutritional properties of food products. In this work some functional properties, namely solubility, emulsifying capacity, gelling and foaming capacity have been tested for different protein fractions of porcine blood. The blood proteins studied were globins (α, β and γ), albumin and fibrinogen and the whole plasma from the plasmatic fraction, and haemoglobin and globin obtained from the haemoglobin by a chemical method from the cellular fraction. The effect of pH and protein concentration on functional properties was determined. Results indicate that blood proteins present good functional properties specially solubility, gellation and emulsifying capacities that could make blood protein useful as food additives in the formulation of food products.     

Comparative studies on the functional properties of various protein concentrate preparations of peanut protein

The effect of different preparations on the functional properties of peanut protein concentrates was studied. Peanut protein concentrates were isolated from defatted peanut flour by isoelectric precipitation, alcohol precipitation, isoelectric precipitation combined with alcohol precipitation, alkali solution with isoelectric precipitation and their functional properties (protein solubility, water holding/oil binding capacity, emulsifying capacity and stability, foaming capacity and rheology) were evaluated. The results showed that the protein solubility, foaming capacity and stability of protein prepared by alkali solution with isoelectric precipitation were the best of all the peanut protein products. But the protein prepared by alcohol precipitation had better water holding/oil binding capacity, which was significantly different from other protein products. The emulsifying stability of protein concentrate prepared by different methods was significantly lower than that of defatted protein flour. The protein prepared by isoelectric precipitation and isoelectric precipitation combined with alcohol precipitation had better gel properties which indicated that they were a potential food ingredient.     

Applications of soy protein hydrolysates in the emerging functional foods: a review

Several applications of protein hydrolysates have been documented including gelation, solubility and emulsifying properties. However, very rare reviews have solely explored the potentials of soy protein hydrolysates (SPHs). Varying and abundant pieces of information on the physicochemical properties of soy proteins, such as foaming, solubility, emulsifying, gelling, fat- and water-holding capacities, suggest their hydrolysates to be equally or more important. In this regard, this review highlights the different methods that have been used to prepare SPHs, coupled with the most promising applications and potentials of SPHs. Nonetheless, further investigations are necessary to validate the potentialities of SPHs as food agents for the emerging functional foods.     

Modified Soy Proteins with Improved Foaming and Water Hydration Properties

Soy proteins were modified by alkali treatment at pH 10.0, followed by papain hydrolysis. Solubility, water hydration capacity (WHC), surface hydrophobicity, foaming and emulsifying properties of unmodified, alkali-treated, and papain-modified soy protein (PMSP) were compared. PMSP exhibited higher solubility (100% at pH > 7.0), WHC (3.13) and hydrophobicity (40.8) than unmodified soy protein which had solubility 68.5%, WHC 0.21, and hydrophobicity 8.1. The PMSP had foaming capacity (22.0 mL) similar to egg white (21.2 mL) at pH 7.0; and enhanced foam stability (36.4) compared to the unmodified control (32.9). In general, alkali-treated soy had lower functional properties. Emulsifying properties of PMSP and alkali treated soy were unchanged by the modification. PMSP could be used as an egg white substitute in foaming applications at neutral pH.     

Improving Functional Properties of Soy Protein Hydrolysate by Conjugation with Curdlan

ABSTRACT:  Soy protein hydrolysate was conjugated with curdlan through the naturally occurring Maillard reaction to extend its application in food processing. The gel-forming and emulsifying properties of soy protein hydrolysates were significantly improved ( P < 0.05) by conjugation with curdlan. The soy protein hydrolysate–curdlan conjugate (SPHCC)–soy protein isolate (SPI) mixed gel had a much thicker network than the soy protein hydrolysate and SPI mixed gel judged from scanning electron microscopic images. The improvement of gelling properties of soy protein hydrolysate by curdlan-conjugate was attributed to both the decrease in the repulsive forces among soy protein hydrolysates and the increase in the solubility. The covalent binding of soy protein hydrolysates and curdlan also showed a profound effect on the antioxidative activity of the soy protein hydrolysates. The higher antioxidative activity of SPHCC was related to the peptide reductants produced from the Maillard reaction and the higher emulsifying property of SPHCC. The conjugates of soy protein hydrolysate and curdlan can be used as a functional food additive having excellent gel-forming, emulsifying properties and antioxidative activity.     

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。     

燕麦麸蛋白的组成及功能性质研究

以燕麦麸为原料制备了燕麦麸浓缩蛋白（OBPC）。同时，也按照Osborne蛋白分级提取方法对燕麦麸蛋白进行了精细的分类，分别得到了燕麦麸清蛋白、球蛋白、醇溶蛋白和谷蛋白。球蛋白和谷蛋白是燕麦麸蛋白的主要组分。清蛋白提取液中含有高含量的可溶性碳水化合物，可以通过（NH4）2S04分级沉淀的方法将其纯度由6．5％提高到67．2％。SDS-PAGE的结果表明OBPC及各蛋白组分有不同的分子组成。OBPC及各蛋白组分的功能性质，包括溶解性、持水持油性、乳化活性、泡沫性质也分别进行了测定，以评价燕麦蛋白作为一种潜在的配料在食品中的应用价值。     

干热处理下焦磷酸钠改性大豆蛋白乳化和起泡性质研究

研究了在80℃干热条件下焦磷酸钠改性大豆蛋白的乳化和起泡性质。研究发现:改性大豆蛋白的乳化性质和起泡性质得到明显的改善,蛋白质结合磷的量随干热处理时间的延长而增加。在干热处理前对大豆蛋白进行适度的预热处理大大提高了蛋白质结合磷的量,80℃预热处理10min使改性大豆蛋白表现出最好的乳化性质,而预热处理20min的改性蛋白质却表现出最好的起泡性质。红外光谱分析发现,焦磷酸钠以磷酸根的形式与蛋白质分子的游离羟基缩合。SDS-凝胶电泳表明,焦磷酸钠能抑制干热处理时大豆蛋白各亚基之间的聚合作用,从而提高其功能性质。该研究为大豆蛋白的改性提供了新的思路。     

大豆蛋白改性产物乳化特性研究进展及其应用

大豆蛋白作为一种安全的乳化剂常被应用于食品乳化体系,通过物理法、酶法和化学法可诱导大豆蛋白的结构变化,改善大豆蛋白乳化性。本文将简要介绍改性大豆蛋白乳化能力及乳化稳定机理,分析影响乳化特性的因素。详细探讨物理法（热处理,超声法,高压处理）、酶法（水解酶,交联酶）和化学法（糖基化法）改性后大豆蛋白的乳化特性改善。最后针对大豆蛋白作为乳化剂在食品行业的应用与发展进行深入讨论。     

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。     

籽粒苋蛋白质功能特性的理论研究(II)—籽粒苋蛋白质发泡性的理论研究

采用碱性提取和等电点法分离出籽粒苋蛋白质 ,测定了不同浓度、pH值、离子强度、蔗糖浓度条件下的蛋白质发泡力和泡沫稳定性 ,探讨了籽粒苋蛋白质在不同条件下发泡性的变化规律 ,为籽粒苋蛋白质在食品加工中的应用提供了一定的理论依据。     

大豆肽的分级膜分离及功能特性研究

本文采用不同截留分子量的超滤膜对大豆肽溶液进行分级分离 ,将Alcalase碱性内切蛋白酶水解大豆分离蛋白制得的大豆肽溶液分成分子量 >30kD、10kD～ 30kD、5kD～ 10kD和 <5kD四个组分 ,并对不同分子量段大豆肽的分子量分布和功能特性进行研究。结果表明 :膜分离方法能对大豆肽进行有效的分离 ;不同分子量的大豆肽在溶解性、起泡性和乳化性等功能特性方面也各不相同     

An enzyme-based extraction process for the purification and enrichment of vegetable proteins to be applied in bakery products

In the current study an efficient aqueous extraction procedure using glucoamylase was developed to produce food grade protein extracts from lentils and white beans. The extracts contained 50.3 ± 0.6 and 49.2 ± 0.05 g protein per 100 g dry extract, respectively. The nutritional value of lentil and white bean protein extracts proved to be satisfying according to the amino acid composition, where methionine was the limiting amino acid. The produced extracts were tested for their technological properties. Both lentil and white bean protein extracts showed similar or even better technological properties regarding foaming and emulsifying capacities, heat stability and gelling properties compared to soy and pea protein extracts. Food application tests in white bread, pound cake and sponge cake proved lentil and white bean protein extracts to be potential alternatives to soy protein in replacing proteins from animal origin.     

Effects of Preparative Processes on the Composition and Functional Properties of Protein Preparations from Candida utilis

Protein preparations were made from continuously grown Candida utilis cells using processes which included cell disruption, aqueous protein extraction, nucleic acid reduction, protein precipitation and freeze- or spray-drying. The composition of the preparations was in the range 48–57% crude protein and 2–11% RNA, depending on the procedures used for concentrating protein and reducing nucleic acid. Functional properties examined included water-binding capacity, emulsifying properties, nitrogen and protein solubility, fat absorption, foaming properties, and bulk density. No single yeast preparation was superior to the others in all properties tested. Although heating processes, and in particular heat shocking of cells at 68°C with subsequent incubation at 50–55°C, were generally detrimental to functional properties, no processing procedure always affected all functional properties in the same way. The functional properties of some of the yeast preparations were found to compare favorably with those of the standard reference proteins, soy protein isolate, and sodium caseinate.