Sunflower proteins: overview of their physicochemical,structural and functional properties

There is increasing worldwide demand for proteins of both animal and plant origin. However, animal proteins are expensive in terms of both market price and environmental impact. Among alternative plant proteins, sunflower seeds are particularly interesting in view of their widespread availability in areas where soy is not or only sparsely produced. Compared with other sources of vegetable proteins, sunflower seeds have been reported to have a low content of antinutritional factors. Although the absence of these factors is important, the functionality of the protein preparations will mainly determine their applicability. This review provides detailed information about sunflower seed composition and processing, including processes to remove phenolic compounds from meals. The main part of the review concerns the structure and functionality of the two major protein fractions, helianthinin and 2S albumins. Regarding functionality, emphasis is on solubility, thermal behaviour and surface activity. Protein structure and functionality are discussed as a function of extrinsic factors such as pH, ionic strength, temperature and the presence of other seed components, particularly chlorogenic acid. In addition, sunflower proteins are compared from a structural and functional point of view with other plant proteins, particularly soy proteins. Copyright © 2007 Society of Chemical Industry     

Effects of ozone on functional properties of proteins

The present study investigates whether the ozone treatment could be an alternative to improve some functional properties of proteins. Ozone treatment was applied on whey protein isolate and egg white proteins which have been extensively used in food products to improve textural, functional and sensory attributes. Ozone treatment of proteins was performed either in aqueous solutions or as gas ozonation of pure protein powders. Foam formation and foam stability of proteins were enhanced extensively. The solubility of proteins were reduced as influenced from the aqueous and gas ozonation medium. The reduction was more pronounced in egg white proteins. Ozone treatment affected emulsion activity of whey protein isolate negatively and reduced the emulsion stability.     

Recent advances in enzymatic modifications of food proteins for improving their functional properties

The tailoring of food proteins by enzymes is a powerful tool to improve their functional properties. Mainly proteinases from various origins have been used for such purposes. Controlled proteolysis leads generally to more soluble products with improved emulsifying properties but relatively poor foaming properties. This latter was the case in our studies on proteolysis of wheat gluten. We also have demonstrated that polypeptides characterized by a high functionality could be produced by proteolysis of wheat gluten. Depending on the conditions of the proteolytic attack, the cleavage sites as well as the type of generated peptides could be modified. In the case of milk proteins, peptic action on the proteins in ethanolic medium or on moderately esterified proteins results in unique fragmentation. Besides fragmentation achieved by proteases, the cross-linking of proteins to yield higher molecular size forms with transglutaminases was shown to improve the functional properties of proteins. These enzymes catalyse the binding of amines to proteins, cross-link the polypeptide chains and deamidate the glutaminyl residues. In the case of soybean isolates, gelification was obtained with lower protein concentrations. In the case of wheat gliadins, enzymatic deamination increased drastically the solubility in a wide range of pH. Additionally, enzymatically deaminated gliadins were shown to be very efficient in stabilizing emulsions, due to the formation of soluble polymers.     

Some functional properties of oilseed proteins

Oilseeds have potential food uses because of their high protein content. Besides, these proteins when added to a type of foods, supply desirable functional properties, such as whipping capacity and viscosity, emulsification and water and oil holding capacities. Rapeseed and soybean protein isolates were found to possess whipping capacity followed by those of sunflower, peanut, sesame, cottonseed and safflower. The addition of sugar improved the whipping properties of oilseed proteins. The whipping capacity of oilseed proteins decreased due to heating at 100 degrees C for time of 15 to 60 min. Soybean protein had the highest emulsifying capacity compared with the other oilseed proteins. The heated oilseed proteins had emulsification properties similar to or better than the control. Glandless cottonseed protein had high water and oil holding capacities. The water holding capacity of oilseed proteins decreased gradually as the duration of heating at 100 degrees C was increased. On the other hand the heated oilseed proteins had oil holding capacities similar to or better than unheated proteins.     

Changes in composition and functional properties of proteins and their contributions to Nham characteristics

Changes in composition and functional properties of proteins during fermentation of Nham, a Thai-fermented sausage, were studied. An alkaline-soluble fraction constituted a major protein component of Nham. The amount of each protein fraction in Nham varied, depending on the fermentation time. As fermentation proceeded, the progressive decrease in sarcoplasmic and myofibrillar protein fractions was accompanied by an increase in the alkaline-soluble fraction and non-protein constituents (P<0.05). Slow pH lowering to pH 4.6 during fermentation as a result of bacterial growth and accumulation of lactic acid affected the molecular conformation of the muscle proteins and resulted in changes in protein functional properties. The acid produced resulted in changes in solubility, water-binding capacity, textural properties, and color characteristics. Proteolysis of Nham proteins occurred during fermentation, resulting in increases in TCA-soluble peptides and free α-amino acids, which may contribute to the taste and aroma of Nham.     

Modification of functional properties of egg-white proteins

Egg-white proteins are extensively utilised as food ingredients due to their unique functional properties. Several attempts have been made in order to improve the functional properties of egg-white proteins and to identify the optimal formulations for unique food products. Experimental data proves that controlled denaturation of egg-white proteins can have a beneficial impact on various functional applications in the food industry such as emulsifying ability, heat stability, and gelation. This review describes the effect of heat-induced denaturation on protein structure and functionality. Studies on the impact of Maillard reaction, which aim to elucidate the structure-function relationship of egg-white proteins, are presented. A novel approach which could be the basis for the development of new methods aiming to improve the functional properties of egg-white proteins is also discussed.     

Evaluation of functional properties of offal proteins

Evaluation of functional properties of beef heart and lip tissue proteins was based on the data obtained in the following determinations: protein extractability, fat emulsifying capacity, emulsion stability, gel forming ability, and water holding capacity after heat treatment. Beef skeletal muscles were used as the control. It was found that extractability of proteins of the raw materials was low as well as their ability to stabilize emulsions was on a low level. Proteins soluble at high ionic strength (fraction HIS) of beef heart and lip tissue emulsified 80.7 ml and 68.9 ml of oil/100 mg of protein, respectively, as compared to 106.6 ml in the control group. Analogically, protein soluble at low ionic strength (fraction LIS) emulsified 77.9 ml, 61.2 ml and 100.4 ml of oil, respectively. Emulsion stability of offal proteins appeared to be dependent on ionic strength. Generally at higher concentrations of salt their ability to stabilize emulsions was better as well as their water holding capacity increased. Their gelation properties as compared to control were also low. In each case, the functionality of cardiac proteins proved to be better than that of beef lip tissue.     

超声波对花生蛋白功能特性的影响

用超声波处理花生蛋白粉溶液,测定不同条件下花生蛋白的功能特性。结果表明,超声波处理20min,起泡性从30%增大到60%,泡沫稳定性从17%增大到50%;超声波处理15min,乳化性从38.9%增加到49.3%;超声波处理6min,吸油性从0.91mL/g增大到1.51mL/g;超声波处理8min使1g/100mL花生蛋白溶液中花生蛋白溶解性从0.10g增大到0.35g,2g/100mL花生蛋白溶液中花生蛋白溶解性从0.23g增大到0.48g;pH大于4时,超声波使花生蛋白乳化性增强;NaCl浓度为0.2~0.4mol/L时,超声波使花生蛋白乳化性增强。      

Alcalase改性豌豆蛋白功能性研究

该研究以生产淀粉的副产物豌豆蛋白粉为原料,采用Alcalase对豌豆蛋白在加酶量0.16%、水解时间32.5 min、pH 8.0、温度55.4℃、底物浓度8%的水解条件下进行限制性水解,对酶改性豌豆蛋白的溶解性和泡沫特性进行研究,并对其相对分子质量分布进行分析。结果表明:水解产物的泡沫特性和溶解性在不同pH和NaCl浓度时均高于未水解样品,和大豆蛋白相当。同时,改性之后产物的分子量分布也有较大改变,小于10 000部分所占比例由未水解时的22.22%提高到79.39%,而相对分子质量小于2 000的比例提高了11.55%。     

Milk proteins: physicochemical and functional properties

Because of the growing trend toward widespread use of protein ingredients in food formulation and fabrication, an understanding of the relationships between the physical properties of proteins and their behavior in food systems is desirable. A range of milk-derived protein preparations, i.e., dry milk, milk proteins, caseins, whey proteins, and lactalbumin, are used in a range of food products for their specific functional attributes. In this paper some of the apparent relationships between the properties of the protein components and specific functional properties are discussed. Thus, the roles of milk proteins in determining some important physical characteristics (i.e. color, bulk density, sinkability, dispersibility) of milk powders and their involvement in a range of functional properties (water holding, solubility, rheological behavior, gelation, film formation, emulsification, and foaming) are reviewed. Because of the various methods and conditions used in determining functional properties and the variability in composition of preparations it is difficult to compare data and/or reconcile differences in published information. The desirability of developing standard methods is emphasized.     

Investigation of functional properties of partially hydrolyzed proteins

Hydrolyzates were prepared from soy protein and milk protein by treatment with Alcalase(R) 0.6 L and Neutrase(R) 0.5 L (NOVO INDUSTRI A/S, Bagsvaerd, Denmark). The pH-stat is a good method to control the change of degree of hydrolysis (DH) during enzymatic reactions and gives as well a good possibility to produce partially hydrolyzed products. In case of both investigated substrates we found a good correlation between the DH-values measured by pH-stat and TNBS-method. Determining the functional properties, we found that the emulsifying activity of hydrolyzates with low DH (below 10%) is significantly improved. At the same time the enzymatic treatment decreases the water-binding considerably but increases the velocity of water binding.     

Influence of selected factors on functional properties of textured milk proteins

Studies were made on the influence of two variable factors—fat content and added salt—on the following functional properties of textured milk proteins: water absorption capacity, thermal shrinkage, consistency, viscosity, fat absorption, emulsifying capacity and emulsion stability.
Variation in fat content of the product (11% and 15%) was obtained by introducing various amounts of fat to skim milk in the course of the production of textured milk proteins. The salt concentration of the preparation was modified by adding sodium chloride, Hamine polyphosphate mixture or both those salts jointly.
The results indicate that the functional properties of the preparation were influenced by the two above mentioned factors in a statistically significant manner. The higher fat content of the product (15%) was accompanied by better fat emulsifying capacity and emulsion stability and lower thermal shrinkage. The salts used for these studies were found to influence favourably the functional characteristics of the preparation. The addition of sodium chloride appears to be most expedient, as it improves important technological properties such as fat absorption and emulsifying capacities.     

糖基化大豆抗原蛋白的结构与功能特性研究进展

大豆球蛋白与大豆β-伴球蛋白是大豆蛋白的主要组成成分,也是主要的过敏原,二者通过影响大豆蛋白的性质改变其营养和功能特性。糖基化会使大豆抗原蛋白发生不同程度的改性,从而影响大豆蛋白产品的品质与特性。因此,研究大豆抗原蛋白在糖基化过程中的结构和功能特性的变化,对促进大豆蛋白深加工具有重要意义。本文分析了大豆主要抗原蛋白组成与结构特点,综述了大豆抗原蛋白在糖基化过程中的结构变化对其功能特性的影响,具体表现在溶解性、乳化性、乳化稳定性提高,凝胶性改善、致敏性降低。这些功能特性的改变为大豆蛋白开发和应用创造了条件。其目的是为大豆蛋白糖基化机理及工业化生产提供理论。     

Mechanical properties of mammalian and fish gelatins based on their weight average molecular weight and molecular weight distribution

Acid porcine skin gelatins (type A), lime bone gelatins (type B) and gelatin from different cold water fish species were compared on the basis of low deformation mechanical properties, Bloom value, weight average molecular weight, molecular weight distribution and isoelectric point. The dynamic storage modulus and Bloom value for all types of gelatin increased with increasing weight average molecular weight. Type A and type B gelatins with similar weight average molecular weight exhibited different dynamic storage modulus (G′) and different Bloom values. This is most probably due to a different molecular weight distribution as well as the presence of different hydrolytic fragments. The present study suggests that it may be possible to improve the mechanical properties by removing low molecular weight molecules from a gelatin sample. The Bloom values for gelatin from haddock, saithe and cod were determined to be 200, 150 and 100 g from a linear correlation between G′ and Bloom.     

Effects of temperature on food proteins and its implications on functional properties

This article surveys the knowledge in the area of protein structure and chemistry of denaturation prior to an indepth review of the effects of heat on soy, milk, and egg proteins. It also reviews the methods available to assess denaturation of proteins. Protein denaturation is an ambiguous phenomenon and the consequences of denaturation on the functional properties of proteins is further confounded by this ambiguity. For each of the three food proteins, the known chemistry of individual proteins is reviewed followed by observations made on changes induced by heat in each protein group. Food proteins are not pure entities and purification and physicochemical characterization of various components of the food proteins have not been thoroughly investigated. Further, food is a complex milieu of water, fat, carbohydrate, vitamin, minerals, etc. along with proteins, and processing affects not only each individual component in the food but also the nature and intensity of intercomponent interactions in a food.     

Effect of heating cast kafirin films on their functional properties

Edible films can be produced from kafirin but the diverse food product requirements necessitate modification of the films. To modify their functional properties, kafirin films were cast, with and without plasticizer, from glacial acetic acid (GAA) and aqueous ethanol (AE), then heated using microwave energy. A power of 80 W for 2 min caused an approximately two‐ and fourfold increase in the tensile strength of non‐plasticized and plasticized films, respectively. Film glass transition temperature increased by about 15%. Film biodegradability was slowed. However, only the digestibility of the non‐plasticized films cast from AE heated for the longest time (4 min) was decreased, by about 25%; while that of the other films was not affected. GAA cast films had higher digestibility than AE cast ones, possibly as a result of acid‐mediated deamidation of kafirin. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis indicated heat‐induced kafirin oligomers. Scanning electron microscopy of heated plasticized films showed more wrinkled structures compared to non‐heated films, whereas the non‐plasticized films appeared more brittle with heating. The results indicate that heat‐induced intermolecular disulfide cross‐linking was involved in modifying the properties of kafirin films. Copyright © 2006 Society of Chemical Industry     

物理法改善鱼肉蛋白功能特性研究概述

鱼肉是优质蛋白的重要来源。为了提高鱼肉蛋白的利用率,可通过物理方法改善蛋白质的功能特性,提升鱼肉蛋白的应用价值和应用前景。该文综述了几种改善鱼肉蛋白功能特性的物理新方法,阐述其对鱼肉蛋白功能特性的影响,并对物理法在鱼肉蛋白改性上深入研究进行展望,以期为鱼肉蛋白改性加工提供指导。     

The use of edible insect proteins in food: Challenges and issues related to their functional properties

Over the past decade, the potential of edible insects as a novel ingredient in high value-added products has been investigated to find alternatives to conventional protein sources that are expensive, over-exploited and harmful to the environment. This review assesses the state of insects as an alternative protein source from production to consumption. More specifically, this review details the conventional procedures related to the production of insect flours as well as insect-derived ingredients such as protein concentrates and isolates. As a source of alternative protein in food ingredient formulations, the available data on the functionalities of edible insect ingredients is also examined and compared to conventional animal- and plant-based protein sources. Finally, the major challenges facing entomophagy in the mainstream food industry are explored. This review highlights the fact that insect proteins can serve as functional ingredients in food preparation. However, additional comparative studies are required to assess the functionality of various insect proteins compared to conventional proteins, regardless of processing method. To be incorporated into large scale industries, more research is needed to optimize processing methods to obtain the best compromise between cost-effectiveness, functionality, tastiness and sustainability, while ensuring consumer safety.     

Peptides from milk proteins and their properties

This review has attempted to study the literature pertaining to peptides derived from milk proteins. Hydrolysis of milk proteins to generate peptides has been practiced for a long time and it was recognized early on in this process that the taste of hydrolyzates might hinder use of these products in food formulations. Modification of protein is necessary to form a more acceptable or utilizable product, to form a product that is less susceptible to deteriorative reactions and to form a product that is of higher nutritionall quality. Modifications may be achieved by a number of chemical and enzymatic means. This review has considered only enzymatic modification of dairy proteins. Modified proteins contain peptides and some of these peptides have been purified and their functionalities have been compared with unmodified proteins. This paper has examined the literature pertaining to improvement in functionality of enzyme-modified proteins. Improvements in solubility, emulsification, foaming and gelation were examined. There is limited information available on the sequence of the peptides necessary to improve the functional characteristics of proteins. Knowing the sequences of desirable functional peptides can lead to genetic alteration of proteins to improve functionality. Addition of synthetic peptides to intact proteins may be another way in which the functionality of proteins can be augmented. Some of the peptides in milk proteins are capable of affecting biological functions of an organism. These effects can be antimicrobial and probiotic, i.e., prevent the growth and proliferation of undesirable and pathogenic organisms, or they may promote the growth of desirable bacteria in the digestive tract of humans and animals. Peptides derived from milk protein have been shown to exert digestive and metabolic effects as well. They may also influence the immune system. These biological effects may play an important role in the development of medical foods that treat or mitigate the effects of diseases. Proteins are allergens and therefore it is possible that products derived from modification of proteins may also be allergens. The known literature about the allergenicity of peptides derived from milk proteins has been examined in this article. Last, but not the least, the taste attributes of peptides is also considered. Bitterness of hydrolyzates is a common occurrence and the origins of these bitter peptides and possible ways of mitigating this sensory defect has been discussed. Many of the peptides that enhance functionality and exert biological activity are likely to be bitter. Therefore, the bitter taste of hydrolysis products has to be dealt with in boosting the functional or nutraceutical aspects of foods containing these peptides. Analytical techniques for sequencing peptides have become more accessible and purification of peptides is commercially feasible. Computer based modeling techniques have aided the prediction of structures in these peptides. These advances, coupled with the advances in biotechnology, promise to revolutionize the future of nutraceutical and functional foods.     

乙酰化改性对米渣蛋白功能性质的影响

采用乙酰化对米渣蛋白进行改性,研究了米渣蛋白在乙酰化改性过程中巯基和二硫键含量、表面疏水性、溶解性以及乳化性的变化。结果表明,随改性程度的增加,米渣蛋白中暴露巯基含量逐渐增加,总游离巯基含量逐渐下降,二硫键含量逐渐增加,表面疏水性先下降后升高。乙酰化改性后的米渣蛋白在p H5~10范围内的溶解性、乳化活性和乳化稳定性明显增加,但是p H2~4范围内的溶解性和乳化活性却有所降低。可见,乙酰化改性能改善米渣蛋白的部分功能性质。