Advancement of food-derived mixed protein systems: Interactions,aggregations, and functional properties

Recently, interests in binary protein systems have been developed considerably ascribed to the sustainability, environment-friendly, rich in nutrition, low cost, and tunable mechanical properties of these systems. However, the molecular coalition is challenged by the complex mechanisms of interaction, aggregation, gelation, and emulsifying of the mixed system in which another protein is introduced. To overcome these fundamental difficulties and better modulate the structural and functional properties of binary systems, efforts have been steered to gain basic information regarding the underlying dynamics, theories, and physicochemical characteristics of mixed systems. Therefore, the present review provides an overview of the current studies on the behaviors of proteins in such systems and highlights shortcomings and future challenges when applied in scientific fields.     

Expression profiles of effector proteins SopB, SopD1, SopE1, and AvrA differ with systemic, enteric, and epidemic strains of Salmonella enterica

The presence and expression of sopB, sopD1, sopE1, and avrA genes encoding virulence associated effector proteins were studied comparatively in 405 Salmonella enterica strains. They belong to different serovars and clonal types (genotypes, phage types) and originated from different clinical (systemic infection, focal enteritis, enterocolitis) and epidemic sources (epidemics, sporadic cases). The sopB and sopD1 determinants were commonly prevalent, but sopE1 and avrA genes only in 55% and 80%, respectively. A correlation of this pattern of absence and presence of the respective genes to the epidemic and clinical origin could not be detected. In contrast, the expression of the respective genes appeared differently: SopB and SopE1 proteins are well produced, but SopD1 and AvrA proteins only rarely under the applied standard culture conditions. However, using a range of different environmental signals (temperature, pH, cations, etc.) some of the S. enterica nonproducer strains (e. g., S. Agona, S. Bovismorbificans, S. Virchow, etc.) begin to produce AvrA and SopD1. They turned now into an expression profile which was found typically for the epidemic strains of S. Typhimurium and S. Enteritidis. Also S. enterica strains from systemic infections could be characterized by their strong SopB and SopE1 expression while SopD1 and AvrA proteins were missing. Although it is premature to outline generally a correlation of these expression profiles and the clinical and epidemiological potency of Salmonellae, the reported results allow a first understanding how a fine tuning of their virulence will take place.     

Comparative study of the physiological properties of collagen, gelatin and collagen hydrolysate as cosmetic materials

The cell biological properties of collagen, gelatin and collagen hydrolysate (<15 000 Da) were studied using murine keratinocytes. Keratinocyte culture experiments demonstrated that only collagen had significant effects on cell attachment and proliferation, but the results of cells cultured on gelatin and collagen hydrolysate showed the rates of adhesion and proliferation were similar to those of cells cultured on plastic as a control. It is concluded that collagen has better physiological effects than those of gelatin and collagen hydrolysate as skin-care cosmetic materials.     

Precipitation of salivary proteins after the interaction with wine: the effect of ethanol, pH, fructose, and mannoproteins

Astringency is a complex sensation mainly caused by the precipitation of salivary proteins with polyphenols. In wine it can be enhanced or reduced depending on the composition of the medium. In order to investigate the effect of ethanol, tartaric acid, fructose, and commercial mannoproteins (MPs) addition on the precipitation of salivary proteins, the saliva precipitation index (SPI) was determined by means of the sodium dodecyl sulphate polyacrylamide gel electrophoresis of human saliva after the reaction with Merlot wines and model solutions. Gelatin index, ethanol index, and Folin-Ciocalteu index were also determined. As resulted by Pearson's correlation, data on SPI were well correlated with the sensory analysis performed on the same samples. In a second experiment, increasing the ethanol (11%-13%-17%), MPs (0-2-8 g/L), fructose (0-2-6 g/L) level, and pH values (2.9-3.0-3.6), a decrease in the precipitation of salivary proteins was observed. A difference in the SPI between model solution and red wine stated that an influence of wine matrix on the precipitation of salivary proteins occurred. PRACTICAL APPLICATION: Results provide interesting suggestions for enologists, which could modulate the astringency of red wine by: (i) leaving some residual reducing sugars (such as fructose) in red wine during winemaking of grapes rich in tannins; (ii) avoiding the lowering of pH; (iii) adding commercial mannoproteins or promoting a "sur lie" aging; and (iv) harvesting grapes at high technological maturity in order to obtain wines with a satisfactory alcoholic content when possible.     

Effect of Chemical Modification, pH Change, and Freezing on the Rheological, Solubility, and Electrophoretic Pattern of Wheat Flour Proteins

ABSTRACT: In this study the effect of chemical modification and freezing of dough on the characteristics of wheat proteins and the rheological properties of dough was investigated. A slight increase in the protein solubility and disappearance of protein bands in the range of 55 to 70 KDa was observed when samples were frozen for 6 to 8 weeks. Ascorbic acid decreased and cysteine and bisulfite increased solubility of wheat proteins. Dough stability increased as pH was raised above 6.5. Two protein bands in the range of 55 to 60 KDa appeared in ascorbic acid treated doughs and the intensity of bands of less than 6.5 KDa increased in cysteine or bisulfite treated doughs. Several protein bands in the range of 30, 50, and 90 KDa appeared when the pH was raised to 7.0 and above. The results of this study suggest that high- molecular-weight proteins of wheat flour have a major influence on the properties of dough and that these proteins are affected by chemical treatment, pH change, and freezing.     

Interactions between milk proteins and polyphenols: Binding mechanisms,related changes,and the future trends in the dairy industry

The biological activity and techno-functional properties of phenolic compounds have gained great importance due to the epidemiologically-proved health benefits. Use of polyphenols as fortification agents for functional food production and nanotechnological approaches using natural vehicles for polyphenol delivery have been recently discussed. In this respect, milk proteins and dairy products represent unique characteristics for polyphenol studies. The conflicting results on the functionality of polyphenols interacting with milk proteins either in model systems or in complex dairy matrices reveal the need for future studies.     

Effect of microbial transglutaminase on the protein fractions of rice,pea and their blends

BACKGROUND: Transglutaminase (TG) is a transferase that has been used for crosslinking proteins. In general, those interactions are promoted within proteins of the same nature, and very few studies have been conducted for creating new bonds between proteins from different sources catalysed by TG. The effect of TG on the protein fractions of rice flour, pea protein isolate and their blends was studied by using different electrophoretic analyses (simple sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS‐PAGE) and multistaking SDS‐PAGE under reducing and non‐reducing conditions). RESULTS: TG induced the disappearance of numerous protein bands as a consequence of the formation of large protein polymers, linked by isopeptidic and disulfide bonds, with reduced solubility. The main protein fractions involved in those interactions were the albumins and globulins, from the pea protein isolate, and the rice flour; and the glutelins were also crosslinked. CONCLUSION: Composite flours containing the rice flour and the pea protein isolate are proposed for obtaining a protein‐enriched dough with better amino acid balance. Also a protein network formed of protein aggregates of high molecular weight can be created in the presence of transglutaminase. Copyright © 2007 Society of Chemical Industry     

蒸谷米糠蛋白功能特性研究

研究在不同温度和不同pH值条件下,酶解提取的蒸谷米糠蛋白（PRBP）溶解性、乳化性和泡沫性,并和大豆分离蛋白（SPI）做比较。结果发现：在不同温度下,蒸谷米糠蛋白的溶解性、乳化性、泡沫性随温度增加,先升高后下降。而乳化稳定性和泡沫稳定性一直下降;在不同pH值下,蒸谷米糠蛋白的溶解性、乳化性、泡沫性与泡沫稳定性随pH值增加,先降低、后升高,而乳化稳定性先升高后降低;大豆分离蛋白的乳化性和泡沫性好于蒸谷米糠蛋白。     

Immunoglobulin E-reactivity of wheat-allergic subjects (baker's asthma, food allergy, wheat-dependent, exercise-induced anaphylaxis) to wheat protein fractions with different solubility and digestibility

Baker's asthma, food allergy to wheat, and wheat-dependent, exercise-induced anaphylaxis (WDEIA) are different clinical forms of wheat allergy. We investigated the correlation of solubility and digestion stability of wheat allergens with the IgE-reactivity patterns of different patient groups. Three wheat protein fractions were extracted according to their solubility: salt-soluble albumins and globulins, ethanol-soluble gliadins, and glutenins soluble only after treatment with detergents and reducing reagents. Sera from subjects with history of each variant of wheat allergy were characterized by CAP FEIA and immunoblotting. There was a high degree of heterogeneity of recognized allergens between the different subject groups as well as within these groups. However, subjects with WDEIA showed similar immunoglobulin E (IgE)-reactivity patterns to gliadins and especially to a 65 kDa protein. Subjects with baker's asthma as well as the food-allergic subjects had the most intense IgE-reactivity to the albumin/globulin fraction. The latter group additionally showed IgE-reactivity to the other fractions. Divergent results of immunoblotting and CAP-FEIA demonstrated that the detection of wheat-specific IgE highly depends on the applied method, thus the diagnostic tool must be carefully chosen. Most wheat allergens were rapidly digested as analyzed by determination of IgE-reactivity on immunoblots to wheat extracts after simulation of gastric and duodenal digestion. However, ethanol-soluble gliadins were stable to gastric enzymes and exhibit low solubility in gastric and duodenal fluids. Therefore, they are likely to be important in food allergy to wheat.     

Plant‐based Milks: A Review of the Science Underpinning Their Design,Fabrication, and Performance

Many consumers are interested in decreasing their consumption of animal products, such as bovine milk, because of health, environmental, and ethical reasons. The food industry is therefore developing a range of plant‐based milk alternatives. These milk substitutes should be affordable, convenient, desirable, nutritional, and sustainable. This article reviews our current understanding of the development of plant‐based milks. Initially, an overview of the composition, structure, properties, and nutritional profile of conventional bovine milk is given, because the development of successful alternatives depends on understanding the characteristics of real milk. The two main production routes for fabricating plant‐based milks are then highlighted: (i) disruption of plant materials (such as nuts, seeds, or legumes) to form aqueous suspensions of oil bodies; (ii) formation of oil‐in‐water emulsions by homogenization of oil, water, and emulsifiers. The roles of the different functional ingredients in plant‐based milks are highlighted, including oils, emulsifiers, thickeners, antioxidants, minerals, and other additives. The physicochemical basis of the appearance, texture, and stability of plant‐based milks is covered. The importance of the sensory attributes and gastrointestinal fate of bovine milk and plant‐based alternatives is also highlighted. Finally, potential areas for future work are discussed.     

Isolation,purification, and alteration of some functional groups of major milk proteins: A review

This review covers selected methods of isolation and purification of mainly α_s‐casein, β‐casein, κ‐casein, β‐lactoglobulin, and α‐lactalbumin. Selected methods of alteration of some functional groups of these proteins also were reviewed. Isolation and purification of milk proteins per se are methods of modifying the individual milk proteins. Gram quantities of these proteins can now be purified in a relatively short time using ion‐exchange resins. Due to the prominent use of non‐food‐grade reagents in the procedures for preparation of these milk proteins, individual proteins are not maximally utilized for the manufacture of food/feed and pharmaceutical products. Therefore, intensive research efforts are needed to obviate the problems associated with underutilization of milk proteins.     

花生醋浸过程中蛋白质、多酚及其抗氧化性的变化

研究了山西老陈醋浸渍过程中花生蛋白质、多酚含量及其抗氧化性的变化.结果表明,花生在醋浸过程中,粗蛋白、可溶性蛋白含量显著降低,浸泡结束分别降低了32％和41％左右;多酚含量的变化较为复杂,但总体上呈降低趋势,而多肽含量在陈醋浸渍过程中呈增加趋势,其多肽质量分数增加了40.8％.在醋浸前期花生多酚提取物对DPPH、ABTS自由基的清除能力显著增加,在浸渍第10天,花生多酚提取物对DP-PH、ABTS自由基的清除能力分别增加了69.5％和95.3％,而到浸渍后期趋于稳定.     

A Rapid Method for the Recovery,Quantification and Electrophoretic Analysis of Proteins from Beer

A previously‐developed method for protein recovery from wine has been applied to beer and beer foam samples. The method involves the complexation of proteins with dodecyl sulfate (added as sodium salts) and subsequently the insolubilization of the protein‐detergent complexes by addition of potassium ions (added as KCl). The protocol allows preparation of proteins from a few hundred microliters of beverage in a few minutes. The precipitated proteins are free from interfering materials and are directly utilizable for quantitative and electrophoretic assays.     

Preweaning to postweaning rumen papillae structural growth,ruminal fermentation characteristics,and acute-phase proteins in calves

This study evaluated pre- to postweaning ruminal structural development, fermentation characteristics, and acute-phase protein levels in calves with a high milk replacer (MR) feeding rate prior to weaning. Six ruminally cannulated Holstein bull calves were fed MR (150 g/L) at 15% of body weight (BW) in 2 equal volumes daily. Volumes were adjusted weekly based on BW. Calves were weaned using a 1-step weaning method, with MR decreased by 50% at the end of wk 5 and full weaning at the end of wk 6. Calf starter, chopped straw, and water were offered ad libitum. Intake was recorded daily, and BW was recorded weekly. From wk 5 to 12, ruminal pH was continuously measured using a ruminal pH bolus. Ruminal fluid was collected weekly from wk 5 to 12 for measurement of short-chain fatty acid concentrations and quantification of total bacteria and protozoa. Rumen papillae were obtained at wk 5, 6, 7, 8, and 12 for histological analysis. Serum amyloid A and lipopolysaccharide-binding protein were measured weekly. Data were analyzed using GLIMMIX procedure of SAS (SAS Institute Inc., Cary, NC), with week as a fixed effect and calf as a random effect. During the weaning step-down, starter intake was 3-fold higher and continued to increase until wk 12. Body weight increased from birth to wk 12; however, BW did not change during wk 6, 7, and 8, possibly due to low metabolizable energy intake caused by the weaning strategy. Preweaning ruminal pH was below 5.8 for approximately 936.3 ± 125.99 min/d, implying ruminal acidosis. Furthermore, ruminal pH below 5.8 reached a peak at wk 8 with 1,203.9 ± 227.65 min/d below pH 5.8 and slowly decreased to 388.1 ± 189.82 min/d below pH 5.8 at wk 12. Papillae surface area, length, and width increased during wk 12 compared with wk 5. Corneum thickness increased by week, whereas spinosum/basale thickness only increased during wk 8 compared with wk 5. The acute-phase protein concentration was highest at wk 1 and then decreased and remained constant until wk 12. In conclusion, even before step-down weaning, calves experienced ruminal acidosis despite low starter intake. Further, the observed prolonged ruminal pH depression suggests that dietary rumen adaptation after weaning can take several weeks in calves with a high MR feeding rate preweaning. The prolonged depressed ruminal pH did not affect acute-phase proteins and this finding, along with the other results, suggests that rumen epithelium barrier integrity is not compromised during weaning.     

膳食蛋白、机体抗氧化调节与健康的关系研究进展

膳食蛋白为机体提供必需氨基酸,还具有广泛的生理功能。膳食蛋白的消化代谢过程中,机体细胞会产生活性氧。活性氧积累可能引发氧化及衰老。细胞中的抗氧化蛋白——硫氧还蛋白、谷氧还蛋白及其他抗氧化酶等共同组成抗氧化系统,抵御活性氧,减少有害物生成。本文综合介绍不同来源的膳食蛋白与相应的抗氧化调节对机体健康的影响,以及活性氧代谢过程中两种抗氧化蛋白的调控作用,结合体内其他抗氧化指标,从而更好地认识不同膳食蛋白的代谢差异,指导个人膳食与健康。