In vitro binding of bile salts by lentil flours, lentil protein concentrates and lentil protein hydrolysates

The binding capacity of bile salts by lentil flours produced from two varieties, Blaze and Laird and their protein concentrates and hydrolysates were studied. Sodium cholate, sodium deoxycholate, sodium taurocholate, sodium glycocholate and sodium chenodeoxycholate were tested individually, and their binding interactions with the lentil products were analyzed using the Trinity Biotech Bile Acids Kit 450-10 and compared to cholestyramine. All tested samples bound the bile salts investigated, and the amount of bile salts bound (> 70%) was sometimes greater than that bound by cholestyramine. Overall, there were no major differences in the bile salt binding capacities of similar samples prepared from the two varieties of lentil. In vitro digestion of the lentil proteins by pepsin/trypsin/??-chymotrypsin, alcalase/flavourzyme and papain significantly reduced the bile salt binding capacity compared to the undigested samples except in the case of sodium deoxycholate where no significant differences in bile salt binding were observed before and after hydrolysis. Binding of bile salts has been linked to cholesterol reduction, thus, the ability of the lentil products to bind bile salts is of interest as it may suggest that lentils could potentially have cholesterol-reducing properties.     

Structure and functional properties of modified threadfin bream sarcoplasmic protein

Surimi wash-water contains up to 30% of protein from fish muscle that is currently underutilized. This paper describes the effect of acetylation, succinylation, trypsin hydrolysis or pre-heating at 55 °C on the emulsification and foaming properties of a threadfin bream sarcoplasmic protein (TBSP) model for wash-water protein. Multiple regression analysis showed that emulsification and foaming characteristics were differentially affected by TBSP surface hydrophobicity (S₀), solubility in water (S_W) and free amino group (fNH₂) concentration. Emulsification activity index (EAI) for TBSP was most enhanced by succinylation, whereas the foaming capacity (FC) was more effectively extended by trypsin hydrolysis. Structure–function relationships for emulsification were different from those associated with foaming or for ensuring the stability of these food dispersions. This study suggests that surimi wash-water protein functionality can be improved by protein modification. Further strategies may be needed to stabilize fish protein stabilized emulsions and foams.     

Some functional properties of fractionated soy protein isolates obtained by microfiltration

Five soy proteins isolate (SPI) fractions were produced using two microfiltration membranes with different pore sizes. Fractionation was carried out on SPI produced by isoelectric precipitation of a crude protein extract. The five fractions were two retentates and two permeates from the two membranes, the fifth fraction was obtained as the retentate on the smaller-pore-sized membrane fed with the permeate from the larger-pore-sized membrane. Solubility, foaming and emulsifying properties of the collected fractionates were investigated. It was observed that in the pH range 3–8 the retentates featured superior solubility compared with permeates. There was no significant difference (p>0.01) in solubility between the retentates and SPI at pH6. Foaming characteristics of the fractions followed the same trend as solubility with regard to foam expansion. There was, however, no particular trend observed with regards to foam stability. Emulsions stabilised by the retentates exhibited higher values (p<0.01) of emulsion stability index (ESI) and emulsifying activity index (EAI) than those stabilised with permeates. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) profiles indicated that the fractions exhibiting high functionality in terms of solubility, foaming and emulsifying properties were also richer in 7S globulin soy protein subunits.Isoelectric focussing (IEF) profiles showed that retentates were richer in species with isoelectric points (pI) between 5.2 and 5.6 while permeates featured more prominently at pIs between 4.5 and 4.8.     

Optimization of lentil protein extraction and the influence of process pH on protein structure and functionality

Response surface methodology was used to optimize alkaline extraction of protein from lentil flour to maximize both protein content and yield. Solid/solvent ratio and pH were the significant factors that determined protein extraction efficiency. At the optimized condition of pH 9.0 and solid/solvent ratio of 1:10 (g:mL), a yield of 14.5 g of protein extract/100 g of flour was obtained with a protein content of 82 g/100 g at (22 °C) after 1 h of extraction. The impact of extraction pH on the molecular structures and functionalities of lentil protein was investigated. Increasing the extraction pH to 10 caused partial protein hydrolysis and unfolding as suggested by size exclusion high performance liquid chromatography and Fourier transform infrared spectroscopy analysis, leading to improved protein solubility and gelling property. Environmental pH influenced protein solubility and surface charge, and subsequently the gelling and foaming properties. The foaming capacity was especially strong, comparable to whey and egg proteins.     

Physicochemical and functional properties of lentil protein isolates prepared by different drying methods

Lentil protein isolate (LPI) extract was converted into powder by freeze drying, spray drying and vacuum drying. Differences in particle size distribution, protein subunit composition and colour and surface morphology were observed amongst the three drying methods. Spray and freeze-dried LPI powders exhibited higher solubility (81% and 78%, respectively) compared to vacuum dried powders (50%). The spray dried powders showed a low water absorption capacity (0.43 ± 0.02 g/g) compared to freeze (0.48 ± 0.02 g/g) and vacuum-dried (0.47 ± 0.01 g/g) LPI powders. Spray and freeze-dried powders displayed better gelation ability and higher gel strength, compared to vacuum-dried powder. Both spray and freeze-dried gels showed typical viscoelastic gel characteristics, with G′ dominating over G″ and very low loss tangent. The holding time required for gelation of vacuum dried powder at 90 °C was significantly longer, compared to spray and freeze dried powders. Hence, drying methods used for preparation of lentil protein isolate powders can affect physicochemical and associated functional properties.     

Interfacial and emulsifying properties of lentil protein isolate

The dynamic interfacial tension (DIFT) at oil–water interface, diffusion coefficients, surface hydrophobicity, zeta potential and emulsifying properties, including emulsion activity index (EAI), emulsion stability index (ESI) and droplet size of lentil protein isolate (LPI), were measured at different pH and LPI concentration, in order to elucidate its emulsifying behaviour. Sodium caseinate (NaCas), whey protein isolate (WPI), bovine serum albumin (BSA) and lysozyme (Lys) were used as benchmark proteins and their emulsifying property was compared with that of LPI. The speed of diffusion-controlled migration of these proteins to the oil/water interface, was in the following order: NaCas > LPI > WPI > BSA > Lys, while their surface hydrophobicity was in the following order: BSA > LPI > NaCas > WPI > Lys. The EAI of emulsions stabilised by the above proteins ranged from 90.3 to 123.3 m²/g and it was 93.3 ± 0.2 m²/g in LPI-stabilised emulsion. However, the stability of LPI-stabilised emulsions was slightly lower compared to that of WPI and NaCas-stabilised emulsions at the same protein concentration at pH 7.0. The ESI of LPI emulsions improved substantially with decrease in droplet size when protein concentration was increased (20–30 mg/ml). Reduction of disulphide bonds enhanced both the EAI and ESI compared to untreated samples. Heat treatment of LPI dispersions resulted in poor emulsion stability due to molecular aggregation. The stability of LPI-stabilised emulsions was found to decrease in the presence of NaCl. This study showed that LPI can be as effective emulsifiers of oil-in-water emulsions as are WPI and NaCas at ?20 mg/ml concentrations both at low and neutral pH. The emulsifying property of LPI can be improved by reducing the intra and inter-disulphide bond by using appropriate reducing agents.     

A review of protein engineering for the food industry

In this review I briefly indicate how the present state of knowledge allows proteins to be mutated to increase or decrease stability. I discuss experiments on both model proteins and those of relevance to the food industry and show how hydrophobic forces are a major driving force for folding as well as having a major role in thermostability. I also indicate the large contribution that hydrogen bonding, electrostatic interactions and, in a less well predicted way, disulphide bridges make to thermostability.     

蚕蛹蛋白制备应用与功能特性的研究进展

蚕蛹蛋白是一种优质的纯天然全价动物蛋白,具有抗肿瘤、抗氧化、降血压和抗疲劳等功效,市场前景广阔。该文对蚕蛹蛋白的营养指数、提取、精制、功能特性及在食品领域的应用进行综述,以期为蚕蛹蛋白的进一步研究和开发提供参考。     

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.     

Gelatin: a valuable protein for food and pharmaceutical industries: review

Many works have appeared in various scientifically reputable journals and publications worldwide that seem to have made potential or satisfactory contribution to our knowledge on the functions and utilization of gelatin--an important source of animal protein. Irrespective of these worldwide publications, room still exists for more work to be done to fully understand the utilization, chemical, biological, physical and functional properties of gelatin. Chemical and enzymatic modifications as well as biological studies should be undertaken with accuracy to be able to extend the utilization of gelatin in food and pharmaceuticals.     

Fish protein hydrolysates: production, biochemical, and functional properties

Considerable amounts of fish processing byproducts are discarded each year. By developing enzyme technologies for protein recovery and modification, production of a broad spectrum of food ingredients and industrial products may be possible. Hydrolyzed vegetable and milk proteins are widely used food ingredients. There are few hydrolyzed fish protein foods with the exception of East Asian condiments and sauces. This review describes various manufacturing techniques for fish protein hydrolysates using acid, base, endogenous enzymes, and added bacterial or digestive proteases. The chemical and biochemical characteristics of hydrolyzed fish proteins are discussed. In addition, functional properties of fish protein hydrolysates are described, including solubility, water-holding capacity, emulsification, and foam-forming ability. Possible applications of fish protein hydrolysates in food systems are provided, and comparison with other food protein hydrolysates where pertinent.     

大米蛋白功能性研究进展

大米蛋白是一种高营养、低过敏性优质植物蛋白源,具有很高开发价值和良好应用前景。该文介绍大米蛋白的结构、组成,并对目前国内外有关大米蛋白功能性质研究进行综述。     

An EPR study into the effect of annealing on both the Mn2+ and free radical signal in lentil

The results of an EPR investigation on dry lentil (macrosperma) are reported in the present work. The EPR spectrum of lentil is composed of an equally spaced sextet and a single weak resonance line appearing at g=2.0050. Whole intact individual and decorticated seeds and testa were studied separately; however, ground lentil was used throughout the work to avoid any possible problems arising from the microwave cavity filling factor. Although intact and decorticated seeds were found to exhibit both Mn²⁺ and radical signals, the testa exhibited only the radical signal. An increase and decrease of Mn²⁺ and radical signals were observed, respectively, below room temperature. Above room temperature, they both decreased and these decreases were irreversible. The kinetics of these decreases were studied in detail over a temperature range of room–423 K by annealing samples at different temperatures for various times.     

Wheat protein composition and properties of wheat glutenin in relation to breadmaking functionality

The unique breadmaking properties of wheat are generally ascribed to the visco-elastic properties of its gluten proteins. While monomeric gluten proteins (gliadin) show viscous behavior, polymeric gluten proteins (glutenin) are elastic. The unique elasticity of glutenin results to a large extent from its polymeric nature. Glutenin is a highly heterogeneous mixture of polymers consisting of a number of different high- and low-molecular-weight glutenin subunits linked by disulfide bonds. Although glutenin obviously is the major polymeric protein in wheat, other polymeric proteins occur as well. Their importance in breadmaking may be underestimated. Nevertheless, variations in both quantity and quality of glutenin strongly determine variations in breadmaking performance. Structural features of different classes of glutenin subunits are described. Variations in glutenin quality may result from variations in its (1) structure, (2) size distribution, and (3) subunit composition. Some hypotheses on glutenin structure and current insights into the role of glutenin size distribution are evaluated. Finally, different ways in which variation in glutenin composition may directly or indirectly (by affecting glutenin structure and/or size distribution) influence glutenin quality are discussed.     

Whey protein concentrates and isolates: Processing and functional properties

Substantial progress has been made in understanding the basic chemical and structural properties of the principal whey proteins, that is, β‐lactoglobulin β‐Lg), α‐lactalbumin (α‐La), bovine serum albumin (BSA), and immunoglobulin (Ig). This knowledge has been acquired in terms of: (1) procedures for isolation, purification, and characterization of the individual whey proteins in buffer solutions; and (2) whey fractionation technologies for manufacturing whey protein concentrates (WPC) with improved chemical and functional properties in food systems. This article is a critical review of selected publications related to (1) whey fractionation technology for manufacturing WPC and WPI; (2) fundamental properties of whey proteins; and (3) factors that affect protein functionality, that is, composition, protein structure, and processing.     

蛋白质凝胶机理的研究进展

凝胶特性是食品蛋白质的重要功能特性,蛋白质的凝胶行为及其流变性质是形成某些食品独特的质构、感官和风味的决定性因素。长期以来,人们对蛋白质的凝胶行为进行了广泛深入的研究,但对蛋白质凝胶的机理和凝胶动力学还没有完全了解。本文对当前有关蛋白质凝胶的类型、凝胶过程中蛋白质分子构象的变化、形成蛋白质凝胶的主要作用力和凝胶动力学过程的研究进展作了综述。随着现代分析研究技术的进步,对蛋白质凝胶行为的认识也逐渐深入。     

Angiotensin I-converting enzyme inhibitory properties of lentil protein hydrolysates: Determination of the kinetics of inhibition

ACE inhibitory activity was studied for different hydrolysates obtained from protein concentrates of two lentil varieties by in vitro gastrointestinal simulation, Alcalase/Flavourzyme, papain and bromelain. Protein/peptide profiles studied by electrophoresis and HPLC-SEC showed a rich composition of the hydrolysates in small peptides ranging in size from 0.244 to 1.06 kDa. ACE inhibitory activity was measured using the HPLC Hippuryl-His-Leu (HHL) substrate method. Significantly different (P < 0.05) IC₅₀ values ranging between 0.053 and 0.190 mg/ml were obtained for different hydrolysates. Furthermore, the inhibition mechanism investigated using Lineweaver–Burk plots revealed a non-competitive inhibition of ACE with inhibitor constants (K_i) between 0.16 and 0.46 mg/ml. These results demonstrate that hydrolysates of lentil proteins obtained by different enzymatic digestions may contain bioactive components.     

糖基化反应改善蛋白质功能特性的研究进展

糖基化反应是改善蛋白质功能特性的一种有效的方法。主要介绍蛋白质糖基化反应机理,糖基化反应对鱼肉蛋白、β-乳球蛋白、卵清蛋白、酪蛋白、精蛋白以及酶等各类蛋白质功能特性影响的国内外研究进展。     

乳清蛋白在食品工业中的应用

乳清蛋白是生产奶酪的副产品(乳清)经浓缩而得的产品.它是一种很有营养价值的原料,并且具有许多独特的功能性质.乳清蛋白在食品工业中的应用具有广阔的前景.     

Marine food-derived functional ingredients as potential antioxidants in the food industry: An overview

Recently, a great deal of interest has been developed by the consumers towards natural bioactive compounds as functional ingredients in the food products due to their various health beneficial effects. Hence, it can be suggested that antioxidative functional ingredients from marine foods and their by-products are alternative sources for synthetic ingredients that can contribute to a consumer's well-being, as a part of nutraceuticals and functional foods. This contribution presents an overview of the marine food-derived antioxidants such as bioactive peptides, chitooligosaccharide derivatives, sulfated polysaccharides, phlorotannins and carotenoids with the potential utilization in the food industry.