Covalent chemical modification of myofibrillar proteins to improve their gelation properties: A systematic review

To improve the quality of meat products is a constant focus for both the meat industry and scientists. As major components in meat protein, the gelation properties of myofibrillar proteins (MPs) predominantly determine the sensory quality and product yield of the final product. Naturally or artificially occurring covalent modifications are known to largely affect MP functionality by changing the protein structure and forming aggregates, leading to both favorable and unfavorable outcomes. The review aims to summarize the mechanisms associated with several covalent modifications and the recent developments in enhancing MP gelation properties. Various extrinsic and intrinsic parameters controlling oxidation, phenolic–protein interactions, enzyme catalysis, glycation, and isoelectric solubilization/precipitation, and their effects on the characteristics of heat-induced MP gels are discussed. This article provides an improved understanding of the covalent modifications that occur mainly in the MP system and how they can be utilized to promote its gelation properties. Covalent modifications exhibited dose-dependent and dual-role manners for MP gelation properties. Mild oxidation, enzyme catalysis, and isoelectric solubilization/precipitation treatment would be beneficial to form more aligned and cross-linked three-dimensional networks for MP gels because of moderate protein aggregation. However, an excessive aggregate impedes the MP gelation behavior, leading to reduced gelation quality. Glycation effectively increased hydrophilicity of MPs and phenolic conjugation provides MPs with novel bioactivity. A proper utilization of such a process or even a rational combination of them allowed us to enhance the gelation properties of MP with assorted appreciated functionalities and further improve the quality of meat products.     

Rheological properties of modified lupin proteins

The properties of acetylated, succinylated and phosphorylated protein isolates extracted from the flour of yellow lupins (L. luteus) were studied by means of oscillatory rheology. The flow behaviour of protein dispersions (15% w/w) and the properties of thermotropic gels were distinctly influenced by the modification. Succinylation increased the viscosity of the dispersions of unmodified protein isolate (LPI) from 99 mPas to 515 mPas and results in the lowest gel point (T = 30.5°C). Acetylation and phosphorylation enhance the pseudoplastic flow behaviour of the dispersions. Acylated lupin samples formed the strongest gels with a small visco‐elastic range while phosphorylation leads to weak and “rubber‐like” gels.     

Technological strategies to improve photostability of a sunscreen agent

Due to the reduction of the ozone layer, there is an increasing need of effective UV protection systems with minimized side-effects. Trans-2-ethylhexyl- p -methoxycinnamate ( trans -EHMC) represents one of the most widely used sunscreen compound. Several studies demonstrated that trans -EHMC is unstable following UV irradiation both in solution and in emulsion formulations. Moreover, various reports of photocontact sensitization induced by trans -EHMC have appeared in the literature. Consequently, in order to ensure adequate efficacy and safety for this sunscreen agent, there is a need for new carrier systems to enhance trans -EHMC photostability. In the present study the photostability of the filter in different formulation types (emulsion–gel, gel and emulsion) with various ingredients is evaluated. In addition, nanoparticles based on poly- D , L -lactide-co-glycolide (PLGA) as carrier for trans -EHMC are investigated. The influence of nanoparticle matrix on the photochemical stability of the sunscreen agent is also presented. The results obtained demonstrated that PLGA nanoparticles are effective in reducing the light-induced degradation of the sunscreen agent. Moreover, the choice of formulation type and the excipients used play an important role in order to obtain a stable cosmetic product containing trans -EHMC.     

Rheological properties of modified lupin proteins.

The properties of acetylated, succinylated and phosphorylated protein isolates extracted from the flour of yellow lupins (L. luteus) were studied by means of oscillatory rheology. The flow behaviour of protein dispersions (15% w/w) and the properties of thermotropic gels were distinctly influenced by the modification. Succinylation increased the viscosity of the dispersions of unmodified protein isolate (LPI) from 99 mPas to 515 mPas and results in the lowest gel point (T = 30.5 degrees C). Acetylation and phosphorylation enhance the pseudoplastic flow behaviour of the dispersions. Acylated lupin samples formed the strongest gels with a small visco-elastic range while phosphorylation leads to weak and "rubber-like" gels.     

Technological properties and non-enzymatic browning of white lupin protein enriched spaghetti

Spaghetti was prepared by replacing semolina with different amounts of lupin protein, in order to increase the protein content. A detailed investigation of the rheological properties of the dough and the cooking quality of pasta was performed in comparison to standard semolina spaghetti. Moreover, the effect of the addition of lupin protein on non-enzymatic browning was evaluated by measuring ε-furoylmethyllysine (furosine) and 5-hydroxymethyl-2-furancarboxaldehyde (HMF), which are considered useful indices of semolina quality and pasta processing conditions. Dried spaghetti fortified with 5% of lupin protein isolate has a colour and rheological features comparable with the semolina sample and also the behaviour during cooking results to be satisfactory. As far as the thermal damage is concerned, the furosine values of fortified spaghetti differ only marginally from standard pasta and the percentage lysine loss is quite small (ranging from 12.1% to 15.7%).     

Contribution of sarcoplasmic proteins to myofibrillar proteins gelation

Surimi, a refined protein extract, is produced by solubilizing myofibrillar proteins during the comminuting and salting stages of manufacturing. The resulting paste gels on heating to produce kamaboko or a range of analog shellfish such as crab claw, filament sticks, fish mushroom, and so on. The myosin molecule is the major myofibrillar protein in gelation. It is believed that washing steps during the traditional surimi process play an important role in enhancing the gel properties of the resultant kamaboko by removing water-soluble (sarcoplasmic, Sp-P) proteins. By contrast, some researchers claim that retaining Sp-P or adding it into the surimi gel network not only does not interfere with the action of myofibrillar proteins during the sol-gel transition step but also improves the gel characteristics of the resultant kamaboko. It seems that retention of Sp-P or their addition into raw surimi does enhance the textural properties of kamaboko gel perhaps by functioning as a proteinase inhibitor, particularly against trypsin and trypsin-like proteinases but this depends on the type of applied surimi process. Among different types of Sp-P, it has been claimed that some proteins such as endogenous transglutaminase (TGase) play a more important role than other Sp-P in bond formation, by catalyzing the cross-linking of myosin heavy chain (MHC) molecules during low-temperature setting of surimi, resulting a more elastic kamaboko gel.     

Effect of water washing of shark (Scoliodon laticaudus) meat on the properties of proteins with special reference to gelation

The effect of water washing of shark meat on the properties of proteins has been investigated. The contents of low-molecular-weight proteins and urea were reduced significantly with three washing cycles. The gel forming ability showed marked improvement with the number of washing cycles. The dynamic viscoelastic behavior of washed and unwashed meat revealed a structure build-up reaction that was more pronounced in the washed meat. The concentration of myosin heavy chain of washed meat increased as revealed by Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Addition of urea at biological concentration (approximately 250 mM) to the washed meat reduced the gel forming ability significantly as compared to unwashed meat. The emulsion capacity showed an increase with the number of washing cycles.     

Some functional properties of lupin proteins modified by lactic fermentation and extrusion

The aim of this work was to determine modifying effects of lactic fermentation and extrusion processes on functionality of lupin proteins. Protein content, surface hydrophobicity, water absorption capacity (WAC), water solubility index (WSI) and emulsifying properties (EAI, ESI) of protein preparations obtained from lupin seeds (Lupinus luteus, Lupinus albus, Lupinus angustifolius), with various contents of hull, were analyzed. Changes of protein properties were affected by lupin cultivar, hull content and applied processing method. An increase of soluble protein content after controlled lactic fermentation of lupin seeds, and changes of surface protein hydrophobicity, WAC and WSI values after each treatment and significant worsening of protein emulsifying properties were observed. Correlations were found between parameters examined in this study.     

凝固剂及凝固条件对大豆蛋白胶凝性质的影响

以大豆蛋白的凝胶强度、持水性、凝固速率这3个胶凝特性为主要指标,测定了包括蛋白浓度、热处理温度和时间、凝固剂种类和添加量、pH值、离子强度在内的这些因素对上述胶凝性质的影响,并确定了最优凝固工艺条件:质量浓度60g/L的SPI溶液经95℃热处理15min后,分别以质量分数0.4%熟石膏(CaSO4·1/2H2O)和质量分数0.28%葡萄糖酸内酯(GDL)作为凝固剂,保温30min后,冷却至室温;最佳离子强度为0.01mol/L(NaCl)。     

玉米胚芽蛋白凝胶特性的研究

利用流变仪研究不同处理条件下玉米胚芽蛋白凝胶特性的变化规律。结果表明:玉米胚芽蛋白在160 mg/m L质量浓度下开始形成凝胶,随着质量浓度的增加,凝胶弹性增强。玉米胚芽蛋白的储能模量G’、耗能模量G″均与蛋白浓度呈线性正相关,提高升降温速率会使其凝胶弹性显著减弱。玉米胚芽蛋白的储能模量G’、耗能模量G″均与升降温速率呈负相关。相同条件下,玉米胚芽蛋白的凝胶弹性较蛋清蛋白差,优于大豆分离蛋白。本研究深入探索了玉米胚芽蛋白凝胶特性,为拓宽玉米胚芽蛋白利用途径打下基础。      

Extractability and functional properties of some legume proteins isolated by three different methods

The extraction of protein from the flour of three grain legumes (faba beans, chick peas and fenugreek) was investigated using three different methods. Three protein preparations were made: by alkaline extraction and precipitation at isoelectric pH (protein isoelectric precipitate, PIP); extraction with 0.5 M sodium chloride solution and precipitation by ionic strength reduction (protein micellar mass, PMM); extraction in aqueous or saline solution in the presence of pepsin or pancreatin (partially hydrolysed protein preparation, PHP). Two of the protein isolates had higher values of water absorption and fat absorption compared to their corresponding parent flours, with fenugreek being the exception. Oil emulsification of the isolates was in the descending order: PMM, PHP and PIP. The PHP isolate had the highest nitrogen solubility index (NSI) values at pH 2.4 followed by PMM at pH 5.7–6.4 and finally PIP at pH 4.5–5.5.     

Impact of phase separation of whey proteins/hydroxypropylmethylcellulose mixtures on gelation dynamics and gels properties

This work constitutes a study of the impact of phase separation behaviour on the gels properties of a low viscosity hydroxypropylmethylcellulose and whey protein concentrate (WPC) mixed system. The phase separation was characterized by drawing the limit of thermodynamic compatibility, i.e. binodal curve, at pH 6.5 and room temperature (25 °C). Gelling properties were studied under thermodynamic compatibility (WPC 12% (w/w)/E50LV 0.25% (w/w) mixed system) and incompatibility conditions (WPC 12% (w/w)/E50LV 4% (w/w) and WPC 20% (w/w)/E50LV 4% (w/w) mixed systems)Under thermodynamic compatibility the WPC/E50LV mixed system shows gelling parameters similar to WPC. Confocal scanning laser microscopy (CSLM) micrographs showed a regular pattern of microdomains of proteins imbibed into E50LV matrix.Confocal microscopy of WPC/E50LV mixture under thermodynamic incompatibility offered details about the constitution of continuous and non-continuous phase and characteristics of non-continuous phase domains. Related to gelling parameters, the solid character upon heating was reinforced in mixed systems since they reflected the concentrating effect arising from phase separation. On the other hand, the solid character of gels upon cooling correlated with the component constituting the continuous phase, and the gelation temperature was similar to polysaccharide-rich phase predicted gelation temperature.Regarding to textural properties, the presence of the polysaccharide diminished the hardness of the mixed gels inducing less resistance to small and large deformation. WPC 20% (w/w)/E50LV 4% (w/w) mixed gel presented an interesting particulated macrostructure. This result would find application in food design and technology if the E50LV concentration is chosen to finely control the rate and extent of WPC aggregation-gelation-particulation. These results could be used in microparticulation or microencapsulation application of whey proteins.     

肌肉盐溶蛋白热诱导凝胶特性研究进展

综述肌肉中盐溶蛋白质的性质、成胶机制,以及影响其成胶的重要因素,并简述肉制品加工中广泛应用的亲水胶体和谷氨酰胺转氨酶对肌肉盐溶蛋白热诱导凝胶特性的影响的最新进展.     

Effect of lupin seed proteins on quality characteristics of fermented sausages

Lupin seed flours (LSF) and lupin seed protein isolates (LSPI) from a sweet (S) variety of Lupinus albus and a bitter (B) variety of Lupinus albus ssp. Graecus were used in the manufacture of fermented sausages at 2% level, based on the weight of meat and pork back fat, and hydrated to a protein/water ratio 1/4, to replace beef and pork meat on a protein to protein basis. LSF and LSPI had no effect (p>0.05) on the microbial counts, the pH, the moisture content and weight losses, the instrumentally measured colour numbers (L*, a*, b*), the firmness, the appearance and the sensory evaluated colour of fermented sausages. Fermented sausages produced with LSPI from the bitter variety had similar (p>0.05) sensory attributes to the control and lower (p<0.05) TBA values after the 28th day of storage. Fermented sausages produced with LSPI from the sweet variety had acceptable sensory attributes but TBA values higher than 1 mg of malonaldehyde/kg. LSF from both varieties had a high pro-oxidant effect and affected negatively the odour and taste of fermented sausages.     

Semolina supplementation with processed lupin and pigeon pea flours improve protein quality of pasta

The objective of this work was to study the effect of processing (alcoholic extraction, fermentation and germination) on protein quality of lupin (Lupinus angustifolius L. var. Troll and Emir) and pigeon pea (Cajanus cajan L. var. Aroito) flours. Second, the effect of semolina supplementation with the processed legume flours on protein quality of pasta was also evaluated. For protein quality evaluation amino acid composition and chemical score (CS) were determined in raw and processed legume flours as well as cooked semolina pasta supplemented and non-supplemented with processed legumes. Alcoholic extraction did not cause important changes in the amino acid profile of lupin seeds. Certainly, sulphur amino acid content of ethanol extracted lupin flours was reduced but levels remained similar to those usually found in other legumes. However, fermentation and germination of pigeon pea seeds improved some essential amino acids and slight changes in CS indexes were observed. Moreover, semolina supplementation with processed lupin and pigeon pea flours improved protein quality of pasta as a result of higher CS and EAA levels compared to the control cooked semolina pasta. Therefore, ethanol extracted lupin, as well as fermented and germinated pigeon pea seeds are suitable protein sources for formulating new pasta products.     

青稞蛋白质凝胶特性的研究

青稞蛋白质弱的凝胶特性限制了其的应用。为了探索青稞蛋白质凝胶形成的条件,采用碱溶酸沉法提取青稞中的蛋白质,并研究了青稞蛋白质浓度、加热温度、加热时间、pH、尿素浓度、中性盐浓度以及丙二醇浓度对其凝胶特性的影响。研究结果表明,青稞蛋白质在碱性和质量浓度大于14%的条件下能形成凝胶;凝胶硬度在加热温度95℃和加热时间40min时达到最大;随着NaCl浓度和丙二醇浓度的升高,凝胶硬度和储能模量呈现先升高后降低的趋势;随着尿素浓度的增加,青稞蛋白质凝胶硬度和储能模量增加,当尿素浓度为7mol/L时,凝胶硬度为90.29g,说明尿素的变性作用可以破坏分子内和分子间的氢键以及疏水相互作用力,使得蛋白质折叠,活性基团暴露、相互作用,这些均有利于凝胶的形成。      

Influence of different organic solvents on the functional and sensory properties of lupin (Lupinus angustifolius L.) proteins

Protein isolates from lupin seeds are promising food ingredients due to their techno-functional properties. De-oiling of the lupin seeds is necessary to produce storable protein isolates. To assess the effects of different solvent extractions, functional and sensory properties of lupin flakes and derived protein isolates were studied. After de-oiling with acetone, n-hexane, 2-methyl pentane, diethyl ether, and 2-propanol, protein solubilities of the flakes ranging between 75% and 87% were similar to full-fat flakes (82%). Increased protein denaturation upon de-oiling with ethanol resulted in decreased solubility (64%) and thus protein recovery upon isolation. Nonetheless, all protein isolates had similar high solubilities (>90%) and emulsifying capacities varying from 710 to 760 mL g⁻¹. Comparing the flavour profile, the protein isolates obtained from ethanol and 2-propanol de-oiled flakes had significantly less “legume-like” flavour. In general, de-oiling lead to protein isolates with improved sensory profiles, thus good consumer acceptance, besides unchanged high functionality.