Conjugation of bovine serum albumin and glucose under combined high pressure and heat

Generation of advanced glycation end products from glycated protein or fructose/glyoxal-protein adducts under in vitro simulated gastrointestinal digestion

Advanced glycation end products (AGEs) are a heterogeneous group of compounds formed both endogenously and exogenously through reactions between reducing sugars and amino acids within the proteins. The digestive tract may also serve as a site for endogenous AGEs generation. This study examined whether additional AGEs are formed during the digestion of glycated protein diets and meal-resembling systems (dietary proteins with fructose or glyoxal). The digestion of glycated protein showed that free AGEs were gradually released, but no additional AGEs were generated. In contrast, co-digestion of dietary proteins with fructose or glyoxal resulted in the formation of additional AGEs, and the reaction substrates (fructose or glyoxal) were depleted during digestion. Additionally, the lysine released from proteins decreased, leading to a loss of nutritional value of the food during co-digestion. The formation of AGEs and the depletion of essential amino acids in the gut may have significant implications for human health.

Matrix effect on the Effectiveness of High Hydrostatic Pressure Treatment on Antibiotic Residues

The use of antibiotics in agriculture and livestock poses health risks to consumers. Treatments such as High Hydrostatic Pressure (HHP) have been shown to reduce antibiotic and pesticide residues in food. This study aims to investigate the matrix effect on the effectiveness of HHP on hydrochloride tetracycline (HTC) and sulfathiazole (STZ) residues in spiked food matrices. The effect of viscosity, as well as carbohydrate, protein, and fat content on the effectiveness of HHP on antibiotic residues, was investigated. The studied matrices were full-fat and fat-free bovine milk and model food systems consisting of aqueous solutions of sugars, aqueous solutions of proteins, and oil in water emulsions. Model food systems were also used to study the viscosity effect. These systems consisted of aqueous solutions of honey, aqueous solutions of apple puree, and aqueous solutions of glycerol. The HHP processing (580 MPa, 6 min, 25 °C) took place under industrial conditions. For both antibiotics, the concentration of sugars and proteins was found to affect the effectiveness of treatment. The concentration of oils affected treatment efficacy only for HTC. Reduction of antibiotics by HHP was also affected by the type of carbohydrate and the viscosity. In conclusion, the composition and the viscosity of the food matrix exert a variable effect on the studied antibiotic residues reduction by HHP indicating different underlying mechanisms of the interactions between food constituents and antibiotics under the same process conditions.

Effect of enzymolysis combined with Maillard reaction treatment on functional and structural properties of gluten protein

In this work, the modified gluten was prepared by enzymolysis combined with Maillard reaction (MEG), and its functional and structural properties were investigated. The result showed that the maximum foamability of MEG was 19.58 m2/g, the foam stability was increased by 1.8 times compared with gluten, and the solubility and degree of graft were increased to 44.4 % and 28.1 % at 100 °C, whereas the content of sulfhydryl group decreased to 0.81 μmol/g. The scavenging ability on ABTS+radical and DPPH radical of MEG was positively correlated with reaction temperature, and the maximum values were 86.57 % and 71.71 % at 140 °C, respectively. Furthermore, the fluorescence quenching effect of tryptophan and tyrosine residues was enhanced, while the fluorescence intensity decreased with the temperature increase. Scanning electron microscopy revealed that the surface of enzymatically hydrolyzed-gluten became smooth and the cross section became straightened, while MEG turned smaller and irregular approaching a circular structure. FT-IR spectroscopy showed that enzymatic hydrolysis promoted the occurrence of more carbonyl ammonia reactions and the formation of precursors of advanced glycosylation end products. These results provide a feasible method for improving the structure and functional properties of gluten protein.

Discovery of novel glucosinolates inhibiting advanced glycation end products: Virtual screening and molecular dynamic simulation

Protein glycation can result in the formation of advanced glycation end products (AGEs), which pose a potential health risk due to their association with diabetic complications. Natural products are a source of drugs discovery and the search for potential natural inhibitors of AGEs is of great significance. Glucosinolates (GSLs) mainly from cruciferous plants have potential antioxidant, anti-inflammatory, and anti-glycation activities. In this study, the inhibitory activity of GSLs on bovine serum albumin (BSA) along with its mechanism was investigated by virtual screening and various computational simulation techniques. Virtual screening revealed that 174 GSLs were screened using Maestro based on the glide score and 89% of the compounds were found to have potential anti-glycation ability with the docking scores less than -5 kcal/mol. Molecular docking showed that the top 10 GSLs were bound to the IIA structural domain of BSA. Among them, glucohesperin (1) and 2-hydroxyethyl glucosinolate (2) had the lowest docking scores of -9.428 and -9.333 kcal/mol, respectively, reflecting their good binding affinity. Molecular dynamics simulations of 1 (ΔG = -43.46 kcal/mol) and 2 (ΔG = -43.71 kcal/mol) revealed that the complexes of these two compounds with proteins had good stability. Further binding site analysis suggested that the mechanism of inhibition of protein glycation by these two active ingredients might be through competitive hydrogen bonding to maintain the structural integrity of the protein, thus inhibiting glycation reaction. Moreover, the ADMET values and CYP450 metabolism prediction data were within the recommended values. Therefore, it can be concluded that 1 and 2 may act as potential anti-glycation agents.

Inhibitory Effects of Myriocin on Non-Enzymatic Glycation of Bovine Serum Albumin

Advanced glycation end products (AGEs) are the compounds produced by non-enzymatic glycation of proteins, which are involved in diabetic-related complications. To investigate the potential anti-glycation activity of Myriocin (Myr), a fungal metabolite of Cordyceps, the effect of Myr on the formation of AGEs resulted from the glycation of bovine serum albumin (BSA) and the interaction between Myr and BSA were studied by multiple spectroscopic techniques and computational simulations. We found that Myr inhibited the formation of AGEs at the end stage of glycation reaction and exhibited strong anti-fibrillation activity. Spectroscopic analysis revealed that Myr quenched the fluorescence of BSA in a static process, with the possible formation of a complex (approximate molar ratio of 1:1). The binding between BSA and Myr mainly depended on van der Waals interaction, hydrophobic interactions and hydrogen bond. The synchronous fluorescence and UV-visible (UV-vis) spectra results indicated that the conformation of BSA altered in the presence of Myr. The fluorescent probe displacement experiments and molecular docking suggested that Myr primarily bound to binding site 1 (subdomain IIA) of BSA. These findings demonstrate that Myr is a potential anti-glycation agent and provide a theoretical basis for the further functional research of Myr in the prevention and treatment of AGEs-related diseases.

Structural and Emulsifying Properties of Soybean Protein Isolate-Sodium Alginate Conjugates under High Hydrostatic Pressure

Soybean protein isolate (SPI) is a kind of plant derived protein with high nutritional value, but it is underutilized due to its structural limitations and poor functionalities. This study aimed to investigate the effects of high hydrostatic pressure (HHP) treatment on SPI and sodium alginate (SA) conjugates prepared through the Maillard reaction. The physicochemical properties of the conjugate synthesized under 200 MPa at 60 °C for 24 h (SPI–SA–200) were compared with those of the conjugate synthesized under atmospheric pressure (SPI–SA–0.1), SPI-SA mixture, and SPI. The HHP (200 MPa) significantly hindered the Maillard reaction. This effect was confirmed by performing SDS-PAGE. The alterations in the secondary structures, such as α-helices, were analyzed using circular dichroism spectroscopy and the fluorescence intensity was determined. Emulsifying activity and stability indices of SPI-SA-200 increased by 33.56% and 31.96% respectively in comparison with the SPI–SA–0.1 conjugate. Furthermore, reduced particle sizes (356.18 nm), enhanced zeta potential (‒40.95 mV), and homogeneous droplet sizes were observed for the SPI-SA-200 emulsion. The present study details a practical method to prepare desirable emulsifiers for food processing by controlling the Maillard reaction and improving the functionality of SPI.

Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

The last two decades saw a steady increase of high hydrostatic pressure (HHP) used for treatment of foods. Although the science of biomaterials exposed to high pressure started more than a century ago, there still seem to be a number of unanswered questions regarding safety of foods processed using HHP. This review gives an overview on historical development and fundamental aspects of HHP, as well as on potential risks associated with HHP food applications based on available literature. Beside the combination of pressure and temperature, as major factors impacting inactivation of vegetative bacterial cells, bacterial endospores, viruses, and parasites, factors, such as food matrix, water content, presence of dissolved substances, and pH value, also have significant influence on their inactivation by pressure. As a result, pressure treatment of foods should be considered for specific food groups and in accordance with their specific chemical and physical properties. The pressure necessary for inactivation of viruses is in many instances slightly lower than that for vegetative bacterial cells; however, data for food relevant human virus types are missing due to the lack of methods for determining their infectivity. Parasites can be inactivated by comparatively lower pressure than vegetative bacterial cells. The degrees to which chemical reactions progress under pressure treatments are different to those of conventional thermal processes, for example, HHP leads to lower amounts of acrylamide and furan. Additionally, the formation of new unknown or unexpected substances has not yet been observed. To date, no safety-relevant chemical changes have been described for foods treated by HHP. Based on existing sensitization to non-HHP-treated food, the allergenic potential of HHP-treated food is more likely to be equivalent to untreated food. Initial findings on changes in packaging materials under HHP have not yet been adequately supported by scientific data.

Tracking the behavior of Maillard browning in lysine/arginine-sugar model systems under high hydrostatic pressure

BACKGROUND

High-pressure processing is gaining popularity in the food industry. However, its effect on the Maillard reaction during high-pressure-assisted pasteurization and sterilization is not well documented. This study aimed to investigate the effects of high hydrostatic pressure on the Maillard reaction during these processes using amino acid (lysine or arginine)-sugar (glucose or fructose) solution models.

RESULTS

High pressure retarded the intermediate and final stages of the Maillard reaction in the lysine-sugar model. For the lysine-glucose model, the degradation rate of Amadori compounds was decelerated, while acceleration was observed in the arginine-sugar model. Increased temperature not only accelerated the Maillard reaction over time but also formed fluorescent compounds with different emission wavelengths. Lysine reacted with the sugars more readily than arginine under the same conditions. In addition, it was easier for lysine to react with glucose, whereas arginine reacted more readily with fructose under high pressure.

CONCLUSION

High pressure exerts different effects on lysine-sugar and arginine-sugar models. © 2017 Society of Chemical Industry.

Control of Maillard Reactions in Foods: Strategies and Chemical Mechanisms

Maillard reactions lead to changes in food color, organoleptic properties, protein functionality, and protein digestibility. Numerous different strategies for controlling Maillard reactions in foods have been attempted during the past decades. In this paper, recent advances in strategies for controlling the Maillard reaction and subsequent downstream reaction products in food systems are critically reviewed. The underlying mechanisms at play are presented, strengths and weaknesses of each strategy are discussed, and reasonable reaction mechanisms are proposed to reinforce the evaluations. The review includes strategies involving addition of functional ingredients, such as plant polyphenols and vitamins, as well as enzymes. The resulting trapping or modification of Maillard targets, reactive intermediates, and advanced glycation endproducts (AGEs) are presented with their potential unwanted side effects. Finally, recent advances in processing for control of Maillard reactions are discussed.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

The influence of glycation on a high pressure denaturation of ubiquitin

The combination of deuterium–hydrogen exchange (DHX) and mass spectrometry (MS) can be used for studying a high pressure denaturation (HPD) of proteins. Herein we present the results of investigations of the influence of glycation on the HPD of ubiquitin. Application of various values of pressure causes different degrees of protein unfolding, resulting in molecules with a different number of protons available for exchange with deuterons. The dependence of this number on pressure gives information on the denaturation state of a protein. On the basis of the obtained results we can conclude that increasing number of fructosamine moieties in ubiquitin decreases the pressure required for its denaturation. It suggests that glycation moderately decreases the protein stability. The present study is the first example of application of hydrogen–deuterium exchange as a method of investigating the influence of posttranslational modification of protein on the HPD.

High-Pressure-High-Temperature Processing Reduces Maillard Reaction and Viscosity in Whey Protein-Sugar Solutions

The aim of the study was to determine the influence of pressure in high-pressure-high-temperature (HPHT) processing on Maillard reactions and protein aggregation of whey protein-sugar solutions. Solutions of whey protein isolate containing either glucose or trehalose at pH 6, 7, and 9 were treated by HPHT processing or conventional high-temperature (HT) treatments. Browning was reduced, and early and advanced Maillard reactions were retarded under HPHT processing at all pH values compared to HT treatment. HPHT induced a larger pH drop than HT treatments, especially at pH 9, which was not associated with Maillard reactions. After HPHT processing at pH 7, protein aggregation and viscosity of whey protein isolate-glucose/trehalose solutions remained unchanged. It was concluded that HPHT processing can potentially improve the quality of protein-sugar-containing foods, for which browning and high viscosities are undesired, such as high-protein beverages.

Nonenzymatic modification of Ubiquitin under high-pressure and -temperature treatment: mass spectrometric studies

The effect of high-pressure and/or high-temperature on the glycation of a model protein (ubiquitin) was investigated by mass spectrometry. This paper reports the impact of high pressure (up to 1200 MPa) on the modification of a ubiquitin using ESI-MS measurements. The application of glucose labeled with stable isotope allows a quantitative assessment of modification under the conditions of high-pressure (HPG) and high-temperature (HTG) glycation. A higher degree of modification was observed for the sample heated at 80 °C for 25 min under atmospheric pressure than for sample treated under high pressure. In samples treated at pressure below 400 MPa an insignificant increase of glycation level was observed, whereas high pressure (>600 MPa) has only a minor effect on the number of hexose moieties (Fru) attached to the lysine residue side chain.

Glycated albumin: an overview of the In Vitro models of an In Vivo potential disease marker

Glycation is a general spontaneous process in proteins which has significant impact on their physical and functional properties. These changes in protein properties could be related to several pathological consequences such as cataract, arteriosclerosis and Alzheimer's disease. Among the proteins, glycation of Human serum albumin (HSA) is of special interest. Human serum albumin is the most abundant protein in the plasma and because of its high sensitivity for glycation, undergoes structural and functional changes due to binding of reducing sugars in vitro. The glycation process occurs by plasma glucose in vivo which has great impacts on the three dimensional structure of protein. These changes are efficient and stable enough which makes the protein to be considered as a new special disease marker instead of HbA1C for diabetes. In some cases, glycated albumin was used as an alternative marker for glycemic control. Glycated albumin reacts with glucose ten times more rapidly than HbA1C and has shorter half-life which makes it more reliable for indicating glycemic states. In this review, glycation of Human Serum Albumin has been overviewed, starting from overall concepts of glycation, followed by some Examples of pathological consequences of protein glycation. The BSA aggregation was reviewed in terms of structural and biological impacts of glycation on the protein followed by reporting documents which indicate possibility of glycated albumin to be used as specific marker for diabetes. Finally, some of the studies related to the models of glycated albumin have been briefly described, with an emphasis on In vitro studies. It is interesting to note the relationship found between in vitro glycation experiments and the propensity of proteins to form amyloid structures, a point that could be further explored as to its significance in hyperglycemic states.

Isolation and characterization of serum albumin from Camelus dromedarius

Serum albumin constitutes 35–50 mg/ml of plasma proteins and performs various physiological activities including the regulation of osmotic pressure on blood, maintaining buffering of the blood pH, carrying different fatty acids and other small molecules, such as bilirubin, hormones, drugs and metal ions, as well as participating in immunological responses. Serum albumin is an extensively used protein in biotechnological and pharmaceutical industries. The camel (Camelus dromedarius) is well tailored to successfully survive in extremely hot and dry climates. Plasma osmolality in the camel increases during water-deprived conditions. In such circumstances serum albumin is crucial in the regulation of blood pressure. The study of biochemical, biophysical and immunological aspects of camel serum albumin (CSA) are likely to provide molecular insights into camel physiology and may render it an alternative to human serum albumin (HSA) and bovine serum albumin (BSA) in all cases. However, these proteins are currently not available or cannot be utilized due to a variety of considerations. In this study, 12 mg of highly pure CSA was obtained from 1 ml plasma. Coomassie Brilliant Blue staining of SDS-PAGE yielded one band and RP-HPLC results revealed a single sharp peak, indicating homogenous preparation of the CSA. The charge/mass ratio and surface hydrophobicity of the CSA was similar to that of BSA. Mass spectrometry analysis of the purified protein confirmed the identity of CSA.