Modification Of Food Proteins Research Articles

Changes in conformation and functionality of whey proteins induced by the interactions with soy isoflavones

Modification of food proteins by interactions with polyphenols has been used to improve the functional properties of proteins. In this study, soy isoflavones-whey protein complexes were prepared via non-covalent complexation. Solubility of soy isoflavones and changes in conformation and functionality of whey proteins were investigated. The results showed that the solubility of soy isoflavones was significantly increased by the complexation with whey proteins (p < 0.05). Soy isoflavones induced decreased α-helix and increased β-sheet of whey protein but increased α-helix and decreased β-sheet of polymerized whey protein. The solubility, foaming properties, and emulsifying activity of whey proteins were enhanced. The thermal stability of whey protein was decreased, but the thermal stability of polymerized whey protein was increased. The thermal gelation behavior of whey protein was enhanced. This study demonstrated that the conformation and functionality of whey proteins could be modified by interaction with soy isoflavones. There were some different changes in the functionalities of whey protein and polymerized whey protein due to the diverse conformation changes. The current study may provide useful information for the modification of whey proteins by polyphenols complexation.

Biological activities and in vitro digestion characteristics of glycosylated α-lactalbumin prepared by microwave heating: Impacts of ultrasonication

The research focuses on application of ultrasonic-assisted glycosylation in food protein modification. Biological activities and in vitro digestion characteristics of the glycosylated α-lactalbumin (UMGLA) and α-lactalbumin (UMLA) prepared by ultrasonic pretreatment and microwave heating at 85 °C for 2 h were investigated mainly through the browning degree, free amino group, reducing sugar and surface hydrophobicity, in vitro digestibility and degree of hydrolysis, total antioxidant capacity, α-glucosidase inhibitory activity, xanthine oxidase inhibitory activity determination methods. The results showed that ultrasonic pretreatment could effectively promote the occurrence of glycosylation reaction, reduce in vitro digestibility and degree of hydrolysis of glycosylated α-lactalbumin and enhance biological activities of glycosylated α-lactalbumin digestive products. Furthermore, after 60 min of ultrasound treatment, the total antioxidant capacity and α-glucosidase inhibitory activity of glycosylated α-lactalbumin digested products were increased by 76.52 ± 0.02% and 12.42 ± 0.04%, respectively, compared with α-lactalbumin without ultrasound treatment. In conclusion, ultrasonic-assisted glycosylation had positive effects on improving the biological activities of in vitro digestion product of α-lactalbumin. It provides a theoretical basis for ultrasonic-assisted glycosylation in the modification field of food proteins.

Receptor Mediated Effects of Advanced Glycation End Products (AGEs) on Innate and Adaptative Immunity: Relevance for Food Allergy.

As of late, evidence has been emerging that the Maillard reaction (MR, also referred to as glycation) affects the structure and function of food proteins. MR induces the conformational and chemical modification of food proteins, not only on the level of IgG/IgE recognition, but also by increasing the interaction and recognition of these modified proteins by antigen-presenting cells (APCs). This affects their biological properties, including digestibility, bioavailability, immunogenicity, and ultimately their allergenicity. APCs possess various receptors that recognize glycation structures, which include receptor for advanced glycation end products (RAGE), scavenger receptors (SRs), galectin-3 and CD36. Through these receptors, glycation structures may influence the recognition, uptake and antigen-processing of food allergens by dendritic cells (DCs) and monocytes. This may lead to enhanced cytokine production and maturation of DCs, and may also induce adaptive immune responses to the antigens/allergens as a result of antigen uptake, processing and presentation to T cells. Here, we aim to review the current literature on the immunogenicity of AGEs originating from food (exogenous or dietary AGEs) in relation to AGEs that are formed within the body (endogenous AGEs), their interactions with receptors present on immune cells, and their effects on the activation of the innate as well as the adaptive immune system. Finally, we review the clinical relevance of AGEs in food allergies.

Chemical Stability of Proteins in Foods: Oxidation and the Maillard Reaction.

Protein is a major nutrient present in foods along with carbohydrates and lipids. Food proteins undergo a wide range of modifications during food production, processing, and storage. In this review, we discuss two major reactions, oxidation and the Maillard reaction, involved in chemical modifications of food proteins. Protein oxidation in foods is initiated by metal-, enzyme-, or light-induced processes. Food protein oxidation results in the loss of thiol groups and the formation of protein carbonyls and specific oxidation products of cysteine, tyrosine, tryptophan, phenylalanine, and methionine residues, such as disulfides, dityrosine, kynurenine, m-tyrosine, and methionine sulfoxide. The Maillard reaction involves the reaction of nucleophilic amino acid residues with reducing sugars, which yields numerous heterogeneous compounds such as α-dicarbonyls, furans, Strecker aldehydes, advanced glycation end-products, and melanoidins. Both protein oxidation and the Maillard reaction result in the loss of essential amino acids but may positively or negatively impact food structure and flavor.

Enzymatically Cross-Linked Sodium Caseinate as Techno-Functional Ingredient in Acid-Induced Milk Gels

Sodium caseinate is widely used as techno-functional ingredient in food processing. However, no studies are currently available on applications of enzymatically cross-linked sodium caseinate although such a modification might have a potential to improve its techno-functional properties and thus reduce the amount of protein necessary to achieve the desired product properties. In the present study, aqueous sodium caseinate solutions were cross-linked by microbial transglutaminase to different extents and subsequently spray-dried. These powders were either redissolved in water or added to reconstituted skim milk to compare acid-induced gels from sodium caseinate solutions to gels from milk with added sodium caseinate. Gelation induced by glucono-δ-lactone was studied using time-based oscillation rheology. The maximum storage modulus (G′MAX) of sodium caseinate gels increased with increasing cross-linking extent, whereas enriched milk gels showed a peak in G′MAX at moderate cross-linking extents. Heat treatment of the enriched milk shifted the highest G′MAX to an even lower cross-linking extent. The results show that constituents of complex food matrices as well as processing routes affect the techno-functional properties of modified food proteins such as cross-linked caseins. It was possible to reduce the amount of added protein from 10 to 7.5 g/kg when cross-linked sodium caseinate was used while obtaining milk gels with similar G′MAX and forced syneresis. Future studies should elaborate ways to further improve the properties of cross-linked sodium caseinate to allow for an even greater reduction in protein enrichment.

Interaction between food antigens and the immune system: Association with autoimmune disorders.

It has been shown that environmental factors such as infections, chemicals, and diet play a major role in autoimmune diseases; however, relatively little attention has been given to food components as the most prevalent modifiers of these afflictions. This review summarizes the current body of knowledge related to different mechanisms and associations between food proteins/peptides and autoimmune disorders. The primary factor controlling food-related immune reactions is the oral tolerance mechanism. The failure of oral tolerance triggers immune reactivity against dietary antigens, which may initiate or exacerbate autoimmune disease when the food antigen shares homology with human tissue antigens. Because the conformational fit between food antigens and a host's self-determinants has been determined for only a few food proteins, we examined evidence related to the reaction of affinity-purified disease-specific antibody with different food antigens. We also studied the reaction of monoclonal or polyclonal tissue-specific antibodies with various food antigens and the reaction of food-specific antibodies with human tissue antigens. Examining the assembled information, we postulated that chemical modification of food proteins by different toxicants in food may result in immune reaction against modified food proteins that cross-react with tissue antigens, resulting in autoimmune reactivity. Because we are what our microbiome eats, food can change the gut commensals, and toxins can breach the gut barrier, penetrating into different organs where they can initiate autoimmune response. Conversely, there are also foods and supplements that help maintain oral tolerance and microbiome homeostasis. Understanding the potential link between specific food consumption and autoimmunity in humans may lay the foundation for further research about the proper diet in the prevention of autoimmune diseases.

Allergenicity prediction of novel and modified proteins: Not a mission impossible! Development of a Random Forest allergenicity prediction model

Alternative and sustainable protein sources (e.g., algae, duckweed, insects) are required to produce (future) foods. However, introduction of new food sources to the market requires a thorough risk assessment of nutritional, microbial and toxicological risks and potential allergic responses. Yet, the risk assessment of allergenic potential of novel proteins is challenging. Currently, guidance for genetically modified proteins relies on a weight-of-evidence approach. Current Codex (2009) and EFSA (2010; 2017) guidance indicates that sequence identity to known allergens is acceptable for predicting the cross-reactive potential of novel proteins and resistance to pepsin digestion and glycosylation status is used for evaluating de novo allergenicity potential. Other physicochemical and biochemical protein properties, however, are not used in the current weight-of-evidence approach. In this study, we have used the Random Forest algorithm for developing an in silico model that yields a prediction of the allergenic potential of a protein based on its physicochemical and biochemical properties. The final model contains twenty-nine variables, which were all calculated using the protein sequence by means of the ProtParam software and the PSIPred Protein Sequence Analysis program. Proteins were assigned as allergenic when present in the COMPARE database.Results show a robust model performance with a sensitivity, specificity and accuracy each greater than ≥85%. As the model only requires the protein sequence for calculations, it can be easily incorporated into the existing risk assessment approach. In conclusion, the model developed in this study improves the predictability of the allergenicity of new or modified food proteins, as demonstrated for insect proteins.

Defining the targets for the assessment of IgE-mediated allergenicity of new or modified food proteins

Many food innovations rely on the introduction and use of new or modified proteins. New or modified food proteins may lead to major health risks due to their inherent potential to cause food allergy. Currently, the pre-market allergenicity assessment for new or modified food proteins and protein sources relies on methods for identifying allergenic hazards based on characteristics of known allergens. However, there is no general consensus on the allergenicity parameters to use and the criteria that should apply for the evaluation and decisions to be made. In this paper, we propose that the strategy for allergenicity risk assessment of new or modified food proteins and the methodologies applied should be governed by the risk management questions to be answered, reflected in the information needed by risk managers to enable their informed decision making. We generated an inventory of health outcome-related assessment parameters and criteria potentially important for risk management decision-making and we discuss the implications of selecting different optional criteria (e.g. cut-off values) for what could be accepted as safe with regards to the health outcomes in the (at risk) population. The impact of these various options on both method development and risk management practices was investigated.

Catalytic properties and thermal stability of a crude protease from the keratinolytic Bacillus sp. CL33A

Abstract Protease production by a feather-degrading mesophilic Bacillus sp. CL33A was performed through submerged cultivations using feather meal as low-cost organic substrate. Soluble protein concentration increased from 1.15 mg/mL at the beginning of cultivations (0 h) to 4.39 mg/mL after 72 h, indicating effective substrate solubilization. Crude protease, recovered as culture supernatants after 72 h of cultivation, was characterized. Optimal temperature and pH conditions for proteolytic activity were 48–62 °C and pH 7.2–9.2. Presence of MgCl2 (1–5 mM), MnCl2 (1 mM), Tween-20 and dimethyl sulfoxide (0.5–1.0%, v/v) increased protease activity at optimal conditions (55 °C; pH 8.0). Contrarily, CoCl2, CuSO4, FeSO4, ZnCl2, MnCl2 (5 mM), sodium dodecyl sulfate (0.05–1.00%, w/v), and β-mercaptoethanol (0.1–1.0%, v/v) decreased enzyme activity. Inhibition by phenylmethylsulfonyl-fluoride (25%), ethylenediaminotetraacetic acid (35%) and 1,10-phenanthroline (31%) indicates that crude protease contains serine and/or metalloproteases. Thermal inactivation of the crude protease at 50–60 °C followed apparent first-order kinetics. Inactivation rates (k) increased at higher temperatures, resulting in half-lives of 38.6 and 2.7 min, and D-values of 128.4 and 8.9 min, at 50 and 60 °C, respectively. Activity decay was modeled as a function of time and temperature by combining first-order and Arrhenius equations. Thermal inactivation was an endothermic process, resulting from conformational destabilization due to a highly positive apparent entropic contribution. Activity at mild conditions and low thermal stability might be beneficial for biocatalytic processes. Crude protease specificity might be explored for the hydrolysis and modification of food proteins, particularly casein and soy protein isolate.

The prediction of the allergenicity food proteins by combining an in vitro and an in vivo model

There is a growing need to develop methods that characterize the allergenic potential of novel and modified food proteins. To date there are no validated in vitro and in vivo models and non-validated assays showed false positive results for non/low-allergenic proteins. Previously, we showed that the combination of a DC-T cell assay and a murine in vivo model was able to distinguish strong allergenic proteins (Ara h1, b-Lactoglobulin (b-LG)) from low/non-allergenic proteins (soy lipoxygenase (SL), gelatin). Here we extended the panel of test proteins (beef tropomyosin (BT), rubisco, patatin, BSA) to investigate the specificity of the assays further. Moreover we tested the sensitivity of the in vivo model by testing whether glycosylation of WPC would result in an increased allergenicity. DC-T assay: A CD4+ T cell pool, containing protein-specific T cells was obtained from protein/alum-immunized C3H/HeOuJ mice. The CD4+ T cells were incubated for 72 hrs with protein-pulsed bone marrow derived dendritic cells (DC). Hereafter,IL-5, IL-10, IL-13 and IFN- y production was analyzed. Mouse model: C3H/HeOuJ mice were sensitized by intra-gastric administration of protein with cholera toxin on days 0 and 7. On day 16, mice were challenged intra-gastrically with protein. Serum was analyzed for protein-specific antibodies and mouse mast cell protease-1 (mMCP-1). Ara h1, b-LG, BSA-, rubisco- and patatin-pulsed but not SL-, gelatin- or BT-pulsed DC induced the production of IL-5, IL-10 and IL-13 from T cells. Thepatatin- and rubisco-induced cytokine production was accompanied by IFN-y induction and likely due to LPS contamination, indicating the LPS-sensitivity of the DC-T assay. In vivo, all allergens induced IgE and mMCP-1 release, whereas the low/non-allergens did not. Rubisco and BT were not tested in vivo. The degree of glycosylation of WPC resulted in similar increase in IgE and mMCP-1 release. Concluding, both the in vitro DC-T cell assay and the in vivo mouse model were able to distinguish known allergens from low/non-allergenic proteins. This may be a promising testing strategy for new (possibly allergenic) proteins in the diet which will be the focus of future research.

Photo-Induced Modification of Food Protein Structure and Functionality

Light processing is nowadays recognised as an efficient technology to non-thermally inactivate a wide range of microorganisms to increase food safety. However, exposure of foods to light can provide further advantages associated with the development of photoreactions involving polymers. Proteins are major target polymers for photoreactions due to abundance of endogenous chromophores, ability to bind exogenous ones and rapid reactivity with other excited state species. As food structure and functions are the result of the status of food constituents, photo-induced structural modification of food proteins can lead to new product characteristics or improved functionalities. This review paper summarises recent developments of the application of light radiation to modify protein structure, inducing changes in their technological and biological functions.

Review on succinylated modification of food proteins

Succinylation is one of the modification method of protein,which increase the net charge of protein and change its structure,resulting in improvement of its functional properties.In this paper,the reaction condition,level of succinylation and change of functional properties of protein were reviewed. It would provide the references for protein modification.

PURIFICATION AND CHARACTERIZATION OF A NEW TRANSGLUTAMINASE FROM STREPTOMYCES SP. ISOLATED IN BRAZILIAN SOIL

A new microbial transglutaminase (MTGase or MTG, EC 2.3.2.13) from a Streptomyces sp. strain isolated from Brazilian soil samples was purified and characterized. Enzyme purification was fast and simple, consisting of two successive chromatographies on Sephadex G-75 columns with yields of 48 and 17%, respectively. The protein purification was successfully achieved to electrophoretical homogeneity on sodium dodecyl sulphate–polyacrylamide gel electrophoresis. The molecular mass of the MTGase was estimated to be about 45 kDa. The enzyme exhibited optimal activity in the pH range of 6.0–6.5 and at 35–40C. It was stable over a broad pH range (4.5–8.0) and up to 45C. The purified MTG's activity was independent of Ca+2, but was activated by the presence of K+, Ba2+, Na+, and Co2+, and inhibited by Cu2+ and Hg2+, which suggests a thiol group at its active site. The purified enzyme presented a Km of 6.37 mM and a Vmax of 1.7 U/mL. PRACTICAL APPLICATION Transglutaminase-catalyzed reactions can be used to modify the functional properties of food proteins. Transglutaminase has been used to catalyze the cross-linking of a number of proteins, such as whey proteins, soy proteins, gluten, myosin and actomyosin. The modification of food proteins by transglutaminase may lead to textured products, help to protect lysine residues in food proteins from various chemical reactions, encapsulate lipids and/or lipid-soluble materials, form heat- and water-resistant films, avoid heat treatment in gelation processes, improve elasticity and water holding capacity, modify solubility and functional properties and produce food proteins of higher nutritional value through the cross-linking of different proteins containing complementary limiting essential amino acids. Due all its potentials, the search for new biotechnological sources of transglutaminase and the study of new enzymes characteristics are essential for the reduction of the enzyme costs and development of new applications for the food industry.

Modification of Casein by the Lipid Oxidation Product Malondialdehyde

The reaction of malondialdehyde with casein was studied in aqueous solution to evaluate the impact of this lipid oxidation product on food protein modification. By using multiresponse modeling, a kinetic model was developed for this reaction. The influence of temperature and pH on protein browning and malondialdehyde degradation was evaluated. The hypothesis that one malondialdehyde unit leads to the cross-linking of two casein-bound lysine residues was in accordance with the data. At higher malondialdehyde concentrations, a different reaction mechanism was operative, probably involving a dihydropyridine cross-link. The results obtained were compared with the reaction of casein with 2-oxopropanal, a well-studied alpha-dicarbonyl compound. The reaction of casein with 2-oxopropanal followed a different reaction pathway. Comparison of the degree of browning of casein by reaction with malondialdehyde and 2-oxopropanal showed a considerably higher degree of browning induced by malondialdehyde. This research has shown that kinetic modeling is a useful tool to unravel reaction mechanisms. Clearly, the contribution of lipid oxidation products, such as malondialdehyde, to protein modification (both in food and in vivo) can be substantial and needs to be taken into account in future studies.

Protein-bound advanced glycation endproducts (AGEs) as bioactive amino acid derivatives in foods

The Maillard reaction or nonenzymatic browning is of outstanding importance for the formation of flavour and colour of heated foods. Corresponding reactions, also referred to as "glycation", are known from biological systems, where the formation of advanced glycation endproducts (AGEs) shall play an important pathophysiological role in diabetes and uremia. In this review, pathways leading to the formation of individual protein-bound lysine and arginine derivatives in foods are described and nutritional consequences resulting from this posttranslational modifications of food proteins are discussed.

Future Approaches to Food Allergy

Food allergy affects approximately 2% of the general US population, and its prevalence seems to be increasing. Despite the potential for a fatal outcome, no definitive therapies are available for food allergy. This article reviews novel approaches for the diagnosis and treatment of food allergy. Improved diagnostic methods include more precise in vitro and in vivo tests for immunoglobulin E-mediated food allergies, in vitro assays for predicting development of oral tolerance, and novel noninvasive tests for cell-mediated food allergies such as patch testing, cytokine assays, and detection of eosinophil activation markers. Several promising novel immunomodulatory approaches to food allergy are discussed, including monoclonal anti-immunoglobulin E; probiotics; traditional Chinese medicine; and immunotherapy with modified food proteins, peptides, bacterial adjuvants, and immunostimulatory sequences.

Clinical and laboratory investigation of allergy to genetically modified foods.

Technology has improved the food supply since the first cultivation of crops. Genetic engineering facilitates the transfer of genes among organisms. Generally, only minute amounts of a specific protein need to be expressed to obtain the desired trait. Food allergy affects only individuals with an abnormal immunologic response to food--6% of children and 1.5-2% of adults in the United States. Not all diseases caused by food allergy are mediated by IgE. A number of expert committees have advised the U.S. government and international organizations on risk assessment for allergenicity of food proteins. These committees have created decision trees largely based on assessment of IgE-mediated food allergenicity. Difficulties include the limited availability of allergen-specific IgE antisera from allergic persons as validated source material, the utility of specific IgE assays, limited characterization of food proteins, cross-reactivity between food and other allergens, and modifications of food proteins by processing. StarLink was a corn variety modified to produce a (Italic)Bacillus thuringiensis(/Italic) (Bt) endotoxin, Cry9C. The Centers for Disease Control and Prevention investigated 51 reports of possible adverse reactions to corn that occurred after the announcement that StarLink, allowed for animal feed, was found in the human food supply. Allergic reactions were not confirmed, but tools for postmarket assessment were limited. Workers in agricultural and food preparation facilities have potential inhalation exposure to plant dusts and flours. In 1999, researchers found that migrant health workers can become sensitized to certain Bt spore extracts after exposure to Bt spraying.

Macronutrient innovations and their educational implications: Proteins, peptides and amino acids

Recent estimates of human requirement for indispensable amino acids have shown that the requirement for key amino acids such as lysine is twofold−threefold higher than previously thought. As a consequence recommended intakes for protein, particularly for vulnerable groups such as the elderly, need to be revised. Indispensable amino acids can also be used directly to improve amino acid supply in diets. A range of nitrogen compounds such as creatine and branched chain amino acids are currently used by groups such as athletes, although their efficacy is open to question. Peptides are natural components of the diet and some of these have been shown to have beneficial effects. The emergence of methods for genetic modification of food proteins raises possibilities of the development of novel foods for a variety of benefits including improved supply of indispensable amino acids, reduced allergenicity, or preformed antibodies to reduce risk of disease.

CHEMICAL MODIFICATIONS OF PROTEINS: A REVIEW

The chemical modifications of proteins are reviewed. Subjects include: (1) modifications done to study protein function; (2) two naturally occurring modifications: carbonylamine reactions and reactions with nitric oxide; (3) applications for bioconjugation and mass spectral analysis; and (4) modifications of food proteins.

Physico-chemical modification of food proteins: food emulsions.

Physico-chemical protein modification involved in food processing is used for "engineering" the structure-property relationship of foods. The three main tools used for protein modification are food formulation, mechanical and thermal (heating/cooling) treatments. They correspond to the main stages of all food technologies. Food structural design is based upon incompatibility and complexing of food biopolymers as well as upon fundamental features of physico-chemical properties of biphasic aqueous systems. Some examples of functional biopolymer modification are considered in systems such as meat extenders, fat replacers, ice cream mixes and wheat flour doughs.