A model study on the site-specificity of (-)-epicatechin-induced reactions in β-lactoglobulin by high-resolution mass spectrometry in combination with bioinformatics

Chocolate microstructure: A comprehensive review

Chocolate is a food with complex microstructure properties. In this study, chocolate surface and internal microstructures are discussed considering final product quality and stability. In addition, the effects of the solids and continuous phase components and the interactions between them, and also process effects on the microstructure were reviewed. Irregularities in the internal microstructure affect the surface and cause problems such as unstable cocoa butter crystals, a whitish, streaky appearance, chewy especially fat bloom in this layer and in general, a low quality and sensory in final product. Optimization of the particle size and cooling conditions of the solids is required to modify the surface topography for roughness and pores morphology. Reducing surface porosity can increase fat bloom resistance. For this purpose, reducing surface hydrophobicity by considering proteins with di-sulfide bonds and their concentrations and the use of different bulk sweeteners should be taken into consideration. The morphology of the surface microstructure may be used for product characterization as well as to investigate the environmental conditions exposed during processing and storage. It should be noted that chocolate has a three-phase microstructural system, considering the air present in the gaps at the interface. The importance of the third phase for continuous phase mobility is critical. Additionally, this phase affects behavior in the oral cavity due to melting and release of volatile components.

Reducing the Allergenicity of β-Lactoglobulin by Covalent Modification with Different Contents of Epigallocatechin Gallate (EGCG): In Vitro and In Vivo Studies

β-Lactoglobulin (βLG) is a major allergen in bovine milk protein. This study was designed to investigate changes in βLG structure, digestibility, and allergenicity induced by covalent binding modification with different contents of (-)-epigallocatechin 3-gallate (EGCG). The reaction of EGCG conjugation with βLG reached saturation at a molar ratio of 1:60 βLG:EGCG. Conjugation with EGCG altered the βLG structure, decreased IgE-binding capacity, and increased digestibility in a dose-dependent manner. In vivo studies showed that covalent conjugation with EGCG can reduce βLG-induced allergic symptoms with reducing levels of IgE, histamine, and mast cell protease-1 (mMCP-1) and the percentage of sensitized mast cells. Allergenicity was reduced more effectively in saturated βLG-EGCG conjugates compared to semisaturated conjugates. Observed changes in IFN-γ, IL-4, IL-5, IL-10, and TGF-β levels suggested that βLG-EGCG conjugates were able to promote Th1/Th2 immune balance. These findings further our understanding of the relationship between the degree of polyphenol conjugation and the allergenicity of food allergens.

Multianalytical Approach to Understand Polyphenol-Mal d 1 Interactions to Predict Their Impact on the Allergenic Potential of Apples

Interactions between phenolic compounds and the allergen Mal d 1 are discussed to be the reason for better tolerance of apple cultivars, which are rich in polyphenols. Because Mal d 1 is susceptible to proteolytic digestion and allergenic symptoms are usually restricted to the mouth and throat area, the release of native Mal d 1 during the oral phase is of particular interest. Therefore, we studied the release of Mal d 1 under different in vitro oral digestion conditions and revealed that only 6-15% of the total Mal d 1 present in apples is released. To investigate proposed polyphenol-Mal d 1 interactions, various analytical methods, e.g., isothermal titration calorimetry, 1H-15N-HSQC NMR, and untargeted mass spectrometry, were applied. For monomeric polyphenols, only limited noncovalent interactions were observed, whereas oligomeric polyphenols and browning products caused aggregation. While covalent modifications were not detectable in apple samples, a Michael addition of epicatechin at cysteine 107 in r-Mal d 1.01 was observed.

Covalent polyphenols-proteins interactions in food processing: formation mechanisms, quantification methods, bioactive effects, and applications

Proteins and polyphenols are abundant in the daily diet of humans and their interactions influence, among other things, the texture, flavor, and bioaccessibility of food. There are two types of interactions between them: non-covalent interactions and covalent interactions, the latter being irreversible and more powerful. In this review, we systematically summarized advances in the investigation of possible mechanism underlying covalent polyphenols-proteins interaction in food processing, effect of different processing methods on covalent interaction, methods for characterizing covalent complexes, and impacts of covalent interactions on protein structure, function and nutritional value, as well as potential bioavailability of polyphenols. In terms of health promotion of the prepared covalent complexes, health effects such as antioxidant, hypoglycemic, regulation of intestinal microbiota and regulation of allergic reactions have been summarized. Also, the possible applications in food industry, especially as foaming agents, emulsifiers and nanomaterials have also been discussed. In order to offer directions for novel research on their interactions in food systems, nutritional value, and health properties in vivo, we considered the present challenges and future perspectives of the topic.

From polyphenol to o-quinone: Occurrence, significance, and intervention strategies in foods and health implications

Polyphenol oxidation is a chemical process impairing food freshness and other desirable qualities, which has become a serious problem in fruit and vegetable processing industry. It is crucial to understand the mechanisms involved in these detrimental alterations. o-Quinones are primarily generated by polyphenols with di/tri-phenolic groups through enzymatic oxidation and/or auto-oxidation. They are highly reactive species, which not only readily suffer the attack by nucleophiles but also powerfully oxidize other molecules presenting lower redox potentials via electron transfer reactions. These reactions and subsequent complicated reactions are capable of initiating quality losses in foods, such as browning, aroma loss, and nutritional decline. To attenuate these adverse influences, a variety of technologies have emerged to restrain polyphenol oxidation via governing different factors, especially polyphenol oxidases and oxygen. Despite tremendous efforts devoted, to date, the loss of food quality caused by quinones has remained a great challenge in the food processing industry. Furthermore, o-quinones are responsible for the chemopreventive effects and/or toxicity of the parent catechols on human health, the mechanisms by which are quite complex. Herein, this review focuses on the generation and reactivity of o-quinones, attempting to clarify mechanisms involved in the quality deterioration of foods and health implications for humans. Potential innovative inhibitors and technologies are also presented to intervene in o-quinone formation and subsequent reactions. In future, the feasibility of these inhibitory strategies should be evaluated, and further exploration on biological targets of o-quinones is of great necessity.

Cocoa polyphenols and milk proteins: covalent and non-covalent interactions, chocolate process and effects on potential polyphenol bioaccesibility

In this study, we discussed covalent and non-covalent reactions between cocoa polyphenols and proteins (milk and cocoa) and the possible effects of these reactions on their bioaccessibility, considering environmental and processing conditions. Better insight into these interactions is crucial for understanding the biological effects of polyphenols, developing nutritional strategies, and improving food processing and storage. Protein-polyphenol reactions affect the properties of the final product and can lead to the formation of various precursors at various stages in the manufacturing process, such as fermentation, roasting, alkalization, and conching. Due to the complex composition of the chocolate and the various technological processes, comprehensive food profiling strategies should be applied to analyze protein-polyphenol covalent reactions covering a wide range of potential reaction products. This will help to identify potential effects on the bioaccessibility of bioactive compounds such as low-molecular-weight peptides and polyphenols. To achieve this, databases of potential reaction products and their binding sites can be generated, and the effects of various process conditions on related parameters can be investigated. This would then allow to a deeper insight into mechanisms behind protein-polyphenol interactions in chocolate, and develop strategies to optimize chocolate production for improved nutritional and sensory properties.