Interactions between bacterial surfaces and milk proteins, impact on food emulsions stability

Abstract

Bacteria possess physicochemical surface properties such as hydrophobicity, Lewis acid/base and charge which are involved in physicochemical interactions between cells and interfaces. Moreover, food matrices are complex and heterogeneous media, with a microstructure depending on interactions between the components in media (van der Waals, electrostatic or structural forces, etc.). Despite the presence of bacteria in fermented products, few works have investigated how bacteria interact with other food components. The objective of the present study was to determine the effects of the surface properties of lactic acid bacteria on the stability of model food emulsions. The bacteria were added to oil/water emulsions stabilized by milk proteins (sodium caseinate, whey proteins concentrate or whey proteins isolate) at different pH (from 3 to 7.5). The effect of bacteria on the emulsions stability depended on the surface properties of strains and also on the characteristics of emulsions. Flocculation and aggregation phenomena were observed in emulsion at pHs for which the bacterial surface charge was opposed to the one of the proteins. The effects of bacteria on the stability of emulsion depended also on the concentration of cations present in media such as Ca 2+ . These results show that the bacteria through their surface properties could interact with other compounds in matrices, consequently affecting the stability of emulsions. The knowledge and choice of bacteria depending on their surface properties could be one of the important factors to control the stability of matrices such as fermentation media or fermented products. r

Preparation and properties of milk proteins-based encapsulated probiotics: a review

“…Several macromolecules are located on the bacterial surfaces which enable bacteria to interact specifically or non-specifically with other compounds through electrostatic, hydrophobic interactions. Addition of bacteria to oil/water emulsions stabilized by milk proteins (sodium caseinate, whey protein concentrate or whey protein isolate) at different pH (from 3 to 7.5) affected the emulsions' stability depending on the surface properties of strains and also on the characteristics of emulsions (Ly et al 2008). The surface charge and hydrophobicity of the bacteria were suggested to be involved in its interaction with proteins (Ly et al 2008).…”

“…Addition of bacteria to oil/water emulsions stabilized by milk proteins (sodium caseinate, whey protein concentrate or whey protein isolate) at different pH (from 3 to 7.5) affected the emulsions' stability depending on the surface properties of strains and also on the characteristics of emulsions (Ly et al 2008). The surface charge and hydrophobicity of the bacteria were suggested to be involved in its interaction with proteins (Ly et al 2008). A study revealed that the interaction of probiotics with milk proteins is strain specific and that the type of milk protein and pH affect these interactions being non-specific in case of casein and specific in case of whey proteins (Burgain et al 2013b).…”

Nanoemulsion of orange oil with non ionic surfactant produced emulsion using ultrasonication technique: evaluating against food spoilage yeast

“…The surface hydrophobicity of yeast cells with or without treatment of nanoemulsion was evaluated by MATH assay (Ly et al 2008). In this experiment, 1.5 ml of freshly grown S. cerevisiae cells that contain approximately 1 9 10 7 CFU/ml cells in PDB medium was collected by centrifugation and then resuspended in 1 ml of orange oil nanoemulsion or PBS (pH 7.4).…”

Nanocapsular Dispersion of Thymol for Enhanced Dispersibility and Increased Antimicrobial Effectiveness against Escherichia coli O157:H7 and Listeria monocytogenes in Model Food Systems

“…For emulsion systems, oil droplets can be kinetically stabilized in the continuous aqueous phase by adopting appropriate emulsifiers and engineered interfaces. Milk proteins are among the best natural surfactants for food applications (29). Interfacial properties of milk proteins, particularly whey proteins, can be improved by conjugation with more hydrophilic oligosaccharides and polysaccharides (25).…”