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

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 Ca2+. 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.Région Bourgogne, Agence Universitaire de la Francophonie

Understanding Business Process Quality

Abstract Organizations have taken benefit from quality management prac-tices in manufacturing and logistics with respect to competitiveness as well as profitability. At the same time, an ever-growing share of the organizational value chain centers around transactional administrative processes addressed by business process management concepts, e.g. in finance and accounting. Integrating these fields is thus very promising from a management perspec-tive. Obtaining a clear understanding of business process quality constitutes the most important prerequisite in this respect. However, related approaches have not yet provided an effective solution to this issue. In this chapter, we consider effectiveness requirements towards business process quality concepts from a management perspective, compare existing approaches from various fields, deduct a definition framework from organizational targets, and take initial steps towards practical adoption. These steps provide fundamental in-sights into business process quality, and contribute to obtain a clear grasp of what constitutes a good business process.

Non-DLVO adhesion of F-specific RNA bacteriophages to abiotic surfaces: Importance of surface roughness, hydrophobic and electrostatic interactions

International audienceWe report on the adhesion features of three F-specific RNA-phages (MS2, GA and Q beta) onto surfaces (1-dodecanethiol gold-coated surface, glass, polypropylene and stainless steel) that significantly differ with regard to their surface roughness and hydrophobic/hydrophilic balance. The number of adhered phages on the surfaces is quantified using RT-PCR. Adhesion experiments are performed under static conditions in the absence of bulk phages aggregation (1 mM and 100 mM NaNO3 electrolyte, pH 7). The nanoscale surface features and the hydrophobicity of the deposition substrates are quantitatively addressed using Atomic Force Microcopy and Chemical Force Microscopy. The hydrophobicity of the phages is evaluated from their propensity to adhere onto flat and highly hydrophobic surface. Results show that, regardless of electrolyte concentration and surface roughness, the adhesion capacity of phages systematically follows the hydrophobicity sequence MS2 < Q beta < GA. The capacity of each phage to adhere onto the surfaces increases with increase in the degree of hydrophobicity and/or the roughness of the deposition substrate. Increasing the electrostatic interactions between phages and deposition surface by decreasing solution ionic strength leads to a reduction in surface concentration of adhered phages except for cases where the roughness of the deposition surface is significant. Altogether, the results obtained confirm the limited ability of the classical DLVO theory to predict the adhesion of complex viral (nano)particles to surfaces and emphasize the necessity to take into account the roughness of the deposition substrate and the hydrophobicity degree of both viruses and surfaces