Transmission of soluble proteins during microfiltration (0.1 µm) of skimmed milk: impact of casein micelles deposit and critical conditions

Autor: Gésan-Guiziou, Geneviève, Jimenez-Lopez, Anne, Lambrouin, Fabienne, Leconte, Nadine
Přispěvatelé: Science et Technologie du Lait et de l'Oeuf (STLO), Institut National de la Recherche Agronomique (INRA)-AGROCAMPUS OUEST, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)
Jazyk: angličtina
Rok vydání: 2013
Předmět:
Zdroj: Journal of Membrane Science
International Membrane Science & Technology, IMSTEC
International Membrane Science & Technology, IMSTEC, Nov 2013, Melbourne, Australia. février 2014, 2013, Journal of Membrane Science
ISSN: 0376-7388
Popis: Crossflow microfiltration (0.1 μm) of skimmed milk is widely used in the dairy industry for the separation of casein micelles from soluble proteins. Microfiltration performance, both in terms of permeability and selectivity, are altered by the accumulation of casein micelles at the membrane surface, that turns into an irreversible deposit in Critical Hydrodynamic Conditions (CHC defined by (J/ w)crit with J : permeation flux, : shear stress at the membrane surface) [1]. Despite the main role of the casein micelle deposit on soluble protein transmission, little attention was paid to the impact of micelle deposit on membrane selectivity. Some studies have focused on the impact of physico-chemical characteristics of soluble proteins on their transmission during microfiltration of milk or dairy proteins suspensions. Others have focused on the impact of hydrodynamic conditions but none of them consider both simultaneously. Le Berre and Daufin (1998) [2] for instance, studied the soluble protein transfer considering the physico-chemical characteristics of individual proteins but this study was carried out under constant hydrodynamic conditions.Hence, this paper aims at understanding the transfer of soluble protein by taking into account both the hydrodynamic conditions of filtration and the physico-chemical characteristics of individual proteins. In that purpose, the transmission of the five major soluble proteins of milk was studied as a function of the hydrodynamic conditions of filtration in presence and in absence of the casein micelles. At pH=6.55 α-lactalbumin, β-lactoglobulin and serum albumin bovine are negative charged, the immunoglobulins (IgG) are globally neutral and lactoferrin, LF is a positive protein. The present work was conducted on thermised skimmed milk (68±1°C, 25 s). MF was operated with a set-up equipped with the uniform transmembrane pressure system and with a 0.1 μm tubular ceramic membrane. An original methodology of filtration based on step by step variation (decrease and successive increase) at constant permeation flux was used to determine deposit characteristics.This study clearly shows that the casein micelle deposit irreversibly alters soluble protein transmission and that the transmission of soluble proteins can be divided into three main groups. For negatively charged proteins, and in the absence of casein micelles deposit, the transmissions of proteins are mainly ruled by steric exclusion through the membrane and accumulated layers. In the presence of casein micelles deposit, the accumulation of micelles at the membrane surface results in a high density of negative charges at the membrane surface. Electrostatic repulsions between accumulated casein micelles and soluble proteins leads then to a significant decrease in transmission of negatively charged proteins. For lactoferrin (positively charged protein), the protein is entrapped in casein micelles deposit. This phenomenon is partially attributed to electrostatic interactions with casein micelles: an increase in ionic strength actually results in charge screening and in a sharp increase of its transmission. For neutral proteins, the transmission is mainly attributed to steric exclusion. Inthe presence of casein micelles deposit, the transmission of neutral proteins is increased due to increase in polarization concentration.For the first time this study shows that the transmission of proteins during microfiltration (in our case microfiltration 0.1 μm of milk) can be partially explain by electrostatic effects between proteins to be transmitted and accumulated colloids at the membrane surface.
Databáze: OpenAIRE
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