Use of High-Pressure Homogenization for Improving the Quality and Functionality of Probiotics

Besides to their industrial importance, Lactic Acid Bacteria (LAB) are currently studied for their potential role as probiotic. In recent years, worldwide interest in the use of functional foods containing probiotic bacteria for health promotion and disease prevention has increased significantly. Thus, probiotics and their technological and functional properties are the focus of an intensive international research that has stimulated innovation and new product development. The study of some process variables able to optimize and enhance probiotic viability and functionality over the storage and to stimulate innovation and the development of new products. Among the innovative technological processes, High Pressure Homogenization (HPH) seems to have a great potential in functional dairy sector. In fact, HPH has been proposed to produce probiotic fermented milk, bio-yogurt and probiotic cheeses with improved sensorial or functional properties (Patrignani et al., 2008; Burns et al, 2008a). Moreover, Lanciotti et al. (2007b) demonstrated that HPH is able to affect, in relation to the strain and to the treatment applied, both the fermentation kinetics and the enzymatic activities of LAB without detrimental effect on cell viability, confirming the pressure tolerance of LAB. Even if the response to the HPH varied according to the species and the characteristics of the individual strains (Burns et al., 2008a), HPH treatment, applied at sub-lethal level, could increase important technological and probiotic properties of some strains. This chapter will focus the attention on the HPH application potential to increase functional features of probiotic strains both in vitro and in vivo. In particular, pressure effects on strain intestinal transit conditions in the gut and on mice immune system stimulation will be described. Moreover, considering that probiotic properties are related to the cell wall, which is also the principal target of HPH, the effects of a sub-lethal HPH treatment on cell response mechanisms will be described. Specifically, the membrane fatty acid composition of cells before and after the sub-lethal HPH treatment will be studied and cellular morphological changes after HPH will be described by using a transmission electron microscope. Also the potential of HPH applied to probiotic strain cells inoculated in milk employed in the production of a traditional Italian cheese will be considered in order to evaluate strain viability and probiotic features over storage as well as cheese quality and functionality.