Effect of high pressure homogenisation on microbial inactivation, protein structure and functionality of egg white Agnese Panozzo a , Lara Manzocco b, ⁎, Sonia Calligaris b , Ingrid Bartolomeoli b , Michela Maifreni b , Giovanna Lippe b , Maria Cristina Nicoli b a Laboratory of Food Technology, KU Leuven, Kasteelpark Arenberg 22, 3001 Heverlee, Belgium b Dipartimento di Scienze degli Alimenti, Università di Udine, via Sondrio 2/A, 33100 Udine, Italy abstract article info Article history: Received 6 March 2014 Accepted 19 April 2014 Available online 26 April 2014 Keywords: High pressure homogenisation Egg white Protein structure Foam Gel Immunoreactivity The effect of high pressure homogenisation (HPH) on decontamination, protein structure (turbidity, particle size, free sulfhydryl groups, protein electrophoretic mobility) and selected functional properties (immunoreactivity, viscosity, foaming and gelling properties) of egg white were evaluated. HPH at 150 MPa for multiple passes allowed the progressive inactivation of Salmonella enterica SDMZ 9898. In addition, HPH modified egg white proteins by inducing unfolding and aggregation phenomena. The latter would occur by means of hydrophobic interactions among partially unfolded proteins. Protein structure modifications induced by HPH decreased egg white immunoreactivity probably due to protein epitopes hiding upon aggregation. HPH was not sufficient to modify egg white foaming properties. Depending on the intensity of the process, HPH allowed the modification of apparent viscosity of egg white and firmness of egg white gel. © 2014 Elsevier Ltd. All rights reserved. Introduction In recent time, the demand for liquid egg products has been growing quickly due to their convenient format and easy use at both industrial and domestic levels. As known, pasteurisation is essential to obtain safe liquid egg products by destroying spoilage microorganisms and pathogens. Salmonella, mainly the egg-associated serotype Enteritidis, is the pathogen of concern. To address the issues of Salmonellosis caused by consumption of contaminated liquid eggs, European Regulation CEE 1441/2007 requires the absence of Salmonella in 25 g of product. The US Department of Agriculture has also established egg pasteurisation standards to produce Salmonella free egg products. In the case of liquid egg white, the product should be held for a minimum of 3.5 min at a pro- cess temperature of 56.7 °C (USDA 1969) or at 55.6 °C for at least 6.2 min (Code of Federal Regulations, 2010). Heat treatment is well known to impair the multifunctional properties of egg white, including its ability to coagulate, make foams upon whipping, beget emulsions, increase binding adhesion and contribute to the texture of various foods such as bakery products, meringues, meat products and cookies (Cunningham, 1995). Heating is also known to modify the nutritional and biological properties of egg white, including its digestibility and allergenicity. To this regard, protein cross-linking, deriving from the development of Maillard reaction, not only causes the loss of essential amino acids, but makes protein ag- gregates less accessible to digestive enzymes. In addition, heating may induce loss of conformational epitopes, giving reason to the changes in egg white immunoreactivity (Martos, Lopez-Exposito, Bencharitiwong, Berin, & Nowak-Wegrzyn, 2011). Several non-thermal technologies have been proposed for egg white pasteurisation, including high hydrostatic pressure, pulsed electric fields, UV-C light, pulsed light and microfiltration (Bridgman, 1914; Dunn, 1996; Jeantet, Baron, Nau, Roignant, & Brule, 1999; Mukhopadhyay, Tomasula, Luchansky, Porto-Fett, & Call, 2010; Unluturk, Atilgan, Baysal, & Tari, 2008). In this context, high pressure homogenisation (HPH) is a prom- ising technique, particularly suitable for continuous production of fluid foods, allowing the limitation of thermal damage (Popper & Knorr, 1990). In general terms, during HPH, the fluid is forced through a narrow gap in the homogenizer valve, where it is submitted to a rapid acceleration (Dumay et al., 2013; Floury, Legrand, & Desrumaux, 2004). As a consequence, phenomena such as cavitation, shear and tur- bulence are simultaneously induced (Freudig, Tesch, & Schubert, 2003; Paquin, 1999), leading to an instant temperature increase whose mag- nitude depends on the intensity of the applied pressure. High pressure homogenisation has been demonstrated to cause inactivation of bacteria and yeasts in several different foods (Cruz et al., 2007; Diels & Michiels, 2006; Lanciotti, Gardini, Sinigaglia, & Guerzoni, 1996; Lanciotti, Sinigaglia, Angelini, & Guerzoni, 1994). However no indication is avail- able about the possibility to exploit this technology to decontaminate egg white. Recently, Patrignani et al. (2013) demonstrated the possibility Food Research International 62 (2014) 718–725 ⁎ Corresponding author. Tel.: +39 0432 558152; fax: +39 0432 558130. E-mail address: lara.manzocco@uniud.it (L. Manzocco). http://dx.doi.org/10.1016/j.foodres.2014.04.051 0963-9969/© 2014 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres