Enhancing the Inactivation of Bacterial Spores during Pressure-Assisted Thermal Processing
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Enhancing the Inactivation of Bacterial Spores during Pressure-Assisted Thermal Processing Jesús Alejandro Aldrete-Tapia 1 & J. Antonio Torres 2 Received: 7 April 2020 / Accepted: 14 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract High pressure treatments have been the best pasteurization alternative to thermal processing due its capacity to reduce microbial safety risks and increase shelf life by inactivating microorganisms and key food spoilage–causing enzymes while retaining food freshness. In spite of these advantages, an important drawback limiting a wider application of this technology is its inability to inactivate bacterial spores which are resistant to several stress conditions, including high pressure. An approach to pressuremediated spore inactivation is to promote spore germination which reduces their resistance to inactivation treatments. However, the germination response, and thus the spore inactivation rate achieved by these treatments, is strongly dependent on the food matrix, process conditions, spore physiology factors, and also on their interactions. Statistical experimental designs, such as the use of the central composite design as an optimization tool to identify effective PATP treatments as opposed to one-factor-at-atime experimental designs, can reveal the importance of the effect of individual and combined factors on the inactivation response. A general review of these factors and examples of agents that could lower the severity of pressure treatments required to inactivate spores is here presented including the modelling of germination as affected by these factors. Keywords Kinetic model . High pressure processing . Pressure-assisted thermal processing . Spore germination . Spore inactivation
Introduction Several nonthermal technologies, and including high pressure processing (HPP), are now available to produce safe foods and beverages with higher sensory quality, fewer additives, and improved retention of health-promoting compounds. Foods with microbiological safety equivalent to products obtained by thermal pasteurization but without the undesirable losses of sensory and nutrition quality are now widely produced by HPP[23]. Packaged (e.g., juices, salsas, and even prepared meals) and unpackaged foods (e.g., oysters, lobsters, etc.) are treated for under 10 min, 100–600 MPa, room or subambient temperature in 50–600-L vessels typically using water as pressurizing fluid [78]. The pressure treatment effect is evenly transferred to the
* J. Antonio Torres [email protected] 1
2
entire product and independently of the product and vessel form or volume [31]. At these pressure levels, molecular covalent bonds are not altered, whereas ionic bonds and hydrophobic interactions are affected, disrupting protein, lipid and polysaccharide conformations [63]. Thus a major effect of HPP is observed in cell membranes [58]. The application of 25–50 MPa treatments has been reported to affect membrane protein function, while 100 MPa can cause partial
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