High-Pressure-Induced Effects on Bacterial Spores, Vegetative Microorganisms, and Enzymes

Abstract

High pressure (HP) processing is an emerging technology used in the food industry. At present, the process pressure ranges from 350 to 800 MPa in ultra HP homogenizers or isostatic HP units, whereas the majority of isostatic HP application is used for food pasteurization at chilled and ambient temperature. In the last decade HP technology was extended to a broad range of products, and the number of industrial HP systems has steadily increased; at present more than 156 industrial pasteurized products (with an annual production of 300,000 t) are in use worldwide. The advantage of isostatic HP is the instantaneous and uniform application of pressure to the product without any delay. During the pressure dwell time, a significant reduction of vegetative microorganisms and a denaturation of proteins (e.g., enzymes) could occur, without affecting molecular bonds. Furthermore, chemical reactions (e.g., Maillard reactions), which produce off-flavors, or the destruction of vitamins can be reduced under HP conditions. To achieve an acceptable inactivation of bacterial spores in low acid foods the combination of HP with an elevated initial temperature (>80°C) is a promising improvement to traditional heat sterilization. This combination can result in a sterilized food product with reduced thermal load and consequently higher nutritional quality and functionalities. A further improved understanding of spore inactivation mechanisms and the possibility to calculate the desired inactivation levels could help introduce high pressure thermal sterilization (HPTS) in pilot and industrial scale.