High oxygen as an additional factor in food preservation

Abstract

In this thesis, the efficacy of high oxygen as an additional hurdle for food preservation is studied. At high oxygen conditions and at low temperature, significant impairment of growth and viability of bacterial cells is found to occur as the result of free radical attack. The imposed oxidative stress leads to an increase of intracellularly generated reactive oxygen species (mainly O 2-, H 2 O 2 and HO · ), which disturbs the cellular homeostasis due to catabolic imbalance and results in growth inhibition. The so-called "free radical burst" probably is responsible for the induction of a host defence mechanism against the destructive impact of high oxygen. Different Lactobacillus sake strains possess endogenous levels of antioxidative properties (metal chelating capacity, hydroxyl radical scavenging and reducing properties) which play an important role in protection against oxidative stress. Superoxide dismutase is demonstrated to be, among others, a main antioxidative enzyme in oxygen insensitive strains and mutants of Lactobacillus sake .Although most aerobic organisms possess biochemical mechanisms that contribute to their resistance to oxygen stress conditions, high oxygen is an efficient preservation strategy if used in combination with other antimicrobial factors (hurdles). The impact of the combined application of high oxygen with refrigeration, carbon dioxide and/or high pressure on microbial stability and physicochemical properties of minimally processed fresh produce (carrots and salmon) is investigated.</font