Interaction of fat and aqueous phase parameters during high-hydrostatic pressure inactivation of Lactobacillus plantarum in oil-in-water emulsions

Abstract

High hydrostatic pressure (HHP) processing of food can inactivate spoilage microorganisms, while largely preserving quality characteristics like color, flavor, texture, and vitamin content. However, the composition of the food matrix can strongly affect HHP inactivation efficiency. As systematic data on the interplay of different food matrix components are rare, we used defined oil-in-water (O/W) emulsions as a model system to investigate the impact of fat on the effect of the aqueous phase parameters sodium chloride (NaCl), sucrose, pH, and proteins on HHP inactivation of Lactobacillus (L.) plantarum strains. To identify a potential interconnection with cell surface characteristics, strains with hydrophobic and hydrophilic surface characteristics were considered. HHP inactivation varied widely among the investigated strains. In general, high NaCl and sucrose concentrations exerted a baroprotective effect, whereas low-pH environments enhanced inactivation, and the impact of proteins followed no clear trend. The presence of fat did not generally influence any of the aqueous phase parameters in its impact on HHP inactivation, but caused sporadic matrix and strain specific; however, cell surface hydrophobicity-independent alterations in inactivation efficiency. Still, fat was able to significantly change, and sometimes even invert, the effect of other food matrix parameters.