Study of apple juice preservation by filtration through silica microparticles functionalised with essential oil components

Abstract Novel non-thermal preservation technologies are needed given consumers’ demand for minimally processed high quality food products with a long shelf life. In this work, novel filtering materials based on silica microparticles functionalized with essential oil components (eugenol and vanillin) were applied as an alternative preservation method for apple juice. After confirming the immobilisation of the antimicrobial compounds on particles’ surface, the capacity of the filtration system to pasteurise apple juice inoculated with Escherichia coli was proven (a reduction of at least 5-log). The influence of filtration on the physico-chemical (pH, acidity, soluble solids, colour) and microbiological (mesophilic, psychrophilic and mould and yeast) parameters of fresh apple juice was evaluated throughout refrigerated storage, as well as the potential leaching of the immobilised bioactive compounds. The results showed the capability of the functionalised particles to completely remove the native flora of fresh apple juice and to preserve the product’s microbial stability throughout the study period (> 120 days). Filtering juice through the eugenol-functionalised particles did not strongly affect the physico-chemical properties, except for the colour attribute. The use of immobilised vanillin significantly affected some product characteristics, probably due to the partial release of compounds to the food matrix. Therefore, the immobilisation methodology should be optimised before applying this support to a real scenario. Nevertheless, the immobilisation of these bioactive compounds on silica microparticles allowed filtration technology to be developed as a promising alternative to existing pasteurisation technologies to provide microbial stable and quality acceptable food products.