Moderate Electric Fields – a processing biotechnological tool

Abstract

During the latest decade, much research on Ohmic Heating (OH) as electro-heating technology has been addressed, and the effects of its moderate electric fields (MEF) have been addressed aiming at fighting pathogens and improving the nutritional and sensory properties of food. In this piece of research, MEF appeared to be an interesting biotechnological tool for food processing, as well as to be used in bioprocesses at large. Our results show that the presence of MEF during heating contributes to a change in protein aggregation kinetics, as well in the shape of the aggregates obtained, thus highlighting the influence of non-thermal effects. Transmission electron microscopy unveiled that MEF can be used to transform e.g. whey products, containing mainly lactoglobulin in their composition, into in vitro small nano-fibrils which can attract the interest of biomedical sciences. Electro-heating treatment can be designed together with cold gelation for development of entirely biodegradable whey protein-based gels as potential devices for incorporation of nutraceuticals i.e. up to 60% of association efficiency, thus creating novel applications for both food and pharmaceutical industries . Electrical and thermal effects were optimized into a single step treatment to enhance thermal stabilization (i.e. inactivation of microorganisms and enzymes) and extraction of added-value or bioactive compounds (i.e. anthocyanins and phenolic compounds) from plant and fruit tissues. High frequency (25 kHz) and electric field (30 V/cm), combined with high temperatures (up to 90 ºC) were well suited for a significant effect (p < 0.05) upon extraction of phenolic compounds. The electro-heating capacity of applying high heating rates with an accurate temperature control, together with putative electroporation effects on cell tissues (due to presence of alternating electric fields), put forward an interesting solution as processing technology toward biorefinery systems.