Metal release in a stainless steel pulsed electric field (PEF) system Part II. The treatment of orange juice; related to legislation and treatment chamber lifetime

In the last decennia, there is an increasing interest in pulsed electric field (PEF) treatment. The product is often treated in a continuous flow treatment chamber with stainless steel electrodes and exposed to short pulsed electric fields, typically 2-4 kV-mm(-1) during 1 - 10 mu s. Due to direct contact of the treatment chamber electrodes with the food product, the main elements of these stainless steel electrodes are able to dissolve in the treated product. The magnitude of the material transfer depends on many factors such as current magnitude, pulse duration, pulse shape, and product constitution. In this contribution, the effect of metal dissolving during a monopolar pulse shape, generated by a pulse forming network, is investigated. Experiments are carried out with single and repeated PEF treatments in orange juice. These experiments showed that, due to PEF treatment, dissolved metals are present in the juice. The four main elements of stainless steel, iron, chromium, nickel, and manganese, have been considered in particular. The metal concentrations found do not exceed the legislation values for fruit juices and the EU Drinking Water Directive [EU Drinking Water Directive, http://www.europe.eu.int/.] for human consumption. From the experiments, a relationship between dissolved metals in orange juice and the transferred charge is derived. In addition, a lifetime prediction of the treatment chamber caused by release of metals has been made. (c) 2005 Elsevier Ltd. All rights reserved.