Comparison of microwaves and conventional thermal treatment on enzymes activity and antioxidant capacity of kiwifruit puree

Enzymes are naturally present in food and can cause product deterioration. For this reason, most food-processing steps try to reduce the enzymatic activity. The aim of this work was to compare, in terms of both the inactivation of kiwifruit puree peroxidase, polyphenoloxidase and pectinmethylesterase and also the maintenance of the antioxidant capacity of the product, the effect of a microwave treatment with a conventional thermal treatment designed to cause the same level of peroxidase inactivation (90%). The microwave power and process time that best permitted the maximisation of both the enzyme inactivation and the antioxidant capacity of the product, were selected by means of the Response Surface Methodology. The results obtained point to microwave heating as an appropriate technology with which to produce a stable kiwifruit puree, since these treatments were more effective at enzyme inactivation and antioxidant capacity retention than the conventional thermal treatment. Industrial relevance Food industry is currently focused on the development of novel and minimally processed products with improved quality. Traditional thermal processing has been assumed to require the use of high temperatures and long times to stabilise food products, which lead to dramatic losses of products' quality. Thus, a variety of different processing technologies are being explored as alternative to traditional thermal processing. The results of this study point out that more than conventional heating, microwave technology can be an appropriate means of achieving the required level of enzyme inactivation at which to obtain a stable kiwifruit puree with an improved antioxidant capacity.