Investigation of non-thermal effects of microwave heating in model systems and fruit juices: determination of molecular structure and conformational changes in endogenous enzymes

Abstract

Fruits are an integral part of a healthy diet. They provide essential micronutrients such as vitamins, minerals, and also antioxidants, phytochemicals, sugars and dietary fiber. Preservation of fruits in the form of purees and juices (FP&J) is very popular as these products are convenient to consume and form an integral part of many formulations. Besides microbial spoilage, quality degradation due to endogenous enzyme activity is also a factor of concern. Nowadays, browning is still a major problem for various fruit products due to lowering of quality, safety, and nutritional value. Microwave heating has been reported to provide superior quality fruit-based products with an extended shelf-life, representing a good alternative to conventional preservation processes. The main purpose of the present research is the investigation of possible thermal and non-thermal effects of microwave heating on the safety and quality aspects of fruit juices. The work is focused on the investigation of the effects of microwave and conventional heating on the molecular structure and conformation of the enzymes polyphenol oxidase (PPO) and peroxidase (POD), which will be measured using Fourier-transform infrared (FTIR), circular dichroism (CD), and intrinsic fluorescence spectroscopy and confocal microscopic techniques. The proposed period at McGill University is important for the acquisition of theoretic and practical knowledge about non-thermal effects of microwave heating, a subject unknown and poorly studied in the literature. The opportunity of Research Internships Abroad (BEPE) at McGill University will contribute to future projects in collaboration with the Department of Chemical Engineering and the Food Research Center (FoRC). (AU)