ABSTRACT
One of the main factors that limit the shelf life of processed fruit and vegetable products are deteriorative reactions catalysed by endogenous plant enzymes. The cell disruption that occurs during processing brings about decompartmentalisation and increased enzyme-substrate interaction leading to changes in color, flavor, juice cloud, consistency and nutritional quality unless a suitable physicochemical approach is used to inactivate or inhibit endogenous enzymes in the product. High pressure processing (HPP) at around room temperature has limited effects on most plant enzymes, although the effect is dependent upon the enzyme, the origin, the physicochemical properties of the medium and the intensity of the process. As a matter of fact, application of moderately high pressures in the range of 200 to 600 MPa near room temperature often results in increased activities of enzymes such as polyphenol oxidase (PPO), peroxidase (POD) and pectin methylesterase (PME) in purees and non-clarified juices. This may lead to undesirable changes in flavor, consistency, color, and nutritional quality attributes during processing and storage. Nevertheless, these deteriorative enzymatic reactions can be controlled to a certain extent through refrigerated storage, the use of appropriate packaging, oxygen scavengers and/or enzyme inhibitors.
