OCCURRENCE IN FRUITS AND VEGETABLES

III. OCCURRENCE IN FRUITS AND VEGETABLES

In most cases, phenolic acids are not found in a free state, except in trace levels, but as combined forms, either soluble and then accumulated in the vacuole or insoluble when linked to cell wall components. Nevertheless, some exceptional situations can cause phenolic acids to accumulate in the free form [2]: brutal extraction conditions, physiological disturbances, contamination by microorganisms, anaerobiosis, processing of fruit juices, and winemaking. As they also accumulate when plant extracts are submitted to hydrolysis, the free HCA profile may characterize the plant material, and it has been used to discriminate between blood and blond oranges [14]. In rare cases, for example, in Capsicum species, the balance between free and combined forms may serve as a chemotaxonomic criterion: free phenolic acids are present in fruits of C. annum, whereas only the glycosylated forms appear in C. frutescens [15].