Nutritional quality of vegetables: effect of chilling on the ascorbic acid content of fennel.

A fundamental part of the human diet should be represented by fruits and vegetables because of their content in fiber, vitamins and antioxidants that can play an important role in reducing the risks of developing several diseases, among which cancer represents one of the most important. The shelf-life of vegetables can last from a few days to several weeks and refrigeration is a preservation technique often utilized to extend the shelf-life of these products; however, also with refrigeration the final content in vitamins and antioxidants can be significantly reduced during the storage. Fennel is a vegetable harvested in the period November-June and finds a wide utilization in the Italian diet, especially in the Southern regions of Italy. Its shelf-life normally spans over a period of 2-7 days and in order to extend its commercialization period the product is often refrigerated for several days before arriving on the tables of the consumers. However, it should be pointed out that the scientific papers dealing with the evaluation of fennel quality during storage are limited. In this work we have studied the nutritional quality of fennels stored under controlled conditions of humidity and temperature (90% R.H. and 6°C respectively) over a period of days and weeks, and the ascorbic acid content was chosen as "quality marker". In order to minimize the ascorbic acid losses during the analyses, a rapid extraction methodology has been set up. The analytical data have shown that the ascorbic acid content in the product had a sharp linear decrease in the first 4 days, with a total loss of about 50% of the initial content. Increasing the storage time did not further affect the ascorbic acid content of the vegetables, that, afterwards, remained constant for more than 2 weeks.