Giustino Mele

Ascorbic acid in exotic fruits: a liquid chromatographic investigation

Abstract The levels of ascorbic acid (AA) have been measured by means of an HPLC method in 11 different exotic fruits (avocado pear, babaco, feijoa, grapefruit, kiwi, kumquat, litchi, mango, papaya, passion fruit, pineapple) and, for comparative purposes, in two citrus fruits (lemon and orange). They were measured in the exotic fruits at two different stages of ripening: (i) immediately after purchasing from a local fresh fruit market, and (ii) after a one-week period of artificial ripening. The results show that all tropical fruits contain relatively high levels of AA (varying between 20 and 90 mg/100g), with the exceptions of avocado pear and feijoa (whose AA levels are markedly affected by oxidation processes). Moreover, the results show that there is a remarkable loss of AA content (usually 30–40%) after the one-week period of artificial ripening, in all the different tropical fruits considered. They seem to indicate that the process of artificial ripening, which is usually carried out during the short-term storage of exotic fruits, can affect the nutritional value of this kind of food as far as the concentration of the reduced form of vitamin C is concerned.

Application of H 2 O 2 -sensing Plant Tissue Electrodes for the Quick Assessment of Meat Freshness

This chapter discusses application of H 2 O 2 -sensing plant tissue electrodes for the quick assessment of meat freshness. Biosensors and especially bioelectrodes are generally very simple to use, endowed with good sensitivity limits, and more economical than most of the other commonly employed techniques. This chapter presents the application of plant tissue-based electrochemical sensors for the direct quantitative determination of biogenic diamines. The biosensors described and evaluated are based on the catalytic activity of the enzyme diamine oxidase (DAO), present in high amounts in the cotyledons of legumes, especially pea and lentil. The sensing element is constituted by an H 2 O 2 -sensing amperometric electrode. These biosensors have been first tested and characterized on standard solutions of putrescine and cadaverine, and subsequently employed to measure the levels of these and other biogenic diamines in some aliments. Particularly, the spontaneous production of biogenic diamines in samples of ground beef as a function of the storage conditions has been investigated, thus revealing that the proposed biosensors could find practical application in food controls.