Fruit characterization of somecactus species from the northwestern region of Argentina

Abstract

There are several endangered native cactus species in the dry Chaco eco-region located in the Northwestern region of Argentina (27° 45’ S, 64° 18’ O, 170 meters over sea level). Their fruits are consumed by wildlife and rural populations. The main aim of this work was the physicochemical characterization and antioxidant activity determination of Harrisia pomanensis (Hp), Cereus forbesii (Cf), and Opuntia sulphurea (Os). Hp fruits were studied during period 2007-2010 while Cf and Os fruits were analyzed in 2010. Polar and equatorial diameters, peel thickness, and total soluble solids (TSS) were measured; peel and pulp colors were evaluated as well as the presence and type of seeds was assessed. Vitamin C concentrations in fruits and their antioxidant activities were determined. Cf and Hp present fruits without glochids, being a comparative advantage in the crop handling. Hp fruit diameters and weights were significantly different during the analyzed period. On the contrary, significant differences in peel thickness and pulp and juice percentages were not found in this 4-year period. TSS values did not exceed 12 ºBrix. Vitamin C content was 18 mg of 100g of fresh fruit although the antioxidant activity was equivalent to 52 mg of vitamin C indicating the presence of other active compounds. Cf fruits have a deep-purple peel which is smooth and thin (0.1 cm), the pulp is also deep purple with small soft seeds. Their antioxidant activity was equivalent to 85 mg vit C/100 g. When the fruit ripens, it opens, which is a problem for fruit quality. The ripe fruit TSS was 12 °Brix and the pulp mucilaginous. Os have pink small size fruits whose TSS did not exceed 10 °Brix and their antioxidant activity was equivalent to 102 mg vit C/100g. Crop improvement studies are required to select fruits with higher sugar contents.