Chemical Characterization of Sicilian Prickly Pear (Opuntia ficus indica) and Perspectives for the Storage of Its Juice Sergio Gurrieri,* ,† Laura Miceli, ‡ C. Maria Lanza, § Filippo Tomaselli, § Raffaele P. Bonomo, ‡ and Enrico Rizzarelli †,‡ Istituto per lo Studio delle Sostanze Naturali di Interesse Alimentare e Chimico-Farmaceutico, Sezione di Catania, CNR, Viale A. Doria 6, 95125 Catania, Italy; Dipartimento di Scienze Chimiche, Universita ` di Catania, Viale A. Doria 6, 95125 Catania, Italy; Istituto di Industrie Agrarie, Universita ` di Catania, Via Santa Sofia 98, 95123 Catania, Italy In this work, Sicilian cultivars of prickly pear (Opuntia ficus indica) were partially characterized from a chemical point of view, and the possibility of long-term storage of their juice was investigated. The acidity of the prickly pear juice turned out to be very low (0.02%) and the pH very high (6.4- 6.5) if compared with values found in other common fruit juices. In the perspective of processing and storage conditions according to Italian law, the acidity has been corrected by adding the proper amount of tartaric and/or phosphoric acid. The sugar content (mainly glucose and fructose) is very high (11-12%), and also L-ascorbic acid is present in considerable amount (31-38 mg/100 g). Among the transition metals, a high content of manganese(II) (1.7-2.9 ppm) and good amounts of iron(III) (0.6-1.2 ppm) and zinc(II) (0.3-0.4 ppm) were found. In particular, such ions appear to be present mainly in the thick skin of the fruit or “trapped” inside the pulp. Pectin methylesterase (PME) seems to be present in very small amount and/or is not highly active. Furthermore, PME activity decreases considerably after the necessary adjustment of the pH and the thermal treatment requested for long-term storage. After ∼2 months, none of the juices prepared was affected by noticeable sedimentation of the pulp. Finally, different samples of prickly pear juice were sensorially analyzed, employing descriptors such as color, aroma, viscosity, acidity, sweetness, and off-flavors. The results obtained can be considered very satisfactory, and the juice has been widely appreciated when compared with other products commonly available on the market such as pear and peach juices. Keywords: Prickly pear; Opuntia ficus indica; fruit juice; sensory analysis INTRODUCTION The prickly pear cactus (Opuntia ficus indica) is a plant highly distributed in the Mediterranean area, Central and South America, and South Africa (Barbera and Inglese, 1993; Mun ˜ oz de Cha `vez et al., 1995). In fact, owing to its crassulacean acid metabolism, this plant is characterized by a high potential of biomass production with very low water consumption (De Cor- ta ` zar and Nobel, 1992; Domı `nguez-Lo `pez, 1995). It is, therefore, extremely drought tolerant and grows abun- dantly under semiarid conditions. The content of pro- teins, carbohydrates, minerals, and vitamins (mostly vitamins A and C) in the fleshy stems (cladodes) is nutritionally significant, and in Mexico people eat them cooked as vegetables with meat or beans. Also, Mexican traditional medicine makes empirical use of nopal cladodes mainly for reducing serum cholesterol levels, regulating blood pressure, controlling gastric acidity, and treating several pathologies such as ulcer, fatigue, dyspnea, glaucoma, capillary fragility, liver conditions, rheumatic pain, and wounds (Mun ˜ oz de Cha `vez et al., 1995; Domı `nguez-Lo `pez, 1995). Some new applications having greater scientific basis are being tried for the treatment of gastritis, hyperglycemia, arteriosclerosis, diabetes, and prostatic hypertrophy (Hegwood, 1990; Frati et al., 1990; Palevitch et al., 1993). The nopal produces delicious juicy fruits containing a large number of hard seeds, and it is usually eaten raw after being peeled. The color of the pulp changes depending on the cultivar, from blood red to pale yellow. The very intense color of some cultivars makes the prickly pear fruit very attractive. This is due to the presence of water-soluble pigments such as betacyanins (purple-red) and betaxanthines (yellow-orange) (Piattelli et al., 1964; Piattelli and Minale, 1964; Forni et al., 1992) that can be isolated and used as natural food colorants (Barbera and Inglese, 1993; Odoux and Dominguez-Lopez, 1996). The fruit has also fairly high vitamin and sugar contents (which give it a very sweet taste) (Sawaya et al., 1983; Sepu ` lveda and Sa ` enz, 1990; Joubert, 1993; Mun ˜ oz de Cha ` vez et al., 1995). There are also a number of traditional prickly pear products (Domı `nguez-Lo `pez, 1995; Sa ` enz, 1996). The juice can be either consumed as such, employed for ice cream preparations, or cooked and semidried to the consistency of toffee. Jams and syrups are also com- * Address correspondence to this author at 150 Mann Laboratory, Department of Vegetable Crops, University of California, Davis, CA 95616 [telephone (530) 752-9096; fax (530) 752-4554; e-mail gurrieri@vegmail.ucdavis.edu; perma- nent address telephone ++39 095 7385096; fax ++39 095 580138; e-mail sgurrieri@dipchi.unict.it]. † Istituto per lo Studio delle Sostanze Naturali di Interesse Alimentare e Chimico-Farmaceutico. ‡ Dipartimento di Scienze Chimiche. § Istituto di Industrie Agrarie. 5424 J. Agric. Food Chem. 2000, 48, 5424-5431 10.1021/jf9907844 CCC: $19.00 © 2000 American Chemical Society Published on Web 09/19/2000