PRODUCTION OF FRUCTOSE RICH SYRUPS USING INVERTASE FROM DATE PALM FRUITS NIZAR CHAIRA 1,3 , ISSAM SMAALI 2,3 , SAMAHER BESBES 2 , ABDESSALEM MRABET 1 , BELGACEM LACHIHEB 1 and ALI FERCHICHI 1 1 Laboratoire d’Aridoculture et Cultures Oasiennes Institut des Régions Arides Médenine 4119, Tunisia 2 Département de Génie Biologique et Chimique Institut National des Sciences Appliquées et de Technologie (INSAT) Centre Urbain Nord BP 676, 1080 Tunis Cedex, Tunisia KEYWORDS Biochemical characterization, dates, Invertase, high fructose-syrups, Phoenix dactylifera 3 Corresponding authors. Nizar Chaira, TEL: +216-75-633005; FAX: +216-75-633006; EMAIL: nizar.chaira@ira.agrinet.tn; Issam Smaali, TEL: 216-71-703829; FAX: 216-71-704-329; EMAIL: Issam.Smaali@insat.rnu.tn Accepted for Publication March 2, 2010 doi:10.1111/j.1745-4514.2010.00487.x ABSTRACT The invertase activity of eight varieties of date palm from the Tunisian oasis of Gabes and Jerid was extracted with distilled water and concentrated by ammonium sulfate precipitation at 80% saturation. The determination of invertase specific activity in these extracts showed that it was variable and higher in fruit from Gabes varieties (from 0.23 to 1.38 U/mg).Additionally, zymogram analysis showed the presence of at least two isoforms for tested extracts. The invertase extracted from Korkobbi variety has been more characterized. It presented an optimal temperature, optimum pH, apparent Km, apparent Vmax and catalytic efficiency of 45C, 3.5–4, 8.4 mM, 17.3 mmol/min/mL and 2.05 mM/mmol/min/mL, respectively. This invertase was mixed with an aqueous extract rich in sucrose prepared from the Deglet Nour variety. A high-fructose syrup was obtained after only 30 min of incubation. This syrup pro- duced with a very low cost could be used as food additive in the food industry. PRACTICAL APPLICATIONS In Tunisia, discarded dates witnessed a remarkable increase during the last years and the amounts reached an average of 50,000 tons per year. Among these abandoned varieties are those of the Gabes oasis and a higher quantity of Deglet Nour varieties that are removed by sorting. In this context, our work focuses on valorizing these dis- carded dates by the implementation of a process aimed at the production of low-cost fructose-rich syrups destined to the agro-alimentary industry. INTRODUCTION The date palm (Phoenix dactylifera) is considered to be the most important fruit tree in the Middle East (Al-Shahib and Marshall 2003), and has been in cultivation for 6,000 years (Copley et al. 2001). Nutritional and therapeutic values of date flesh have been reported (Mohammed et al. 1983; Fayadh and Al-Showiman 1990; Reynes et al. 1994; Ahmed et al. 1995; Al-hooti et al. 1995; Al-Hooti et al. 1998; Vayalil 2002; Al-Shahib and Marshall 2003; Al-qarawi et al. 2005; Al-farsi et al. 2007; Allaith 2008; Biglari et al. 2008; Besbes et al. 2009; Chaira et al. 2009a; Chaira et al. 2009b). Besides the direct consumption of date flesh, dates are utilized tradi- tionally in many ways, including the production of paste, juices and syrups (Yousif et al. 1996; Cheikh-rouhou et al. 2006; Mrabet et al. 2008). Moreover, the biotechnological use of dates, as a source of carbohydrates to produce metabolites, has been reported by many studies (Barneveld 1993; Roukas and Kotzekidou 1997; Nacib et al. 2001; Chinnici et al. 2005). In 2007, the Tunisian annual production of dates reached about 124,000 tons (FAOSTAT 2009). However, more than 40% of this annual production is formed by the secondary Journal of Food Biochemistry ISSN 1745-4514 1576 Journal of Food Biochemistry 35 (2011) 1576–1582 © 2010 Wiley Periodicals, Inc.