PRODUCTION OF FRUCTOSE RICH SYRUPS USING INVERTASE FROM DATE PALM FRUITS

Abstract

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 µmol/min/mL and 2.05 mM/µmol/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 produced 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 discarded dates by the implementation of a process aimed at the production of low-cost fructose-rich syrups destined to the agro-alimentary industry.