INTRODUCTION Fructose can be found in plant foods in a variety of forms including the free monosaccharide form or polymerized to form fructans. Fructans with a short chain length (degree of polymerization of 2-9 units) are known as fructooligosaccharides (FOS), and those with a longer chain (degree of polymerization over 10 units) are termed inulins (Muir et al., 2007). Inulin function as a reserve carbohydrate in plants such as Jerusalem artichoke, dahlia and chicory, being found in smaller amounts in garlic and onion (Chi et al., 2011; Singh and Gill, 2006). Inulins are a group of naturally occurring polysaccharides that can be hydrolysed by two types of inulinases: exo-inulinases (β-D-fructanfructohydrolase, EC 3.2.1.80) and endo- inulinases (2,1-β-D-fructanfructanohydrolase, EC 3.2.1.7). Exo-inulinases split the terminal units of the inulin with a lower degree of polymerization and liberates fructose. Endo- inulinases hydrolyse inulin by breaking the bonds between fructose units that are located away from the ends of the polymer network, to produce oligosaccharides. Inulinases are enzymes that have different catalytic properties: molecular weight, optimum pH and temperature of action, stability, according to the sources. The inulinase produced by Aspergillus niger has optimum catalytic properties at pH of 4.4-5.0 and temperature of 40 °C (Chen et al., 2012; Pandey et al., 1999). Fructose is a simple carbohydrate found naturally in plants (fruits and vegetables). Because fructose have a higher power of sweetening compared to glucose, it is use as food sweetener. The fructose is important for diabetic products because replace sucrose in various foods and beverages. Fructose as fructose syrup is use in the food industry for the production of carbonated soft drinks, fruit beverages, yogurts, ice cream, bakery goods, puddings, dairy products and baby food etc. Also it is used in pharmaceutical industry as excipient in pharmaceutical formulations (tablets, syrups, and solutions) (Lima et al., 2011). So, the production of fructose is very important for human nutrition and health. Since 1989 fructose syrups was produced by hydrolyzing the inulin extracted from Jerusalem artichoke, chicory, dahlia, yacon (Hodgins et al., 2014). Response surface methodology has been successfully used to model and optimize biochemical and biotechnological processes related to food systems (de Lima et al. 2010). Optimization of process by statistical experimental designs is very useful, as it helps in understanding the interactions among the process parameters at varying levels and in calculating an optimal level of each parameter for the maximal product yield (Trivedi et al., 2012). Both the Central Composite Design (CCD) and the Box-Benken (BB) design can be utilized, but they have different structures, and if the experimental region is such that extreme points are a problem, then there are some advantages to the BB. Compared to CCD, the BB design requires fewer experimental runs and less time. Compared to the conventional processes of formulating and optimization, BB provides a far more effective and cost- effective technique. The aim of the present study was to establish the optimal conditions for hydrolysis of fructans from chicory flour by Pak. J. Agri. Sci., Vol. 53(2), 455-460; 2016 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/16.1562 http://www.pakjas.com.pk OPTIMISATION OF FRUCTOSE PRODUCTION BY ENZYMATIC HYDROLYSIS OF CHICORY FRUCTANS Octavian Baston and Octavian Barna * 1 Department of Food Science and Applied Biotechnology, Faculty of Food Science and Engineering, Dunarea de Jos University, 111 Domneasca Street, 800201, Galati, Romania. * Corresponding author’s e-mail: octavian.barna@yahoo.com The response surface method and Box-Behnken design were used to determine the effect of inulinase concentration, pH, hydrolysis temperature and time on chicory fructans. Enzyme concentration between 8 and 80 INU·g -1 , temperatures of 50 °C, 57.5 °C and 65 °C, pH of 4.0 to 6.5 and hydrolysis time between 1 and 96 hours were studied to establish the optimal conditions of chicory fructans hydrolysis. Enzyme concentration, hydrolysis time and pH were the most important variables which have positive effects on enzymatic hydrolysis. The maximum quantity of fructose released from substrate is produced when the concentration of enzyme is 44 INU/g, for a temperature of 65 °C, a hydrolysis time of 48.5 hours and a pH of 6.5. The minimum fructose amount was produced at an enzyme concentration of 44 INU·g -1 , temperature of 57.5 °C, the hydrolysis time of 1 hour and pH of 4.0. Keywords: Inulinase, chicory flour, response surface method, fructose.