MULTIOBJECTIVE OPTIMIZATION OF TOTAL MONOMERIC ANTHOCYANINS AND TOTAL FLAVONOIDS CONTENTS IN ULTRASOUND-ASSISTED EXTRACTION FROM PURPLE POTATO TUBERS ALEXANDRU WOINAROSCHY 1,2,4 and FLORENTINA DAMS ¸A 1,3 1 Department of Chemical and Biochemical Engineering, Politehnica University of Bucharest, Bucharest, Romania 2 Academy of Technical Sciences of Romania, Bucharest, Romania 3 National Institute of Research and Development for Potato and Sugar Beet, Bras ¸ov, Romania 4 Corresponding author. TEL: 140 744984792; FAX: 140 214185900; EMAIL: a_woinaroschy@chim.upb.ro Received for Publication March 7, 2016 Accepted for Publication May 9, 2016 doi:10.1111/jfpe.12422 ABSTRACT The total monomeric anthocyanins (TAC) and total flavonoids (except anthocyanins) contents (TFC) in ultrasound-assisted extraction from purple potato tubers have been established by analytical methods. In order to study the influences of two ultrasound-assisted extraction parameters (sonification time and solvent/ solid ratio) on TAC and TFC, a 2 3 experimental design was performed. The second- order polynomials calculated by regression have shown very good predictions. The sensitivity of the considered ultrasound-assisted extraction parameters have been investigated by Monte Carlo simulations. The simultaneous maximization of TAC and TFC was the aim of a multiobjective optimization problem which has been solved by two methods, namely weighted sum and Pareto-optimal front. The maximum of TAC is obtained for the lower bound value of sonification time (5 min) and for a solvent/solid ratio of 20.66. The maximum of TFC is obtained for a sonification time of 13.39 min and for a solvent/solid ratio of 21.09. PRACTICAL APPLICATIONS Anthocyanins and flavonoids present an important antioxidative activity and can play an important role in protection against neuronal and cardiovascular diseases, cataract, cancer, diabetes and aging-related disorders. This research explored the use of polynomial regression of experimental data, sensitivity analysis and multiobjective optimization to find the best values of sonification time and solvent/solid ratio for maximization of total monomeric anthocyanins and total flavonoids contents in ultrasound-assisted extraction from purple potato tubers. Both multiobjective optimization methods used here give large sets of optimal solutions. From these can be selected the solution corresponding to the best compromise of two objectives. On the base of the experimental and mathematical investigations it is proposed a small scale, batch industrial process. INTRODUCTION Potato is the fourth food culture of the world, after corn, wheat and rice, with a production of 329 million tons per year. Worldwide, in terms of harvested area potato ranks seven after wheat, rice, corn, barley, sorghum and rapeseed. In terms of consumption, potato ranks third after rice and wheat. In Romania, currently, from the total cultivated area of 8.9 million hectares, potato ranks third with a share of about 3.2% after cereals which represent 62% and oilseeds 15% (FAOSTAT 2012). Potatoes are a significant source of natural antioxidants and exhibit antioxidant activity as dem- onstrated in recent times by many authors. It has increased Journal of Food Process Engineering 00 (2016) 00–00 V C 2016 Wiley Periodicals, Inc. 1 Journal of Food Process Engineering ISSN 1745–4530