M. Ruskova1*, T. Petrova1, I. Bakalov1, N. Penov2, A. Simitchiev2

1Food Research and Development Institute, 154 V. Aprilov, 4000 Plovdiv, Bulgaria
2Department of Canning and Refrigeration Technology, Technological Faculty, University of Food Technologies, 26 Maritza, 4000 Plovdiv, Bulgaria
(Manuscript received 10 June 2015; accepted for publication 9 May 2016)

Abstract. Combinations of different raw materials (beans, einkorn wheat, and buckwheat) for obtaining formulations with high protein content and balanced amino acid composition were studied using simplex centroid design. The target functions for optimization were content of protein, sulfur-containing amino acid methionine and cysteine, lysine, and tryptophan. The optimal area of combinations of raw materials in the food formulas with balanced biochemical composition was obtained. Optimized ternary mixture consisting of 50% bean, 40% einkorn wheat, and 10% buckwheat with different moisture content (16, 22, and 28%) has been extruded in a laboratory single screw extruder (Brabender 20 DN, Germany). Extrusion parameters were as follows: feed screw speed 50 rpm, die diameter 3 mm, screw compression ratio 2:1, temperature profile 100/140/160ºC, screw speed 160 rpm. The three extrudates with different initial moisture were evaluated by sectional expansion index, water absorption index, water solubility index, and density, with the aim of choosing the best treatment. The results demonstrated that the 22% initial moisture content yielded an extrudate with good physicochemical characteristics overall but an optimization study is needed to confirm this.