OPTIMIZATION OF EXTRUSION COOKING OF CORNMEAL AS RAW MATERIAL FOR BAKERY PRODUCTS

Abstract

ABSTRACT The objective of this work was the optimization of extrusion process for the production of extruded cornmeal (ECM) that may be used in the production of corn bread by a direct procedure. The extrusion process variables, barrel temperature, Et (111–159C), moisture content, Mc (12.10–24.77%) and screw speed, Ss (160–460 rpm), were considered and their influence on moisture content of milled extrudates (ME), expansion index (EI), bulk density (BD), water solubility index (WSI), water absorption index (WAI) and cold paste viscosity (CPV) of extrudates was investigated. The influence of ECM addition on viscosity of wheat flour and cornmeal mixture was monitored. The optimimum combination of extrusion conditions was Mc = 21.21%; Et = 145C; Ss = 263.5 rpm. The properties of ECM under optimal extrusion conditions were Mc, 10.97%; EI, 4.22; WAI, 7.84 g gel/g dm; WSI, 14.88%; BD, 36.35 g/100 mL and CPV, 1,220 BU. In the quantity of 30% calculated on the wheat flour quantity, the ECM can be used for the production of corn breads by a direct procedure. PRACTICAL APPLICATIONCorn flour obtained by dry milling of maize, namely in a mixture with wheat flour, has been used in Southeastern Europe for centuries in theproduction of bakery products. Cornstarch granules swell more slowly and gelatinize at a higher gelatinization temperature than starch granules of wheat flour, while corn proteins are incapable of dough formation. The properties of finished corn bakery products depend significantly on the quantity and temperature of the boiling water used for the mix (60–100% of total water quantity added to the mix) and the steaming time of the corn flour (3–12 h), which is the first and critical stage in the process of corn bread and rolls production. The quality of finished products depends significantly on the baker's experience.The purpose of this work was to determine the optimal extrusion process variables for the production of the gelatinized cornmeal that can be used in the production of bakery products by a direct procedure, without prior steaming of cornmeal. This could significantly reduce the processing time and energy consumption, while the product will still be of consistent and even better quality.