engleski

Properties of wheat and hulless barley flours modified by extrusion cooking

Flours obtained by extrusion cooking and posterior milling of the extruded products can be used in starch - based recipes, allowing for the change of functionality of native flours. The objective of this research was to determine the effect of extrusion and different barrel temperatures in the die section (90, 100 and 110 °C) on the properties of two cultivars of wheat and hulless barley flours. Samples with 30% moisture content were extruded in the laboratory single screw extruder Brabender 19/20 DN, at the temperature profile of 70/90/90, (100), (110) °C, using a die with a 5 mm diameter and the scr ew configuration 1:1. The obtained extruded flours were air - dried and milled, and the pharinographic parameters (AACC 54 - 21.02), falling number (AACC 56 - 81.03), Zeleny sedimentation value (AACC 56 - 61.01), and pasting properties (by Micro Visco - Analyser) we re determined. The extrusion resulted in the decrease of peak, hot, and cold viscosity of all samples, which is found to be correlated with higher degradation and gelatinisation of starch during the extrusion process. Further, the extrusion caused a signif icant reduction of the falling number and sedimentation values, but the increment of the water absorption index. The dough stability for all extruded samples was low, probably due to gluten “dilution” and degradation. The extruded flours had a higher dough development time, resistance, and the farinograph quality number, but lower softening degree. The obtained results showed no statistically significant correlation of differences in barrel temperature and the observed changes, except for water absorption, which increased proportionally with the increase in temperature. The pharinographic values defined that all extruded flours belong in the strong quality group and can be used as bread improvers.

extrusion, wheat, hulless barley, flour

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