Studies on preparation, popping and functional properties of bulgur wheat

Abstract

AbstractWheat was steeped to 36% moisture and agitated for 2 min in sand heated to 170 °C. This dry heat bulgur was comparable to bulgur prepared by steam treatment. The dry heat bulgur of 14% moisture content was popped in hot (230 °C) sand medium. The expansion ratio of popped bulgur was 2.1. Some of the functional properties of popped bulgur flour were compared with native, 48 h malted and roller dried wheat flours. Water absorption index was highest for roller dried followed by popped and malted wheat, whereas water solubility index was highest for malted followed by roller dried and popped wheat. Roller dried wheat exhibited higher cold paste viscosity (360 BU) than popped (30 BU) wheat. Popped wheat had a peak viscosity of 300 BU. The viscogram of malted wheat was typical of cereal flours when the enzyme activity of malt was inhibited. The gel permeation chromatograms of popped and roller dried wheat indicated thermal degradation of starch during popping and roller drying. The in vitro carbohydrate digestibility of popped wheat was higher than roller dried and malted samples. The scanning electron microscopic examination of native and popped bulgur revealed that the endosperm of bulgur wheat was a homogenous mass containing gelatinized starch whereas that of popped bulgur was made up of thin layers of popped starch with irregular air spaces.