Effect of water and air content on the rheological properties of black gram batter

Abstract

Bori, a popular pulse based culinary item in the Indian sub-continent, is generally prepared from aerated paste (batter) of soaked black gram ( Phaseolus mungo). Black gram batter was prepared with varied water contents (61.89–62.11%, 63.98–64.99%, 68.19–66.11%, 69.14–69.93%, 71.59–72.42% w/w) and air incorporation (14.06–14.23%, 15.03–15.14%, 16.11–16.19%, 17.07–17.16% and 18.07–18.17% v/v). The rheology of the batter was assessed at 22 ± 2 °C using a co-axial rotational Brookfield Viscometer using a cylindrical spindle. The Herschel–Bulkley model adequately fitted the data ( r 2⩾0.976: p⩽0.05). Flow behaviour indices varied in the range from 0.321 to 0.485, which increased with the increase in air incorporation and water content in the batter. The Consistency index varied in the range from 80.28 to 18.54 Pa s n , and decreased with increase in water content or increasing level of air incorporation in the batter. Density of the batter decreased (903–818 kg/m 3) as the level of air incorporation or water addition to the batter increased. The spreadability of the batter was tested on a galvanized iron sheet by measuring the radial growth rate. This was directly proportional to the water content but inversely related to the air incorporation in the batter. The radial growth decreased linearly with increase in apparent viscosity of the batter ( r 2⩾0.810: p<0.05).