105°C).Normal corn starch was extrusion-cooked in a C. W. Brabender Laboratory model single-screw extruder at various extruder barrel temperatures, screw speeds, feed rates, and moisture contents. The expansion ratios and shear strengths of the products were highly dependent on extrusion-cooking conditions. The maximum expansion ratio of 16.1 was obtained when 14% moisture content (d.b.) starch was fed at a rate of 60g min-' with a screw speed of 150 rpm, a barrel temperature of 140°C and a die-nozzle L/D ratio of 3.1. The shear strengths of the extruded starch products were inversely proportional to the expansion ratios.For convenience, these moisture values are reported in round figures in the text, as 6, 12, 14, 16, 18, 20, 25, and 30%. Extrusion A C. W. Brabender laboratory extruder (Model #2902) with a 1.90 cm barrel diameter, and 2O:l barrel length-to-diameter ratio was used. The extruder was powered by a 2.2 kW motor with speed variable from 0 to 200 rpm. A 3:l compression ratio screw was used. The die-nozzle diameter and length were 3 mm and 15 mm, respectively. The feed zone barrel temperature was 8O"C, and the compression and die zone temperatures were varied from 110" to 200°C and were controlled by electrical resistance band heaters.

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Optimum conditions of parboiling, milling and puffing for making expanded rice were studied on a smaI1 laboratory scale. Optimum puffing was obtained'by heating milled parboiled rice at a moisture content of 10.5-11% with 15 times its weight of fme sand at 25O'C for lo-11 sec. Raw and mildly parboiled rice gave minimal expansion, which increased with increasing severity of parboiling up to a steam pressure of 1.5 kg/cm'. However, rice parboiled by heating with sand (25O"C, 2.5 min) expanded best. Starch retrogradation after parboiling reduced expansion, as did cracked and broken grains and insufficient milling of the rice. Addition of salt increased expansion. Expansion initially increased and then decreased with increasing age of paddy after harvest.