Physical analysis of friction cooked RTE snacks

Extrusion is widely applied for production of ready to eat snacks. The existing technology is capital intensive and requires preconditioning the raw grains before extrusion, dedicated drying after extrusion and post extrusion addition of fat and sugar where required. A novel technology, friction cooking, has been developed to greatly lower capital costs and overcome the limitations of conventional extrusion. The production conditions (temperature and moisture content) and resulting physical properties from eight friction cooked raw grains were compared to the equivalent properties of conventionally extruded products from these grains. Properties were expansion ratio, bulk density, hardness and colour. Friction cooking temperatures were lower (60–98 °C versus about 150 °C), and products were softer but with a lower expansion ratio and higher densities. In friction cooking colour differences between raw grains and cooked product were minor. Many of these differences were attributed to lower temperatures and moisture contents in the friction process.