Development of Semi Automated Multigrain Continuous Hot Air Puffing System

Abstract

The puffing process can broadly be classified as the sand puffing, salt puffing, air puffing, oil puffing and roller puffing. Puffing is the simplest inexpensive and quickest traditional method of dry heat application, wherein grains are exposed to high temperature for a short time (HTST). The semi-automated multigrain continuous hot air puffing system developed was operated with 1 hp electric power source for a blower, 11 heaters each with the capacity of 0.75 kW with puffing capacity of 6 to 8 kg/h. The system consisted of an electric heating assembly, continuous feeding system, continuous outlet system, cyclone separator and re-circulation of the air unit. The optimized parameter for hot air puffing of sorghum and Bajra were 0.025 and 0.22 kg/kg dm initial moisture content, 285C and 355C puffing temperature, 5.5 and 4 m/s air velocity and 7982 and 8250 g/h feed rate, respectively. As the moisture content of whole-grain was too low to impart puffing, the moisture content of whole-grain was increased to a predetermined level for maximum expansion effect and puffing yield. The sample of finger millet, Kodo millet and Kutki did not require additional moisture, because the whole grain moisture content was adequate for better puffing. The finger millet is not amenable for puffing in the form of whole grains, because, the seed coat of the finger millet grains, if not removed, it not only affects the puffing quality but also its expansion ratio. The endosperm of the millet is covered with the rigid seed coat. Since the seed coat is firmly attached to the endosperm, the decortications become inevitable for puffing purpose. The optimized parameters for hot air puffing of decorticated finger millet, Kodo millet and Kutki were 330, 270, and 380C puffing temperature, 2.5, 3.5 and 2.5 m/s air velocity and 6608, 6608 and 7686 g/h feed rate, Since the process for hot air puffing of millet grains, involved heat treatments, it is necessary to verify the changes occurring during hot air puffing of sorghum, Bajra, finger millet, Kodo millet and Kutki grains.