Performance Evaluation of Batch-type Multigrain Puffing-cum-popping Machine for Production of Puffed Soynuts

Soynut is a nutritious and tasty snack made by puffing soybeans. The puffing of soynuts were carried out in a batch-type semiautomatic multigrain puffing cum popping machine; which is designed and developed by the Department of Agricultural Process Engineering, CAET, VNMKV, Parbhani. This machine works on the High Temperature Short Time (HTST) principle. The table salt was used as a heating medium. The grain-to-salt ratio of 1:4 was kept constant in the puffing pan. Soybean grains (1 kg) were dipped in hot water at 100oC for 3 min and then surface dried for 3 hours. Pretreated soybean grains were then fed to the machine for puffing. The optimization of the machine parameters for the production of puffed soynuts contained three independent variables: puffing temperature (°C), stirrer speed (rpm) and puffing time (min), assessed at three levels of 140, 150,160 °C; 35, 40, 45 rpm; 4, 5, 6 min, respectively. The seventeen experiments were carried out using Box-Behnken Design (BBD). The dependent variables, viz. puffing efficiency, expansion ratio, bulk density, color, hardness and crispness were determined. The experimental data was analysed using Response Surface Methodology (RSM) and optimal operating machine parameters were found as puffing temperature of 150 °C, stirrer speed of 40 rpm and puffing time of 5 min. The puffing efficiency and capacity of the developed machine were 97.24 % and 80 kg/day, respectively. Benefit cost ratio and breakeven point were found1.42 and 33.07 %, respectively. The developed batch-type semiautomatic puffing-cum-popping machine was found well-suited for the production of puffed soynuts at cottage level industries.