The application of high intensity, pulsed infrared radiation for roasting of groundnuts is attempted and the product quality is compared with that of the conventionally roasted samples. Product qualities such as lightness (color), compressive strength (texture) and free fatty acid content are analyzed for different combinations of roasting duration (4-12 min) and temperature (160-200°C), selected based on central composite rotatable design (CCRD). Pulsed infrared roasting at 178-188°C for 6.8-9.2 min resulted in optimum product quality in terms of color, texture and free fatty acid content. The other parameters such as oil and moisture content, peroxide value and sensory characteristics of roasted nuts are also evaluated for the select temperature-duration combinations. The oil yield increased marginally with roasting duration and temperature. Peroxide number, an indicator of the stability of fat, did not vary during infrared roasting. Groundnuts processed at 180°C for 8 min scored high in terms of sensory attributes. Infrared roasting resulted in better product quality as compared to drum and sand roasting.
Biodiesel Production from High Free Fatty Acid-Content Oils: Experimental Investigation of the Pretreatment Step