Reduction of Cyanogenic Compounds in Flaxseed (Linum usitatissimum L.) Meal Using Thermal Treatment

Abstract

Flaxseed (Linum usitatissimum L.) provides multiple nutritional benefits, including high quality protein, dietary fiber, and is the most abundant source of α-linolenic acid (C18:3). However, the presence of anti-nutritional factors, such as cyanogenic compounds, restricts flaxseed's consumption as a food or feed. This study investigated the reduction of cyanogenic compounds, measured as hydrocyanic acid (HCN), in full-fat flaxseed using extrusion processing without a die by following the response surface methodology. The ranges of processing variables selected were: barrel exit temperature of 76.3–143.6°C; screw speed of 59.6–160.5 rpm; and feed rate of 26.4–93.6 kg/h. The experimental values of HCN reduction obtained were from 60.8 to 86.6%. Optimum extrusion conditions of barrel exit temperature, screw speed, and feed rate were found to be 143.6°C, 133.5 rpm, and 57.8 kg/h for maximum (89.1%) reduction of HCN. This effect was mainly dependent on barrel exit temperature, whereas screw speed and feed rate had no or minimal effect. The mutual interaction effect of barrel exit temperature and screw speed was found to be significant (p ≤ 0.01). The degree of correlation (R2) for HCN reduction was 97.2%, which showed the validity of applied second-order response model. The results of this study demonstrated that significant reduction of HCN in flaxseed can be achieved commercially using an extruder without a die.