Effect of microwave and conventional cooking on insoluble dietary fibre components of vegetables

Effects of microwave and conventional cooking methods were studied on neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose, hemicellulose and lignin contents of 10 vegetables. Cabbage, carrots, cauliflower, eggplant, onions, peas, potatoes, radish, spinach and turnips were cooked by these methods. Dietary fibre components from these vegetables were reduced to various extents, depending on the type of cooking method. Pressure-cooking showed a more pronounced effect on the reduction of these dietary fibre components than ordinary and microwave cooking. Pressure cooking caused reductions in NDF (22.6–38.8%), ADF (18.1–33.6%), cellulose (24.4–43.8%) and hemicellulose (31.3–47.4%). Lignin contents remained almost unchanged on cooking. It is apparent that reduction in NDF contents was comparatively greater than that of ADF contents as a result of cooking. Similarly, amount of hemicellulose was greatly reduced compared to cellulose on cooking the vegetables.