Influence of Cooking Method on the in Vitro Digestibility of Starch from Sweet Potato Roots

Sweet potatoes (SP) have gained attention in the media as foods recommended for healthy diets. When preparing the roots for consumption, however, cooking methods do alter their chemical, physical and nutritional properties. In order to assess the changes in carbohydrates of four SP accessions, after common cooking treatments (pressure cooker, convection oven and microwave oven), the contents of sugars and total starch, as well as the starch digestibility were evaluated. The pressure-cooked and convection oven-cooked samples showed high levels of both total reducing sugars (TRS) and soluble reducing sugars (SRS). Among the samples, white pulp sweet potatoes showed the highest starch contents. When cooked by microwave oven without adding water the roots had higher contents of resistant starch (RS). The results demonstrate deep transformations in the carbohydrate profile after cooking, with increase in maltose levels and consequent reduction in starch levels.