Effect of Soaking, Sprouting and Cooking on Chemical Composition, Bioavailability of Minerals and in vitro Protein Digestibility of Roselle (Hibiscus sabdariffa L.) Seed

Abstract

Chemical composition, bioavailability of minerals and in vitro digestibility of proteins in karkade seed (Hibiscus sabdariffa L.) as affected by soaking, sprouting and cooking were studied. The different methods showed varied deviation of nutrients and antinutrients from the raw seeds. Sprouting and cooking significantly increased protein content and decreased starch and soluble carbohydrates levels. K, Na and all the trace elements studied were decreased by processing methods. Cooking was more effective in improving bioavailability of minerals studied than soaking or sprouting. Total polyphenols reduced more by cooking, while phytic acid did not change significantly by processing. In vitro protein digestibility was significantly reduced by all processing methods, with soaking gave the highest percentage of reduction and cooking the lowest percentage. The results also indicated that domestic processing methods changed total acidity and fat acidity as well as N solubility in water and 1 M NaCl. Amino acid profile of the karkade seed indicated that sulfur amino acids and threonine are the limiting amino acids. With respect to FAO pattern, considerable proportion of the essential amino acids were retained on processing, except for lysine on soaking and sprouting and sulfur acids on sprouting and cooking.