Compositional Changes Associated with Successive Boiling of Wild Cynophalla retusa (Indian Bean) Pods Collected from the Paraguayan Chaco

Cynophalla retusa, known as “Indian bean”, is an important traditional food for the ethnic groups of the Gran Chaco. However, its contribution of minerals to the diet is unknown and the toxic nature of its raw pods has been reported. The aim of this investigation was to evaluate the composition of minerals, oxalic acid and phytate contents in whole raw and cooked pods, with successive changes of boiling water every 1 h for 4 h in total, as well as the alkaloid content in the cooking water. Bivalent mineral composition determinations (Ca, Fe, Cu and Mg) were made, as well as measurements of the phosphorus and antinutrient contents, such as phytate and oxalic acid, to determine the mineral contribution. The raw pods (C. retusa) contained 6.67% ash, with high contents of Ca, Fe, Cu, Mg and P. Loss of minerals occurred with successive boiling and significant decreases in antinutrients, with significant changes after each boiling period (1, 2, 3, 4 h). The boiling improved the bioavailability of Ca by removing oxalic acid from the sample cooked in the fourth boiling period. However, the phytate contents were not reduced to the same extent (only up to 40%). The results show that C. retusa pods can be a source of minerals (Ca, Fe, Cu and Mg) under controlled conditions of cooking and decreases in antinutrients like oxalic acid. From this perspective, this food source can be a viable alternative to increase food safety and nutrition, using one of many Paraguayan species that are little-known. Therefore, domestication and conservation studies are necessary.