Domestication of Irvingia gabonensis: 4. Tree-to-tree variation in food-thickening properties and in fat and protein contents of dika nut

Dika nut kernels were extracted from the nuts of 24 Irvingia gabonensis fruits collected from 151 trees in three villages in Cameroon and Nigeria. Methods were developed for the milling, de-fatting, hot-water pasting and rapid visco-analysis of the samples, to simulate the cooking of dika nut meal as a food-thickening agent. Two parameters (viscosity and drawability), thought to relate to the soup-thickening quality of dika nut meal, were derived from the traces. The samples exhibited significant tree-to-tree variation in viscosity, drawability and fat content, and differences between their villages of origin were significant. Thickening was found not to be directly associated with protein content. Similarly, the fat content did not contribute to the thickening properties at temperatures above fat melting point. Fat determination and fatty acid profiling indicated that the fat content ranged from 37.5% to 75.5% and identified myristic and lauric acids as the major fatty acid components. This study is part of a wider tree domestication project characterising tree-to-tree variation in fruit, nut and kernel traits of I. gabonensis with the aim of improving the livelihoods of subsistence farmers.