Evaluation of nutrients and some anti-nutrients in lesser-known, underutilized oilseeds

Abstract

The levels of anti-nutritional factors and the chemical composition of five underutilized and not well known commercial oilseeds - castor bean, conophor nut, 'egusi' melon, African oil bean and locust bean - were determined. The crude protein values for the respective oilseeds were 201.8, 227.5, 314.1, 206.3 and 290.6 g kg-1 DM, whereas the crude fat values were 449.6, 491.8, 439.3, 522.8 and 261.9 g kg-1 DM respectively. The results show that oilseeds may be a good source of vegetable oils, whereas defatted cakes might be useful in food fortification or as animal feed ingredients. The crude fibre contents of oilseeds were found to be significant (31.4-90.6 g kg-1 DM), which suggests that consumption of oilseeds and their products would aid bowel functioning. The seeds were found to contain high concentrations of phosphorus and potassium (2.6-4.6 and 3.9-6.5 g kg -1 DM, respectively); the low sodium content observed is in agreement with the generally low sodium encountered in unprocessed foods. The energy values of the seeds range from 4.1 Meal kg-1 DM in locust bean to 5.9 Meal kg-1 DM in conophor nut, which could be considered adequate for supplying useful amounts of calories. Oxalates, phytates and tannins occurred in varying concentrations in the oilseeds. Whereas castor bean contained the highest level of oxalates (6.5 g kg-1 DM), the same seed was relatively low in its content of the other anti-nutritional factors analysed. Phytic acid, phytate phosphorus and tannins had their highest values in African oil bean seed (4.1, 1.2 and 0.8 g kg-1 DM, respectively), which may be considered a major barrier to the use of the seed. However, it is expected that traditional methods employed in processing the seeds, namely hydrothermal treatment, soaking and fermentation, would considerably reduce the levels of the anti-nutritional factors.