Effect of thermal processing methods on the proximate composition, gross energy, minerals and ricin content of undecorticated castor oil seed (Ricinus communis)

Abstract

The nutritive value of raw and thermal processed castor oil seed (Ricinus communis) was investigated using the following parameters; proximate composition, gross energy, mineral constituents and ricin content. Three thermal processing methods; toasting, boiling and soaking-and-boiling were used in the processing of the seed as a way of improving its nutritive value. The three methods achieved a drastic reduction in the ricin levels. Toasting, boiling and soaking-and-boiling reduced ricin level by 93.05%, 94.84% and 97.76% respectively. Apart from Iron and potassium the thermal processing methods significantly (P<0.05) reduced the levels of all other measured constituents. Toasting, as a processing method, achieved a higher proximate components (apart from crude protein and crude fibre), gross energy, mineral and ricin content than boiling and soaking-and-boiling methods. However, the higher level of ricin retained and the lower level of crude protein of toasted seed, make it the least preferred among the thermal processing methods, while soaking-and boiling that gave the least level of ricin and high level of crude protein is to be more preferred.

KEYWORD: Ricinus communis, toasting, boiling and soaking-and-boiling.