Effect of Processing on Proximate Composition, Antinutritional and Toxic Contents of Kernels from Cucurbitaceae Species Grown in Nigeria

Dry seeds of melon—Citrullus vulgaris_Schrad, Citrullus lanatus (Thunb.) Mansf. syn. Colocynthis citrullus Linn. O. Ktze, Cucumeropsis mannii Naud (Cult.) syn. Cucumeropsis edulis (Hook.f) Cogn. and gourd—Lagenaria sicceraria var. 1 (Molina) were used. The effects of germination, toasting and boiling on proximate composition, phytic acid, oxalate, total phenols, hydrocyanic acid and saponin contents were determined on control and treated samples. Apart from fibre and ash, protein and oil, contents changed in concentration with pre-treatments. There was about 2–4% protein increase in kernels from 48 h germinated seed but subsequent germination reduced the protein content by 9–10%; oil was also reduced by 7–10%. Antinutritive and toxic contents of raw kernels were phenols 1.6–2.4 mg catechin/g, hydrocyanic acid 12.1–15.9 mg/100g and saponin 3.1–4.2%. Toasting reduced 22–44% saponin and 24–54% total phenol contents of the kernels; germination reduced phytic acid, oxalate and phenols by 31–50, 26–41 and 17–67%, respectively; whereas boiling appreciably reduced all the components by about 40–81%, with phenols having the greatest reduction. The soluble antinutritional and toxic components of the kernels were found in traces in the boiled water. In general, the data obtained in this investigation tend to suggest that the use of kernels from some species of Cucurbitaceae for food may have no health hazard potentials.