The effect of processing and preservation methods on the oxalate levels of some Nigerian leafy vegetables

Abstract

Titrimetric analysis was used to estimate the level of oxalate in some Nigerian leafy vegetables treated in different ways in two sets of experiments. The treatments were boiling with retention of the water used for boiling, and freezing followed by boiling without retention of the water used for boiling. Results obtained showed that the former in which five different vegetables were used led to significant increases (p<0.05) in the oxalate content of the vegetable preparations. The exception was Vernonia amygdalina in which there was a significant decrease in the oxalate content after boiling. The latter in which three selected vegetables were used however led to significant decrease (p<0.05) in the level of oxalate of the vegetable preparation, a significant amount having been lost in the decanted water. Boiling and then discarding the water used for boiling vegetables provides a good means of reducing the oxalate content of leafy vegetables and consequently the associated food safety problems.