The effect of soaking and cooking on the oxalate content of taro leaves

Pacific Island people commonly eat taro (Colocasia esculenta var. Schott) as a staple food in their home islands and also like to consume this familiar food when living in New Zealand. Some of these foods are imported from the islands and some attempts are, currently, being made to grow these crops in New Zealand. The taro leaves in this experiment were grown in a greenhouse in the North Island of New Zealand. The soluble oxalate content of the raw leaves was 236.10 mg oxalate/100 g wet matter (WM). Soaking the raw leaves in water for 30 min marginally reduces the soluble oxalate content by leaching into the tap water. Soaking for 18 h results in a 26% reduction in the soluble oxalate content of the raw leaves. During the soaking treatments the insoluble oxalate (calcium oxalate) content of the leaves remained constant (mean 171.64 mg oxalate/100 g WM). Boiling the taro leaves resulted in a 36% loss of soluble oxalates, while the soluble oxalate content of baked tissue was very similar to the raw tissue. The mean insoluble oxalate content of the raw, boiled and baked tissue was 226.28 mg oxalate/100 g WM. Overall, boiling the taro leaves was an effective way of reducing the soluble oxalate content of the cooked tissue.