Browsing by Author "Savage, G.P."

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    Composition of oxalates in baked taro (Colocasia esculenta var. Schott) leaves cooked alone or with additions of cows milk or coconut milk
    (2009) Savage, G.P.; Martensson, L.; Sedcole, J.R.
    Taro (Colocasia esculenta var. Schott) is a major staple food crop in parts of Asia and the Pacific Islands and two different cultivars of taro plants Taro Tonga (C. esculenta) and Taro Futuna (Xanthosoma sagittifolium), known respectively as Maori and Japanese, are grown as a minor crop in New Zealand. The leaves are either boiled or baked before they are consumed. In this experiment the leaves were baked at 150 8C for 1.5 h either alone or with additions of cows milk and coconut milk prior to baking. Oxalate contents of both cultivars of leaves were determined following extraction by either hot distilled water (80 8C) to give soluble oxalates or hot (80 8C) acid (0.2 mol/l HCl) to give total oxalates. The extracted oxalates were then determined by HPLC chromatography. Baked Maori-type taro leaves contained 719.3 12.0 mg total oxalates/100 g fresh weight (FW) and 365.9 11.4 soluble oxalates/100 g FW while baked Japanese-type leaves contained 533.9 14.9 mg total oxalates/100 g FWand 352.6 8.4 mg soluble oxalates/100 g FW. The total and soluble oxalate content of the baked leaves was considerably reduced when the leaves were baked with cows milk, coconut milk or mixtures of these two (mean % reduction of total oxalates was 43.2 3.8% while the mean % reduction of soluble oxalates was 58.7 1.8%).
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    Oxalate content of purslane leaves and the effect of combining them with yoghurt or coconut products
    (2009) Moreau, A.-G.; Savage, G.P.
    The total oxalate of purslane (Portulaca oleracea L.) leaves grown in a green house was 1072.7 23.2 mg/ 100 g dry matter (DM) while the level was 1234.1 37.5 for leaves grown in shaded light in the same greenhouse. Lightly cooking the leaves grown in full and shaded light had no effect on soluble or insoluble content of the leaf tissue. Overall, leaves grown in shaded light contained higher levels of insoluble oxalates leading to an increased amount of total calcium within the leaves being bound to oxalate compared to the levels in the leaves grown in full light in the greenhouse. Addition of yoghurt, coconut milk or coconut cream to the raw leaves had the effect of reducing the overall oxalate content of the mixture by simple dilution. However, the addition of yoghurt to raw purslane leaves significantly reduced the soluble oxalate content of the mixture. The soluble oxalate content of the raw leaves was 53.0% which reduced to 10.7% when yoghurt was added to the leaves. Addition of coconut milk or coconut cream to fresh purslane leaves, while they both gave themixture an acceptable taste, had no effect on reducing the percentage soluble oxalate content of the mixture.