Mineral composition of frozen taro for determination of geographic origin

The mineral composition of frozen food of taro [Colocasia esculenta (L.) Schott] was analyzed to categorize the geographical production place of taro. The concentrations of Co and H2PO4− were found to be useful to separate the producing place between Japan and China. The analysis was performed by instrumental neutron activation analysis (INAA) and ion chromatography (IC). In the case of INAA, the samples were dried and sealed in a vinyl bag and irradiated with thermal neutrons from JRR3M, installed at Japan Atomic Energy Agency (JAEA). The activated samples were cooled down for a few weeks and the elements (Co, Cr, Fe, Rb, Zn) were determined. Cobalt concentration of frozen taro from China was higher than that from Japan. The tendency was the same in the fresh sample of taro. When concentration of H2PO4− of frozen sample was measured, taro from Japanese product was higher than that of Chinese one, contrary to fresh sample. This result might be caused by the leakage of H2PO4− during freezing process, indicating that we should be careful to apply the discrimination indicators. In addition to Co, there was a significant difference of Rb and Fe concentrations between frozen taro from Japan and China.