Technique for Checking the Geographic Origin of Pumpkin by Inorganic Element Composition

Imported pumpkins (Cucurbita maxima), mostly from New Zealand and Mexico, account for two-fifth of the pumpkins distributed in Japan. As correct labeling of geographic origin is also required for pumpkins grown in Japan, we examined techniques to determine the geographic origin of pumpkins using 113 lots : 49 from Japan, 33 from Mexico and 31 from New Zealand. From each lot, seeds were collected from 10 pumpkins and pulverized. Approximately 1-2 g of test seed material was digested with nitric acid in a microwave digestor. Twenty-three elements (Mg, P, K, Ca, V, Mn, Co, Ni, Cu, Zn, Rb, Sr, Y, Mo, Cd, Cs, Ba, La, Ce, Nd, Sm, Gd and Tl) were analyzed by ICP-AES and ICP-MS. Linear discriminant analysis (LDA) was applied to two models to discriminate the geographic origin between Japan and Mexico (J-M) and between Japan and New Zealand (J-N). Using the established J-M LDA model using 6 elements (P, Ni, Zn, Rb, Sr and Mo) on 38 samples, 89% were correctly determined. Using the established J-N LDA model with 8 elements (P, K, Ca, Ni, Zn, Rb, Sr and Ba) correctly assigned the location of 87% of 39 samples. This technique was evaluated by three laboratories. (Received Aug. 17, 2009; Accepted Oct. 25, 2009)