A study of selected elements present in Vietnamese rice

Abstract

Various rice samples along with their relevant information such as geographical origin, growing seasons and physio-biological characteristics were collected from different sources in North Vietnam. These samples, together with some others from Yaneo, Australia were decomposed and analysed for 14 elements (P, K, Mg, Ca, Mn, Zn, Fe, Cu, Al, Na, Ni, Mo, As, Cd) using microwave digestion and two analytical spectroscopic techniques, namely inductively coupled plasma atomic emission spectrometry (ICP­AES) and inductively coupled plasma mass spectrometry (ICP-MS). The analytical procedures were carefully calibrated and validated. Literature suggests that this is the first significant systematic investigation of the elemental content of Vietnamese rice together with an attempt to relate the contents to various environmental and growth conditions. The elemental analyses of the rice samples were consistent with the concentration ranges reported in previous work for the rice grain. Further, the determined elemental data in conjunction with the available information were used to investigate the influences of environmental and production factors on the mineral levels of the rice samples, as well as to evaluate other aspects of rice quality. This interpretative study was facilitated by chemometrics methods, viz., principal component analysis (PCA), fuzzy clustering (FC), and multicriteria decision-making procedures (PROMETHEE). Application of chemometric methods on the rice data revealed some of the influences of geographical locations, varietal differences, soil conditions, and some other production factors, on the elemental profiles of the selected rice samples. These effects were most pronounced between the Australian and Vietnamese samples, sticky and non-sticky rice, samples grown on upland and flooded soils, and brown and white rice. Quality assessment of the rice samples by multivariate ranking according to selected criteria also provided some useful results. For example, with the Vietnamese rice, samples grown during the dry season were shown to contain somewhat higher amounts of nutritionally significant elements than those grown in the wet, but the wet season seemed to provide better climatic conditions for the overall (nutritional and physio­biological) rice quality. The findings helped to give some suggestions for future studies in the field