Distribution of Mineral Elements and Contaminants in Italian Rice Grain Fractions: Evidence from ICP Analysis and Chemometrics

In the Italian rice supply chain, byproducts such as husk and bran represent up to 30% of the total grain mass and differ markedly in their elemental composition compared to polished rice. This study analyzed husk and bran samples, separated from their respective white rice (WR) counterparts and sampled across different Italian regions, to investigate the distribution of 27 elements using ICP-MS and ICP-OES. Statistical comparison using t-tests revealed highly significant differences in the concentration of more than 20 elements between husk and bran. Phosphorus (P), magnesium (Mg), sulfur (S), and zinc (Zn) were significantly more abundant in bran, while chromium (Cr), strontium (Sr), calcium (Ca), manganese (Mn), iron (Fe), cobalt (Co), and nickel (Ni) showed higher levels in husk (FDR-adjusted p < 0.001). The mineral composition of rice fractions reflects their anatomical structure: whole grain consists of endosperm (70%), husk (20%), bran (8%), and germ (2%) (Khir and Pan, 2019). White rice retained significantly lower proportions of most elements, particularly micronutrients and regulated contaminants such as As and Ni, due to their preferential accumulation in the outer layers. These trends confirm the progressive depletion of minerals from husk to endosperm and are consistent with the known localization of minerals in the aleurone layer and pericarp, influenced by tissue-specific chelation and transporter activity (Zhang et al., 2023). Multivariate analyses including PCA, LDA, and PLS-DA effectively discriminated rice commercial types, particularly in bran and WR samples.