The aim of this study is to assess the influence of various industrial processes on total Arsenic (TAs) and inorganic Arsenic (iAs) in rice grains, from brown rice to white rice, with application of parboiling treatment and polishing process. The location of TAs in rice grains has been evaluated by laser ablation-inductively coupled mass spectrometry (LA-ICP-MS) and ICP-MS, while arsenic speciation has been determined using high performance liquid chromatography-inductively coupled mass spectrometry (HPLC-ICP-MS).

In this work, 256 samples were analysed for TAs and As speciation (only some representative samples by LA-ICP-MS), representing two European commercial categories (Long A grain and Long B grain groups) and 15 varieties according to their use for parboiling processes. Out of them, 53 sample pairs of paddy rice and corresponding parboiled paddy rice were collected directly from different Italian rice millers. Polished and brown rice aliquots of the same sample were also compared for TAs and As speciation.

This investigation shows that the polishing process, besides modifying the physical characteristics of rice, decreases the concentration of As compared to the brown rice. Indeed, there was a statistically higher arsenic content (TAs and iAs) in brown rice than in white rice, with differences close to 50%. Removing the bran layer during polishing process is thus useful to reduce iAs in rice grain.

The parboiling process, conversely, increases the As content of the polished rice grain with respect to the not parboiled white rice. The hydration and thermal phases of the parboiled process mobilize the high content of arsenic present in the bran layer, so that TAs and iAs contents in parboiled rice bran were 3-times lower than those in the bran of not parboiled rice. The As removed from the bran was though partly transferred into the endosperm, as evidenced by LA-ICP-MS, rising the overall As content of the parboiled grain.

In the rice grains subjected to different industrial processes, from polishing to parboiling, the main form of As remains As(III) as iAs and DMA(V) as organic Arsenic (oAs).