Amino acid contents and toxically relevant arsenic of rice varieties consumed in Portugal

This study evaluated amino acids, antioxidant capacity, and arsenic species present in Indica and Japonica rice cultivars (Oryza sativa L.) grown in similar regions, as well as brown rice. Essential amino acids in brown rice exhibited a greater abundance when compared to white rice. Lysine was the only essential amino acid with higher concentration in white rice than in brown rice. Results showed antioxidant activity of 0.46 IC₅₀ (mg mL⁻¹) and TPC 0.11 mg eq. GA/g of sample. Total arsenic content in rice samples was about 200 µg/kg. HPLC-ICP-MS determinations revealed iAs as the predominant species in bran samples. Through Spearman's correlation, negative correlations between six amino acids and total arsenic content in japonica white rice were observed. Sulphur amino acid cysteine presented the highest negative correlation (ρ = −0.758, p-value = 0.011). Based on our results, a regular benefit-risk assessment for rice products to enhance the consumption choice is recommended.