Impact of traditional and innovative cooking techniques on Italian black rice (Oryza sativa L., Artemide cv) composition

Due to its high polyphenol content, black rice plays a significant role in good nutrition; however, these antioxidant compounds are affected by heat treatments required for the rice consumption. The aim of this work was to investigate how cooking affects the composition of Artemide black rice, comparing innovative methods, such as sous vide, with traditional domestic techniques (risotto and pilaf). Proteins and ashes were not affected by cooking, except for pilaf rice, where a 42 % ashes decrease was observed; fiber content increased after all cooking methods, reaching a 29 % increase in the risotto. Antioxidant activity, total polyphenols, anthocyanins and proanthocyanidins were reduced on average of 40 %, 34 %, 43 % and 39 %, respectively. Individual anthocyanins decreased, while phenolic acids and other flavonoids presented different behaviours, also depending if considered in their free or bound form. Cyanidin-3-O-glucoside was reduced up to 56 % in the sous vide cooked rice at 99 °C, and only by 45 % and 37 % in the risotto and sous vide cooked rice at 89 °C, respectively. Traditional risotto preparation and the innovative sous vide cooking at 89 °C also maintained the highest antioxidant polyphenols content, saving 63 % of the antioxidant activity in respect to the raw black rice. Concluding, these last techniques can be suggested for a better preservation of bioactive compounds.