Impact of Polishing on Physicochemical Properties, Cooking Behaviour, and Anthocyanin Content in Njavara Red Rice

Abstract

The aim of this study was to assess how rice polishing properties affect the nutritional value and anthocyanin composition and cooking performance of Njavara rice which grows as a traditional red rice variety in Kerala's Indian region. Red rice exists as unpolished rice which was examined together with 5% polished rice and 7% polished rice including their bran components. Red rice contains the highest nutritional value because it holds 8.565 mg GAE/g of total phenolic content which exceeds the 8.180 mg GAE/g found in 5% polished rice and 7.537 mg GAE/g found in 7% polished rice. Total anthocyanin content was highest in the 7% bran fraction (8.28 ± 0.06 mg/100 g), followed by red rice (6.81 ± 0.05 mg/100 g), 5% bran fraction (4.56 ± 0.08 mg/100 g), 5% polished rice (3.51 ± 0.02 mg/100 g), and 7% polished rice (2.53 ± 0.03 mg/100 g). The cooking properties showed red rice needed the longest cooking duration of 45 minutes while 5% polished rice needed 35 minutes and 7% polished rice needed 30 minutes with respective elongation ratios of 1.11, 1.18, and 1.21. The protein content was higher  in red rice (9.42 ± 0.15%) as compared 9.23 ± 0.56% found in 5% polished rice and 8.12 ± 0.48% present in 7% polished rice. The research shows that polishing reduced bioactive compounds and antioxidant potential while decreasing cooking time and increasing solid loss during cooking.