Quality characterisation and estimation of phytochemicals content and antioxidant capacity of aromatic pigmented and non-pigmented rice varieties

Two pigmented and two non-pigmented aromatic rice varieties were analysed for physical dimensions, physicochemical properties, colour, viscosity changes while cooking, phytochemicals content and antioxidant capacities. The rices were also evaluated for the effect of cooking on phytochemicals content and antioxidant capacities. While Bakul joha (BJ) and Keteki joha (KJ) varieties are non-pigmented, Poreiton chakhao (PC) is purple coloured and Chak-hao-amubi (CA) is red coloured. The varieties differed in size and shape of the kernels; varying from tiny to big in size, short to long in length, and round to bold in shape. KJ contained the highest amount of protein (9.9%) and PC had the maximum amount of fat (2.1%). Non pigmented rices were of high amylose and of high pasting profile parameters and the pigmented ones were of vice-versa nature. Highest levels of total phenolics, total flavonoid content and ferric reducing antioxidant property (FRAP) were observed in CA (579.00 mg GAE 100− 1 g, 220.5 mg QE 100− 1 g and 5.45 mM 100− 1 g respectively); PC recorded maximum levels of anthocyanin content (35.87 mg cyanidin-3-glucoside equivalent 100− 1 g). Both PC and CA possessed good DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity with 94.19% and 96.43% abilities, respectively. Cooking drastically reduced the phytochemicals and antioxidant capacities. These properties further decreased with keeping time of the cooked rices; PC, however, retained maximum amounts compared to others. The study revealed wide differences in the properties of the aromatic rices. PC (purple) was superior to CA (red) for cumulative phytochemicals content and antioxidant properties.

► Pigmented waxy varieties showed very low viscosity on heating, cooking and cooling.
► The pigmented rices had high phytochemicals content and antioxidant capacities.
► Cooking caused drastic reduction in phytochemicals level and antioxidant capacities.
► Pigmented Poreiton chakhao (purple colour) had high levels of anthocyanins.
► Purple rice was superior in phytochemicals content and antioxidant properties.