Screening Out the Phytochemicals and Colour Values in White and Black Rice Lines and Its Interrelationship

Abstract

Problem: Kavuni is a traditional black rice variety of Tamil Nadu, India it rich in nutritional and therapeutic properties.  These traits it is not being cultivated widely, due to long duration, poor tillering and low yielding agronomic characters. Objectives: In the  study, twenty three breeding rice lines from the cross between black kavuni and Co 50  were investigated for colour values and phytochemical viz., total phenols content (TPC), total flavonoids content (TFC) and total anthocyanin content (TAC). Methods: Twenty five rice samples were grouped as black and white rice based on colour of aleuronic layer by visual inspection. The color values expressed as L* (lightness), a* (redness), b* (yellowness), H° (hue) and C (chroma). TPC by the Folin–Ciocalteu method and expressed as milligram of gallic acid equivalent (mg GAE/g) per g. TFC by aluminum chloride method and expressed as mg catechin equivalent (mg CATE) per 100 g. TAC was measured by pH differential method, expressed as mg cyaniding 3-glucoside per 100 g (c3-glucoside/100 g). Main results: The black phenotype rice had low value in L*, b*, C, H° and high values in a* than the white color rice. In the black rice group, 145-6 breeding line had darker black aleuronic layer than other black rice. The TPC, TFC and TAC ranged between 0.74 -3.24 mg GAE/g, 12.79 – 82.58 mg CATE/100 g and 0.4-223.76 mg c3-glucoside/100 g, respectively.  High level of TPC, TFC and TAC were recorded in black phenotypic rice, where as lower levels in white rice. The maximum amount of TPC and TAC were observed in 145-6 rice line, which on par with parent black kavuni rice.  The maximum level TFC was observed in 144-2 rice line than the parent rice kavuni. The TPC, TFC and TAC were negatively correlated with L*, b*, C and H° values and positively correlated with a* values at 0.01 probability level. Among the 23 rice lines, based on TPC, TAC and TFC the superior breeding rice lines were 145-6 and 144-2 respectively. The results showed that dark black grain has higher phytochemicals than white grain. Main recommendation:  The results indicate provide the opportunities to further increase the nutritional benefits of some food products from black rice in terms of therapeutic properties.