Milling and thermal treatment induced changes on phenolic components and antioxidant activities of pigmented rice flours

Abstract

Processing methods involved in value addition to pigmented broken rice, a milling by-product may affect the nutraceutical qualities. Hence the effect of pulverisation and toasting on nutraceutical content in brown rice flours of red and black rice varieties were studied. Plate milling reduced soluble, bound and total polyphenols in red, but increased in black; increased insoluble polyphenols and oryzanol, and reduced anthocyanin in both varieties; antioxidant activity is reduced in red, but increased in black. Toasting caused reduction of soluble, insoluble and total polyphenol, anthocyanin and antioxidant activity in both varieties with an increase in bound polyphenols, and retention of flavonoids and oryzanol. HPLC characterization of phenolics showed changes on processing in content of catechin, caffeic, vanillic, protocatechuic and ferulic acid. It can be concluded that processing impacts the phenolic components of pigmented broken brown rice flour and this information is useful for functional food industry.

Effect of Thermal Treatments on Soluble-Free, Soluble-Conjugated, and Insoluble-Bound Phenolic Components and Free Radical Scavenging Properties of Tomato Seeds

“…In comparison with the previous studies, the effects of thermal treatments on TPC values of soluble- and insoluble-bound phenolic fractions in natural products were contradictory, which may be due to the different conditions for thermal treatments and different samples used for study. For example, Sapna et al found that thermal treatment significantly increased TPC in the soluble-conjugated fraction but decreased the TPC value in soluble-free and insoluble-bound fractions of red rice flour, which was in line with the results of tomato seeds after baking for 15 and 60 min in the present study. Kim and colleagues found that the content of free phenolics generally increased after heat processing in rice hull, whereas the content of bound phenolics decreased compared with that of the raw rice hull .…”

Chemical, physical, and functional properties of Thai indigenous brown rice flours

“…Grain phenolic compounds were eliminated during rice milling and flour preparation, as indicated by a low TPC in CMRF. In comparison to unmilled rice, Sapna et al [ 37 ] found that the TPC of milled rice retained roughly 73–89% of the overall TPC.…”

Microwave subcritical water pre-treatment and enzymatic hydrolysis of geographical identification (GI) tag Indian black rice (Chakhao Poireiton) straw for fermentable sugar production

“…Rice can be differentiated based on its colours such as brown, white (polished brown rice), red, purple or black, and more importantly based on its geographical origin. White rice is the most widely consumed rice, however, pigmented rice such as black rice has higher overall health-beneficial components [6,7] (Table 1). Geographical origin or place of production influences the characteristics or quality of food, and ultimately the purchasing decision of consumers [8].…”