Stabilization treatment of rice bran alters phenolic content and antioxidant activity

Background and objectives

Rice bran (RB), a by-product of the rice milling process, is known to be a rich source of bioactive phytochemicals. This study aimed to evaluate the influence of RB stabilization treatments, usually applied to inhibit rancidification, on its phenolic composition and antioxidant activity.

Findings

Total phenolic content (TPC) and antioxidant assays were performed on RB that was exposed to extrusion, drum-drying, microwave, and oven stabilization treatments. Chemical profiling was conducted using ultra-high performance liquid chromatography (uHPLC) coupled to an online ABTS system, and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS).

Extrusion and drum-dried stabilization significantly increased TPC when compared to non-stabilized RB (NS-RB). All stabilization treatments increased antioxidant capacity and radical scavenging activity. uHPLC/online ABTS and LC-QTOF-MS identified all treatments to increase the concentration of free phenolic compounds and antioxidant activity compared to NS-RB. More specifically, drum-dried RB significantly altered RB phenolic composition when compared to all other treatments.

Conclusions

All stabilization treatments significantly altered TPC and antioxidant activity of RB. Drum-dried RB treatment was most effective in improving free phenolic composition and antioxidant activity.

Significance and novelty

This study demonstrated that drum-dried stabilization treatment may be a crucial technique that can be applied to RB to ensure essential phenolic compounds with antioxidant activity remain intact, thereby adding value to the functional and nutritional quality of RB.