Optimizing dry-air preheating conditions for enhancing bioactive constituents, stability, and physiochemical attributes of niger [Guizotia abyssinica (Lf) Cass.] seed oil

Abstract

The study employed dry-air preheating (DAP) at different temperatures (140 °C, 160 °C, and 180 °C) and exposure times (5, 10, and 15 min) to improve niger seed oil (NiO) qualitative attributes. The changes in physicochemical characteristics, tocopherols, pigments, phytosterols, phenolic acids, flavonoids, and Maillard products in NiO were explored after DAP of niger seeds. The structural changes induced by DAP promoted the release of beneficial components and restrained the development of harmful oxidative products. The NiO yield and oxidative stability index increased from 32.94 to 41.64 % and 2.71 to 5.17 h upon DAP at 160 °C and 180 °C for 10 min, respectively. The total flavonoids (140.58 mg/kg), hydroxycinnamic (36.39 mg/kg), and hydroxybenzoic (2.724 mg/kg) acids were highest upon DAP at 180 °C for 10 min, while the browning index (0.130), 5-hydroxymethylfurfural (3.089 mg/kg), carotenoids (1.023 mg/kg), and viscosity (61.33 mPa·s) were highest upon DAP at 180 °C for 15 min. The tocopherols and phytosterols were augmented in NiO upon DAP at 140 °C for 10 min, while they were declined by further elevating temperature (180 °C) and exposure time (15 min). The results suggest the potential industrial application of DAP for enhancing NiO quality characteristics.