Silica gel 60 removes bitterness from cold-press produced grapefruit seed oil by adsorption principle

Abstract

The aim of this study was to remove bitterness from cold-press produced grapefruit seed oil by adsorption principle. The 14 different materials and 5 different metal–organic frameworks (MOFs) were tested for this purpose. Best performing adsorbents were selected based on the analyses of sensory bitterness measurements, as well as oil loss, free fatty acidity (FFA), peroxide value (PV), and color measurements. The silica gel 60 and MIL-101 MOF were selected as the best performing adsorbents and tested against control oil. There were some changes in oil color. Oil FFA and unsaponifiable matter values were decreased, and PV and turbidities were enhanced after the treatments. Similarly, unsaturated fatty acid content and tocopherols were decreased expectedly. Although MIL-101 caused great sterol losses, it was in fewer quantities with silica gel 60 treatment. Silica gel 60 treatment resulted in the complete removal of the bitter-tasting flavonoids: naringin and neohesperidin. The non-bitter flavonoids were also decreased after both treatments. Most importantly, sensory descriptive analysis proved that after silica gel 60 treatment, the bitter taste was totally removed, and the astringent, menthol, and raw vegetable attributes significantly reduced compared with the control sample. Overall, the silica gel 60 treatment provided total success in removing bitterness from the oil. Further studies for the reusability of the silica gel 60 and possibly other similar adsorbents for the same purpose were suggested.