Bitterness Reduction of Cold Pressed Grapefruit Seed Oil by Adsorbent Treatment

Abstract

The goal of this study was to remove bitterness of cold pressed grapefruit seed oil by adsorbent treatments. The oil was treated with amberlites XAD7, IR120, and IRA400 resins, and natural zeolite, sepiolite, and montmorillonite at 3% (w/w) level. Oil physicochemical properties, oil flavonoid, phenolic acid and phytosterol compositions, oil sensory descriptive analysis, oil consumer preferences as well as properties of the adsorbents were determined. The largest surface area, pore radius, pore volume and oleic acid adsorption capacity were observed for natural sepiolite, zeolite and XAD7 amberlite. Adsorbent treatment usually reduced oil viscosity, free acidity, and soap content. In removal of flavonoids, natural sepiolite, zeolite and XAD7 resin were the most successful. Reductions from 3.0 to 60.0% were quantified. Phytosterol composition was not changed significantly by adsorbent treatment. Quantitative sensory descriptive data showed that natural sepiolite at first, followed by natural zeolite and amberlite XAD7 reduced bitterness and throatcatching scores almost by half, but consumer preference test results showed that these reductions were not enough for consumers to accept the taste/flavor of the treated oils. Hence, bitterness removal from grapefruit seed oil still remains as a research challenge.

Practical applications: To utilize cold pressed grapefruit seed oil for direct human consumption, the inherent bitterness needs to be removed. This study showed that almost half levels of sensorially perceived bitterness could be removed by natural sepiolite, zeolite and amberlite XAD7 adsorbents. Although consumers found the treated oils still bitter, the treated oils could be used in formulated food preparations or in blend with other vegetable oils.

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