Bitterness Reduction of Cold Pressed Grapefruit Seed Oil by Adsorbent Treatment

Abstract

The goal of this study is to remove bitterness of cold pressed grapefruit seed oil by adsorbent treatments. The oil is 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 are determined. The largest surface area, pore radius, pore volume, and oleic acid adsorption capacity are 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 are the most successful. Reductions from 3.0 to 60.0% are quantified. Phytosterol composition is not changed significantly by adsorbent treatment. Quantitative sensory descriptive data shows 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 shows 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 shows that almost half levels of sensorially perceived bitterness could be removed by natural sepiolite, zeolite, and amberlite XAD7 adsorbents. Although consumers find the treated oils still bitter, the treated oils could be used in formulated food preparations or in blend with other vegetable oils. Cold pressed grapefruit seed oils are treated with various adsorbents to remove bitterness, and then evaluated by analytical techniques and sensory evaluations.

Debittering of cold pressed grapefruit seed oil by metal‐organic framework adsorbents

“…During washing and extraction treatments, both pigment partitioning into solvent and possibly some microemulsions formation due to solvent droplets caused to change oil color and enhance oil turbidity. In a previous study (Aydeniz Güneser & Yılmaz, ), amberlite resins treatment of the cold pressed grapefruit seed oil created very similar results for color values. There was no significant difference for the refractive indices of oil samples among the treatments (Table ).…”

“…The seeds were washed under tap water, drained, and dried at room temperature overnight. Then, the seeds were cold pressed in our laboratory following our previous procedures (Aydeniz Günser & Yılmaz, ) with a laboratory scale cold press machine (Koçmaksan, ESM 3710, İzmir, Turkey) with 40 rpm screw speed, 10 mm exit die, and maximum 45°C oil exit temperature. The extracted oil was centrifuged at 6,797× g (Sigma 2‐16K, Postfach, Germany), placed in colored glass bottles, and flushed with nitrogen.…”

“…The 37‐component FAME mix (C4‐C24; Supelco, Prep‐Inc.) were used for fatty acid determination and quantification (Aydeniz Güneser & Yılmaz, ).…”

“…During the last 15 years, cold pressed oils became a market reality around the world for special purpose applications. These gourmet oils have been used as nutraceuticals, functional food ingredients, and encapsulated products as well as direct edible oils, and for aromatherapy, cosmetics, chemical syntheses, and bio‐energy generation (Aydeniz, Güneşer, & Yılmaz, ; Aydeniz Güneşer & Yılmaz, ; Dündar Emir, Güneşer, & Yılmaz, ). Cold pressed oils are defined as “the oils produced from suitable seed or kernel materials only by mechanical processes without any refining, and readily available for consumption” (Codex, ).…”

“…Hence, removal of bitterness from cold pressed citrus seed oils emerged as a research challenge. Accordingly, we have attempted (Aydeniz Güneser & Yılmaz, ) to remove the bitterness of cold pressed grapefruit seed oils through adsorption principle by utilizing three amberlite resins, natural zeolite, sepiolite, and montmorollonite. Although sensory bitterness was reduced to some extent, it was not enough for consumers to readily accept the treated oils.…”