Effect of fruit ripeness and method of fruit drying on the extractability of avocado oil with hexane and supercritical carbon dioxide

Abstract

BACKGROUND: Oil yield from avocado fruit may be influenced by fruit pre-treatment and extraction method. Unripe and ripe avocado fruit pieces were deep-frozen at − 20 °C and either freeze-dried or oven-dried (80 °C). Oil yield from these samples was determined after extraction with hexane and supercritical carbon dioxide (SC-CO₂). The fruit samples were examined using scanning electron microscopy before and after oil extraction.

RESULTS: Average oil yield from ripe fruit (freeze-dried and oven-dried combined) was 72 g kg⁻¹ higher than from unripe fruit for SC-CO₂ extracts and 61 g kg⁻¹ higher for hexane extracts. This may be due to enzymatic degradation of parenchyma cell walls during ripening, thus making the oil more available for extraction. Freeze-dried samples had a mean oil yield 55 g kg⁻¹ greater than oven-dried samples for SC-CO₂ extracts and 31 g kg⁻¹ higher for hexane extracts. However, oil yields from ripe fruit (freeze-dried and oven-dried) subjected to hexane extraction were not significantly different. All hexane extracts combined had a mean oil yield 93 g kg⁻¹ higher than SC-CO₂ extracts.

CONCLUSION: SC-CO₂ may be more selective and may create paths of least resistance through the plant material. Hexane, on the other hand, is less selective and permeates the whole plant material, leading to more complete extraction and higher oil yields under the experimental conditions. Copyright © 2007 Society of Chemical Industry