Effect of refining process on some quality attributes of screw-pressed avocado oil

Abstract

Avocado (Persea americana) is a source of vegetable oil abundant in unsaturated fatty acids, vitamins, and diverse nutrients, rendering it a valuable source of functional oil. Refining is a necessary step to achieve avocado oil with high-quality attributes. This research delved into the impact of the refining procedure on some quality attributes of avocado oil obtained through screw pressing. The study encompassed four distinct samples, each corresponding to a specific stage in the refining process, i.e. degumming, neutralization, bleaching, and the crude oil as the control. Findings from the experiments revealed that the yield of avocado oils subjected to cooking pre-treatment (49.19±0.65 %) exceeded those without pre-treatment (45.10±1.71 %). Compared to crude oil, the quality of bleached oil was improved by reducing free fatty acid (52.94 %) and peroxide value (59.38 %). There were noticeable increases in free fatty acid and peroxide value during storage. The physicochemical properties of the extracted oil were affected by the stages of refinement and the duration of storage. FTIR analysis showed that the bleaching stage played a role in removing peroxides, hydroperoxides, and residual moisture. There were no significant changes in fatty acid composition during refinement. Oleic acid (52.0–53.1 %) constituted the largest proportion, trailed by palmitic acid (24.0–24.4 %), linoleic acid (17.2–17.8 %), and palmitoleic acid (4.9–5.6 %). However, unsaturated fatty acids content in avocado oil decreased significantly during storage.