Quality assessment of avocado pulp oils during storage

Recently, consumers’ awareness is becoming a crucial aspect driving the food industry to develop new products with high nutritional value. Oil industry explores the use of less known plant materials such as avocado fruit which is a rich source of bioactive compounds. The objective of this study was to assess quality and oxidative stability of avocado pulp oils during a 2-month storage period. Two avocado varieties, Hass and Reed were selected and oil extraction was performed with the use of hexane. The extent of oxidative deterioration and oils stability were tested by measuring the acid value and peroxide value. The PDSC method was applied to evaluate the oxidative induction time. The composition of fatty acids and their distribution in internal (sn-2) and external (sn-1 and sn-3) positions in triacylglycerols were also analysed. The acid value and the peroxide value of fresh extracted avocado oils reached approximately 0,6 mg KOH g^-1 fat and 5 meq O₂ kg^-1 fat, respectively. Generally, during avocado oils storage both the acid values and the peroxide values were in accordance with Codex Alimentarius requirements (the limit of acid value is 4 mg KOH g^-1 fat, while for the peroxide value is 15 meq O₂ kg^-1 fat). The Hass avocado pulp oil was characterized by higher value of the oxidative induction time, about 111 min, compared to the oil extracted from Reed avocado pulp (61 min). The GC analysis revealed that avocado pulp oil could be considered as a source of monounsaturated fatty acids. The dominant fatty acid found in this group was oleic acid with percentage share of above 60%. In accordance with the results of fatty acids distribution in triacylglycerols molecules, the main fatty acids in the sn-2 position were linoleic acid and oleic acid and their percentage share in this item was up to 59% and 34%, respectively. It was also noticed that after a 2-month storage period, the acid value and the peroxide value increased about 7-fold and 2-fold, the oxidative induction time decreased about 2-fold and the percentage shares of fatty acids groups changed. In conclusion, the results obtained in this research indicate that storage period has significant impact on avocado pulp oils quality.