Storage Stability of Phenolic-Fortified Avocado Oil Encapsulated Using Different Polymer Formulations and Co-extrusion Technology

Abstract

This study compares the stability and phenolic contents of avocado oil fortified with phloridzin (at 300 ppm) and encapsulated with alginate or the combination of alginate and hydroxypropyl methylcellulose (HPMC) (at a ratio of 3:1), over a 90-day storage period at 37°C. The storage stability of unencapsulated avocado oil (control), and encapsulated oils without any added antioxidant, or with butylated hydroxytoluene (BHT) were also examined for comparison. Results of peroxide value, p-anisidine value, Totox value, free fatty acid and extractable phenolic content analyses suggest that the combined use of encapsulation and an antioxidant (BHT or phloridzin) were synergistically beneficial for improving the oxidative stability and suppressing hydrolytic rancidity of avocado oil at 37°C. Alginate alone was a better encapsulant for avocado oil than the combination of alginate and HPMC, which was supported by the results of optical and environmental scanning electron microscopy examinations which showed that alginate beads were bigger and stronger than alginate–HPMC beads. The finding that phloridzin was still significantly retained in the encapsulated oil after the 90-day storage indicated that the final encapsulated oil product possessed additional nutritional values derived from this phenolic antioxidant. Thus, both the encapsulant polymer matrix and the types of added antioxidant are ultimately important when using the antioxidant fortification and oil encapsulation approaches for tackling oil stability issues.