Effect of cooking pre-treatment on the properties of dried avocado flesh and its oil extract

Abstract

Avocado (Persea americana) has been recognized as an excellent source of functional oil, as it is rich in unsaturated fatty acids and other nutrients. This study was conducted to investigate the effect of cooking pre-treatment with water and CaCO3 on the properties of dried avocado flesh and its oil extract, in an effort to develop a more efficient industrial process. The extraction was conducted using hexane as a solvent for 30 min using an extractor unit at 25 °C. The proximate analysis showed that dried avocado flesh is a rich source of fat, containing 45.12±3.73%. Through experimentation, it was observed that both the yield and the properties of avocado flesh and oil extracted were influenced by the pre-treatment method. Cooking pre-treatment with CaCO3 and material size ≤1.19 mm resulted in the highest oil yield (45.53±8.98%). Scanning electron microscopy revealed a clear damaged cell structure in the avocado particles after extraction, indicating that the extraction was successful. However, the functional groups of dried flesh were not changed after extraction, as indicated through Fourier Transform Infra-Red (FTIR) analysis. X-ray diffraction showed that dried flesh is a polymorphous structure with the highest peaks in the 2θ range (19–22 °C). The polymorphous structure was converted to amorphous crystal after extraction. Physicochemical properties of oil extracted were influenced by the pre-treatment method used. FTIR analysis indicated that the pre-treatment method had no significant influence on the oil composition. The properties of oil extracted were generally similar to commercial avocado oil except peroxide value, indicating the potential use of this method in industrial processes.