Estimation of Avocado Oil (_Persea americana_ Mill., Greek \"Zutano\" Variety) Volatile Fraction over Ripening by Classical and Ultrasound Extraction Using HS-SPME-GC-MS  
mesocarp (pulp) of the fruit and has a high nutrition value, biological effects, and healing properties [4,6,7].  
The process of avocado oil extraction is quite similar to olive oil extraction. Generally, the extra virgin oil is extracted from high-quality fruit with minimal levels of rot and physiological disorders, while some rots or physiological disorders are permitted in virgin oil. In each case, extraction is carried out using only mechanical methods at low temperatures (<50 \({}^{\circ}\)C). For pure avocado oil, quality is not important, with low acidity, color, and a bland flavor, and for mixed avocado oil, blends with other oils are allowed. According to [PERSON], [8] avocado oil might be classified as \"extra virgin\", \"virgin\", \"pure\", or \"mixed\". However, no global standardized physicochemical measurements have been implemented for such a categorization. The composition, quality, and yield of avocado oil are dependent on several factors, including fruit variety [9, 10, 11], harvesting time, and ripening stage [10,12,13]. The majority of scientists have focused their endeavors on assessing the \"Hass\" and \"Fuerte\" varieties or others with commercial value, while the \"Zutano\" variety has been studied by few researchers [14], i.e., there is a dearth of data regarding the cultivation of this variety within the Mediterranean. A further feature of the avocado is that if the fruit were to remain on the tree, ripening would not occur. Ripening takes place over a period of time, i.e., between 3-4 and 18-21 days following harvest [8]. The time duration is impacted by storage parameters, amongst additional extrinsic factors. Over-ripening may also occur. Different extraction techniques, conditions, and solvents are factors determining the avocado oil quality and yield [4,5]. An overview of extraction methods used in the last 20 years includes mainly liquid extraction using Soxhlet apparatus [15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27], homogenization [26, 28], and microwave-assisted extraction (MAE) [19, 25, 27]. Several studies have focused on supercritical fluids [15, 16, 19, 20, 21, 22, 29] and mechanical extraction by cold pressure [17, 18, 30, 31]. Lesser-used methods include extraction by enzymes [32] and ultrasound-assisted extraction (UAE) [15, 16, 19, 30].  
Volatile compounds of avocado oil have a well-established role in aroma profiles and are one of the most important characteristics of the quality of the product. The combination of different volatile compounds forms the aroma character of avocado oil [33, 34]. Some studies demonstrate that volatile compounds may differ depending on the variety [35, 36], oil extraction solvents, or treatments [25, 37]. One possible influence on the aromatic profile of avocado oil is the ripening phase, which, to date, has been poorly investigated.  
In the current work, the volatiles from Greek Zutano avocado oil were acquired during three ripening phases, i.e., breaking, ripe, and overripe. Two diverse extraction methods were employed, i.e., Soxhlet extraction (SE) and ultrasound-assisted extraction (UAE). Headspace-solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) techniques were utilized to characterize the respective volatile fractions obtained.