The Effect of Vacuum Storage on the Preservation of Extra Virgin Olive Oil After Opening

Introduction: When a bottle of Extra Virgin Olive Oil (EVOO) is opened and used by consumers, its degradation accelerates, leading to a gradual loss of its bioactivity and sensory attributes. This study aimed to assess if vacuum storage can be regarded as an effective method to increase the shelf life of EVOO after opening, simulating domestic use. It also examined how different closing systems affect the quality and sensory attributes of EVOO in these conditions. Methods: Two chemically distinct samples of commercial EVOO were obtained, one from the northern region (N) of Portugal and the other from the southern region (S). One set of bottles were sealed using a conventional closure system employing plastic stoppers (C) and the other set of samples were sealed using a manual vacuum system (V). To simulate domestic usage, approximately 20 mL of oil was collected every 2 days from each bottle over 84 days, with analyses conducted every 8 days. Parameters assessed included acidity, oxidation indicators such as peroxide value and UV absorption, fatty acid composition, hydrolysable phenols, and vitamin E. Results: The acidity and fatty acid composition remained stable over time for both samples. Although oxidation occurred in all samples, as expected (measured via the peroxide value and UV absorbance), vacuum storage delayed oxidation rate, ranging from -7% (N) to -18% (S) for the peroxide value and from -3% (N) to -20% (S) for UV absorbance. Concurrently, there was a decrease in the antioxidant pool irrespective of the closure system used, particularly in vitamin E. However, the vacuum-stored samples showed a higher preservation of vitamin E, with a reduction of only 3% (S) to 6% (N). Conclusion: These findings suggest that, under the tested conditions, the benefits of using vacuum storage are apparently diminished.