Diversity of yeast community composition in olive oil from two different areas in Tuscany

Olive oil, a basic component of the Mediterranean diet, is considered an important functional food, due to its content in polyphenols contributing to the protection of blood lipids from oxidative stress. In particular, extra virgin olive oil (EVOO) phenols, such as tyrosol and hydroxytyrosol and their derivatives oleocanthal and oleacein, respectively, show antioxidant, anti-inflammatory, antiproliferative and neuroprotective activities (EFSA Journal 2011; 9(4): 2044). Such beneficial phenolic compounds show variable levels in diverse EVOOs, depending on olive cultivars, fruit ripening state at harvest, soil characteristics, agronomic management, oil processing and storage conditions. Recent works showed that, during olive processing, oil-borne yeasts originating from olive plants (leaves and branchlets) may migrate into olive oil, which represents a special environmental niche. Although in the past the presence of microorganisms in olive oil had been considered irrelevant, several authors demonstrated that they play a role in oil transformation, being able to improve or even worsen its organoleptic characteristics and quality. The quoted researches assessed the identity of olive oil microbiota by culture-dependent methods and described a number of yeast species. In this work we utilized a culture-independent method, PCR denaturating gradient gel electrophoresis (PCR-DGGE), to investigate the occurrence, diversity and community composition of yeasts in olive oil produced in two different areas in Tuscany. The content of tyrosol, hydroxytyrosol, oleocanthal and oleacein was also assessed.