In official tastings, panels look not only for good aromas but also for defects. The most common are “fusty” (olives stored too long before pressing, which start to ferment), “musty” (mouldy olives), “winey” (vinegary notes) and “rancid” (old, oxidised oil).
A single noticeable defect is enough for an oil to lose its extra virgin status. That is why one thing matters above all: healthy olives that are pressed quickly after harvest.
