How does crushed fruit vinegar stay good for so long if you use fresh crushed fruit?

The vinegar base is a natural preservative. When fresh fruit is combined with vinegar, the acidity prevents bacterial and mould growth -- no artificial preservatives needed. Kosterina Crushed Fruit Vinegars contain no preservatives, additives, or added sugars: just white cooked grape must (from Italy), white wine vinegar (from Greece), and real crushed fruit.