Supermarket shoppers are urged to follow a 'five-day rule' when buying avocados to ensure maximum freshness. Unlike most fruits like bananas, apples or pears, it can be difficult to tell the just from the way it looks on the outisde, so are advised to apply a strict five day rule to their purchases instead. Experts at Fresh Avocados - Love One Today say if you're for a specific occasion or event, then you should look for one that is green in colour and feels firm to the touch, and always buy it exactly five days in advance.

The experts say it takes around five days on average for firm or green fruit to ripen at room temperature, so buying five days in advance gives the fruit chance to fully ripen and should guarantee it will be ready to eat in time for your event.

The nutrition website explains: "Unripe, firm green avocados can be purchased four to five days ahead of an event. Ripe fresh avocados that yield to gentle pressure should be eaten within a day or two. For events that are four to five days out, purchase firm avocados instead. Unripe, firm or green fruit can take four to five days to ripen at room temperature, perfect for celebrations that are a few days out.

"Just be careful to watch the fruit to make sure the temperature in your kitchen does not cause them to ripen too quickly. If they begin to yield to gentle pressure, place them in the refrigerator to slow the ripening process."

Fresh avocados that are almost ripe will feel less firm, be darker in colour and won't quite yield to gentle pressure. When avocados are at this stage it is advised that you wait one to two days to allow the fruit to fully ripen, otherwise the flesh inside will be hard and difficult to mash.

If avocados are almost black in colour with just a hint of green, and yield to pressure, this is when they are at their ripest and should be eaten right away.

The colour of the fruit can vary depending on the variety you choose. For example, Fuerte, Ettinger, Reed, and Sharwill avocados stay green when ripe so it's best to go by firmness, as well as colour, to determine if the fruit is ready to eat.

If an avocado feels mushy to the touch and has deep indentations, with darker yellow or brown coloured flesh, then it is overripe and best avoided.