The secret to ripe fruit: You’re better off buying it firm

Patience is all you need to ripen fruit such as peaches at home. And a bit of vigilance

Truly ripe fruit is one of the great joys of summer. Peaches so juicy they dribble down your chin. Melons so fragrant they entice you from across the room. But given the state of most fruit you buy in the market these days, you’d be forgiven for thinking that those are only food writer fantasies.

Not so. Getting ripe peaches and melons is easier than you think. In fact, there’s one simple trick that will vastly improve your summer fruit.

But beware, there’s a bit of science involved.

To start off, it’s important to remember that when it comes to fruit, ripeness and maturity are two separate processes. You can think of maturity as the assembling of the building blocks that will result in deliciousness – sugar, and the other basic components that will make up aroma and flavour. Ripeness is the process that puts them all together.

During ripening, the cell walls of the fruit soften and become more permeable. This allows those simple components to mix and create new, more complex combinations. Rarely does chemistry become so delicious.

In some fruits, maturity and ripening happen at the same time. In others, they don’t. The first group, which includes things such as berries, grapes and citrus, is relatively simple to buy because they’re as good as they’re going to get.

Botanists call the second group “climacteric”. These are the tricky ones. For the most part, climacteric fruits achieve maturity well before they become fully ripe (sadly, as the parent of any teenager will attest, this is the opposite of what happens in humans).

Many, if not most, of our favourite summer fruits are climacteric: peaches, plums, nectarines, many types of melons, and figs, as well as tomatoes.

(At this point your produce pedant lets slip a weary sigh: Never mind where they fit in the menu, botanically, anything that contains a seed is a fruit, and yes, that includes tomatoes, as well as cucumbers, aubergines and courgettes. But of those only tomatoes are climacteric.)

Furthermore, though we say that a fruit is ripe, it’s important to remember that ripeness is not a single fixed point. Rather, it is a process that begins with hard, green and sour and ends in a puddle of fermented mush. The ideal spot is somewhere in between, but exactly where depends upon your taste.

All of this is not just botanical mumbo-jumbo. It has tremendous practical implications. You can buy peaches rock-hard and, provided they were harvested at a reasonable level of maturity, they will still become delicious and juicy. They won’t actually get any sweeter. Sugar only increases on the tree. But they may actually seem sweeter because they taste and smell so good.

In fact, you are probably better off buying them firm. Fruit that is ripe and soft is extremely susceptible to damage, particularly given the kind of rough handling that is common in harvesting and shipping. One of my favourite growers in California picks his peaches as ripe as he can, but places them immediately in foam rubber cups to keep them intact just for the two-hour drive to the farmers' market. Imagine what a tree-ripe peach shipped from Spain might look like by the time it arrives in Ireland.

So how do you work this magic? You really don’t need to do anything special. Patience is all that is required to ripen fruit at home. The only thing that peach really needs is a little bit of time. Leave it on the counter at room temperature for a few days and that’s it.

If you want to speed the process, put it in a paper bag. Ripening fruit gives off ethylene gas, which actually hurries along the process. The paper bag will collect the gas, without collecting the moisture that will lead to spoiling. If you really want to speed it up, add an apple or a banana – these are super ethylene generators.

Just don’t forget to check it every day. A watched pot may never boil, but an unwatched peach will turn to rot before you know it.

There is one thing you never want to do with any climacteric fruit. And it is the first thing that most shoppers do almost reflexively as soon as they get home from the grocery: put them in the refrigerator.

Chilling these fruits before they’re ripened stops the process dead and, in fact, even damages the fruit. Flavourless, mealy tomatoes and peaches were probably refrigerated at some point. In fact, if you go into a grocery and see them sitting in the chiller, walk back out and go someplace that knows how to take care of its fruit. It’s just science.