Ripened to perfection
Ripening is a way for fruits to beckon birds and other animals to eat them and spread their seeds. Just think of a green strawberry: in a matter of days it loses its hard, acidic character and becomes a red, juicy, fragrant delight. In a word, it becomes irresistible.
The final stage in achieving perfect ripeness is the culmination of a highly complex process. Just before ripening, some fruits give off a gas called ethylene. The gas sets in motion a series of chemical reactions that transform the unripe fruit into a succulent thing of beauty.
Some of the reactions cause the flesh to soften, while others enhance flavour by producing sugar (mainly glucose and fructose), reducing acidity, taming astringency and synthesizing aromatic compounds. The result is a sweet, fragrant package. Other reactions also take place, such as the destruction of chlorophyll (which makes plants green) and the synthesis of other pigments that produce the red, orange and blue hues of the ripe fruit.
To ripen or not to ripen:two kinds of fruit
Some fruits keep ripening after harvest. But for others, picking brings the process to a halt. The list on page 2 will help you know which is which and act accordingly.
Fruits that stop ripening at harvest
Blueberries, strawberries, watermelons and pineapples all stop ripening once picked. So when buying these fruits, it’s important to choose specimens that are fully ripe and have the desired colour and sweetness level—sample them if you can. Because they are purchased at their peak, it’s best to store these fruits in the refrigerator and eat them fairly soon. You can, however, keep citrus fruits in the refrigerator for a few weeks. When it comes to pineapples and watermelons, choose fruits that are heavy for their size and give off a pleasant aroma. The old advice to tug on a pineapple leaf to test for ripeness is actually useless.
If you make the mistake of buying one of these fruits under ripe, don’t get your hopes up: a few days on a sunny window sill or on the kitchen counter won’t in any way improve its flavour.
Fruits that ripen after harvest
Peaches, nectarines, bananas, mangoes and avocados all ripen after harvest thanks to the ethylene they emit. If not quite ripe at the time of purchase, all except apples should be stored at room temperature until ready to eat. Depending on the fruit, this might take a few days.
Be careful not to refrigerate fruit before it’s fully ripened, as cold storage may cause irreparable damage. Have you ever bitten into peaches that look beautiful but turn out to have mealy flesh? Or cut a perfect-looking pear only to find soft brown flesh around the core? These defects are signs of chilling injury, which occurs in fruits that have spent too much time in cold storage before ripening. Cold storage may also prevent these types of fruit from ripening when they are finally brought to room temperature. The consumer is often not to blame for chilling injury, since the damage may have been done before the fruit even reached the market.
Giving nature a boost
If you want to accelerate the ripening process, the trick is to increase the concentration of ethylene around the fruit; light doesn’t promote ripening. Place unripe fruit in a paper bag (don’t use plastic bags, as they trap too much moisture) along with an apple, since all apples except Fujis and Granny Smiths give off a great deal of ethylene gas. Close the bag loosely. Store at room temperature and check the fruit daily. It’s ripe when slightly soft to the touch and noticeably more aromatic than before. Ripe fruit must be used as soon as possible or stored in the refrigerator (except bananas, which are best kept at room temperature if you want the peel to stay yellow).
Did you know?
The ethylene given off by fruits has detrimental effects on vegetables. It can cause bell peppers and beans to shrivel; make broccoli, lettuce and cucumbers turn yellow; and give carrots a bitter taste. That’s why refrigerators have separate crispers for fruits and vegetables.
Continue ripening after harvest
- Apricot
- Avocado
- Banana
- Kiwi
- Apple (1)
- Nectarine
- Papaya
- Peach
- Pear
- Melons (cantaloupe, honeydew) (2)
- PLum
(1) Apples ripen too fast at room temperature. It's better to always keep them in the fridge.
(2) This fruit will become softer and juicier but will not get any sweeter.
Didn't ripening after harvest
- Ananas
- Blueberry
- Cherry
- Strawberry
- Raspberry
- Melons
- Orange
- Grapefruit
- Raisin
