How To Find A Perfectly Ripe Avocado, According To Science

“Keep it in a bag, poke toothpick-sized holes in said bag, and throw in an apple. Leave it at room temperature for one to three days.”

“Wrap it in tin foil and bake it in the oven at 200 degrees Fahrenheit for 10 minutes. Alternatively, you can just use a hair-dryer and blow-dry it.”

“Cut it in half and microwave it for 120 seconds and then immediately douse them with cold water.” 

“Put it in the airing cupboard in a brown paper bag.” 

“Watch it like a hawk until it ripens. Don’t go out, don’t sleep. Don’t even pee.”

These are all tips my friends have shared with me for ripening avocados, the trickiest of all vegetables to properly ripen (though they’re actually a fruit, and more specifically a berry).

Ripening an avocado takes time, love and patience. You buy it when it’s rock hard, thinking it’ll certainly be ready to eat within a day or two. Six days later, your avocado stubbornly remains solid. Two days later, you check again, fingers fumbling over its rough green coat, prodding in anticipation. But still nothing. You sit back stumped. The avocado, at first laden with promise, has become a taunt. It gazes at you mockingly from its perch in the fruit bowl. Defeated, you toss it in the bin, the guilt of spending $3 on a single avocado coupled with the dark, deep shame of wasting food. 

But fear not! There is a way to make Martha Stewart proud and tuck into your avocado toast like there’s no tomorrow (after all, it is breakfast month).

The Science: How Avocados Ripen

Kantha Shelke, a food and nutrition scientist and member of the Institute of Food Technologists, explained the science behind the mysterious ripening process of avocados.

“The fruit does not ripen while attached to the tree, even when physiologically mature, because of an inhibitor in the fruit stem,” she told HuffPost. “It appears to be nature’s way of protecting the fruit from damage from high temperatures. Even exposing the fruits on the tree to ethylene gas will not ripen it.” (Ethylene is the hormone released by avocados ― and other fruit and vegetables ― as they ripen.)

However, once picked, it’s a different story. Avocados must only be picked when mature so they have adequate oil content and dry matter. As they mature, their dry matter ― which is made up mostly of carbohydrates ― and oil content increase. This contributes to the creamy, soft texture we associate with avocados. Normal softening occurs only with a certain level of maturity in the fruit, which only develops after they have been picked from the tree. Fun fact: Softening begins at the round end of the fruit and then continues up to the stem end.

Avocados picked before they are ready will never produce the oil content needed to make the fruits taste smooth when they’re soft. Instead, they’ll remain rubbery and will taste bland and watery.

There’s even a law to prevent your avocado from being too hard.

“According to California law,” Shelke said, “avocados with less than 8 percent fat should never be picked for sale, because they will never soften.”

You can shake an avocado to check if its seed rattles. If it does, that’s a sign that the avocado is will ripen quickly (which is a good thing).

As for some of the old housewives’ tips for ripening avocados, there is a method behind the madness.

“Placing the avocado in a paper bag will trap the ethylene gas given off by the avocado, which in turn ripens it,” explained Shelke. “Placing the avocado in a rice or flour bin will also do the trick, and adding a banana, apple or tomato in will increase the level of ethylene.”

Producers Are Using Technology And Planning To Help Us Out

The art of ripening avocados is such a delicate issue that companies are turning to technology to master the process. It’s Fresh! is a U.K.-based company that has developed a filter to absorb ethylene and prevent avocados from getting too ripe too quickly.

“There are many dark arts associated with ripening avocados,” said Simon Lee, founder of It’s Fresh! “There’s no real secret formula.” 

Lee’s technology comes in the form of a sheet that can be slotted into packaging and attracts and absorbs ethylene. However, the technology is not currently available for consumer purchase.

A spokesperson from the California Avocado Commission said growers determine how ripe the fruit needs to be based on the order from the retailer. In turn, retailers decide at what stage they sell avocados based on demand from customers.

What To Look For At The Store

The CAC suggested that shoppers should look for a classic pear shape and avoid avocados with loose skin or where the stem end is showing decay. If there are pockets or portions of the fruit that seem softer than the rest of the avocado, choose a different one. The pockets are likely bruises related to transportation or other avocado shoppers who have squeezed the fruit with their fingers (this avocado attack actually has a name: “digitizing.”)

Blemishes on the skin should generally be ignored, as they’re grown in bundles surrounded by leaves, branches and tree limbs, and so can naturally have scuffs here and there.

You can also check the label to see where your avocado was grown, because that can indicate how quickly your fruit will ripen.

Avocados grown in different areas of the world will ripen at varying paces. They are native to Guatemala, and varieties grown there and Mexico ― tropical highland environments ― tend to grow and mature slowly, but in the process, develop more dry matter and oil content. This means that they will ripen more quickly when they are detached from the tree.

Fruit exposed to high temperatures on the tree, in climates such as Israel and Arizona, produce significantly more dry matter and oil content, and therefore, ripen even more quickly.

Perfectly ripening your avocado starts before you’ve even taken it home. The secret is in the selection. The CAC defines avocado ripeness in five stages, as outlined in the graphic above.

If you want an avocado to eat two to three days from now, then select one in the third “breaking” stage so it’s ready to eat in time. If you are looking for one to eat that day, select a stage five. 

Tricks That Actually Work

As mentioned above, putting an avocado in a paper bag, rice bin or other sealed container can help speed up the ripening process at home. Add fruit, but for best results use either Red Delicious or Golden Delicious apples, as the older varieties (as opposed to Gala or Fuji) produce more ethylene, according to the CAC.

Despite rumors that heating an avocado will help ripen it, you shouldn’t actually put the avocado in a microwave or other warm area. “It won’t work,” confirmed Francesco Brachetti, co-founder at Avocaderia, a New York-based avocado restaurant that claims to be the world’s first avocado bar. “You could put it in an oven, turned off though, as the contained space would help contain the ethylene. But adding heat doesn’t help.”

If you have an over-ripe avocado, pop it in the fridge, as cool temperatures slow down ripening but room temperatures encourage it.