Over many years, if I’ve wanted avocados to ripen fast I’ve tried the method of putting them in a paper bag or box with a banana or apple, but I never saw them clearly ripen faster. I became curious to test the method properly.
The experiment
On June 25, I split a harvest of GEM avocados into three groups. There were fifteen avocados used in the experiment, five in each group. The five that I chose for each group were as similar as could be achieved. They each weighed approximately 10 oz. and had green skin with a slight black blush. That is, they were at the same stage of maturity, as far as I could tell, which is important because maturity level influences the rate of ripening. (More mature avocados ripen faster.)
One group of five avocados I placed in an open basket. A second group I placed inside a cardboard box, and then closed the top. And a third group I placed inside a cardboard box with both a banana and an apple and then closed the top. All three of these groups of avocados were set next to one another on a table in my house.
The temperature was 73 degrees on that first day and it didn’t change much until rising a few degrees toward the end of the experiment. Avocados ripen well at these temperatures. (Between about 65 and 75 degrees is optimum for ripening avocados and not inducing rot inside.)
The avocados in the open basket remained open to the air throughout. The two groups of avocados in cardboard boxes had their tops closed throughout.
The claim is that bananas and apples naturally emit ethylene gas and this ethylene hastens the ripening of the adjacent avocados. By keeping the box top closed, I thought I would be enhancing the concentration of ethylene and exaggerating its purported effect.
I chose to also keep the top closed of the cardboard box with only avocados so as to only have the one variable, the inclusion of a banana and apple.
The results
On the morning of July 7, I detected the first ripe avocados. (I had been peaking on them each day.) I found that one avocado in the box with a banana and apple was ripe. And one avocado in the open basket was also ripe. No avocados alone in the box were quite ripe.
I determined ripeness first by feel, and then I used the toothpick method to confirm. (The toothpick method is where you attempt to insert a toothpick into the flesh through the stem hole. If it sinks in easily, then the avocado is ripe.)
On the following morning, July 8, I found two more avocados ripe in the banana and apple box. Additionally, all four of the remaining avocados in the open basket were ripe. And four of the five avocados alone in a box were ripe.
That left the following unripe avocados: two in the banana and apple box, and one in the box alone.
On the evening of July 8, I tested the remaining three avocados again and found that they had all reached ripeness.
Conclusion
Putting avocados with a banana and apple in a cardboard box did not ripen them faster in this experiment.
Generally speaking, they all ripened at the same speed.
Notes
It’s important to keep in mind a few things about the avocados that I used in this experiment.
I harvested these avocados myself, and from a couple of adjacent trees in a single location.
In contrast, avocados found on a single shelf in a store are sometimes not even from the same country let alone the same farm or tree. And so they might have been grown in different climatic conditions, have different maturity levels, have been off the tree for far different lengths of time, haven been grown under different fertilization regimens, and so on. All of these factors and more affect the rate of fruit ripening.
My direct selection of the avocados was an attempt to reduce or eliminate variables such as these.
I would consider the results from the same experiment using avocados pulled off a grocery store shelf as dubious.
Let me know if you have ideas for how I could have improved my experiment’s design though.
Explanation
Why didn’t the banana and apple “work?” It might be that they simply didn’t emit enough ethylene.
In the 1960’s, Irving Eaks performed some of the seminal experiments with ethylene on avocado ripening at U.C. Riverside, and one thing he found was that small amounts or short exposure to ethylene had no effect on the ripening rate. (See “The effect of ethylene upon ripening and respiratory rate on avocado fruit” by Eaks in the 1966 Yearbook of the California Avocado Society.) So maybe a whole bunch of bananas put together with some avocados would yield different results.
From here?
If just one banana and one apple don’t speed up the ripening of a handful of avocados, what does?
Warmer temperatures.
Up to a point (around the upper 70’s), the warmer the temperature, the faster avocados ripen (and maintain quality).
(See this experiment from Erickson and Yamashita in the 1964 Yearbook of the California Avocado Society: “Effect of temperature on the ripening of Hass avocados.”)
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