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Kitchen Notes

Fruit Ripening

by Michael Chu
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One question that I keep getting asked (and that I keep asking myself when standing in the produce section of the market) is whether or not a particular type of fruit will ripen at home. It turns out there are only a handful of fruits which get sweeter after being picked: apples, bananas, kiwifruit, mangoes, and pears. There are a dozen additional fruits that continue to ripen (through aroma or textural changes) and all the rest do not. I put together the following chart listing the fruits which do ripen after being picked as well as those which do not from a variety of sources including but not limited to On Food and Cooking, Cookwise, Modernist Cuisine, and The Science of Good Food.

Like most things we try to classify one way or the other, there tend to be some exceptions or outliers. Apples, for example, ripen after being picked and increase in not just sweetness but also get softer over time. Most people prefer apples underripe (since the varieties generally eaten uncooked tend to be fairly sweet right off the tree) and do not prefer them at full ripeness due to how soft (and mealy) the flesh becomes. (Because apples do ripen after harvesting and we don't often allow them to reach full ripeness, if you've got an apple in your house, it's probably in the process of ripening and therefore outgassing carbon dioxide and ethylene. The latter gas - for reasons not yet fully understood - will trigger and speed up ripening processes in other fruits which can be ripened after picking - see chart below). Another example is the pineapple (a fruit that doesn't ripen after harvest) which does change color after being picked but does not get sweeter or develop a stronger aroma. For this reason, they should be selected not by how golden the skin is but by how fragrant it is.

Since fruits which ripen release ethylene gas, they should not be stored with or near vegetables. The ethylene will cause most vegetables to spoil faster. (Many vegetables can be heat treated - by blanching in boiling water for a minute or two - which deactivates the enzymes which cause wilting and spoilage. It is possible that heat treating could prevent spoilage from ethylene exposure, but I have not found any documentation of this and have not performed the experiment yet.)

Conventional wisdom states that fruits which are ripened on the plant will be superior to those picked early (and possibly ripened later if it is one of those lucky fruits that can continue to ripen). There is much truth in this, but again there are some interesting exceptions. The first is the avocado which does not ripen on the tree at all. This is one fruit which has to be picked (or fall off the tree) to begin ripening. I was surprised to learn during my research that Modernist Cuisine claims pears also do not ripen on the tree. This is not technically true as pears do ripen on the tree but many varieties do not taste good when tree-ripened with particular complaints regarding off-flavors. Pears are one of the few fruits which are best ripened off the tree. Bananas are another interesting case as it is the ultimate example of ripening after harvest - bananas improve in every aspect (sweetness, color, aroma, and texture) dramatically when ripened at home and, by all accounts, is as good as when plant-ripened.

Fruits that ripen after being picked can have their ripening processes accelerated easily in two ways: heat and ethylene. Keeping fruits in a warm environment will ripen the fruit by accelerating the activity of the ripening enzymes. This process speeds up until the temperature rises past that at which the enzymes remain intact (which is lower for fruits from colder weather regions and higher in tropical fruits). This can also increase the rate of spoilage as surface bacteria and microorganisms will generally thrive in warm temperatures up to the deactivation temperature of the enzymes. Washing the fruit with a fruit wash is advisable before attempting to heat ripen it.

Ethylene gas ripening is probably easier since all it takes is an ethylene producer (the fruit itself will work, but an apple is even better). Simply place the fruits in a paper bag with the top folded over. This creates an environment which allows some airflow but will increase the concentration of ethylene gas around the fruit. When fruits which will ripen after harvest are exposed to a high ethylene concentration, ripening is promoted.

In this chart, I have listed fruits in alphabetic order after separating them into two sections. The first section contains those which ripen after harvesting (and can be assumed to produce ethylene gas until fully ripe). The second section lists fruits known to not ripen after being picked (a few of these fruits may change colors but they do not actually ripen). For the fruits that continue to ripen, I have marked which characteristics increase while ripening - sweetness, scent, and/or softness.

FruitSweetnessScentSoftness
Fruits Which Ripen After Harvest
ApplesXXX
ApricotsXX
AvocadosXX
BananasXXX
BlueberriesXX
CantaloupesXX
CherimoyasXX
FigsXX
GuavasXX
HoneydewsXX
KiwifruitXXX
NectarinesXX
MangoesXXX
PapayasXX
Passion FruitsXX
PeachesXX
PearsXXX
PersimmonsXX
PlumsXX
RaspberriesXX
TomatoesXX
Fruits Which Do Not Ripen After Harvest
Black Currants
Blackberries
Cacao
Cherries
Cranberries
Dates
Gooseberries
Grapes
Grapefruits
Lemons
Limes
Lychees
Olives
Oranges
Pineapples
Pomegranates
Red Currants
Stawberries
Watermelons

I did find some conflicting information on cherimoyas with some sources claiming they get sweeter and others claiming they do not. I decided to list it as a fruit which does not get sweeter after being picked because that's how it is listed in On Food and Cooking.


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Written by Michael Chu
Published on October 01, 2012 at 04:25 AM
13 comments on Fruit Ripening:(Post a comment)

On October 01, 2012 at 11:45 AM, Kevin (guest) said...
Subject: Pineapple ripening
Although a pineapple doesn't ripen before it's cut, I've found that it ripens after it's cut. If I cut a good pineapple into quarters, wrap the quarters in saran wrap, and then put it in the fridge, it is much sweeter the next day. It tastes just like fresh pineapple I had in Costa Rica if I do that. It stays tasty for over a week when stored that way.


On October 01, 2012 at 07:29 PM, Michael Chu said...
Subject: Re: Pineapple ripening
Kevin wrote:
Although a pineapple doesn't ripen before it's cut, I've found that it ripens after it's cut. If I cut a good pineapple into quarters, wrap the quarters in saran wrap, and then put it in the fridge, it is much sweeter the next day. It tastes just like fresh pineapple I had in Costa Rica if I do that. It stays tasty for over a week when stored that way.

Do you leave the rind on when cutting in quarters or are the quarters completely trimmed? I'll have to experiment with this next time I pick up a pineapple.


On October 01, 2012 at 10:01 PM, Jim Cooley said...
I'm a pineapple fanatic and I remove the rind. I keep the wedges fresh for days in the fridge in a tupperware container.

A couple years a go I wrote up my method for slicing a pineapple at http://crazygora.blogspot.com/2009/12/off-dole.html


On October 02, 2012 at 08:17 AM, an anonymous reader said...
Subject: figs
I just have to point out that you've got figs in both lists.


On October 02, 2012 at 07:49 PM, Michael Chu said...
Jim Cooley wrote:
I'm a pineapple fanatic and I remove the rind. I keep the wedges fresh for days in the fridge in a tupperware container.

Jim, I cut my pineapples in a very similar method (with an added step of carving out all the eyes after removing the rind which forms kind of a spiral pattern of grooves). I also store mine in airtight containers in the fridge and find it stores well in that condition. What I've never experienced is the increased ripeness after being cut that Kevin mentioned. I thought it might be because I was leaving only the flesh of the fruit and perhaps if it was attached to either the rind or the core it would act differently over time. You probably eat more pineapples than I do, what has been your experience?

Quote:
I just have to point out that you've got figs in both lists.

Thanks, I've removed the listing for figs under "does not ripen" because it was in error. They do not get sweeter, but do continue to ripen.


On October 02, 2012 at 09:15 PM, Jim Cooley said...
Michael Chu wrote:
What I've never experienced is the increased ripeness after being cut that Kevin mentioned. I thought it might be because I was leaving only the flesh of the fruit and perhaps if it was attached to either the rind or the core it would act differently over time. You probably eat more pineapples than I do, what has been your experience?


No experience, but it doesn't make sense to me that a pineapple would get sweeter if you left the rind on cut pieces AND refrigerated them. Maybe Kevin's right??? I'm not going to experiment.


On October 03, 2012 at 06:31 AM, Michael Chu said...
Jim Cooley wrote:
No experience, but it doesn't make sense to me that a pineapple would get sweeter if you left the rind on cut pieces AND refrigerated them. Maybe Kevin's right??? I'm not going to experiment.

If I remember, the next time I buy a pineapple, I'll quarter it (lenthwise), cut a slice from the center of each quarter (so I'll have a sample from each quarter in the middle. Trim the sample so it is without core and without rind then store it in the fridge next to the quarter (in two pieces) it belonged to. Then the next day I can taste it to see if there is a difference between fully trimmed and kept in wedge form. Log results. Repeat for three days.


On October 03, 2012 at 05:16 PM, Barron (guest) said...
Subject: Ripening
I'm a fruit grower (and an engineer), and this is a pretty nice description. The average customer does get confused about this kind of thing.

Two additional columnns would make it really helpful: "Usually eaten..." and "...so you should" to help people understand how it really ought to be stored. For example, peaches and nectarines are usually eaten "soft around the stem", so you should "remove from refrigerator 2 days before eating." Apples are usually eaten "crispy" so you should "keep refrigerated." Blueberries ripen quickly, and are usually eaten "tender but firm" so you should "refrigerate." Pears are usually eaten "slightly soft" so they should be "ripen in paper bag with an apple."

Good job!


On October 04, 2012 at 11:36 AM, Kevin (guest) said...
Subject: Pineapple ripening
I leave the rind on the pineapple. I cut it in quarters and wrap each quarter tightly with plastic wrap and put it in the fridge. It gets sweeter by the next day. I found this accidentally. After visiting Costa Rica, I was finally brave enough to buy an entire fresh pineapple. In Costa Rica,the pineapple was exceptionally sweet and always served to me in cut pieces sitting on the rind. At home, I ate 1/4 of the pineapple right away, and it wasn't nearly as sweet as the ones in CR. I wrapped up the other 3/4 and put them in the fridge. The next day, it tasted just like the ones in CR. I experimented and found that this effect happened consistently.


On October 04, 2012 at 11:43 AM, Kevin (guest) said...
Subject: Pineapple
Note that I also start with a ripe pineapple. I choose one that is heavy for it's size, has a sweet scent, and is mostly yellow. I'm not sure if this would work with an unripe pineapple. With a ripe one, the pineapple does get significantly sweeter.


On October 11, 2012 at 11:09 PM, an anonymous reader said...
Dates do absolutely ripen after harvest. Several years ago, we planted a date palm mostly for aesthetic reasons as part of our landscaping here in Southern California. This is the first year our crop of dates was big enough to go to the trouble of wrapping the fronds in large brown paper cones as they do at commercial date farms—to protect the fruit from birds and rodents. One of the six or seven fronds did ripen on the tree and those dates were relatively dry and small, like you'd buy at the store. At that time, we cut all the fronds. Some of the dates had begun to ripen and were a bit wrinkled, but many were plump and hard and a golden yellow, rather than the dark brown they would eventually turn. We had hundreds of dates, and over the next few weeks, almost all ripened. We used the brown paper bag method, and they were exceptional, delicious: much sweeter and much less dry than commercial dates. They were sticky and gummy and even people who swore they hated dates became addicted to these.


On October 12, 2012 at 07:39 AM, zoyee said...
Subject: reply
Aceymac apple
Resembles McIntosh in taste, appearance, shape, and flesh. Slightly firmer than McIntosh. Aceymac may be Spartan with new name

Adams's Pearmain apple
Classic Victorian 'pearmain' shape apple with a nutty sweet flavour.


Adanac apple
Medium-sized, yellow-green underecolor with striped red wash. Good dessert quality. The apple name, Adanac, is Canada spelled backwards.


Aerlies Red Flesh apple
A red-fleshed apple variety from the USA, sometimes known as Hidden Rose or Airlie Red Flesh.


On October 17, 2012 at 04:31 AM, JVD (guest) said...
Lemon and lime juice also gets sweeter if left for a few days after being squeezed; I prefer the bottled stuff to freshly squeezed.

Though have you ever had a fully ripe apricot straight from the tree? There is no comparison between that and a home ripened fruit. There are gorgeous scent/flavour compounds that are simply missing, in as little as a day after the fruit has been picked. They are heavenly from the tree.

I often think people who say they don't like a particular fruit have just never had a properly ripe specimen, and now I can see why! Though technically a fruit is defined by their ability to ripen off the tree, if there's no increase in sugar, has it really 'ripened'?

I guess it's personal preference as to whether the non-sweet ripened fruit are worth eating from the supermarket - I'd say no for most of them but then I'm a sweet tooth and dislike anything remotely sour. I'm suddenly thankful mangoes are so delicious by the time they've travelled the thousand or so miles between where they're grown and my mouth.

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