Moseying around these, our intertubes, I’ve found much advice about how to ripen an avocado: in a brown paper bag.
In a bag? This I get.
In a brown paper bag? Why would this matter? Does it?
Storing them in a paper bag allows some of the ?ethylene? gas to escape and allows regular air in. They’ll ripen faster because of the increased concentration of ethylene.
Storing them in a plastic bag doesn’t allow the gas exchange and they tend to rot rather than ripen.
I just learned about this the other day (Alton Brown, maybe?), but it’s true in my experience. I just didn’t know why.
Also a plastic bag keeps moisture in, which makes many things very nasty.
So some of the gas escapes, and that causes an *increased *concentration of the gas? :dubious:
Look, the fact is that most plastic bags are polyethylene. Poly-ethylene. It’s inherently unstable. The stuff breaks down naturally. All the time. Constantly releasing ethylene.
Ethylene is a plant hormone. It plays a major role in ripening of most fruits. If the concentration gets too high the fruit ripens in odd ways. In avocados that means that the layers of flesh next to the skin ripen well before the inner layer, and then starts to decompose. So you end up with a fruit that is mushy and brown on the outside and hard as a rock on the inside. Not very appetising.
By using a paper bag you are not exposing the fruit to ethylene from the plastic bag. Fruit naturally produces ethylene too, and the paper also allows this to escape, preventing a buildup.
Why brown paper bags? Because most white paper bags are treated to make them smoother and, incidentally, more gas tight. That’s why mots white paper bags are shiny. That treatment ranges from applying a layer of starch to actual plastic coating. Of the bags that commonly available, only the brown paper type have the coarse surface fibres that are needed for free gas exchange. So rather than confusing people with the technical details of which bags to use, the advice is simply to use brown paper bags.
But the paper bag allows some buildup of ethylene, so they ripen faster than if they were sitting in a bowl on the counter.
If you have more than one avocado, they share their gas with each other and it helps them to ripen. If you just have one, you can put an apple or a banana in with it to help it along.
Do you have a cite that polyethylene is inherently unstable, breaks down naturally without the presence of heat or UV light or that an otherwise empty polyethylene bag will fill with ethylene gas?
Polyethylene breaks down very slowly. The problem with a polyethylene bag is indeed that it is airtight. Increasing the local concentration of fruit produced ethylene is one thing, and indeed causes artificial ripening, but enough CO2 has to get in and O2 out. A microperforated polyethylene bag works great. Both that and brown paper bags keep enough ethylene in to ripen while being permeable enough to keep the CO2/O2 balance at acceptable levels.
Sometimes I just roll up the fruit in a page of the newspaper. Works for me, but I don’t know if the paper bag is better or not.
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Why CO2/O2 ?
I think the water issue is at play here too. You don’t want condensation on your fruit.
Fruit respire while ripening.
Sunlight is the best ripener for avocados. In the winter time I might leave them on the window sill all day. In the summer just take them out for an hour or two, turn and another hour or two.