Alas, there may be a problem with my favourite brand of pitted prunes (= Organic House - containing no preservatives etc.). Within days of opening the sealed plastic bag they come in, the prunes become covered (to various degrees) with a fine white powder.
Being the germophobe that I am, my first thought was that the white stuff was some sort of fungus (that’s why I mentioned the “no preservatives” above; personally I don’t care one way or the other). Initially, I would simply remove the powder-covered part of any affected prunes, and then munch away. Lately, though, the powder is developing more quickly than it used to (within a day or two after opening the bag) and, more inconveniently, it’s affecting more prunes, and more surface of any prunes so affected (which means the large majority of them a week or so after the bag has been opened).
Any ideas just what the white powder is? Fungus? Crystallized sugars? Whatever it is, it NEVER used to happen at all (and I have not changed brands). It never even developed a month or more after the packet was opened (and it still doesn’t ever develop in an unopened bag - I deliberately left one unopened for six weeks and never saw any powder form). So, something is different, but I don’t know what. Again, any thoughts?
Thanks!
ETA: Having now composed this post, it’s just occurred to me to write the company and see what they say. Maybe I will give that a try, but regardless, I am still very interested to hear what you ‘guys’ say.
This is just a wild-assed guess, but does it look like the white powder could be something like corn starch? Corn starch is used in many foods (like marshmallows) to prevent sticking, perhaps the company started adding it to their prunes for the same reason?
My theory is when you first open the bag, the prunes are moist enough that the starch is “wet” and not really visible. After a few days, the surface of the prunes dry out enough for the corn starch to become visible.
That’s a neat thought! But, I just checked - according to the label on the package, it contains nothing other than “certified organic pitted prunes”. Nothing else.
ETA: As far as I can tell, neither the original company nor the distributor has an online presence (very organic, eh?)
This is my first post on the forum, but I read this thread and had to reply.
The white substance on prunes is, as speculated by other users, crystalline sugar. If you look on the back of the bag - under “Nutrition Facts” - you’ll find that prunes are sugar (like most fruit, so no big surprise here). The sugar is fructose (almost 13% of the weight of the prune, to be exact). Unlike a banana or orange which have protective skins, prunes are exposed to the air. Fructose dries out and becomes a noticeable solid not suspended in the fiber and tissue of the prune itself, but rather on the outside in a white powdery form. Generally, the older the prune, the more crystalline sugar.
From Wikipedia: “Pure, dry fructose is a very sweet, white, odorless, crystalline solid and is the most water-soluble of all the sugars.”
As you can see, your organic prunes are, still, organic and just prunes.
I consume non-organic prunes, um, regularly - and I’ve never seen any white powdery substance on them, even after the box has been opened for a long period of time and the prunes have started to dry out.
I don’t know what the OP is concerned about though - even if the powdery-looking stuff is fungus, it’s still organic.
Look at the prunes with a magnifying glass (as Mangetout mentioned). Mold/fugus type organisms appear filamentous. Or just wipe some onto your fingertip and taste the sweet goodness.
Do you eat bread? Ever had bread develop mold? Do you realize that before there is obvious blue/green fuzz there is mold there too small to be seen by the naked eye?:eek:
Even if it is, powdery white mold is generally okay. When I hang sausages to ferment and dry after curing, white mold will often form on them (which is a good thing.) Fuzzy blue, green, and black mold is a bit more iffy.
WAG: If it’s not crystallized sugar (most likely) it could be something like potassium bitartrate, also known as Cream of Tartar, which can crystallize inside of wine bottles kept at low temperatures. Low temperatures would also contribute to the formation of sugar crystals (I think).
My vote is with yeast. (assuming we are talking a very fine powder) Its visibly present on grapes, apples, blueberries. It is probably on the surface of most fruit.
I would imagine prunes are washed as plums before their drying to remove yeast and such. A culture of yeast introduced somewhere in the processing at a later time would explain the appearance of the powder after exposure to the moisture and oxygen of the fridge.
Swab some and introduce it into a sugar water solution and see if it ferments. Or better yet, add it to a flour and water mixture and see if you can make sourdough with it.
The problem I see with this test is that we already know there’s yeast on the prunes - to get rid of yeast, you’d have to nuke them from orbit to be sure. What we don’t know is whether the white powder is a visible growth of yeast, a crystallization of sugar, or something else. Culturing a swab, though, will always be positive for yeast, regardless of the white powder’s actual contents.
