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I'm having a problem where the blackberries I buy from the store on Sunday seem to be spoiled on Monday. On Sunday, I specifically look around the outside of the box and check if any blackberries have white fluff on them. If I don't see it then, then when I actually open the berries on Monday I will see the fluff. This is irritating because I don't know whether I am supposed to throw these out, and I buy large quantities of these berries to last me the week.

So my 2 questions are:

  1. How do I know whether a blackberry is safe to eat? If some blackberries have that white mold on it, but the others don't, can I throw that berry out and use adjacent berries?

  2. How am I supposed to store blackberries to prevent it from molding after 1 day? I highly doubt my grocery store will be selling moldy berries deliberately so maybe I am storing it incorrectly.

RonJohn
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Jeremy Fisher
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    How are you storing them? – J Crosby Jul 08 '19 at 15:15
  • I just put them straight in the fridge in the same box they came in. When I need to use them I just pull them out and use the amount I need and return it to the fridge. It's very strange since this problem started only in the last 2 months. I don't know if the grocery store is continuously selling moldy berries or not. – Jeremy Fisher Jul 08 '19 at 16:36
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    You might have mold lurking elsewhere in your 'fridge. If so, a good cleaning, ending with a spray/wipe-down of all interior surfaces with 3% Hydrogen Peroxide may help. – Catalyst Jul 09 '19 at 12:26
  • If this started in the past 2 months it might be your fridge temp has risen in summer? Are you monitoring high and lows? – user76453 Jul 10 '19 at 07:11

3 Answers3

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As soon as you get them home, inspect for damaged berries & discard any that are not perfect. Wash the rest in a colander or sieve under cold running water. Drain well.

Spread on dry paper towel for 30 mins to fully drain & dry, then put them in a new box with paper towel under & over - don't seal them with a snap lid.

Place in the fridge, in the salad crisper if you have one.

Life-span should now be more like a week.

The rapid spread of mould is from possibly just one single damaged berry. If they are touching & sweating, that can spread like wildfire. If they are clean, dry & cold, in air that can circulate around them, then you should be fine.
You could possibly be OK eating ones from the opposite side of the original punnet, but I wouldn't really. Safe rather than sorry, so do the preventative work first.

If it happens again even after you took proper care, pick a new store, or complain at the first one - though bear in mind that even with care, they are still fragile & won't last forever. Your sign of end-of-life when clean & dry should be shrinkage, they will eventually start to dry out & look wrinkled, rather than mould.

From comments under the OP [1] - it's possible that the mould spores are in the fridge not in the berries. The berries, if damaged in any way, simply provide a suitable breeding ground.
I'd recommend a fridge-sanitisation day. My method will prevent fast cross-contamination, but won't kill existing spores.

[1] "It's very strange since this problem started only in the last 2 months. I don't know if the grocery store is continuously selling moldy berries or not"

Tetsujin
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  • Thanks for the suggestions. So do you think the mold developed because of my handling of them, or that there was actually a moldy berry in the container and I didn't notice it? – Jeremy Fisher Jul 08 '19 at 16:35
  • Also, could I store the berries in tupperware? I don't really have any other boxes. What sort of box/container would you recommenn storing them in? – Jeremy Fisher Jul 08 '19 at 16:35
  • Damaged today == mouldy tomorrow. Same goes for most berries, & tomatoes etc. And no. I specifically said in paper, not sealed. Sealed == sweaty == mouldy. – Tetsujin Jul 08 '19 at 16:37
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    Rough handling seems to be a significant factor, maybe before you buy them. – Chris H Jul 08 '19 at 16:37
  • The 'box' is for simple containment, so they don't go everywhere - the paper is for 'breathing' – Tetsujin Jul 08 '19 at 16:38
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    I got it now. Just basically a tupperware container with paper towel under and over the berries, without sealing the container. – Jeremy Fisher Jul 08 '19 at 16:42
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    Jeremy - from your comment under the original question, I added a new part to the answer. – Tetsujin Jul 08 '19 at 17:02
  • Will sanitize my fridge with some Lysol to be safe. However, I do think part of the blame lies on the store. When I was picking the berries, I had to look at 3 boxes before choosing the one I did because the other boxes had visible spores on them. – Jeremy Fisher Jul 08 '19 at 18:39
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    Lysol is toxic and meant to go on floors, not anywhere near food. Especially not in a fridge where it won't ever evaporate properly. –  Jul 08 '19 at 23:34
  • I'd never heard of Lysol, so I Googled it. It's any of a dozen or more cleaning products, some of which are fridge- & baby-safe... so just make sure to pick the right one. – Tetsujin Jul 09 '19 at 08:30
  • @GeorgeM you don't need to go as far as Lysol, just use alcohol or diluted white vinegar – Luciano Jul 09 '19 at 09:59
  • I would not use alcohol on plastic surfaces without doing a test first to be sure it doesn't damage the finish. – barbecue Jul 09 '19 at 14:50
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    Alcohol is a good antiseptic, which means it kills bacteria. Mold spores are.. mold. So alcohol is useless for that. Really the best way to kill mold spores without toxic outgassing or risking poisoning yourself is a borax solution. But that's not easily available in every country –  Jul 09 '19 at 19:33
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How am I supposed to store blackberries to prevent it from molding after 1 day?

Buy frozen.

  1. They're fresher (picked ripe and flash frozen, versus picked unripe so they last to the grocery store).
  2. You can defrost only the ones you need.
RonJohn
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    If you only want them for making a couli or some kind of cooked pudding, frozen is fine. If you want them for a cold pudding like a pavlova, or to eat, freezing destroys the structure of the fruit. When you thaw it, it becomes mush. – Graham Jul 09 '19 at 07:36
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    @Graham The whole point of flash freezeing ("vapour freezing" etc.) is that this doesn't happen. This is not the same as putting the fruit in your freezer. Of course, you need to make sure the fruit didn't at any point refreeze (often a problem in supermarkets). – Luaan Jul 09 '19 at 08:09
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    @Luaan The point is that you can't stop it happening. Water expands as it freezes, and that's simply physics. For anything which is basically firm or fibrous, this isn't a problem - pineapple freezes really well, for example. But frozen soft fruit like strawberries, raspberries or blackberries are basically bubbles of fruity water, and that delicate structure is *always* broken down by freezing, whatever freezing technique you use. – Graham Jul 09 '19 at 11:16
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    @Luaan ... Using "supermarket varieties" of soft fruit like Elsanta, which are chosen to be firmer but inevitably don't taste of very much, you get a less bad result. Raspberries can be less visibly affected, because they have a firmer skin. Either way though, the texture when you eat them is clearly not the same as fresh fruit. I don't disagree that there's a place for frozen soft fruit, but anyone who's eaten fresh fruit should recognise the texture difference between thawed-out soft fruit and fresh. – Graham Jul 09 '19 at 11:20
  • @Graham the faster the freeze, the smaller the crystals (thus minimizing the damage). That's the whole purpose of **flash** freezing. – RonJohn Nov 29 '19 at 22:25
  • @RonJohn Whatever you do, for soft fruit the freezing damages the texture. No-one with working eyes or palate could possibly mistake a frozen strawberry for a fresh strawberry. Flash freezing is really good for stuff with firmer structures like meat or fibrous veg, but it's not magic. The point of flash freezing is to stop crystals forming which slice through stuff - but soft fruit is damaged by water expansion as it freezes too, and you can't stop that. – Graham Nov 29 '19 at 23:13
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I wouldn't even try to squeeze a week out of blackberries. Basically they should be eaten the instant you get a hold of them, they're too fragile and not meant for storage. Tetsujin's answer would prolong their life by a few days, but not indefinitely. And any blackberries that lasted much longer would be so impregnated with preservatives that you should probably steer clear of them.

That said it's not at all unusual for a basket of soft berries, whether from the store or a market, to contain one or more that didn't even make it to you. I throw out any that are really moldy, eat the rest without ever having any sort of problem.

Don't use Lysol in your fridge, that's worse than any spores. Just clean it out well using baking soda as a scouring powder, making sure to clean any crannies, that for instance you pull out the drawers to clean under them. Or if you really have a raging mold problem, rinse it down with a borax solution, if you can get your hands on some (7-mule team brand in the US is usually sold with laundry).

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    Using any kind of abrasive on the plastic walls of a fridge also sounds like a bad idea. – David Richerby Jul 09 '19 at 08:40
  • The only mention of Lysol in cooking SE is this post. Why is it bad? – J. Chris Compton Jul 09 '19 at 18:18
  • Baking soda is a mild enough abrasive to use on your teeth, so it's fine for your fridge too. As to Lysol, it's meant to wash floors, it's not a food-grade product by any means. –  Jul 09 '19 at 19:31
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    @GeorgeM Lysol is a brand name, not a product, and the brand includes a food surface sanitizer. Just because the floor cleaning product you're used to is not food grade does not mean no product they make is food grade. – Beofett Jul 10 '19 at 19:45