Sometimes when you buy unripe fruit - which is mostly what supermarkets sell - it never gets ripe - it just stays hard and dried out. I think it is because it is overchilled for too long and it is not ripe enough when harvested. Sainsburys are particularly guilty of that (well our local one anyway) Tesco doesn't seem quite as bad. I've tried the banana thing, sometimes it just makes it go mould really fast.
I hate doing that too em, I get fed up wasting it both from an environmental aspect and becasue of the cost. I rarely buy plums now and necatarines/peaches are a hit or a miss.
I'm with Jim - take them back.
Once however the customer care lady in Sainsbugs stood tasting the battery-acid grapes I had returned saying 'no- they're alright'.....I still got my money back.
The only thing that makes me a little sad is that the supermarkets tend to take it out on the grower, who might already be selling them fruit at a very low price.
they were bought in the market, usually a safe place to buy, as i have been using the same fruit and veg stall holder for years. Not going to take them back, seems no point this time. Had it been from a large retailer i would do.
sour plums make a great sauce...stew them in half a cup of very dry red wine...add some chinese 5 spice mix (about half a teaspoon, and some black pepper, when they go soft allow to cool and squish the stones out,,, blend or press through a sieve and add a tablespoon of honey use to cook chicken breasts, duck or pork
take them back to the shop and find a green grocer where you can pick out some nice ripe ones....try to look for some that were grown closer to the point of sale as they are less likely to have been pre chilled