your best bet is to starting buying produce regularly at your local greengrocers.
Fruit and veg is seasonal here with massive variations in quality, availability and price depending on the time of year. I've found that the best choices are found at local verdulerias...You may not be able to get exactly what you want but you can usually find the best "in season" goods there. You can also ask if red apples are available. I know mine will keep a look out when there is something specific I want.
I know the supermarkets are the most convenient places to buy. However, there doesn't seem to be any quality controls implemented and things tend to stay on shelves until they're visibly rotting! A few months ago, I found some avocados in Jumbo...all of which, on closer inspection, were liquid inside. The guy I spoke to about it wasn't at all bothered...The onions at my local supermarket are often swarming with flies as the stock gets low.
