I have been buying ready-to-eat salad from a local store. It comes in different varieties and pretty big unwieldy transparent plastic boxes. One of the issues I have noticed is some boxes of salad go bad pretty fast, the leaves turning dark pretty quickly and ultimately reducing to unpalatable dark colored pulp. I also noticed they turn to mush much earlier than the stated best-by dates on the label. I just had a box of salad turn half bad today but the best-by date on the label is July 15, a good 5 days from now. What am I not doing right? I have a very old, small fridge where I store my salad so I think the temperatures inside were not always even, neither temporally (over a period of time) nor spatially (I can tell the fridge works better towards the back). Could that be the reason?
I agree that it's very likely the fridge. Beside it swinging too wildly, there can be another problem though: too cold.
I've seen people, especially Americans, turning fridges down as cold as they will go. This can result in food partially freezing, at least for a little bit of the cooling cycle. If this happens in your fridge, you'll probably recognize it from sometimes noticing a bit of crystalization in yogurt. But it may also happen with loose salad leaves only, because they have very little mass and will be the first thing to freeze, maybe even only the outer layers.
Salad leaves which have been frozen and thawed exhibit the exact problem you describe: they turn to dark, unappetizing mush. This happens as soon as they've thawed, and at least at the beginning, there is no bad smell at all, just the changed texture.
If you suspect this might be the case, see if you can find (borrow?) a thermometer that can record the temperature over a period of time. Wireless would be ideal, but you can also use a thermometer with a probe on a long cable, fridge door seals close over probes without leaks. Just make sure it's accurate for low temperatures, so not a grill thermometer that was calibrated for the 50-250 C range only.
If you don't want to bother with a thermometer, and are already using a very low setting, turn it up a bit and see if the problem is solved.
As others have covered the likely problems with your fridge, I'm just adding tips on how to give maximum lifetime to your salad greens after you fix the fridge:
The ideal container for greens is spacious yet sealed. This gives salad some air but seals in moisture, and prevents the leaves from being crushed. As such, those "unwieldy plastic boxes" are actually a better place for the salad ingredients than a produce bag; when I put salads in a bag, I often inflate the bag and tie it off.
One way you can improve the storage lifetime of the salad in those boxes is to take the salad out of the box, line the bottom with paper towels, and put it back in and seal it. This prevents moisture that pools at the bottom of the box from wilting the salad.
It's probably your refrigerator. Old, crappy refrigerators end up with high hysteresis (that is, they don't turn on until it gets pretty warm, and then don't turn back off until it's way too cold). Depending on how the refrigerator is set, this means that the salad leaves are too warm for too long (causing decay mushiness) or repeatedly frozen (causing refreezing mushiness). Or both.
Try putting your salad near/under containers of liquid (milk, ketchup, w/e) to even out temperature variations. Also try playing with the thermostat on the refrigerator, turning it up if you've ever noticed ice collecting in your food or turning it down if the salad leaves smell moldy. Remember, once you've changed the thermostat, wait at least 24 hours before evaluating the results.
Out of personal experience:
- avoid squeezing the bag too hard against other solid objects in the fridge.
- Avoid as much as possible direct contact with the fridge wall where the cooling circuit is located. The cooling circuit is way colder than the fridge, as you can tell from the ice that sometimes forms on it.
- if the bag has been opened, try to close it but not too tight: you want some air circulation to prevent moisture condensation spoiling the leaves, but not so much to dry it quickly. I usually do a 2-3 rolls of the top and then let free.
Once salad begins to wilt, I rinse in a few charges of fresh water to remove the putrid goop, then I steam it and freeze it like spinach. In fact, those general green salad mixes make a very good substitute for wilted spinach in many applications, like spanikopita, dips, smoothies, etc. If on the other hand, the salad shows mold, I toss it. I really expect to finish it off within 5 days of opening it tops. If your boxes consistently expire before then, there is either an issue with your refrigerator or the store's refrigerator.
I keep salad in a plastic lidded container, put some paper towels on top, then store it upside down, so that excess water drips into the paper towels. I then change those daily.
I first started doing this for my pet iguana's food, since I had to make it by hand from various veggies/fruits/greens, and she ate every day.