My refrigerator is small, so often I have to keep some vegetables outside the refrigerator, in room temperature. I was wondering, whether spraying alcohol and/or salt around the vegetables can help in keeping bacteria away for them and thus lengthen their shelf life. Do you have any experience with this?
No, salting or spraying alcohol on your vegetables will not help keep them fresh at all, in fact salting them would probably have the opposite effect.
You are probably connecting the fact that salt is used as a preservative with keeping food fresh, but these are 2 different concepts. Keeping things fresh involves trying to keep a plant metabolizing as long as possible as @rumtscho says, while preserving food is about slowing the growth of bacteria and other microbial life which rots food and can make it harmful to life so it can be safe a long time. This can be done through a combination of any or all of the below:
- Exposure to cold: refrigeration and freezing
- Sterilization: this usually means heating food for a certain length of time and storing it in a sealed container like a can, jar, or carton
- Preservatives: preservatives create an environment that is hostile to bacteria and other microbes, these can be natural (salt, vinegar, citric acid), or artificial (sulfites, benzoic acid). Note that alcohol is not listed among them - you'd need to use alcohol in such concentrations as it could be dangerous in a kitchen (think explosions and fire so don't do it!)
Often food preservation is a combination of the above, like a preservative and sterilization. In any case preserving food means making changes to the texture and often flavor of the food, so in no case would it ever be considered fresh.
So save your salt and your alcohol, they won't help you there.
No, it won't help you at all. Your vegetables aren't being eaten by bacteria or similar (and this is a good thing, foods which are rendered unsafe by bacteria shouldn't be kept more than 4 hours at room temperature). They are simply wilting.
There is no way to stop the wilting process. It is the plant cells dying off and stopping being able to "take care of themselves". You have to buy vegetables more frequently if you want them to be pleasantly fresh. The only thing you can do is to cool them, which slows down their metabolism and so prolongs the time they have left until they die. For a few types of vegetable, providing water helps, e.g. carrots or any bunch of leafy herbs, but this is an exception.