What is the fine-grained topic of the following text: A fresh, tasty salad is a great way to get more leafy greens into your diet, whether it's a side at dinner or an impromptu snack when you're rummaging through the fridge, but I've found that bags of salad and re-closable plastic bins of salad both start to rot from the inside out pretty quickly. Only return the topic.
Preservation of bagged salad and its potential degradation