It’s a bit of a misreported myth that spoiled salad mix will balloon outward. According to USA Today, the food myth was reported on social media sites like Facebook. According to the myth, you can tell how fresh salad mix is by how flat the bag is — the puffier the bag, the higher the chance that the salad mix has spoiled. However, that is false and shouldn’t be used to gauge the freshness of the salad.
According to Industrial Packaging, bagged salad mixes use special packaging that is designed to lengthen the shelf life of the produce by providing an artificial atmosphere. While to the naked eye, it may look like oxygen in those packages, it’s a mix of gases including carbon dioxide. According to a 2009 study in the Critical Reviews in Food Science and Nutrition, carbon dioxide is used to create the needed temperature and humidity for produce.
Instead of puffiness, you want to examine whether your bagged salad mix has a lot of moisture. Moisture, given off by spinach in the bag, can cause bacteria to grow as a result. So the less liquid in your salad mix, the better the chances that it’s still good to eat.
