Blowing into a bag of salad greens is rumored to help them last longer. Why would this work?
The notion seemed pretty wacky to us (not to mention unsanitary), but in the interest of science we divided fresh salad greens into two batches, placing both samples in zipper-lock bags and lightly inflating one of them with a few exhales before sealing. The salad leaves stored in the regular bag started to wilt after five days, while—much to our surprise—those that had received a few puffs lasted almost twice as long.
Here’s why: Fresh produce ripens and eventually decomposes by the process of respiration (the conversion of glucose into carbon dioxide and water). However, exposing produce to elevated levels of carbon dioxide can retard the process. Air contains only 0.03 percent carbon dioxide, human breath as much as 4 to 5 percent. A couple of breaths into a zipper-lock bag full of salad greens increased the concentration of carbon dioxide enough to decelerate the respiration process. Despite its effectiveness, we don’t recommend this practice since the human breath can contain airborne pathogens.
Manufacturers harness the power of carbon dioxide in a much more sophisticated way, using a method called modified atmosphere packaging to replace some of the oxygen in packages of greens.