In the past few years, vacuum packaging food has become a microtrend among home cooks. The practice removes oxygen from packaging (at home, this is usually zip top bags) to make it harder for certain bacteria to reproduce. This helps make food last longer by slowing down the possibility of mold growth, and changes in flavor and discoloration caused by spoilage bacteria that love oxygen and moisture.
The great benefit of this is that you end up throwing less food away, which, in turn, saves you money. If you buy groceries in bulk, there are so that batches last for months. You can also use a vacuum sealer to keep foods like nuts and grains fresh even longer, which is especially useful for people who need to keep emergency food supplies for things like natural disasters.
But despite their many benefits, vacuum sealers can run from about $30 to hundreds of dollars, and not everyone is willing or able to dish out that amount. Instead, a countertrend suggests foregoing the fancy-schmancy equipment and just using a straw to suck the air out of bags yourself. The idea is to squeeze out as much air as possible by hand, seal the ziplock while leaving a small gap at the end, and then insert a straw to suck the remaining air out of it.
Although in essence, yes, this trick works about the same as a sealer, it's not foolproof and certainly not a solution for long-term storage. Use a straw when there is no other option Though, whether you are using a machine or not, there are risks involve.