This little valve is, in my view, good engineering. The object can be mass produced cheaply and there is much more to the design than the average coffee drinker pays attention to. Notice the fiber filter which is backed by a plastic frame to give it strength. I assume that the purpose is to keep coffee particles away from the sealing lip but then it may also keep small life forms out of the bag.
Interestingly, the valve is required to preserve the bag rather than the coffee. In the days after roasting the coffee beans will produce enough CO2 to burst the bag ( it depends on the bag material but I found that 250 to 350 grams was the limit for un-vented vacuum packed bags). I suspect that the "longevity improving" aspect was more an invention of the marketing department than an engineering criteria.
A marginal improvement in longevity might be possible with vacuum packed vented bags. If the bags are packed within the hour after roasting they will need the valve even if they are vacuum packed. The porosity of the bean is relatively low and it takes time for the CO2 to migrate from the bean. Without a vent even vacuum packed packages look like overstuffed pillows. Obviously that would not allow efficient boxing of the bags.
Rather than believe that the bag was not kept in a warehouse for months and or spending days in truck trailers I prefer to buy from a local roastery or from Fresh Cup because they expedite the order on the day it is roasted. Oh well, that offer is only for Canada which means that more than Alaska and Hawaii are hit by the shipping restriction.
