Re: How can we avoid the effect of pressure difference of packaged foods?

Packages are decreasing in volume when they travel from highlands to lowlands and increasing in volume from lowlands to highlands. The temperature ranges 18-20C in the highlands to (–5)-35C in the lowlands. The elevation of the highlands is 1886ft and the lowland elevation is not given (It will be assumed to be about sea level).

This effect is caused by the change in temperature and pressure. The formula PV/T=PV/T can be found in any physics book. P=pressure, V=volume, T=temperature in Kelvin. According to the encyclopedia Britannica.com, atmospheric pressure decreases 3.5 millibars per 100 ft. (1886ft/100ft)*3.5mb=66.01. The pressure at sea level is 1013.25mb. This means that the pressure in the highlands is 947.24.

The effect of the higher pressure of the lowlands is lessened by the high temperature in summer. Let's look at the winter situation. I am going to use the volume of 1 liter in the highlands for better comprehension, but you can do it with just V2. (1013.25mb*V1)/(273.15+(-5)K) = (947.24mb*1L)/(19+273.15K) therefore V1=.858L. This means that the package has lost a volume of .142L or 14.2%. The same is probably not true in the opposite direction because the factory is not kept at -5C. If the factory temperature in the lowlands is kept at room temperature which is close to 19C the volume will increase about .07L for a 1L package. This may still be enough for it to burst, but it is only half of the difference the other way around.All of this can be affected depending on whether you keep the package in the fridge or in your car on a hot or cold day.

You can correct the problem of bursting at the factory by vacuuming some of the air out of the package or increasing the temperature during packaging. Perhaps you could also increase the packaging materials permeability to air. A food scientist may be able to better answer that question. The loss of volume is not as important, but you could correct it by blowing up the package or decreasing the temperature during packaging.

I don't know if you asked this question for your packaging business or you just make trips back and forth from the lowlands and highlands. If you want to keep your packaged goods fresh, you can clean a spot on the package with alcohol, poke a hole with a pin, squeeze out the air and cover the hole with the sterile tape of a Band-Aid. I really don't know if it will work, but you can give it a shot. I hope that this answers your question.