Kennerth said:
Mac Baren creates a 40% vacuum in their tins (60% of atmospheric pressure), so that's why you hear and feel the pop. I can't imagine why they chose that percentage figure.
Vacuum sealing a tin will deprive the aerobic bacteria of the oxygen necessary for proper aging. But if you're interested in faithful preservation, not aging, then I guess a vacuum would not cause a problem.Every tin I have ever bought is vacuum sealed. That's why they they make that air rushing noise when you open them.
Mac Baren creates a 40% vacuum in their tins (60% of atmospheric pressure), so that's why you hear and feel the pop. I can't imagine why they chose that percentage figure.