I brought some ready to eat vacuum packed meals made in the USA but sold in the UK back into the USA. I declared them at Customs and they inspected the packaging in case they had 'become contaminated outside the USA' (their words ...). They approved them once they were happy that the packaging was indeed original, from a reputable source, and the vacuum was undamaged.

Oh, and by the way, the exercise was actually a complete waste of time as the 'meals' were quite revolting ... but that is a different story!