hiya

vacuum sealing is probably best option.

I do this for commercial samples and they can last weeks.

However the best bags are a kind of metal foil - but this would not be
allowed to be sent overseas due to metal detectors.

Try a zip-seal food bag, insert a plastic drinking straw, seal bag tight to
straw, suck out air and fully seal bag as you pull straw out. Then wrap the
packs in bubble wrap for posting.

Hope it works with your recipes

Good Luck

Adrian