Biltong that was off

I bought biltong yesterday. The packed date on the package was Saturday and it was suppose to be still good. I don't think the heat we had the last few days was good - so the biltong became wet and a little slimy. I didn't realize it, since I bought it for my daughter and gave her the sealed package. She ate a lot of it and late last night my mum who wanted to eat some too said it was off and slimy. Yes I should have made sure it was ok for my daughter to eat, but I can't open the package in the shop to make sure it's ok to buy, that is why we as customers place a lot of trust in the shops. Biltong is one of those things people can't buy everyday, and is seen as a huge treat - and to then find out all the money was wasted it's beyond not nice.