Earlier this year, I found a package of gelatin sheets in my cupboard, which looked extremely old. I couldn't exactly tell how old, but the packaging mentioned a refund procedure with the refund price not in Euro, but what I think was either Dutch Guilders, or Belgian Francs, although the price was quite high, mentioning something around 200 of the currency. I assumed that this meant that the package predated the Euro, which meant it was over 10 years old.
I tried to use it in a recipe I learned in a cooking class, but the packaging was already completely broken, making the gelatin exposed to the air. The recipe wasn't that successful, with shreds of undissolved gelatin littering my chocolate mousse. I later was told that the only reason we used gelatin in the cooking class was because we didn't have enough time to properly set the mousse.
Does gelatin keep 12-13 years?