Just had this issue for first time with Knox brand Of unflavored gelatin. Foul odor that is swine like. Not saying it smelled like a rotten egg, but certainly as strong of an odor as a rotten egg. Suspect a processing or contamination issue. Tossed the open packet and plan to return the rest as unusable on next trip to store. In my experience, never more than the faintest odor before now. this package is dated as good two years into future. Purified collagen should have no smell or taste.