I just did your test. You are right. The campden tab did have an onion smell/taste to it. I'm thinking I may take some down to my local brew store and see what they think. If I learn anything I'll share it here.
I've done 3 batches so far. 1st no campden with nottingham yeast Wonderful smell/taste
2nd with campden and Lalvin 1118 yeast - same bad smell/taste as described.
3rd with campden and nottingham - same bad smell/taste as described.
smell is not Rhino Farts (I know the smell of H2S)
taste of...
I really hope it dissipates.. I hand milled and pressed 32 gallons of the stuff... I don't think i'll be using Campden again. I'll just make sure everything is sterile and take my chances...
smell is medicinal/salty. I licked a campden tab and the taste is the same. Taste/smell is dissipating very slowly. I'm just wondering how long it usually takes? Cider is in an airlocked carboy.
I added 4 tabs/5 gallons to my cider, 48 hrs before pitching. It has been 4 months and the smell/taste of the campden is still very strong. How long does this take to dissipate? Is there any way to speed it up?
Thanks!