Off taste all of a sudden?

I am making my first batch of cider and wanted to get some feedback as to what my problem may be, or if I have a problem at all. This is a approx 5 gallon batch.

I went by some recipes I took off the forums, using applejuice mixed with dextrose with blackberrys added all tossed into the primary, let it sit a few weeks, OG of 1.062 dropped down to 1.005. took a taste at this point, and it tasted great! of course a little dry, which I knew it would be. So I racked into a secondary adding some apple juice concentrate to sweeten a little ( 2 cans) and added a second bag of blackberrys ( defrosted and at room temp) figuring most of the berry flavor was fermented out I wanted a little more of it in the final product. I made a minor mistake here, as I planned to add cambden ( bad sp.) tablets at this point as in the recipe to halt fermentation. I forgot to do this until 2 days later, when I added them and continued to let it sit. 2 days after that I kegged it. When I kegged it the FG reading I took was 1.010, everything looked and smelled fine, and took a sample out to taste. This is when I tasted an off almost chemically flavor to the finish of the cider... would this be after taste of the tablets that will wear off with time? I cant believe it was due to me forgetting to put them in, as it should have just continued fermeneting then, which would potentially dry it out more, but not add any off taste, right?

I tossed the CO2 on it right after kegging ( which was last night) and of course haven't touched it yet, plan on checking the carb level tonight, and since i dont want it super carbed it will most likely be done ( 30 psi on it for 24 hrs)...

any suggestions as to what might have added this flavor? The cleaning process I used on the secondary was the same as I have always done with all my fermentors so I don't think its anything there... I do use plastic fermentors, but they are pretty much new! no scratches or anything like that, and it only sat in the secondary for 4-5 days, simply to sweeten and incorperate more blackberry flavor.

thanks for any suggestions!

It maybe that the campden tablets added the flavor. Since it is kegged you could try blowing off the gas a few times to clear out the flavor. I don't know if it will work but seems like it might be worth a try.

Remember that campden is an antioxidant, but doesn't kill wine yeast. It might stress it a bit, though- so that could be where the smell is coming from.

Next time, if you want to sweeten a wine or cider, make sure you ferment it all the way out. Rack to make sure there are no lees, and very little yeast in suspension. It might take a couple of rackings.

Then, stabilize with sorbate while adding campden (sorbate works better with campden present) and let it sit for a few days. By then, it should be safe to sweeten.

Sorbate doesn't kill yeast, either, but it inhibits yeast reproduction. Adding it to an active fermentation won't do anything (as there are plenty of yeast in there) but adding it to a fermented and clear wine that is racked off of the lees means the yeast can't reproduce so fermentation should stop if the wine is sweetened.

thanks for the replys and suggestions!

today I took a taste out of the keg, its not fully carbed yet, but the "off taste" changed to more of an "acholol" taste...

I will try the idea of purging the keg some in attempt to lose the taste, hopefully it will just go away as it ages in the keg!