Potassium metabisulfite / sorbistat K questions...

I'm pretty new to brewing and I've jumped in with both feet. The info that I have found on HBT has been priceless, but there are some things I guess I'll have to learn by trial and error and personal experience...

I've made two 5 gallon batches of wine so far; one from a muscat concentrate and one from a merlot concentrate. (Both Alexander's, both with Red Star Premiere Cuvee yeast.) The muscat I treated with potassium metabisulfite and sorbistat-K upon racking to the secondary, so that I could backsweeten it to make the ol' SWMBO happy. (She likes the sweet moscatos that are common at the grocery store like Barefoot and Gallo.) The merlot I have no intent of sweetening since that one is more for me and I prefer my reds dry, therefore I did not use any potassium metabisulfite or sorbistat-K yet. (I just racked that to the secondary and added sparkalloid to clear it.) The muscat has a slight sulfur smell/taste that's not intolerable. It's definitely there, but the wine is drinkable. One of our friends that tried it seems to be very sensitive to sulfites and had a bad headache the next day after only a couple of glasses, but the other 4 of us that drank it had no problems. The merlot is exactly what I was hoping for and expecting.

So, I have two questions:

1) Could I have overdosed the potassium metabisulfite or sorbistat-K in the muscat? I used 1/4 level teaspoon of potassium metabisulfite and 2 and 1/2 level teaspoons of sorbistat-K in 5 gallons. When I do a search for sulfur, sulfur smells, and sulfur related problems, I find threads about the H2S04 problem during ferment, but this smell/taste didn't start in mine until after racking to the secondary and adding the chemicals.

2) Since I'm so happy with the merlot right now and I don't want to add any funny flavors and I don't want to add any more sugar for sweetness, can I just bottle it without adding the chemicals once it's cleared and rely on the ethanol to preserve it?

Thanks for helping a newbie!

It is important to note that potassium metabisulfite is not only a preservative but also a sanitizer. All of your wine should contain potassium metabisulfite for the sake of these two things (aging and sanitation). Potassium metabisulfite is sold typically as what are called campden tablets, and is commonly measured by weight not by volume. It is recommeneded that you use 1 campden tablet per gallon on wine, each tablet weighing .44g (wikipedia) and 10 roughly equal 1 tsp. In a 5 gallon batch you should have theoretically used 1/2 tsp. of the potassium metabisulfite.
Don't think of the potassium metabisulfite as a chemical, but a necessity really. It will not effect the quality of your wine. Allow some time for the wine to sit before bottling after adding the potassium metabisulfite.
The sorbistat-K is for use to prevent renewed fermentation and doesn't have anything to do with any kind of sulfur smells, be careful though if your wine isn't done fermenting when you add the sorbistat-K then try to sweeten your wine you'll be popping corks if you aren't careful.
The sulfur smell definately may have something to do with the potassium metabisulfites, but it is difficult to say, you should've added more... The off smell may have been from the yeast straining, improper sanitation, or something else altogether. It may seem easy to blame the chemicals for this problem, but I would advise you to not give up on them yet. Try it again, use the potassium metabisulfite from the beginning. I would suggest allowing your wine to clear naturally, you don't need sparkloid, just a few weeks or so. Also, (speaking from experience) store your back sweetened bottles upright for a week or so, just in case they decide to pop the corks, I couldn't figure out how my kitchen floor got so sticky until I decided to try a bottle of apple wine...

Thanks for the reply, Zwetschgen. That helps me understand a bit more about stabilizing wine. I've also been reading more about stabilizing from other sources. I've managed to find some other threads on here with similar questions and helpful links.

I checked in my journal for any possible mistakes I may have made with the batch, and I did dose the muscat twice with sparkalloid (total of 2 tablespoons) because the first round didn't clarify it the way I had hoped. Yeah, I know, I was impatient... I'm working on that.

Also, I understand what you said about the yeast possibly being stressed. I think the batch was around 10% ABV, according to hydrometer readings and ambient temperature should have been around 70-72 F for all of the ferment and (brief) aging. Are those conditions far enough out of line to cause stress on the yeast?

I think I do have some campden tablets, so I might try them next time, rather than using loose potassium metabisulfite. I might try separating my 5 gallon batch of merlot into 1 gallon jugs and dose them slightly differently with potassium metabisulfite and see what the results are.