Jim, Those are cool labels. I also noticed that your fruit is from Suisun Valley. How did it turn out? I made Sangiovese from Suisun Valley fruit last year. How did you get your fruit? Thanks.
If you sanitize your hydrometer and tube, you can test the sample in the tube (take a small taste from the tube) and pour it back in. Don't worry about oxidizing that small amount in the tube and don't worry about contaminating if you sanitized your equipment.
I tasted it tonight and was pleasantly surprised. It's so much better than it was a year ago. Still, I added some oak cubes. Will leave them in for a month or two and plan to let the wine sit for another 6-12 months before bottling.
From what I've read, you do not want to put a port or any other dessert wine through MLF. They need that malic acid to balance the sweetness.
Also, using my method of interrupting the primary fermentation to ensure residual sugar, I couldn't put it through MLF if I wanted to, because it's...
If you're feeling adventurous, go for it. If you're researching the common methodology for white wine, then you don't add any grapes or raisins. The juice is all you need. Cheers.
One barrel is fine. You can rack out to carboys and back into the barrel after cleaning it. Inoculating MLF in a barrel is the same as in anything else. Do it either during or immediately after alcohol fermentation.
I've made great wine from frozen must by winegrapesdirect.com and I think they're in or near Sacramento. There's also a great wine making club in Sac that sources a lot of good fresh fruit.