Moldy Sirah grape

[Mars Colonist]

The local wine guild got our wine grape from California Monday nite. At the crush, the Sirah came in substantially moldy (white mold... not my grape, but looked like this). We picked through the grape and pulled the parts that looked the worst (pulled 3/4 lug from 5 ... ~15% loss). Looks like it was raining in California and the mold developed in transit (Suisun valley, CA to Austin, TX). The ripest grapes were the ones most affected.

At crush, Brix was 22.5 and pH was 3.8-3.9. I added 90ppm via 10% Kmeta solution. I have no idea of the TA. The must tasted fine (but then again, Im fairly new at tasting fresh vinifera grape).

Last night I added about 4.5g/L of tartaric acid to fix the pH (down to 3.23 this morning), French Oak chips, VR Supra tannin, OptiRed, Lallzyme and some pectinase. Everything is sitting <60°F. Ill aerate, add nutrients and yeast (RP15) tonite.

Anyone have any other info I should consider?

 

[wayneb]

Do you have a way to measure the net sulphite level? Reason I ask is that even though you may have added 90ppm, I'm betting that a significant amount of is has been bound, and thus isn't going to do much to handle the mold. You can get a successful fermentation from grapes that have gone moldy, by doing what you've already done (i.e. remove all macroscopic signs of moldy fruit), and by sulphiting -- but you'll want to be more assertive about it, taking the equivalent free sulphite up to around 100 ppm, in order to make sure that the mold doesn't take hold in your must once you do start fermentation. Then allow the fruit to rest until sulphite levels drop to something within the tolerance of your yeast, and then get fermentation going as rapidly as possible by pitching a generous dose of yeast (I'd use at least twice the amount of yeast that I'd normally consider for a ferment of "sound" fruit).

 

[Mars Colonist]

Do you have a way to measure the net sulphite level?

Unfortunately I dont have the equipment to test SO2 or TA.

... taking the equivalent free sulphite up to around 100 ppm

Ill have do some reading to get a better understanding of bound versus free SO2. What it is that gives the impression that the 90ppm I added will be mostly bound prior to fermentation? I just havent done my homework yet....

...get fermentation going as rapidly as possible by pitching a generous dose of yeast (I'd use at least twice the amount of yeast that I'd normally consider for a ferment of "sound" fruit).

Ive got about 16g of Rockpile 15.. that should be good enough for 1.5 lugs of grape.

Is it Sirah, or Syrah? Looks as if I am misspelling it....

 

[wayneb]

For your reading pleasure, here's probably the most comprehensive single source of info on SO2 in winemaking. Enjoy!

Oh, and if it's syrah (or shiraz), then it is a noble French Rhone grape. If it's sirah (aka California Petit Sirah), then it is a poor French cousin.

 

[Mars Colonist]

Ah. Got Petite Sirah last year, and Syrah this year.

Thank for the link. This is what Ive been using.