Day 4 - Rosella's

Time to make some wine! On Day 4, we brought our four fermenting bins of Rosella's out from the cold room into our fermentation room. The four days of cold soaking has really brought out some lovely citrus and feminine sweetness in the juice. Yummy!

In order to inoculate we culture up some yeast. At Kosta Browne, we predominately use a strain of Saccharomyces cerevisiae called RC212 to run our fermentations. RC212 is a Burgundy strain that works well on Pinot Noir and is known to give great color extraction - important in Pinot Noir where sometimes wines can be thin on the looks front. RC212 is also quite alcohol tolerant (can survive up to 14-16%) and heat tolerant as well (up to around 94° F) which helps in California where we have ripe fruit (and thus alcohols in the 14-15% range) and with the new wood tanks we use for some of our fermentations. The wood fermentation vats give an incredibly sexy mouth feel to the finished wine but the wood retains a lot of heat. Thus it helps to have a yeast strain that won't die on you and leave you with a "stuck" fermentation. RC212 is known to need a lot of nutrients (remember the YANC) or it will start using any sulfur compounds in the juice to create hydrogen sulfide.

To culture yeast we take dried powdered yeast from the fridge and slowly adding water we allow the yeast to wake up from their slumber. Once our yeast starts to froth we slowly add juice from the bin/tank we are inoculating until the temperature of the yeast is within 10° F of the juice temperature (since we just brought the bins out from cold soak the juice was 58° F when we inoculated) both to give the yeast some food to eat, live free and multiply, and also to make sure they don't get "shocked" by the cold temperature when we pour it into the juice.

Once the juice is inoculated we now call it the "must". We now sit back and wait and see how our little yeast babies adjust.

I love punchies!

Once fermentation is underway, we punch down the cap twice a day. Our little friends, Saccharomyces cerevisiae, are chomping away on grape sugars and turning it into ethanol, CO₂ and heat. The CO₂ that is released pushes the grape skins to the surface and the heat "bakes" the skins into a soft cake that we call the cap. Above you can see that half the tank is punched (look at all that creamy goodness bubbling up - thats CO₂ coming up) and the other half is still caked.

The problem with a cap is that the skins are where all the flavor, color and tannins are so we need to push the skins back under the juice occasionally. It also has the effect of helping the fermentation lose some excess heat which it especially important in these wooden tanks since the staves hold their temperature well. At Kosta Browne we punch down twice a day during fermentation.

I love doing punch downs. The smells and the exercise remind you that wine is a living thing and keeps you close to the wild side of nature. Because at the end of the day, wine is just rotten grapes!

Microbiology of wine

Smack bang in the middle of harvest I needed to fly back to Australia as part of my Wine Science degree to stare at microbes under a microscope for four days.

Microbes are a very important part of a winery. Of course, wine is made through the action of our favorite friend, Saccharomyces cerevisiae or wine yeast, which converts sugar in the berries into ethanol (alcohol) and CO₂. There are also other friendly microbes like Oenococcus oeni that help give red wines and many Chardonnays their soft mouth-feel.

However there are also many nasty bacteria and yeasts that if given a chance would love to screw up your wine. The most well known is a family of bacteria called Acetobacter that converts ethanol into acetic acid - more commonly known as vinegar! Not only is this a major wine fault but it is also very noticeable since acetic acid is what we call volatile - in other words it likes to leave the wine as a gas and thus is picked up by our nose very easily. Acetic acid is also often converted through some other chemical reactions into Ethyl acetate which smells of nail polish. Tasty! So next time you have a glass of wine that you think might not quite be "right", stick your nose in and see if it is because of a vinegar or nail polish taint. If it is you can say damn those nasty Acetobacters!

So what can a winemaker do? Luckily, for us Acetobacters need O₂ to survive and once fermentation by our wine yeast (you remember our friend Saccharomyces cerevisiae) is underway enough CO₂ is given off to kill any Acetobacters. But before and after fermentation we need to be very careful. This means after crushing the grapes, the must (winemaker term for the juice and skins) needs to be covered with a blanket of CO₂ at all times until fermentation is happily chugging along. After fermentation it means keeping all the barrels topped up with wine and during bottling it means that we need to flush the bottles with an inert gas like Nitrogen or Argon so there is no O₂ in the ullage (winemaker term for space between the wine and the cork/screwcap) that can let Acetobacters get a foothold when your wine is happily sleeping in the cellar.

All of these nasties mean that we spend a lot of time keeping things clean in the winery. In fact, for each hour of what you might term "romantic winemaking" there are three hours of washing up. Its all worthwhile though to ensure that your next glass of vino doesn't smell like yesterday's salad dressing or your overly made up Aunt Ethel!