It’s a Jungle in There

I am often asked how Spanish cider makers achieve consistency in their spontaneous wild yeast fermentation. I am encouraged by the question, because it indicates a pretty good grasp of how cider is made and that many are making their own cider as well. And, it indicates a growing interest in natural fermentation. America: Cidery as Laboratory
Saccharomyces yeast culture
In the U.S. potassium meta-bisulphite is used to sterilize the juice. Proper selection of and inoculation with a commercial yeast is considered part of the craft. Serious cider makers regard cultured yeast varieties to be as important a variable in projecting cider outcomes as apple varieties. Some even select yeasts that will more assertively express themselves in the finished cider than the fruit. These are legitimate aesthetic choices. From a practical standpoint sterilization and inoculation offer predictability. Much professional cider making in the U.S. is laboratory intensive. Having measured acidity, specific gravity and other factors, and controlling temperatures in the fermentation vessels; the cider maker can apply data provided for a cultured yeast to predict the development of alcohol and residual sugar levels along a predictable timeline. All this permits a high degree of manipulation and uniformity of desired cider characteristics. For the cider maker with limited cooperage, or the large commercial producer, controlling fermentation also facilitates a high turnover production schedule. This is FAST CIDER. How do the Spanish manage these variables with a spontaneous fermentation? Well, they don’t. I used to follow this reply with the observation that with generations of experience comes a familiarity with the result and that predictability comes with long experience. But that’s too glib. After all, those wild yeasts are coming in on apples from diverse slopes and valleys in Asturias. Should we be tempted to speculate that a predictable, common set of yeast strains has spread over time across the region, then we have to consider the importation of apples from Galicia and even Normandy. Not to mention the coexistence of diverse strains in any one place, on the apples and environment of the llagar (cider house). Spain: It’s a Jungle in There
Dance Party in the Juice
Fermentation in Spain is exactly the opposite of our yeast selective approach. In Spain a whole pack of hungry microbes are left free to feed unhindered on the nutrients in freshly pressed juice. First, saccharomyces yeast burn off entrained oxygen while converting natural sugar to alcohol. Like wolves at the kill the more aggressive strains feed first, followed by strains that can hang around longer as oxygen is depleted. This results in a layered and complex fermentation with aromatic results as varied as the multiple vats filled from juiced apples from different orchards. Sidra is fermented at ambient temperature. In Asturias, at harvest time that is in the mid-fifties Farenheit. Within a few days the saccharomyces fermentation has mostly depleted the oxygen it requires, having produced nearly 90% of the total alcohol that will be generated. With the cider then racked and sealed with an air-lock, lactobacyllis begin their anaerobic conversion of endogenous malic acid to lactic acid in what is known as malolactic fermentation. The lactic acid is softer on the tongue than its precursor, but this process is what generates the notorious earthy aromas of sidra, once strange to Americans, but now increasingly popularized as “the funk”. (“Gotta have it.”) But wait. Even though oxygen has been depleted, once significant alcohol is present, endogenous acetobacteria will begin a restrained aerobic conversion of alcohol to a limited amount of acetic acid – aka vinegar – yielding a modest tang. Sidra is not considered matured for release until April, but most is reserved longer, for up to two years, in huge vessels. Only then do sidra makers actively intervene, responding to the varied outcomes in the many vessels – more than the keys on a piano – which they have been sampling throughout their evolution to shape chords that please finely-tuned, personal sensibilities. This is where the art of blending takes over. This is SLOW CIDER. In my next post I will introduce Spanish apple varieties and be able to discuss the blending process in detail.
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