Guest Post By Sarah Meadows
This is the third article of a three part series exploring wine fermentation :
- Fundamentals of Wine Fermentation
- Chemical Reactions during Wine Fermentation
- Unconventional Methods of Wine Fermentation
Yeast fermentation is the most popular method of making great wine but it’s certainly not the only method. Yeast strains are abundant, inexpensive, and can be easily controlled and predicted. But there are benefits to alternate fermentation sources.This article will describe two other widely used methods that produce delicious wines with unique characteristics: Carbonic Maceration and Malolactic Fermentation. These two fermentation techniques use drastically different yet equally interesting organic compounds to assist with wine production.
Carbonic maceration is an enzymatic driven fermentation. Enzymes are complex proteins that bind to predetermined substrates to produce a specific product. Enzymes are vital to processes in life because they speed up chemical reactions by lowering the activation energy or the initial energy required to begin a reaction. Here is a simple example; when our bodies experience an injury resulting in blood loss, enzymes are responsible for clotting at the injury site to prevent further loss of blood. Without enzymes, a relatively mild cut could result in significant hemorrhaging or death. Outside of the human body, enzymes play a multitude of important roles catalyzing chemical reactions; grape fermentation is one such role.
In contrast with yeast fermentation, wine grapes are not crushed to release their juices. The whole grapes are placed in an anaerobic environment, one that lacks oxygen, and left to rest in high levels of carbon dioxide. Because grape skins are relatively permeable, carbon dioxide can easily access the interior of the grapes. Enzymes within the grapes utilize this increase in carbon dioxide to catalyze chemical reactions. Thus, the natural breakdown of sugar within the grapes by enzymes during carbonic maceration produces ethanol. Wines created by carbonic maceration, such as Beaujolais, are typically consumed young. Some tasting notes describe these wines as fruity and lacking in significant tannins.
Unlike carbonic maceration, malolactic fermentation utilizes tiny organisms to chemically alter grape juice resulting in lactic acid production. Lactic acid should sound familiar since it’s the same byproduct partly responsible for sore muscles after a workout. Our muscles breakdown carbohydrates (sugar) to use as energy, but during a workout when oxygen levels have decreased, the body can switch to anaerobic respiration which takes advantage of lactic acid for energy production. Bacteria can metabolize malic acid, present in fruit, into lactic acid. Winemakers accomplish this by intentionally introducing these microorganisms to the grape juice.
Usually, malolactic fermentation is coupled with standard fermentation since it does not actually result in ethanol production. Rather, after primary fermentation, bacteria are used to achieve malolactic fermentation resulting in different flavor characteristics. Because lactic acid is less harsh than malic acid, the wine will have a smoother mouth feel and a more buttery finish. Malolactic fermentation is used frequently with red wines to reduce some of the acidity and harshness imparted by the malic acid.
Malolactic fermentation and carbonic maceration further prove the complexity of wine making. The world of wine has come a long way since its birth from wild grapes and ambient yeast. Now, almost every detail of wine production and wine storage can be controlled. Winemakers know how to use quality grown grapes, precisely set wine coolers and refrigerators, and effective aging techniques. But winemakers still owe much gratitude to the amazing results of chemical reactions and our learned ability to manipulate these reactions. Without enzymes, bacteria, and yeast, we would not have such a wonderful and diverse alcoholic beverage to enjoy.