Malo-lactic bacterial fermentations can be a challenge to any cellar. Outside of these conditions, winemakers often select a desired malo-lactic bacterium to perform the desired job, giving a wine a desirable flavor and aroma attribute, while eliminating malic acid from the wine, or less likely, the must/juice. Many winemakers today control the malo-lactic fermentation process through cleanliness, pH, sulfur dioxide, temperature and controlled conditions to support or suppress the bacterial growth. These small bacteria, often rampant in nature, can cause serious issues to any wine in the bottle or cellar that may undesirably undergo a potentially unwanted, uncontrolled wild fermentation. Oenos and predominantly responsible for the “sterile filtration” standards of 0.45 absolute microns used as a wine industry standard today. This process of converting the harsher malic acid, the acid dominant in most apples, to lactic acid, the softer acid dominant in most milk and cheeses is done by malo-lactic bacteria. Unlike what the term indicates, this is not a fermentation done by yeast. In making that decision, many factors come into consideration: How much malic is present? What is the pH now? What will the pH be after alcoholic fermentation? What is the predicted pH to be after malo-lactic conversion? In some traditional roles of winemaking such as wines made from the Bordeaux varieties, Burgundy varieties and Rhone varieties a decision by the winemaker may need to be made as to whether or not to perform a malo-lactic fermentation on those wines. Cherry’s and apple’s principal acid is malic. Further note fruits other than grapes such as cherries and apples have wide ranges of malic contents. Riper fruit generally has less malic than under ripe and so on yet, winemakers should be cautioned not to try and use a measurement of malic acid as a sole predictor to grape ripeness for winemaking. Cool climates often have grapes higher in malic acid and warmer climates often have lower quantities of malic acid in the fruit. In most cases it is secondary only to tartaric acid in quantity and then followed by succinic, citric, fumaric and other small quantity acids all contributing to a total acid or titratable acidity.Įvery variety of grapes has a potential difference in the amount of malic acid that may proportionately exist in the grapes at harvest and much of this is predicated by the growing season, amount of rainfall, overall heat summation temperatures and night time temperatures. Malic acid is one of the major acids in grapes used to make wine.
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