Cider Quiz Answers: Question #4

1. Kills Yeast and Acetic Acid Bacteria: Incorrect Answer – You can use sulfites, Campden, to sanitize equipment but the concentration is extremely high and potentially toxic to humans so this level is not something you would ever add to your cider. Normal treatment levels of sulfites will inhibit yeast and acetic acid bacteria but yeast recover and acetic acid bacteria has been found to be active with as much as 30 mg per liter of free SO2. Sulfite doesn’t kill yeast or acetic acid bacteria so don’t use it if that is your goal. 

2. Binds Oxygen: Incorrect Answer – There is a common misconception that treating with sulfites allows the sulfites to bind with oxygen and prevent oxidation from occurring. Sulfites can bind with oxygen but the process takes a significant amount of time. In cider, sulfites would take too long to bind with oxygen and therefore, it never actually happens. Oxygen more readily binds with other compounds found in the cider, like phenolics. Sulfites can help prevent or even reverse oxidative reactions, but it’s not the oxygen it’s binding. It’s the other compounds. This is how sulfites can help prevent oxidation. Just remember that it’s not removing or binding oxygen, it’s just blocking oxidative reactions. Also note that this blockage is usually not permanent as the effects can be lost during fermentation or aging when phenolic compounds are further transformed. 

3. Inhibits Lactic Acid Bacteria and Binds with Phenolics: Correct Answer – In cider, sulfites are good at doing two things. They will kill and inhibit lactic acid bacteria and readily bind with phenolic compounds. As noted in the first response, sulfites don’t have a long-term impact on yeast or acetic acid bacteria. Lactic acid bacteria is more susceptible to the influence of sulfites. Its addition is used in wine to prevent malolactic fermentation (MLF), a process carried out by lactic acid bacteria, as well as the prevention of further lactic acid bacteria reactions during the aging process. 

4. All of the Above: Incorrect Answer: If you selected this answer, it wouldn’t surprise me. There is a lot of incorrect information floating around about what sulfites (Campden, sulphite, potassium metabisulfite) do and their ubiquitous use creates common misconceptions. It took me several years of researching to understand that the use of sulfites has been driven by two unique conditions in wine. The desire to inhibit heterofermentative lactic acid bacteria from forming acetic acid during aging and the elimination of laccase, an enzyme secreted by Botrytis (grey mold) that is highly oxidative.  

Unfortunately, the addition of sulfites in cider is often misapplied. Adding sulfites to juice can delay fermentation, which can aid mold growth in an oxygen rich environment (yes, sulfites don’t inhibit mold either). Adding it to cider can prevent malolactic fermentation, but MLF is generally a desirable reaction in cider. Also, because cider has lower alcohol levels, the predominate lactic acid bacteria should be homofermentative strains of Lactobacillus and Pediococcus. This is different from wine, which usually has acetic acid producing heterofermentative strains. In wine, homofermentative strains die off as alcohol levels increase and more alcohol tolerant heterofermentative strains take their place. These strains produce acetic acid during aging. Having homofermentative strains that don’t produce acetic acid, means lactic acid bacteria is the cider makers best friend not the enemy as it is cinsidered by wine makers. You want to encourage lactic acid bacteria to speed the MLF process and promote the positive effects during aging. Without lactic acid bacteria (i.e. adding sulfites), your cider can remain overly sharp and less well rounded. 

(1) P. Ribereau-Gayon and associates, Handbook of Enology Volume 1, The Microbiology of Wine and Vinifications 2nd Edition, Chapters 4-6, John Wiley & Sons, Ltd, 2006, ISBN: 0-470-01034-7

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