From Press to Palate: The Science Behind Apple Cider
What’s your favorite kind of apple? Today, over 7,500 varieties of Malus domestica, or domestic apple, are cultivated and produced worldwide. Research from Reedy et. al indicates that 728 of these varieties, with names like Slack Ma Girdle and Pig’s Nose, are specifically grown for cider production.
Classic apple-based juice and cider beverages have been around for centuries; the word “cider” dates back five thousand years to the epic of Gilgamesh. Apples have been part of the American cultural identity for centuries, evolving from colonial survival foods to beloved fall flavor staples.
In modern times, apple cider is enjoyed by Americans as a seasonal fall treat, while apple juice is widely available year round and typically served with breakfast. Both beverages start with crushed apples- the difference between them lies in the post-pressing process.
To make apple cider, the whole apple is pressed and all resulting liquid is collected, bottled, and sold as the final product. Cider retains pulp, which contributes dietary fiber and vitamins to the drink and lends to its characteristic cloudiness, thick texture, and flavor variation. Apple juice attains its clear and uniformly sweet qualities when pulp is removed using tools and techniques including centrifugation, enzymatic degradation, and filtration.
Another key difference between apple juice and cider lies in the pasteurization process. In the late 1990s, outbreaks of E. coli from contaminated fruit juices and apple cider brought FDA regulations established in 2001 requiring non-retail commercial entities to treat their juice products, including cider, using either heat pasteurization or ultraviolet germicidal irradiation (UVGI) procedures to achieve 99.999% elimination of pathogens of concern.
Most apple juice in America is produced, sold and shipped in bulk, classifying it as non-retail, meaning that it must be pasteurized under federal law. Cider production is more likely to be small-scale and locally distributed, classifying it as retail and allowing producers to bypass the pasteurization requirements- as long as the container advertises a warning label.
During heat pasteurization, liquids are quickly heated to a FDA-approved temperature for a set amount of time, then rapidly cooled. Temperature and time vary by the chemical makeup and quantity of liquid. It is important that the liquids are not exposed to too much heat as this could change the taste or texture of a product, reducing its quality.
UVGI is another method of disinfection that uses UV light to inactivate microorganisms by damaging their DNA. Research by Gan et. al indicates that some UV treatments have successfully reduced enzymatic browning, a natural oxidizing reaction occurring in apple juice. These treatments help preserve the taste and nutritional value of the juice when it is exposed to oxygen during the processing stages.
Raw, unpasteurized cider can become fermented by yeast cells from the apples, air or environment, which metabolize its natural sugars (glucose, fructose and sucrose) and convert them into ethanol and carbon dioxide, typically achieving a 4-8% alcohol by volume. Americans refer to this fermented cider as “hard cider”, while to the rest of the world it is known as simply “cider” and all nonalcoholic apple beverages, including American cider, are considered to be “juice”.
Historically, all cider was left in a raw state, and the increased alcohol content from the fermentation process would naturally inhibit harmful bacterial growth, making it safer to drink than water. Modern refrigeration slows the natural fermentation process, which allows contamination to occur during any interruption to the cider’s refrigerated state, as microorganism populations grow faster than the fermentation process occurs. Some microorganisms, including yeasts, bacteria and molds are useful or harmless, while others cause food-borne illness or spoilage.
Pasteurization processes work by damaging the structure of microorganisms, preventing them from surviving and reproducing. The removal of microorganisms from juice and cider sterilizes them, lowering the chance of food-borne illness contraction by consumers, and increasing the shelf life and stability of the product.
Pasteurized cider can also go through alcoholic fermentation, but only if commercial strains of yeast are artificially added, because pasteurization kills the wild yeasts that normally start fermentation. The type of yeast used for fermentation affects the maximum alcohol by volume the cider can reach, as each strain has a different alcohol tolerance and fermentation efficiency. Lalvin EC-1118, a yeast strain favored by brewers for its notably high alcohol tolerance, can be used to create hard cider up to 18% alcohol by volume.
Even in a refrigerated environment, raw cider (or pasteurized cider artificially introduced to yeast) will gradually become fermented within 2-3 weeks. If hard cider is exposed to atmospheric oxygen and the right kind of bacteria, it undergoes natural acetic fermentation after 5-7 weeks and becomes apple cider vinegar.
The acetic fermentation process which produces apple cider vinegar is chemically distinct from the alcoholic fermentation process that produces hard cider. To create apple cider vinegar, bacteria (primarily Acetobacter aceti) oxidize the ethanol in hard cider to produce acetic acid. This process cannot be reversed, as the higher acidity of the vinegar environment will kill ethanol-producing yeast.
By Nora Schneider
