You are here.
Preservation and Shelf Life
Microbiology of Cider
The types and numbers of microorganisms (bacteria, yeast, and mold) that contaminate freshly packaged cider come from (1) the surface of apples, especially if they are rotten, slightly decayed, or damaged, and (2) the facility, equipment, air, water, or people involved in making cider.
High-quality unpasteurized cider will keep 12 to 14 days if the cider is cooled quickly and stored at 32 to 36°F. Shelf life is the range of time (expressed in days, months, or years) that any food product can be stored at a specific temperature before any of the following quality characteristics degrade: aroma, flavor, texture, color, safety, and nutritional quality.
Uncontrolled microbial growth is the main cause of shortened shelf life in cider. Native acids in apples limit the growth of many bacterial species, but their presence favors the rapid growth of the aciduric bacteria, yeast, and mold species. Usually harmless yeast and bacteria cells grow and multiply many times, producing alcohol and eventually some acetic acid, as in vinegar. Normal populations of these microorganisms range from 1,000 to 100,000 cells per gram, or about 30,000 to 3 million cells per ounce of unpasteurized cider. The shelf life of unpasteurized, refrigerated cider is shortened by higher counts of these microorganisms. Aciduric cells grow most rapidly at temperatures ranging from 70 to 80oF. Growth is reduced as the temperature of cider is lowered, but some species continue to grow slowly even at 32 to 36oF. As the cells grow, they use mainly sugars in the cider and produce many by-products. Most consumers perceive that cider loses its shelf life or “spoils” about the same time as its aciduric cell population increases to 1 to 10 million per gram or 30 to 300 million per ounce of cider.
Aciduric cells also grow in juice residue and on apple pieces that accumulate on and in the equipment used in processing. These cells also grow in pools of juice on the floor and in pomace. In addition to practices recommended for controlling those species that pose a public health concern, the following manufacturing recommendations will help to maximize shelf life by minimizing the initial population of aciduric cells and by preventing or reducing their growth rate in freshly pressed cider.
Unpasteurized cider is unsafe to drink if it becomes contaminated with pathogens. The most effective way to ensure the safety of cider is to pasteurize it. The potential for contamination to occur is reduced by following the Good Management Practices and HACCP plan development procedures provided in Part VIII, Maintaining the Safety of Pennsylvania Apples and Apple Products. Cider can additionally become unsafe to drink if mold growth occurs. Discard any cider that, by flavor or visual observation, contains mold.