Food poisoning refers to an illness caused by consuming food or drinks contaminated with infectious pathogens, such as bacteria, viruses, or parasites. The risk of contracting a classic foodborne illness from a sealed bottle or can of soda is extremely low, though not impossible under specific circumstances. Sickness associated with soft drinks more commonly stems from non-infectious causes, such as chemical contamination or the growth of spoilage organisms that thrive in the beverage’s unique environment.
Risk of Classic Foodborne Illness
Most commercially produced soft drinks are highly resistant to common foodborne bacteria due to their low pH level. Sodas typically have a pH range between 2.5 and 4.0, with colas often having the lowest acidity. This acidic environment rapidly kills most pathogenic bacteria, such as Salmonella or E. coli, which generally struggle to survive below a pH of 5.0.
The manufacturing process further reduces risk, as the water used is purified and containers are sterilized before filling. Because of the high acidity and strict manufacturing controls, sealed carbonated soft drinks are not usually pasteurized in the United States. A sealed container of soda is therefore a poor environment for microbes that cause serious foodborne illness.
A more realistic risk of classic foodborne illness exists with fountain sodas, where contamination occurs after the initial product is made. Studies show that dispensing nozzles and interior components of fountain machines can harbor bacteria, including coliforms, which indicate possible fecal contamination. This contamination often stems from inadequate cleaning, poor maintenance, or biofilm formation on the internal tubing. Pathogens like E. coli and Salmonella can be introduced through the water supply or improper handling at the dispenser nozzles.
Non-Infectious Causes of Illness
The most frequent reasons people experience sickness after consuming a soft drink relate to spoilage organisms or chemical contamination, causing discomfort rather than an infectious disease. Yeasts are the primary spoilage organisms because they can grow in acidic, low-oxygen environments. A specific yeast, Zygosaccharomyces bailii, is adept at tolerating the high concentrations of preservatives and carbonation found in soft drinks.
When yeasts contaminate a product, they ferment the sugar into alcohol and carbon dioxide, leading to off-flavors, cloudiness, and pressure that can cause the container to bulge or burst. Lactic acid bacteria, which also tolerate low pH, may grow in soft drinks containing fruit juices, producing haze, sediment, and a rope-like texture. These spoilage organisms may cause mild gastrointestinal distress due to fermentation byproducts, but they rarely lead to severe infectious illness.
Accidental chemical contamination during production or dispensing is another non-infectious hazard. This occurs if cleaning agents or sanitizers are not properly rinsed from bottling equipment or fountain lines before the next batch is mixed. Ingestion of these chemicals, which may include strong irritants, can cause acute symptoms like gastrointestinal irritation or chemical burns.
Non-infectious discomfort can also stem from the drink’s composition, particularly ingredients like caffeine or artificial sweeteners. Excessive caffeine consumption can lead to symptoms like nausea, heart palpitations, and anxiety. Some individuals also experience acute gastrointestinal symptoms, such as bloating or diarrhea, after consuming large quantities of certain sugar alcohols or artificial sweeteners.
Identifying and Preventing Contamination
Consumers can identify a spoiled or contaminated soft drink by looking for specific physical signs before opening. A bulging can or bottle cap strongly indicates yeast spoilage because the organisms produce gas inside the sealed container. If the beverage appears cloudy, has sediment, or exhibits an unusual odor or taste, it should be discarded immediately.
Preventing contamination starts with careful purchasing and storage of sealed products. Storing sodas in a cool, dark place and checking the expiration date helps minimize the risk of spoilage. Consumers should also avoid buying or drinking from containers that are visibly damaged, such as those with deep dents, punctures, or compromised seals.
The risk associated with fountain sodas requires a different approach, as the issue is typically with the dispensing equipment rather than the packaged syrup. Consumers can check the dispensing nozzle for signs of slime or discoloration, which may appear pink, brown, or orange and indicate bacterial or mold growth. Opting for a bottled or canned beverage is the safest choice when the cleanliness of the dispenser is uncertain.