Thanks to lactic acid — which kills harmful bacteria during fermentation — fermented foods are arguably among the safest foods that humans eat. But if critical errors are made, there is the risk of food safety hazards.
“When we talk about fruit and vegetable ferments, there is a very long history of microbial safety with traditionally fermented fruits and vegetables,” says Erin DiCaprio, extension specialist at University of California, Davis, Department of Food Science and Technology. “While outbreaks associated with fermented fruits and vegetables are rare, vegetable and fruit fermentation is not without risk.”
DiCaprio, a food safety expert, detailed proper food safety protocols during a webinar for EATLAC, a UC Davis project putting scientific knowledge and research behind fermentation. DiCaprio shared two documented instances of fermented foods causing a foodborne illness, both from small-scale batches of kimchi. But she emphasized that, when all food safety concerns are mitigated, fermented foods do not pose a risk.
“From the food microbiology standpoint, bacteria really are the most important group of microorganisms because bacteria, certain types of bacteria, are a food safety concern,” she adds. “There are many different types of bacteria that contribute to food spoilage and, of course, there are specific types of bacteria that are used beneficially for fermentation.”
What happens during fermentation that makes food safe? Lactic acid bacteria are created, which convert sugars into lactic acid, acetic acid and CO2. Those antimicrobial compounds help fight off pathogens, competing with other microbes for nutrition sources.
Biological hazards — bacteria, viruses and parasites that can cause foodborne illnesses — are the biggest concerns. Botulism, E. coli and salmonella are the main hazards for fermented foods. Botulism can form in oxygen-free conditions if a fermentation is not successful and acid levels are too low. E. coli and salmonella form when sanitation practices are not followed.
“Commercially, when someone is developing a valid fermentation process, they are typically going to be looking to see that sufficient acid is produced during fermentation, to inactivate some of these acid tolerant (bacteria),” DiCaprio says. “Our traditional vegetable fermentations — things like fermented cucumber, sauerkraut, kimchi — they’ve all been shown to produce sufficient acid to inactivate the sugar toxin producing e-coli, so from a safety standpoint, sufficient acid production is the critical control point for ensuring the safety of a fermented fruit or vegetable. “
There are seven critical factors to keep a ferment safe:
- High-quality, raw ingredients. “If there are a high number of spoilage microorganisms to start with, it will be really difficult for the lactic acid bacteria to dominate the fermentation,” DiCaprio says.
- Research-based recipe. Following a tested recipe ensures the proper balance of ingredients to keep the food safe.
- Proper sanitation. Cleaning of all utensils and surfaces ensures no pathogens will contaminate the food. This mitigates cross-contamination risk, too.
- Preparation of ingredients. Food particles should be uniform in size, either cut in small slices or shredded. Smaller pieces release more water and nutrients, promoting the growth of lactic acid bacteria.
- Salt concentration. Lactic acid bacteria thrive in a salt brine. The key amount: anywhere from 1-15% salt brine by weight of the ferment.
- Appropriate temperature. A temperature between 65-75 degrees fahrenheit is ideal to keep spoilage microorganisms at bay.
- Adequate time. “It takes a while for significant acid to be produced, so be patient and follow the directions in the recipe,” DiCaprio advises. Most fruit and vegetable ferments take 3-6 weeks to be completed.
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FAQs
Are there any risks associated with consuming unpasteurized fermented vegetable foods like pickles, sauerkraut, kimchi and olives, or am I fine eating fermented foods? No. Fermented foods are intrinsically food safe due to their pH level, which measures at about 3.5.
What are the safety risks associated with the consumption of fermented foods draw up a list? ›
Biological hazards — bacteria, viruses and parasites that can cause foodborne illnesses — are the biggest concerns. Botulism, E. coli and salmonella are the main hazards for fermented foods. Botulism can form in oxygen-free conditions if a fermentation is not successful and acid levels are too low.
What are the safety precautions for fermentation? ›
Fermented foods must maintain proper temperature throughout the entire fermentation and reach a pH of 4.6 or less within the allotted time to be considered safe and free from harmful pathogens. The specific temperature and allotted time safety interval your food requires will be listed on your starter culture packet.
What is the safe pH for fermented food? ›
Fermented food must have a pH level of 4.6 or lower to be considered safe for human consumption. It is important to ensure that a pH of less than 4.6 is achieved within 24 hours of the start of the fermentation process and that the alcohol content of the final product does not exceed 0.5%.
Is it OK to eat a lot of fermented foods? ›
While there are currently no official guidelines regarding how often you should eat fermented foods, adding a few servings to your daily diet may be beneficial ( 44 ). For the best results, start by eating one or two servings per day, and then slowly work your way up.
Why should you not eat fermented foods? ›
If the food you're fermenting isn't properly prepared (e.g., not washing hands, supplies, ingredients, etc.) or stored, you risk having harmful bacteria in your food, which can lead to food poisoning. People with weakened immune systems, pregnant women, and children should especially watch out for this.
Is it bad to eat slightly fermented fruit? ›
Generally speaking, you're looking for a flavor that's somewhere in the range of “slightly tart” and “almost boozy.” If they taste properly boozy, you can absolutely still eat them, but they are quite fermented at this point.
What poison is in fermented food? ›
However, fermented foods may pose a potential food safety risk due to various microbial toxins, including biogenic amines, mycotoxins, and bacterial toxins. These toxins may be produced during the fermentation process or may be added during the food processing stages.
What should you not do during fermentation? ›
Opening the Jar During Fermentation
If you do, you expose your vegetables to all sorts of moulds, yeast, and other microorganisms. Undesirable organisms could then develop on the surface of the vegetables. The best thing to do is to leave the lid on and leave your jars alone.
What vegetables should not be fermented? ›
“There's no vegetable you can't ferment,” he said, but added that leafy greens such as kale — because of their chlorophyll content — aren't to most people's liking. During an NPR interview, Katz explained that pickling and fermentation are not the same, although they are “overlapping” categories.
Low pH levels limit the growth of spoilage bacteria. Some studies have shown that the pH of finished sauerkraut is in the range of 3.0–4.0 [23].
What pH is vinegar? ›
Vinegar is very acidic, with a pH of 2–3. Apple cider vinegar is nutritionally similar to other types of vinegar. Some believe it's more alkalizing than other vinegars, but there's no evidence to support this.
Is botulism a risk in fermented foods? ›
Although lacto-fermentation requires an anaerobic environment, botulism is not a risk. In a lacto-ferment, beneficial bacteria grow and create lactic acid, which is not a friendly environment for Clostridium botulinum and neither is a salty (brine) environment.
Can fermented food affect gut health? ›
Naturally fermented foods are getting a lot of attention from health experts these days because they may help strengthen your gut microbiome—the 100 trillion or so bacteria and microorganisms that live in your digestive tract.
Do fermented foods need to be pasteurized? ›
If the product comes from a manufacturer you trust and it's made properly, it's safe for most healthy adults to consume unpasteurized, fermented products like sauerkraut, kimchi, and kombucha.
