A live culture refers to living microorganisms, typically specific strains of bacteria or yeasts, which are intentionally introduced into a food product or supplement. These microscopic organisms are biologically active entities that perform a specific function within their host medium. The importance of these cultures lies in their dual role: they are fundamental to the creation of many foods and are also recognized for their potential contributions to human health.
Defining Live Cultures and Their Role
Live cultures are comprised of beneficial microbes that remain metabolically active, meaning they are alive and capable of reproduction when consumed. These microorganisms are primarily used as starter cultures, which drive the process of fermentation by breaking down carbohydrates like sugars into organic acids, gases, or alcohol. For instance, the bacteria Lactobacillus bulgaricus and Streptococcus thermophilus are the standard cultures used to convert milk into yogurt.
This biological activity transforms the raw materials, creating the characteristic tangy flavor and texture of fermented foods. When these live cultures are consumed in adequate amounts and are shown by scientific evidence to provide a benefit to the host, they are then formally classified as probiotics. Probiotics are a subset of live cultures specifically selected and studied for their positive effects on the digestive system and overall health. The viability of these cultures—their ability to survive—is what determines their functional impact on both the food product and the person consuming it.
The Critical Difference Between Live and Active Cultures
The terms “live” and “active” cultures are often used interchangeably, but the distinction is significant. “Active cultures” simply means the microorganisms were present and biologically active during the fermentation process that created the product. However, “live cultures” signifies that these microbes remain viable and alive at the point of consumption, which is the crucial factor for achieving potential health benefits.
This difference is most often a result of post-fermentation heat treatment, such as pasteurization. Manufacturers may apply heat to fermented products to extend their shelf life or to achieve a milder flavor profile by stopping the acid production. This heat process effectively kills the cultures, meaning the product no longer contains “live” organisms. For the consumer, this distinction matters because the potential benefits associated with probiotic consumption require the cultures to be alive when they enter the digestive system.
Common Sources and Labeling
Live cultures are naturally found in a variety of fermented foods that have not been heat-processed after their creation. Common dietary sources include yogurt, the fermented milk drink kefir, pickled vegetables like raw sauerkraut and kimchi, and the tea-based ferment known as kombucha. Beyond whole foods, these cultures are also available in concentrated forms as dietary supplements, often labeled with the specific microbial strains.
To help consumers identify products with a verified level of viable microbes, industry groups have established specific labeling standards. For example, the National Yogurt Association’s “Live and Active Cultures” seal indicates that a yogurt product contained at least 100 million cultures per gram at the time of manufacture. For supplements, the label often lists the Colony-Forming Units (CFU), which is a quantitative estimate of the number of viable microbial cells per serving.
Maintaining Viability in Products
Because live cultures are living organisms, their viability is sensitive to environmental conditions, which directly impacts the product’s effectiveness. Heat is the most significant factor that reduces their number, which is why cooking fermented foods or adding them to hot beverages should be avoided if the goal is to ingest the live microbes. The presence of oxygen and exposure to light can also contribute to the degradation and death of the cultures over time.
Most food products containing live cultures require refrigeration, as the cold temperature slows the metabolic rate of the microbes and dramatically reduces the speed at which they die off. Storing these products consistently at or below 40°F (4°C) helps preserve the number of viable organisms until the expiration date. Consumers should also note that even with refrigeration, the count of live cultures naturally decreases over the product’s shelf life, making it beneficial to consume these items well before the printed expiration date.