A "starter culture" refers to a specific mixture of microorganisms, such as bacteria or yeast, used to initiate fermentation in food production. Commonly used in making products like yogurt, cheese, and sourdough bread, these cultures help develop unique flavors and textures while preserving the food. The microorganisms in a starter culture are carefully selected for their ability to thrive in specific conditions and produce desired results. For example, Lactobacillus species are often used in yogurt, while Saccharomyces cerevisiae is a popular yeast for baking bread.