What method of food preservation is being used when bacteria in milk produce lactic acid, turning the milk into yogurt?

The method of food preservation described involves the natural process where bacteria convert sugars present in milk into lactic acid, leading to the transformation of milk into yogurt. This process is known as fermentation.

During fermentation, specific microorganisms, particularly lactic acid bacteria, metabolize lactose (the sugar found in milk). As they digest this sugar, they produce lactic acid, which lowers the pH of the milk. This increase in acidity helps inhibit the growth of spoilage-causing bacteria, thereby preserving the milk while also giving yogurt its characteristic tangy flavor and thick texture. The controlled fermentation process not only preserves the food but also enhances its nutritional profile, making it a prime example of biotechnology in food processing.

The other methods mentioned, such as canning, involve sealing food in jars and heating it to destroy bacteria, which is a different preservation technique altogether. Freezing is a method that halts bacterial growth by lowering temperatures, while dehydration removes moisture from food to inhibit microbial activity. Each of these methods serves different purposes and employs different mechanisms compared to fermentation.