Why Does Milk Go Sour? Understanding the Science Behind Milk Spoiling

Learn why milk sours over time due to bacterial conversion of lactose to lactic acid and how refrigeration slows this process.

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Milk goes sour due to bacterial action. Bacteria present in milk convert lactose into lactic acid, which lowers the pH, leading to the sour taste. This process is accelerated by warm temperatures, which is why keeping milk refrigerated helps to slow down the souring process.

FAQs & Answers

  1. What causes milk to go sour? Milk goes sour due to bacteria converting the sugar lactose into lactic acid, which lowers the milk's pH and creates a sour taste.
  2. How does refrigeration affect the souring of milk? Refrigeration slows down bacterial growth, which in turn delays the souring process of milk.
  3. Can sour milk be consumed safely? While naturally soured milk can sometimes be used in cooking, consuming spoiled milk that has an off smell or mold is unsafe and not recommended.

Watch More

For more insights into dairy science and food storage tips, check out our related videos on milk pasteurization and how temperature affects other perishable foods.

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