In the milk market of Bangladesh, every customer who wants to buy milk from the farmers will test its quality with his own hands. He dips his hand or fingers into the milk in the kettle and immediately sees if it is worth it. Bangladesh has a tropical climate with high temperatures that can reach 30–40 °C. In a warm environment, milk can turn sour in just 6-12 hours if it is not stored in the refrigerator. If the milk starts to have a sour smell or taste, it is better not to consume it raw, but to use it for cooking or baking.