Natural yoghurt is made by fermenting milk with specific bacteria cultures, thickening it into a creamy, tangy treat.
Here's a breakdown of the process:
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Milk Preparation: The process begins with milk, which can be cow's milk, goat's milk, or even plant-based alternatives (though the result technically isn't yoghurt). The milk is often pasteurized to kill any unwanted bacteria and then may be homogenized for a smoother texture. Sometimes, milk solids are added to increase the yogurt's thickness and richness.
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Heating: The milk is heated to around 80-85°C (176-185°F) for a period of time, typically 10-30 minutes. This accomplishes several things:
- Denatures the whey proteins in the milk, which helps create a firmer gel structure during fermentation.
- Reduces moisture content, concentrating the milk and contributing to a thicker consistency.
- Ensures a sterile environment for the beneficial bacteria to thrive.
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Cooling: The heated milk is then cooled down to a temperature suitable for the yoghurt cultures to grow, usually around 40-45°C (104-113°F).
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Inoculation: At this temperature, a yoghurt starter culture is added. These cultures typically consist of two main bacteria: Streptococcus thermophilus and Lactobacillus bulgaricus. These bacteria are responsible for fermenting the lactose (milk sugar) into lactic acid.
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Incubation: The inoculated milk is then incubated at a consistent temperature (40-45°C) for several hours, typically 4-12 hours, depending on the desired tanginess and thickness. During this time, the bacteria consume the lactose, producing lactic acid, which lowers the pH and causes the milk proteins to coagulate, resulting in the characteristic yoghurt texture. The longer the incubation, the tangier the yoghurt will become.
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Cooling and Storage: Once the yoghurt has reached the desired consistency and tanginess, it is cooled to slow down the fermentation process and prevent it from becoming too sour. The cooled yoghurt is then stored in the refrigerator.
Therefore, making natural yoghurt requires controlling milk preparation, heating, cooling, inoculation with specific bacterial cultures, and controlled incubation.
