Live Yogurt Culture (starter): This is crucial for fermentation. You can use a few tablespoons of plain, unsweetened yogurt with live active cultures from a previous batch or store-bought yogurt, or a powdered yogurt starter culture.
Optional (for thicker yogurt): 1-2 tablespoons of powdered milk per liter of milk. This boosts the protein content, resulting in a thicker yogurt.
Tips
The magic of long-lasting yogurt lies in precise temperature control, meticulous sanitation, and the right milk. Here are the tips to ensure your yogurt stays fresh for months:
Sanitation is Paramount: Before you begin, sterilize all your equipment—pots, whisks, spoons, and storage containers. You can do this by boiling them in water for 10 minutes or running them through a hot dishwasher cycle. Any lingering bacteria can contaminate your yogurt and shorten its shelf life.
Choose Your Milk Wisely: As mentioned, UHT milk or milk pasteurized at a higher temperature is ideal. If using regular pasteurized milk, you’ll need to heat it to a higher temperature (around 195°F or 90°C) and hold it there for 5-10 minutes. This denatures more of the whey proteins, preventing them from separating and making the yogurt more stable and less likely to become watery over time.
Cooling is Crucial (and Quick): After heating, cool the milk rapidly to 110-115°F (43-46°C). You can do this by placing the pot in an ice bath. Rapid cooling minimizes the time for any undesirable bacteria to grow.
Introduce the Starter Gently: Once the milk is at the correct temperature, whisk in your live yogurt culture. Ensure it’s fully dissolved and evenly distributed.
Maintain Consistent Incubation Temperature: This is perhaps the most critical step for long-lasting yogurt. The optimal temperature for yogurt bacteria to thrive is 105-115°F (40-46°C). An insulated cooler with jars of yogurt submerged in warm water, a yogurt maker, or even an oven with the light on (check temperature with an oven thermometer) can work. The longer the incubation (12-24 hours), the tangier and often thicker the yogurt will be, and some argue this longer fermentation contributes to better stability.
Refrigerate Immediately and Properly: Once your yogurt has reached the desired consistency, move it to the refrigerator immediately. The cold temperature slows down the fermentation process, preventing it from becoming overly sour and extending its shelf life.
Store in Airtight Containers: Transfer your finished yogurt into sterilized, airtight containers. Glass jars with tight-fitting lids are excellent choices. Limiting exposure to air is key to preventing spoilage.
Serving and Storage Tips
Serving:
For the best flavor and texture, allow the yogurt to come to room temperature for about 15-20 minutes before serving.
Stir well before serving, especially if any whey has separated.
Enjoy it plain, with fresh fruit, granola, honey, or as a base for smoothies and savory dishes.
Storage:
