How to Make Yogurt From Yogurt: A Guide to Perpetual Culturing
You can indeed make yogurt from yogurt! The key is to use a small amount of existing, active culture yogurt as a starter to inoculate fresh milk, allowing the bacteria to multiply and transform the milk into a new batch of yogurt.
The Magic of Yogurt Cultures: A Brief Background
Yogurt isn’t just a tasty breakfast or snack; it’s a living ecosystem of beneficial bacteria. Specifically, two key strains, Streptococcus thermophilus and Lactobacillus bulgaricus, are responsible for the fermentation process that converts lactose (milk sugar) into lactic acid. This lactic acid gives yogurt its characteristic tangy flavor and thick texture. When you make yogurt from yogurt, you’re essentially propagating these beneficial cultures, creating a continuous cycle of yogurt production. This process, often called “perpetual culturing,” allows you to enjoy homemade yogurt without constantly purchasing new starter cultures.
Why Make Yogurt From Yogurt? Exploring the Benefits
Making yogurt from yogurt offers a plethora of advantages:
- Cost-effectiveness: Eliminates the need to buy commercial starter cultures regularly, saving you money.
- Sustainable practice: Reduces waste by reusing existing yogurt instead of buying new products every time.
- Customization: Allows you to tailor the taste and texture of your yogurt to your liking through variations in milk, incubation time, and storage.
- Freshness guaranteed: You know exactly what’s in your yogurt – no added sugars, artificial flavors, or preservatives.
- Empowerment: Mastering the art of yogurt making is a satisfying accomplishment, connecting you to a time-honored food tradition.
The Simple Steps: Crafting Your Own Yogurt at Home
Here’s the breakdown of how to make yogurt from yogurt, step-by-step:
Gather Your Supplies: You’ll need:
- Fresh milk (pasteurized or ultra-pasteurized works, but raw milk is not recommended).
- Plain yogurt with active cultures (store-bought or homemade). Avoid flavored or sweetened yogurt.
- A clean container (glass or food-grade plastic).
- A thermometer.
- A heat source (stovetop or slow cooker) and a method to maintain a stable warm temperature during incubation (yogurt maker, oven with pilot light, insulated cooler).
Heat the Milk: Pour the milk into a saucepan and heat it to 180-185°F (82-85°C). This pasteurization step kills any competing bacteria and denatures the milk proteins, resulting in a thicker yogurt. If using ultra-pasteurized milk, this step can be skipped or reduced, but it generally improves the result.
Cool the Milk: Allow the milk to cool down to 110-115°F (43-46°C). This is the optimal temperature for the yogurt cultures to thrive.
Inoculate with Yogurt: In a separate bowl, whisk together about 2 tablespoons of your active culture yogurt starter with a small amount of the cooled milk. This helps to temper the yogurt and prevent it from curdling when added to the warmer milk.
Combine and Incubate: Gently stir the yogurt mixture into the remaining cooled milk, ensuring it’s evenly distributed. Pour the mixture into your clean container.
Incubate: Maintain a stable temperature of 110-115°F (43-46°C) for 6-12 hours, or until the yogurt has reached your desired consistency and tanginess. Longer incubation times will result in a tangier yogurt.
Refrigerate: Once the yogurt has set, refrigerate it for at least 2 hours to stop the fermentation process and allow it to thicken further.
Troubleshooting Your Yogurt: Common Pitfalls and Solutions
Even with careful execution, yogurt making can sometimes present challenges. Here’s how to overcome some common hurdles:
- Thin or Runny Yogurt: Often caused by insufficient incubation time, low incubation temperature, or weak starter cultures. Try incubating for longer, ensuring a consistent temperature, or using a fresher starter culture. Using milk powder (about 1/4 cup per quart) can also improve the thickness.
- Grainy Texture: Can occur if the milk is overheated or the incubation temperature is too high. Use a thermometer to carefully monitor the temperature.
- Mold Growth: Indicates contamination. Discard the batch and thoroughly sanitize all equipment before trying again. Ensure your starter yogurt is fresh and free of mold.
- No Tang: The yogurt wasn’t incubated long enough. Keep it at the appropriate temperature for a longer duration.
Beyond the Basics: Advanced Techniques
For the adventurous yogurt maker, consider these advanced techniques:
- Straining Yogurt: Strain your yogurt through cheesecloth or a yogurt strainer to create Greek yogurt or labneh.
- Adding Flavorings: Incorporate extracts, honey, fruit purees, or spices after incubation and refrigeration.
- Different Milks: Experiment with different types of milk (goat, sheep, soy, almond) to create unique flavor profiles.
- Making Yogurt Cheese: Incubate for an extended period (24-48 hours) and strain to make a spreadable yogurt cheese.
FAQ: Your Burning Yogurt-Making Questions Answered
Can I use flavored yogurt as a starter?
No, you should only use plain, unflavored yogurt that explicitly states “active cultures” on the label. Flavored yogurts often contain added sugars and preservatives that can inhibit the growth of the beneficial bacteria.
How many times can I re-culture yogurt?
Generally, you can re-culture yogurt for 5-7 generations before the cultures become weakened and the yogurt quality declines. After that, you’ll need to start with a fresh batch of starter yogurt.
What temperature is too hot for the yogurt cultures?
Temperatures above 120°F (49°C) can kill the yogurt cultures, preventing fermentation.
What temperature is too cold for incubation?
Temperatures below 100°F (38°C) will slow down the fermentation process significantly, resulting in thin or no yogurt.
Can I use raw milk to make yogurt?
While some people make yogurt with raw milk, it is not generally recommended due to the risk of harmful bacteria contamination. Pasteurization helps to eliminate these risks.
How do I know if my yogurt has gone bad?
Signs of spoilage include mold growth, an unusual odor, or a slimy texture. If you notice any of these, discard the yogurt.
How long does homemade yogurt last in the refrigerator?
Homemade yogurt typically lasts for 1-2 weeks in the refrigerator, when stored properly in an airtight container.
Does the type of milk affect the yogurt’s consistency?
Yes! Whole milk will produce a richer, thicker yogurt, while skim milk will result in a thinner yogurt. You can also use milk powder to improve the thickness.
Can I use a slow cooker to incubate yogurt?
Yes, but be careful with the temperature. Many slow cookers run too hot even on the “warm” setting. Use a thermometer to monitor the temperature and adjust accordingly. You may need to unplug the slow cooker periodically to maintain the desired temperature range.
What if my yogurt separates?
Some separation of whey (the watery liquid) is normal. Simply stir it back in before serving. If there’s excessive separation, it could indicate over-incubation.
How do I store the yogurt I want to use as a starter for the next batch?
Store the starter yogurt in a separate, clean container in the refrigerator. This prevents contamination and ensures you have a fresh, viable culture for your next batch. Use it within a week for best results.
My yogurt tastes too sour, what did I do wrong?
This usually means the yogurt was incubated for too long, or at too high a temperature. Reduce the incubation time for the next batch. You can also add a touch of honey or fruit to the finished product to offset the sourness.