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Making your own yogurt at home: How safe is it?

A bowl of homemade yogurt.I’ve been making yogurt at home safely for many years. The first time I made my own fresh yogurt was an awakening. It was my first real attempt at processing my own food beyond regular cooking and baking. The experience was life-changing and lit the spark that became my journey of self-sufficiency. I was yogurt-woke. Since I also had heaps of experience with food safety, I knew yogurt would require a little extra attention to food safety.

If proper food handling and safety methods are followed, yogurt can be made safely at home without fear of foodborne illness taking over the product.

Turning milk into yogurt is an excellent way to extend the shelf life of milk by a week or two and is a safe dairy choice for those of us who are lactose intolerant.

Why it’s Safe to Make Your Own Yogurt

First, let’s talk about how the process works, and, with safety procedures, takes milk and turns it all into yogurt.

Lactobacillus is the name for a group of bacteria that convert sugars, or lactose, into lactic acid. This process called fermentation. These helpful bacteria strains help us preserve more foods than just yogurt. We also use them in the fermentation and preservation of fruits and vegetables, such as sauerkraut and pickles.

In yogurt fermentation, we wipe the bacteria slate of our milk clean, inoculate it with a starter culture, and set it aside to let the bacteria ferment the milk sugars.

Assuming all safety precautions are taken, the yogurt will stay safe because as lactic bacteria cultures grow, the acidity level of the milk rises. This creates an unwelcoming environment for other bacteria.

Cleaning and Preparation

Making sure your work area is clean is the most crucial factor in making yogurt safely. If your kitchen is dirty, it’s likely contaminated with bacteria waiting to compete for whatever food they can, and your milk is an easy target.

Take the time to clean off your countertops and scrub them down. Scrub your sinks and sanitize your sponges, too, as some of the most harmful bacteria will lurk there.

As far as actual cooking hardware is concerned, as long as they have been washed recently in hot soapy water or in the dishwasher, they’re probably fine. If it makes you feel safer, run your equipment through the sanitize cycle in your dishwasher or through a bowl full of water and bleach, but it’s not necessary.

Make Sure Your Milk is Safe

Don’t overlook your milk. The best type of milk to use is full fat pasteurized milk, for reasons of safety and quality. Skim or part-skim milk won’t thicken up like low-fat varieties of commercial yogurt, as they won’t have the same thickening additives commercial versions use.

Though technically the safest milk is ultra-pasteurized milk, the process can cook the proteins necessary for fermentation. Some brands of UHT milk may work better than others.

Raw milk, or straight out of the cow (or another animal), can carry loads of harmful bacteria. Microbes like campylobacter, salmonella, and E. coli love raw milk. These types of bacteria are harmful to some people, especially pregnant women and the elderly. This is why the FDA is against drinking it, and why many states ban its sale entirely. Coming down with a case of food poisoning from raw milk is rare, but we’re talking about safety here.

You CAN still use raw milk to make yogurt, but you will need to make sure to heat it to the proper temperature. Lucky for us, the temperature required to properly denature specific proteins in the milk is higher than the temperature the milk needs to get to kill off all the bad bugs.

Lastly, don’t use milk that’s close to the end of its life. If the milk was left out or is past its expiry date, it shouldn’t be used regardless of how good it still looks. Spoilage may already have started, and that can interfere with the fermentation. No level of good bacteria can undo spoilage.

Heating Milk to the Correct Temperature

There are a few reasons why we want to heat milk to a specific temperature before introducing a yogurt starter, but since we’re talking about safety, we will focus on that.

Heating milk is a necessary step in yogurt making. If you have an unopened supply of UHT milk, this step can be skipped.  For all other types of milk, whether it is raw or pasteurized, this step should not be ignored.

Milk does not need to be boiled to kill off any existing bacteria, which is good, because boiling milk does not make good yogurt. According to this OSU leaflet, heating milk to 165°F (74°C) for at least 15 seconds is enough to pasteurize your milk.

Since yogurt making requires you to denature the whey proteins by heating it up in a range of 180°F to 200°F (82.2°C to 93.3°C), pasteurization doesn’t need to be an extra step.

I’ve run across many suggestions that you don’t need to heat your milk up to that high a temperature to make yogurt. I’m sure the results from not heating up milk still produce yogurt, but it is not safe. Contamination can occur at any step, and this is the best safeguard in the process.

Using a Safe Yogurt Starter

There are three ways to culture your yogurt. You can buy a commercially prepared starter that has multiple bacterial strains. It can be cultured from store-bought yogurt. Or, you can use your own yogurt from a previous batch.

All three of these methods are relatively safe, though some are obviously safer than others.

A commercially prepared culture is the safest because the bacterial strains are produced and packaged under strict standards.

A container of yogurt from the grocery store is also produced under strict standards, there is no real control for what happens to it after it’s opened. Consider how old it is, and if Uncle Henry contaminated it by eating directly from the container.

Making your own starter from a previous batch is a good balance between a commercially prepared yogurt and a commercially prepared starter. It’s economical, and you can package up enough for your next batch the minute the current batch is done. It’s not foolproof, but it is in your control. One downside is that cultures can lose strength after a few batches. Another disadvantage is that the starter should be used within a week.

Related: These yogurt makers are great for beginners.

Cool and Store Appropriately

Mina's bowl of yogurt

My daughter’s bowl of fresh homemade yogurt, complete with frozen wild blueberries.

As soon as the incubation period is done, your finished yogurt is mostly safe from a foreign bacterial invasion. It has become too acidic for most bacteria to gain a foothold in.

But it’s not entirely done. Your yogurt is going to keep fermenting until it cools completely, and even then, it will continue to ferment in your fridge at a much slower rate. Store your yogurt in a food-safe container with an airtight lid to keep the refrigerator smells out and freshness locked in.

Though the risk of spoilage is low, it still needs to be handled with the same common sense that all dairy products do. Use clean utensils to serve from the container. Keep it cold. Don’t leave it out for more than a few minutes before putting it back in the fridge.

And if it looks or smells funny, throw it out.

Conclusion

Overall, just how safe is making yogurt at home? I always use the recommendations I’ve laid out above, and I’ve never contaminated a batch in over 15 years.

For those of us who like to be in control of our food supply, making yogurt is one of the easiest ways to introduce yourself to self-sufficiency at home. It’s also one of the best ways to start teaching yourself about food safety when processing and fermenting at home. The level of safety required is more than average home cooking and food handling, but much less than other types of fermentation.

You may read other recommendations to buy bunches of tools. You most likely have everything you need in your kitchen to make yogurt safely at home. You may need to pick up a decent probe-style food thermometer and a dedicated food-safe container just for your yogurt.

And don’t forget to enjoy the fruits of your labor with a little fresh fruit and honey. Or maybe some nuts with maple syrup.