Thursday, August 13, 2009

"Body" -> The Bacteria In You, Yogurt

On most Sunday mornings, before we go to Church as a family, you will find me up in the morning eating my breakfast and, at the same time, making yogurt.

Normally, when I tell most people that I make my own yogurt, they look amazed. They think that making yogurt is exceptionally hard. However, yogurt has been made for almost 5000 years. So, if it was that hard to make, the heritage wouldn't be so old.

And making your own home made yogurt can be strangely addictive. This week I went up to visit my family and my Dad in Seattle, Washington. Every summer, I try to send the kids up to spend time at my Father's rather enormous spread outside of Seattle. While this is a great family experience that the kids will remember forever, it is rather lonely for my wife and myself, who are basically two peas in a pod, and we hate to be separated for this length of time.

This year, after my wife had been in Seattle for about week and half, I snuck out of
work, and came up to see them. There was a lot of hugs and smooches, we talked about about what the kids had been doing, and the how we missed each other.

After about 15 minutes, my wife looked deeply in my eyes, and she said, "And man, I really miss your yogurt."

Love finds it form in many ways, and evidently one of the way it finds my wife is in my bacteria growing art of yogurt making.

To make yogurt, you need the right tools.

With the right tools yogurt making is exceptionally fun and easy to do. You need to follow a simple set of steps. In this blog post we are going to look at making yogurt with me in my kitchen on Sunday morning.

Probably the most important thing to making your yogurt is simply having a good double boiler.

As a matter of fact, I have a variety of tools that I am going to show you. However, there are really only two critical tools: A thermometer and a double boiler.

So, what do you want in a double boiler? Well the question is how much yogurt are you going to eat in a week? If you are used to having a small little cup of yogurt every day, then you can get by with a small Faberware double boiler from Walmart.

"Well, I don't eat that much yogurt, so this sounds fine," you might say.

Before, you decide to replicate your yogurt habits, you need to ask yourself "why do I eat this much yogurt?" Chances are that the cost of the yogurt is pretty expensive. If you eat a lot of yogurt, the cost would simply be a lot of money. However, once you understand how to make yogurt, your cost is going to be just a little more than the raw cost of the milk.

For my wife and I, it might not be uncommon to fill up a 30 ounce glass with yogurt and eat it as a meal replacement. If you do this once per day, you need a much bigger batch of yogurt.

So, if you look at the picture up above, you will see how we make yogurt. It is one gallon of milk per week. So, in this case, you want a double boiler that can handle this amount of yogurt with some room to spare. For my weekly dose of 1 gallon of yogurt, I bought a 7 quarter double boiler. If you use my tools for making yogurt, having a bigger container is key.

If you decide to get a bigger double boiler, it is important to understand that double boilers basically coming in two flavors. The smaller double boiler is generally two sauce pans that nestle together. This is good for making things like melted chocolate and small doses of yogurt.

For the gallon size batches you need the big double boilers are made for soup stock. I recommend a nice stainless steel one, and you can buy them from either Overstock.com or Amazon.com. My seven quarter double boiler was bought from Overstock for $47. (My only complaint is that the bottom has a ridge, which makes it harder to clean. However, $47 is hard to beat.)

Now, we need to look at the other tools of the trade. The picture shows a nice hand held food processor. This is actually an unbelievable helpful tool. The important thing about this food processor is the attachment at the end of the mixer bar. You might be able to see that it is basically a Milkshake attachment. This attachment mixes yogurt brilliantly and quickly, and is a snap to clean up.



I wish I knew where to tell you to buy it. The maker of my mixer is Hamilton-Beach, and I bought it at Walmart. I was so impressed with it, that I was going to buy a backup and I went back to Walmart. Why they still have the same hand held food processor, they removed the milkshake mixer in the kit of accessories with the mixer. I was very disappointed.

However, you can just mix with normal mixer, or even a spoon (which I think is suboptimal, but will work in a pinch.)

The last thing to get to make sure that you can make yogurt is a thermometer. This is another place to be a bit picky. Now, if you are in a pinch, you can go to Walmart and get a candy thermometer for a little over a buck. However, it is all the nicer to get a yogurt specific thermometer.

While you can Google "Yogurt Thermometer," I use the Yogourmet version that has made it through hundreds of batches of yogurt. It is nice that the clip stands makes the dial stand out nicely on top of the double boiler. It also has key temperature markings on it. While it got a lower rating at Amazon, the people that complained where obviously misusing it (they put it into a high temp oven or dropped it).

Okay, so now you should have your milk, your double boiler, and your thermometer. What you do is fill the bottom of the double boiler with about an inch or two of water. If you never used a double boiler, the idea of a double boiler is ingenious. By having a lower container with water, the water will keep the temperature in the upper container to less than the boiling point. This is because the upper container is only heated by the steam of the the lower container, and the steam temperature is about 212 degrees.

By heating the milk in a double boiler, the temperature of the milk is raised to around 190-200 degrees and no higher. This is exactly what you want to do with the milk for you yogurt. You want to bring it to around 190-200 degrees.

(Post edit: See next entry in my blog. After 20 years of making yogurt, I got interested in the denature process. For a good rule of thumb, you want to bring the temperature up to 90C or roughly 195 degree Fahrenheit and let it sit at this high temperature for around 5 minutes to get the milk denatured. You'll need to experiment with this, since the milk sees some denaturization as you raise the temperature.)

So the process is simple enough. Put in water into the base of the double boiler, put on the second pan of the double boiler, then pour in your milk, and wait for the temperature to rise.

So, why are raising the temperature of the milk so high?

There are two reasons that are often mentioned, and only one that really makes sense to me. The first reason that does make sense to me is that you need to raise the temperature of the milk up to the place that the molecules relax, which will produce a better texture of milk. In my mind, this does make sense as most milk is already pasteurized, which should have caused the desired effect to happen (if this really does happen.)

(Again, after reading "Manufacturing Yogurt and Fermented Milks" by Ramesh C. Chandan, the research is clear that you need to leave the temperature up higher to denature the protein. Pasteurization only increases the milk temperature up to 161F for 15-20 seconds (Wikipedia), but this clearly doesn't cause the range of denaturization necessary to get good yogurt.)

The second reason makes a lot more sense: You raise the temperature up to really kill any bacteria in the milk. Why do we kill all the bacteria? So we can introduce new bacteria. Our bacteria that makes yogurt.

So back to our yogurt. We have taken out double boiler, our milk, and a stove and we are raising our temperature up to 190 degrees Fahrenheit. However, once the milk gets up to around 140 degrees, I suggest you add something special. That something special is non-fat dried milk.

In our family, we make the non-fat version of yogurt. When you buy store bought non-fat yogurt, it is very firm. The firmness of the yogurt is easy to get used to. However, the reason that the yogurt is so firm is because the manufacturer of the yogurt has added thickeners. Now, we could add thickeners, but we are going to use the non-fat milk to both thicken and increase the nutritional value of the yogurt we are making.

Now mind you, yogurt made without thickener is perfectly eatable. As a matter of fact, when I travel to Asia-Pacific for business, they normally put me up in pretty nice hotels. In these hotels, they almost always have yogurt in a great big bowl. And this yogurt is almost always more of a running type. A lot of people like this thinner yogurt, so this is maybe something that you'll want to try.

However, let us go back to putting in non-fat dried milk. As I said, you want to let the milk warm up just a bit so that the milk melts easier. I add roughly 25-28 ounces of non-fat instant dried milk to my one gallon of yogurt. This adds calcium, a bit of calories, and ups the protein. It also makes the yogurt much thicker, and more like US commercial yogurt.

Once you've added your non-fat dried milk, you can take your hand held food processor (or spoon) and mix it in until it is nice and smooth. Continue to watch the temperature of your milk, and once it hits 190-195 degrees, you can pull it off the stove. (Since I do this on a weekly basis, I have this timed just right. Once I start the double boiler and pour in the milk, I can put in the dried milk around 20 minutes into the heating cycle, and in 35 minutes the temperature is up to the point where I pull it off the stove.)

By the way, the secret of a double boiler is making sure that the bottom pan never runs out of water.

It might not be obvious, but when the milk is very cold, the steam actually rises, hits the bottom of the milk pan, and cools back into water and drops back into the bottom pan. This means that in the earlier stages of the heating, you lose very little water in the bottom pan. However, as the milk heats up, less and less steam goes back into water since the milk doesn't cool it much. You need to watch out for this, because you can actually boil all the bottom water away. Since you are looking at the milk, you might forget that without water, the bottom pan is going to get red hot. So, make sure you have enough water in the bottom pan and that it doesn't go dry.)


Now that the milk is up to 190-195 degrees, you simply pull the milk off of the burner. The goal now is to have the milk cooler to 115 degrees. When it hits 115 degrees, you simply take a store bought container of yogurt and mix it in with the milk. This is probably the trick to making yogurt. You need to make sure that the milk gets to the right temperature. You heated the milk to kill at the bacteria that might be in it. You need to get the milk to the point where it won't kill the yogurt bacteria.

If you wait for the milk to cool naturally, you will be waiting a very long time. It may take 1-1.5 hours for the milk to get to the right temperature. This is a very, very long time. If I waited for the milk to cool gradually, I would never make it to church.



Some people simply throw ice into the milk to cool it off, but this is going to make the yogurt much more thin and closer to water. If you've taken my advise, the double boiler is going to help you again.

The secret is to fill the bottom container for the double boiler with ice. I fill it almost 1/2 to 3/4 full. Once you have the ice in the bottom, you place the top contain onto the bottom. Since there is only a thin layer of metal between the ice and the milk, the milk will cool very quickly if you stir the milk at all. I will us the hand held mixer to stir the milk, and you will actually be able to see the temperature needle move. After 5-10 minutes, you will start to reach the right temperature.

At this point, you need a commercial container of yogurt as a starter. You can also buy packages of dry starter, but the store bought stuff works great. For the most part, almost any yogurt will work. I've used all types, since most yogurts claim they have live cultures (bacteria). As a matter of fact, if it doesn't work, it says that your store bought yogurt was somehow damaged. You might want to never buy the same brand of yogurt, or change stores. Yogurt without the live cultures isn't yogurt.

However, there is a down side to this. If the temperature gets too cold, the yogurt bacteria don't like replicating. So if the temperature gets under 100 degrees, you probably won't have very good yogurt. You need to grow the yogurt cultures in the perfect range of temperatures, which means that you need to have it around 105-115 degrees.

There are different ways of introducing the cultures. Some people like to take out a bit of milk and mix it with the culture. However, I just take 3-4 big dollups of yogurt (some times an entire small container of Yoplait) and just dump it into the yogurt. Again, if you dump in the yogurt when the milk is too hot, it will kill the bacteria. If, on the other hand, the milk is pretty cool, and you dump in a bunch of cold yogurt, you will lower the temperature too much.

For my gallon of milk, if I dump in a whole container, I know that the milk will lower from 115 degrees down to about 110. This is the perfect temperature for the yogurt bacteria to grow.

Once I've dumped in the yogurt, I take the mixer and give the whole milk container a good mix. You want to thoroughly mix the two together and get the bacteria spread into every part of the milk.

If you remember, you have been mixing the milk a lot. You mixed in the non-fat dried milk, you mixed the milk to cool it down in the double boiler, and you mixed the milk to get the yogurt culture spread. After all this mixing, you will normally find a very thick layer of bubbles on top of the yogurt. This layer of bubbles does not impact the yogurt at all from a creation standpoint. The bubble normally stay around during the next stage, and it makes the top of the yogurt look a little funny.

So, I normally get a very large strainer and skim off the worse of the offending bubbles. The bubbles get throw down the sink, and it does waste a little bit of milk. However, the top of the yogurt, when it is down, does look nicer. Just think of this routine as a bit of art work on your good.

After you are done with this, we need to now grow the yogurt. You can do this in the top of the double boiler, but this is not the best of all containers. I suggest that you find plastic containers or glass jars to transfer the yogurt into. Depending on the the method you will "culture" the yogurt (or allow the bacteria to grow), you want to make sure that the you don't get the yogurt and milk mixture to get too cold. So, generally your transfer your new mixture and quickly pick a method to culture the yogurt.

So now you have everything set up and ready to grow to make your yogurt. Here is where the next decision comes in. How should you keep the temperature at just the right level. There are several ways of doing this.

1. You can use the natural temperature of your just finished product to complete the process.

2. You can pop it into a warm environment

3. You can get a specialize yogurt warmer

If we look at the first of these three options, I have used yogurts own heat to be very successful in making yogurt. To do this correctly, you need to remember that we start to introduce the yogurt into the milk at 115 degrees. If you push that up just a bit (to maybe a 120) you won't kill the yogurt, and after you've introduce the yogurt into the milk, the temperature is still going to be 115 degrees. If you then wrap up the yogurt in a blanket and put it into an insulated container, the yogurt own internal heat will stay in the range of the temperature needed for the bacteria to grow for the next 3-4 hours, and the yogurt will come out just fine.


The rule of thumb when you use this method is that you want to make sure that the yogurt starts a little on the high side for temperature. If you introduce the yogurt into the milk at 100 degrees,it will cool to such and extent that the yogurt bacteria won't grow and make the yogurt that you want.

Another variate on this idea is to pour the new mixture into a wide mouth thermos and put the top on. Since the thermos holds the heat, the temperature will stay in the right range to make yogurt. When I was first making yogurt 25 years ago, I used this method with an old wide mouth container for my very first batch. I had read about yogurt making, and I'll never forget opening the container and being floored that the milk had turned from a liquid into a solid. It was amazing to me that first time.

The second way is very popular if you have the right type of oven. Some gas ovens have a pilot light running all the time. In this case, you can check what the temperature of your oven is. Chances are that the temperature of the oven is around 100-120 degrees, thus making this the perfect place to put your yogurt. Millions of batches of yogurt have been made this way.

Some people will take an insulated chest (like in method one) and then put the yogurt in the chest with a low wattage light bulb inside. The heat from the light bulb makes the chest the perfect temperature. Now, you need to be very careful to pick a low wattage bulb, but this method has been used a lot.

The last method is the one that is clearly the best to me. I show pictures of the specialized yogurt warmer. The one that I use is the Yogourmet Yogurt Maker, which is actually made in Canada. This is just a great piece of equipment, and nothing to go wrong on it. If you have followed the post this far, you know that the milk and yogurt mixture is in the top of your double boiler. If you think about it, you may not want to store your yogurt in this container. So, you have the option to transfer it out of the double boiler into a glass or plastic container for the growth phase as I mentioned before.

The Yogourmet maker is made of two pieces, a container that holds two quarts of your mix, and a bottom heating container. For my yogurt, I transfer the milk and yogurt mixture into the yogurt container. I then put a little warm water into the bottom heating element. This is also like another double boiler. The water in the bottom unit completely surrounds the yogurt container. Since I make a gallon of yogurt every week, I have two Yogourmet makers.

After putting in the mixture, I put the Yogourmet off to the side. When the yogurt is culturing, it does not like to be disturbed.

After 4 hours, I pop off the top. If you tilt the container side to side, you can see the miraculous event that just took place. The liquid milk has turned to nice solid, a little bit like jello.

Now don't panic if the yogurt looks a little runny, because it will firm up once you put it into the refrigerator and it cools down. If the mixture doesn't look solid at all, then something went wrong. Here are the normal culprits:

1. You put in the starter culture or yogurt when the milk was too hot. You killed the bacteria and they couldn't grow.

2. You never got the mixture warm enough. You allowed the mixture to cool so much that the bacteria could never grow.

3. You haven't waited long enough. Give it 2-3 more hours.

4. The original yogurt had dead cultures.

By the way, you can allow the yogurt to grow too long. The bacteria basically chew up the milk sugar, and create a structure that is solid. If you allow these bacteria to continue to grow, they will eat all of the milk sugar. You can normally tell that you left it in a bit too long because when you pop off the top, you will see a lot of yellow liquid on top. This liquid is simply whey protein, and is good for you. (Don't throw it away.) Over growing the bacteria doesn't hurt anything other than the yogurt being a bit more sour. Some people may even like this version. This is the fun of making your own yogurt.

Finally, I normally make a smoothy with my homemade yougurt. Normally a bunch of yogurt mixed up with a 20% of Pomegranate or Blueberry juice. You can put sugar in it, but I love it with just yogurt and juice. It has a bit of a twang and it is good stuff.

Yogurt has been around for thousands of years. There are thought to be numerous health benefits to yogurt, which are still a bit debated, but I'll list them here.

*Yogurt may help with weight loss.

*Yogurt may reduce the rate of infection with colds and bacteria.

*Yogurt may help women lower their rates of vaginal infections

Less debated is the fact that milk is a pretty cheap way of getting calcium and protein into your diet. So, yogurt has the benefits of being based on milk.

However, yogurt is definitely the preferred source of milk products for those that are partially lacking lactase in their system. Generally, if you are from European genetic stock, you can digest milk sugar or lactose because you have lactase in your system. However, many people from other parts of the world (southern Europe, African, and Asia) have a large portion of their population unable to digest this milk sugar.