One of the most common questions I get from users of my website has to do with reusing their current batch of yogurt to make their next batch. Being able to "reuse" or perpetuate the starter from one batch to the next can be a huge cost savings in making yogurt, completely eliminate packaging waste, and to gain even more control over the finished product as compared with starting from a new starter culture each time. But like a lot of my users, I have not had great success with keeping a starter going beyond four or five batches, before noticing a dropoff in quality of the finished yogurt. Until now that is.
As a quick review, the first time you make yogurt at home you need a starter and some milk. I recommend using 2-3 Tbs. of a high quality, store-bought, plain yogurt, such as Dannon or Stoneyfield. Alternatively, you can purchase freeze-dried cultures from health-food stores or online. Once you have made your first batch of yogurt, you can reserve 2-3 Tbs. of it to start your next batch, eliminating the need to buy more store-bought yogurt or cultures. Theoretically, this should work indefinitely, and in homes where yogurt making is a multi-generational tradition, it does. Yet, I have observed my yogurt starting to get less thick and less tangy by batch five, and have shied away from going beyond four batches for several years.
Back in June of this year, however, I decided to give perpetuating a culture another go. So I read up on yogurt cultures, and re-examined my process for defects. What I learned is that not all yogurt cultures are capable of continual perpetuation. Some cultures are "direct set", meaning that you use them once, and that is it. You need to buy new starter for each and every batch. Many freeze-dried cultures that accompany home yogurt makers are of this variety. Other cultures, however, are capable of being perpetuated indefinitely - under the right conditions. Two of the most common are almost always found together in good quality yogurt. They are Lactobacillus bulgaricus and Streptococcus thermophilus. They also happen to be the two strains found in Dannon plain yogurt, from which I started this latest experiment.
The other thing that I learned is that the longer your current batch of yogurt sticks around in the fridge, the less likely it is to be a good starter for the next batch. I sort of knew this intuitively, since we've all had yogurt go bad on us before we could finish it. But as long as the yogurt hadn't "turned", I figured it was okay. But if you think about the yogurt making process, the clock is ticking on those cultures for lack of anything to eat. Remember, the bacterial cultures in yogurt consume the lactose in the milk, converting it to lactic acid. This not only gives yogurt its distinctive tanginess, it also preserves the milk by creating an acid condition in which pathogenic bacteria will not grow. So your finished yogurt has much less lactose in it upon which the cultures can feed. Eventually, they run out of fuel entirely and die, and the bad bacteria moves in.
So how long is too long? I don't really know, and am open to comments from any biologists in the audience. But since June, we have been awash at our house in various forms of fresh berries followed by jams made from said berries. As a result, our yogurt consumption is way up. Our family of three has been ripping through a half gallon of yogurt in about seven to eight days. So the batch that will become the next starter is never more than 8 days old. However, we went out of town twice during this experiment, and I froze 2-3 Tbs. of the current batch, and picked it up anew upon our return. We will finish batch number seven this week (I know that's a whole lot of yogurt) and I will be making batch number eight this weekend. So far each batch has turned out just like the batch before it. Now I don't have commercial heating and freezing equipment in my home (I am sure you don't either) and there is certainly going to be variability in how cold it is in your fridge vs. mine. With that said, if you make a new batch - or freeze some starter from the current batch - within a seven or eight days, my results seem to indicate that you can keep these two strains going indefinitely. Time will tell of course, and I would not plan on freezing your cultures for more than a few weeks.
I will continue with this experiment for as long as I can, and provide updates in the form of comments to this thread. Please track my results and chime in with your own findings.
Friday, September 2, 2011
Wednesday, July 6, 2011
Is it Really Cheaper to Make Yogurt at Home?
"Is it really cheaper to make my own yogurt?" That is a question I get from a lot of visitors to my homemade yogurt website. It's a fair enough question, because many things simply cannot be made for less at home. Cream cheese, for example. Other items, like baby food, are clearly overpriced. But the "homemade vs. store-bought" argument is a specious one to me. Do the people who ask me "with all the heating/energy required, do you really save that much" put their own grocery bill to this level of scrutiny? Is it even possible to know how much of your paycheck went into producing the store-bought stuff in the form of agricultural and petroleum subsidies and tax breaks/credits for large-scale producers? Or how about the cost of disposing of the packaging waste? Regardless, I decided it would be a worthwhile exercise to calculate the numbers on my homemade yogurt process, to the best of my ability.
Prior to running these calculations, I advised users to look at the cost of the individual ingredients vs. plain yogurt itself. What you will typically find is that you can get a half gallon of milk for the same price as a quart of yogurt. Yet the only ingredients in a good quality plain yogurt are milk and active cultures. So why does the price double when milk becomes yogurt? Is it the active cultures? Certainly not. It must be all of that heating and energy cost, right? Let's have a closer look.
Let's first tackle the natural gas to heat the milk to 185F. If you've watched my videos, or made yogurt yourself, you know that it takes about a half an hour to take the milk from room temperature to 185. I accomplish this by turning my largest burner on high for the entire half an hour. In the manual for my rangetop, I learned that the input for that burner on the highest setting is 12,000 BTU per hour. Great! But when I look at my gas bill, I am being charged in units of one hundred cubic feet (CCF) of gas. Fear not, this gas usage conversion involves a very basic formula. One cubic foot of natural gas contains about 1,031 BTU. Therefore I divide 12,000 by 1031 and get 11.63 cubic feet. But remember, my bill is based units of 100 cubic feet. So I need to divide that figure by 100, and arrive at 0.1163 CCF per hour for my burner. Since I am only using the burner on high for a half an hour, that is 0.058 CCF. Finally, my natural gas provider charges me $0.819 per CCF. Rounding to the nearest penny, that is $0.048 (less than a nickel). Not exactly breaking the bank there either. But, there is still the electricty to consider.
Many users of my site have written to me saying that they don't use a heating pad to incubate their yogurt. This is either because they don't own one, or they can accomplish it with a thermal approach involving a cooler and hot water bottles. I have even heard of using a solar oven, which is basically a box with a clear lid on it, set out in the sun. I find these techniques inconsistent and cumbersome, and prefer the heating pad. But what is this preference costing me? This one is dead easy, using this electricity usage calculator. My heating pad uses 50 watts and my provider charges me $0.11 per kilowatt hour, which is $0.0055 per hour. So over the course of the seven hour incubation, it is costing me $0.04, rounded to the nearest penny.
So I can make a half gallon of super high quality yogurt, with no added ingredients, for $3.94 per half gallon, or $1.97 per quart. As I have already stated, I doubt you could find any store-bought yogurt using milk anywhere near the quality I am using. I suspect the best large-scale option would be Stonyfield Whole Milk Organic Plain Yogurt, which at present will set you back about $4 per quart. Another way to look at it would be to use your store brand milk, which is probably about $2.50 for a half gallon. That would bring your homemade yogurt cost down to about $1.38 per quart. Compare that with Dannon Plain Yogurt, which is probably about $3.30. Do you see the pattern there? Rendering milk into yogurt effective doubles the price when you buy store-bought. But where is the value added? All they are doing is heating the milk, adding cultures, incubating, and then chilling. When I do this at home, it adds exactly $0.25 or ~6% to the cost of the milk. So what about the other 120% associated with the store-bought stuff? It's called profit - or if you choose to make your own - savings. Your choice.
Prior to running these calculations, I advised users to look at the cost of the individual ingredients vs. plain yogurt itself. What you will typically find is that you can get a half gallon of milk for the same price as a quart of yogurt. Yet the only ingredients in a good quality plain yogurt are milk and active cultures. So why does the price double when milk becomes yogurt? Is it the active cultures? Certainly not. It must be all of that heating and energy cost, right? Let's have a closer look.
It's All About the Milk
For my homemade yogurt I use a half gallon of milk from a local dairy which costs me $3.69. Now these cows are grass fed on a family farm, and given no antibiotics or hormones. I doubt you could even find a yogurt on the market that uses milk of this quality. So plug in a suitable number for the milk in your area. Just remember that the better the quality of the milk you use, the better your yogurt will be.Get Cultured
So if you are making a batch of yogurt using your previous batch as a starter, your cost here is exactly $0. But let's say that this is your first batch, or you are starting over because your starter has become weak. 3 Tbs. of Dannon plain yogurt will set you back $0.16.All That Heat and Energy
So if the store-bought yogurt is actually a better deal - compared to making your own - the cost of heating the milk to 185 F and then incubating it on the heating pad for seven hours is going double the price of the milk and starter cultures. I have to admit that I had no idea how to calcuate either. So I pulled out my utility bills, and hit the interwebs.Let's first tackle the natural gas to heat the milk to 185F. If you've watched my videos, or made yogurt yourself, you know that it takes about a half an hour to take the milk from room temperature to 185. I accomplish this by turning my largest burner on high for the entire half an hour. In the manual for my rangetop, I learned that the input for that burner on the highest setting is 12,000 BTU per hour. Great! But when I look at my gas bill, I am being charged in units of one hundred cubic feet (CCF) of gas. Fear not, this gas usage conversion involves a very basic formula. One cubic foot of natural gas contains about 1,031 BTU. Therefore I divide 12,000 by 1031 and get 11.63 cubic feet. But remember, my bill is based units of 100 cubic feet. So I need to divide that figure by 100, and arrive at 0.1163 CCF per hour for my burner. Since I am only using the burner on high for a half an hour, that is 0.058 CCF. Finally, my natural gas provider charges me $0.819 per CCF. Rounding to the nearest penny, that is $0.048 (less than a nickel). Not exactly breaking the bank there either. But, there is still the electricty to consider.
Many users of my site have written to me saying that they don't use a heating pad to incubate their yogurt. This is either because they don't own one, or they can accomplish it with a thermal approach involving a cooler and hot water bottles. I have even heard of using a solar oven, which is basically a box with a clear lid on it, set out in the sun. I find these techniques inconsistent and cumbersome, and prefer the heating pad. But what is this preference costing me? This one is dead easy, using this electricity usage calculator. My heating pad uses 50 watts and my provider charges me $0.11 per kilowatt hour, which is $0.0055 per hour. So over the course of the seven hour incubation, it is costing me $0.04, rounded to the nearest penny.
Survey Says!
So if you are keeping score at home, you already know how much it is costing me to make my yogurt. But, endulge me just the same:| Milk | $3.69 |
| Active Cultures | $0.16 |
| Natural Gas | $0.05 |
| Electricity | $0.04 |
| Total | $3.94 |
So I can make a half gallon of super high quality yogurt, with no added ingredients, for $3.94 per half gallon, or $1.97 per quart. As I have already stated, I doubt you could find any store-bought yogurt using milk anywhere near the quality I am using. I suspect the best large-scale option would be Stonyfield Whole Milk Organic Plain Yogurt, which at present will set you back about $4 per quart. Another way to look at it would be to use your store brand milk, which is probably about $2.50 for a half gallon. That would bring your homemade yogurt cost down to about $1.38 per quart. Compare that with Dannon Plain Yogurt, which is probably about $3.30. Do you see the pattern there? Rendering milk into yogurt effective doubles the price when you buy store-bought. But where is the value added? All they are doing is heating the milk, adding cultures, incubating, and then chilling. When I do this at home, it adds exactly $0.25 or ~6% to the cost of the milk. So what about the other 120% associated with the store-bought stuff? It's called profit - or if you choose to make your own - savings. Your choice.
Sunday, January 16, 2011
Homemade Yougurt with Lactose-free Milk
A question I get a lot from visitors to my homemade yogurt website is: "Can I make homemade yogurt from lactose-free milk?". Strictly speaking, the answer is no… but yes.
Let me explain. Lactose is the sugar in all milk from mammals. Coconut, soy, almond and rice milk are not really milk, do not contain lactose, and will be the subject of a future blog post. So individuals who are lactose-intolerant typically cannot enjoy milk, and the reason is that they lack the enzyme lactase. Lactase breaks the lactose down into two simple sugars: glucose and galactose, which can easily be consumed by anyone who can ingest sugar.
It is worth noting that most of the world's population (as much as 70% by some estimates) lacks this enzyme after about the age of three or four. This is nature's way of weaning us off of our mother's milk. But variety is the spice of life, and some humans never lost the ability produce lactase. Primarily of Middle Eastern and European decent, these people went on to domesticate mammals and drink their milk. Other groups of people, like Native Americans, are almost exclusively lactose-intolerant, and therefore never domesticated mammals for their milk. So as a "disorder" it would be more accurate to say that a minority of people are "lactose-tolerant", since intolerance is the usual condition. But I digress…
So brands of milk like Lactaid have come on the market, specifically to address this issue of lactose-intolerance. If you look at the ingredient labels of regular cow milk, and a lactose-free brand, you will see that the sugar content is the same. Why would this be if the lactose was removed? Well, it is because Lactaid has lactose in it when it goes into the container. But it also has lactaid, the enzyme needed to break the lactose down into glucose and galactose. So it is true that the milk no longer has lactose when it gets to you — which is why they can market it that way — but it accomplishes this by converting it to two other sugars. The bacteria cultures in yogurt would do this anyway, so it actually saves them a step. This is why you can indeed make homemade yogurt from lactose-free milk, but not because there is no lactose in it. Rather, because lactase has been added for you.
It is worth noting that there is not much lactose left in yogurt even when you use regular old milk. As a result, many lactose-intolerant individuals can enjoy it. You might want to try a small amount of good quality plain yogurt, and if all goes well, start making your own. If that fails, use Lactaid or other lactose-free brand.
Let me explain. Lactose is the sugar in all milk from mammals. Coconut, soy, almond and rice milk are not really milk, do not contain lactose, and will be the subject of a future blog post. So individuals who are lactose-intolerant typically cannot enjoy milk, and the reason is that they lack the enzyme lactase. Lactase breaks the lactose down into two simple sugars: glucose and galactose, which can easily be consumed by anyone who can ingest sugar.
It is worth noting that most of the world's population (as much as 70% by some estimates) lacks this enzyme after about the age of three or four. This is nature's way of weaning us off of our mother's milk. But variety is the spice of life, and some humans never lost the ability produce lactase. Primarily of Middle Eastern and European decent, these people went on to domesticate mammals and drink their milk. Other groups of people, like Native Americans, are almost exclusively lactose-intolerant, and therefore never domesticated mammals for their milk. So as a "disorder" it would be more accurate to say that a minority of people are "lactose-tolerant", since intolerance is the usual condition. But I digress…
So brands of milk like Lactaid have come on the market, specifically to address this issue of lactose-intolerance. If you look at the ingredient labels of regular cow milk, and a lactose-free brand, you will see that the sugar content is the same. Why would this be if the lactose was removed? Well, it is because Lactaid has lactose in it when it goes into the container. But it also has lactaid, the enzyme needed to break the lactose down into glucose and galactose. So it is true that the milk no longer has lactose when it gets to you — which is why they can market it that way — but it accomplishes this by converting it to two other sugars. The bacteria cultures in yogurt would do this anyway, so it actually saves them a step. This is why you can indeed make homemade yogurt from lactose-free milk, but not because there is no lactose in it. Rather, because lactase has been added for you.
It is worth noting that there is not much lactose left in yogurt even when you use regular old milk. As a result, many lactose-intolerant individuals can enjoy it. You might want to try a small amount of good quality plain yogurt, and if all goes well, start making your own. If that fails, use Lactaid or other lactose-free brand.
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