The MOMA Birthday Edition follow-up
November 8, 2008
All in the name of science, I sampled all eight jars of yogurt from last nights batch in various combinations. You may wish to refer back to the table at the end of the previous post to see the difference between each jar.
Q: Is there a difference between Nancy’s Organic Yogurt culture and Voskos Greet Style Yogurt culture?
A: Not a strong difference. Voskos may make a slightly tangier result — in a B vs D tasting, D was slightly tangier.
Q: What happens when you use almost sour milk as your base?
A: It’s not good! The sour milk gets sour-er. Jars A and E were so unpleasant that I set them aside and didn’t use them for more tasting. I could maybe use them in a cake recipe, but Maria’s birthday isn’t for several months.
Q: Does heating the base first make a difference?
A: There’s no evidence that heating the milk first makes a difference. B and F were indistinguishable, as were C and G. Note, however, that the milk was only heated up to 120F, whereas some recipes will call for heating to 180F. But since the point of pre-heating the milk is to kill bacteria that would prevent making a good batch, and since the batches seem fine without pre-heating, I think this step can be safely skipped in the future. (Do any readers have evidence to the contrary?)
Q: Does it make a difference whether the jar is tightly sealed or open during incubation?
A: YES! The answer is: don’t do it. The jars that were sealed during incubation ended up much runnier than those that were left open: the yogurt in jars C and G (which has been sealed) was runnier than yogurt in jars that were left open during incubation: B, D, F, H.
Other: Since I ran out of milk, I made the last jar (H) with my last remaining bit of liquid milk (200 ml) and with powdered milk, mixed with 4 tbsp of powder per cup of water (500 ml). It’s texture was fine, but once again, it had a peculiar taste — this time with a somewhat “chlorine-y” overtone. As I write this, I realize that’s the problem: I forgot to use filtered water and used plain tap water instead. Moral: if you’re going to use powdered milk, be sure to use good-tasting water.
The Yogurt Diaries, MOMA Birthday Edition
November 7, 2008
On this day in history: November 7 1929, The Museum of Modern Art in New York City opened.
Questions, always with the questions…
Today’s batch tries to answer a few different things:
- Is there a difference between Nancy’s Organic Yogurt culture and Voskos Greet Style Yogurt culture?
- What happens when you use almost sour milk as your base?
- Does warming the base first make a difference?
- Does it make a difference whether the jar is tightly sealed or open during incubation?
The process
As usual, I started with eight wide-mouth quart jars, cleaned and dried in the dishwasher. Each jar was given a label, A-H. The table below details the differences for each jar.
After filling the jars with 700 ml of base liquid (milk, or in one case, powdered milk, milk and water), I put four of them (A-D) in the microwave for 15 minutes. To the other four jars (E-H), I added 1/4 cup of culture, shook vigoursly and set them aside.
At the end of 15 minutes, I was hoping that the first four jars had gotten heated to at least 130 F, since many recipes call for heating the milk to 180 briefly in order to kill any bacterial. But when I measured, the liquid was only at 120 F. No matter — I went with that and put all eight jars (A-H) in the insulated cooler in a water bath. I inserted the aquarium heater and let the temperature of the liquids stabilize for an hour before adding culture to the jars that were previously too hot (A-D).
I gave all the jars an extra good shake to make sure the culture was mixed in, then removed the lids from half of the jars (see the table below for which jar got which treatment).
Culturing started at 9:30pm. I’m planning on a 7.5 hour incubation. That’s longer than usual, but I’ve been waking up at 5am regularly, so this is convenient.
Today’s Innovation
In the last batch, I put the aquarium heater in its own jar in the middle of the insulated cooler in order to keep it from falling into the water bath. My thought was that the thermal conductivity of the glass and water was good enough that everything would settle into the same temperature. It didn’t really work out that way — the water in the rest of the bath was 5 degrees cooler than the water in the jar with the heater.
Heater Holder
So in today’s batch, I simply cut a hole in the top of a plastic lid and used that to prop up the heater. While I was at it, I poked another hole in the lid and put the thermometer there — that’s much easier than dipping the thermostat in and waiting for it to stabilize each time I want to make a measurement.
This seems to be working well.
The Variants
| ID | base | culture | pre-heat? | sealed? |
|---|---|---|---|---|
| A | “old milk” 700 ml | Nancy’s 1/4 cup | Y | Y |
| B | Horizon 700 ml | Nancy’s 1/4 cup | Y | N |
| C | Horizon 700 ml | Voskos 1/4 cup | Y | Y |
| D | Horizon 700 ml | Voskos 1/4 cup | Y | N |
| E | “old milk” 700 ml | Nancy’s 1/4 cup | N | Y |
| F | Horizon 700 ml | Nancy’s 1/4 cup | N | N |
| G | Horizon 700 ml | Voskos 1/4 cup | N | Y |
| H | Horizon 200 ml, Water 500 ml, Powdered 8 tbsp | Nancy’s 1/4 cup | N | N |
Notes:
- “old milk” = Trader Joe’s Organic 1% with a date code of 19 October (today is 7 November). It’s not yet sour, but my nose detects a distinct tang.
- Horizon 1% = Horizon Dairies Organic 1% milk, purchased recently.
- Nancy’s = Nancy’s Organic Nonfat Yogurt, with L. acidophilus, S. thermophilus, L. bulgaris, L. casei, L. rhamnosus, B. bifidus
- Voskos = Voskos Greek Style Yogurt “Thick and Creamy Style”, with L. acidophilus, S. thermophilus, L. bulgaris, L. casei, B. bifidus. It turns out that the texture is a result of straining the yogurt, not due to any special culture.
- pre heat? = brought to 120 degrees F by putting in microwave for 15 minutes. My intention was to get it hotter — as high as 180 degrees F — in order to kill any lingering bacteria, but impatience won out.
- sealed? = cultured with the jar lid screwed on, otherwise left open for the duration of incubation.
The Results
You’ll have to check back on the next post.
The Yogurt Diaries
November 7, 2008
I’ve been remiss in describing the outcome of the previous batch. Here it is:
Taste Tests
- Sample 081017 A: 800 ml goat milk. At first I was hopeful for this, but for whatever reason, it didn’t set. It was slightly thicker than the original milk out of the carton, but not much. Perhaps goat’s milk is too acidic? This requires some research. Confession: I didn’t bother to taste it.
- Sample 081017 B: 800 ml Kirkland Vanilla Soy milk. As mentioned in the previous post, the Soy Milk did set nicely, which I would have predicted if I’d done some research. It’s texture is a little different than cow milk — it tends to form larger chunks, but not in a bad way. Truth of the matter is that I don’t like soy milk as much as cow milk. Perhaps I’ll teach myself to like it.
- Sample 081017 C: 800 ml water, 3/4 cups powdered milk. When I first tasted the powdered milk batch, I really didn’t like it as much as regular milk: it had a subtle “burned” taste to it, which is probably part of the process of making milk into powder, so I relegated it to the back of the fridge. But when my regular yogurt samples ran low after two weeks, I brought this one out and tasted it. Surprisingly, the burned taste had faded, so this ended up being perfectly good. See my note below about the economics of using powdered milk over regular milk, though.
- Sample 081017 D: 800 ml 1% Trader Joe’s Organic Milk, 1/4 cup powered milk. This one was regular milk with some powdered milk added. It may have been a little thicker than the other samples, but I would not promise that.
- Sample 081017 E: 800 ml 1% Kirkland Organic Milk. Good, everyday yogurt.
- Sample 081017 F: 800 ml 1% Kirkland Organic Milk. Ditto.
- Sample 081017 G: 800 ml 1% Trader Joe’s Organic Milk. Ditto. I couldn’t detect any difference between samples E, F (with Kirkland milk) from samples G, H (with Trader Joe’s milk).
- Sample 081017 H: 800 ml 1% Trader Joe’s Organic Milk. Ditto.
Note on the economics of using powdered milk versus whole milk
In local supermarkets, a gallon of 1% organic milk costs between $5.00 (on a good day) and $6.00. I’ve been purchasing it for about $5.50.
A 12 oz bag of Organic Valley Nonfat Dry Milk costs about $7.00, and has about 40 tablespoons. Although the ordinary directions call for 3 tablespoons per 8 ounces, they also suggest using “4-5 tablespoons for a richer taste.” If we use the metric that 40 tablespoons makes ten 8 ounce servings (80 ounces), that’s just 5/8 of a gallon for $7.00. If we made a full gallon, it would cost us $11.20 to make a full gallon. Not a particularly good bargain.
On the other hand, it is possible to buy powdered milk in bulk. But even then, the prices I see aren’t particularly good: Amazon (HerbalLoveShop.com ?!?) sells 5 lbs for $36. If 12 ounces of dry milk makes 5/8 gallons of liquid milk, then 5 lbs (80 ounces) will make 4.16 gallons of liquid milk. That’s still much more expensive than buying a gallon for $6.00.
The Yogurt Diaries
October 18, 2008
Today’s batch will be an exercise in different culture media. We have low-fat organic milk. We have organic powdered milk. We have goat’s milk. And we even have sweetened, vanilla flavored soy milk. I have little confidence that S Thermophilus and L Acidophilus will find soy milk a hospitable environment in which to grow, but I thought I should try with one sample.
Here are the samples, ready to be heated in the microwave (of course I remove the metal tops first).
Samples ready for pasteurization
As before, I heated up the quart jars, four at a time, in a microwave oven to bring the temperature of the contents up to 130.
Microwaving the milk
I’m incubating the samples in a water bath in an insulated cooler. To keep the temperature stable, I’m using an aquarium heater. So the heater won’t tip over (that could be very bad, electrically speaking), I put it in its own jar in the middle of the cooler.
Heater set for 110F
After heating the samples up in the microwave, I moved them to the insulated cooler, along with an aquarium heater, and let them sit until their temperature stabilized at 110 degrees.
I then added 1/4 cup (4tbsp) of Pavel’s Russian Style yogurt to each jar, shook vigorously to mix in the yogurt culture. Here, you can see the samples ready for incubation.
Ready for incubation
I incubated the batch for 6.5 hours. I was expecting a temperature of 110F, but when I measured the water bath after 6 hours it was at 105F. This is probably because the heater was in its own jar. The thermal conductivity is good, but this approach probably reduces the amount of convection currents in the water. (Note to self: in the future, consider an aquarium circulation pump.)
Here’s the line up of the samples. Each sample had 60 ml (1/4 cup) of Pavel’s yogurt added as a culture.
- Sample 081017 A: 800 ml goat milk
- Sample 081017 B: 800 ml Kirkland Vanilla Soy milk
- Sample 081017 C: 800 ml water, 3/4 cups powdered milk
- Sample 081017 D: 800 ml 1% Trader Joe’s Organic Milk, 1/4 cup powered milk
- Sample 081017 E: 800 ml 1% Kirkland Organic Milk
- Sample 081017 F: 800 ml 1% Kirkland Organic Milk
- Sample 081017 G: 800 ml 1% Trader Joe’s Organic Milk
- Sample 081017 H: 800 ml 1% Trader Joe’s Organic Milk
Surprisingly, all of the samples, including the soy milk based one, appeared to have set nicely.
In retrospect, I shouldn’t have been so surprised: I looked up “soy milk yogurt” on the web, and learned that sweetened soy milk is a perfectly good medium for culturing yogurt — you even use ordinary dairy yogurt as your starter.
The results of taste and texture tests will be next…
The Yogurt Diaries
October 17, 2008
Maria and I bought an insulated cooler, able to hold eight of the wide-mouth quart jars I’m using for yogurt. That, plus the nifty 50 Watt aquarium heater I modified, will do a good job in keeping all the yogurt incubating at 110 F.
So today I’m making eight quarts.
Yogurt Batch 081906 [A-G]
- Wash 8 wide mouth quart jars in heated dishwasher to make sure they’re clean.
- Fill each jar with 800 ml of low-fat (1%) organic milk. This batch was from Costco.
- Heat the jars, 4 at a time, to 130F in a microwave oven. This required 15 minutes for each batch in our little Sanyo microwave. The milk started at about 40F, and I measured a 30F rise for each 5 minutes in the microwave.
- Stand the jars in a water bath in the insulated cooler with the aquarium heater — let stabilize to 110F.
- Added the following cultures for the different samples:
- Sample 081906 A: 4 tbsp Mountain High yogurt
- Sample 081906 B: 4 tbsp Mountain High yogurt
- Sample 081906 C: 3 tbsp Mountain High yogurt (I was running out)
- Sample 081906 D: 4 tbsp Pavel’s Russian Style yogurt
- Sample 081906 E: 4 tbsp Pavel’s Russian Style yogurt
- Sample 081906 F: 2 tbsp Pavel’s Russian Style yogurt
- Sample 081906 G: 3 tbsp Pavel’s Russian Style yogurt
- Sample 081906 H: 5 tbsp Pavel’s Russian Style yogurt (“shaken, not stirred”)
- Incubated all samples for 6.5 hours at 108F except for Sample 081906 A, which was incubated for 5.5 hours (we needed some yogurt in time for breakfast).
- Placed samples in refrigerator (40F) to halt incubation.
Incubation started at 0130. Should be done at 0800. More news then.
Notes
To mix the culture into the milk base, a bit of stirring followed by vigorous shaking appears to work well.
Don’t forget to measure how much water bath is in the cooler — if I know that, it will help me stabilize the temperature of the batch more quickly.
Results
Well, all the results were good. There was generally very little difference between batches made with the two yogurt cultures (Mountain High and Pavell’s), and the system seemed quite tolerant of different amounts of culture: there was not a strong difference between five tablespoons and two tablespoons of culture. Perhaps the two tablespoons batch (Sample 081906 F) was a bit “wigglier” and less creamy than the five tablespoon batch (Sample 081906 H), but the main lesson is that the process tolerates large variations in the amount of culture.
The Yogurt Diaries
October 1, 2008
The ineffable Maria and I like yogurt smoothies for our daily breakfast. And we like to make them with organic yogurt, but organic yogurt is be expensive. So I’m re-learning how to make yogurt, partly so we can economically indulge in our daily smoothies, partly to see what variations in texture / tanginess we like.
Last night I made the first experimental batch. Here are the lab notes:
Yogurt Batch 081001 [A,B,C,D]
- Wash 4 one quart (~1 liter) wide mouth canning jars in the dishwasher with heated drying. This does a reasonable job of sterilizing the jars.
- Fill each jar with three cups (0.7 liters) of organic low-fat (1%) milk.
- Immerse in water bath (in this case, in a slow cooker), heat water bath to 110F (43.3C)
- Once the bath has reached the target temperature, stir in 4 tablespoons (0.06 liters) of live-culture yogurt purchased at the local supermarket. In this case, we used Mountain High All Natural Plain yogurt containing L.Bulfaricus, S, Thermophilus, L Acidophilus, B Bifidus and L Casei.
- Mix well! It required a surprising amount of stirring to get the yogurt broken up and distributed though the milk.
- Wrap the jars and water bath in an insulating blanket and incubate. The incubation times for each sample:
- Sample 081001 A: 3h40m
- Sample 081001 B: 5h00m
- Sample 081001 C: 6h20m
- Sample 081001 D: 7h40m
- Put sample in refrigerator to stop incubation process
Notes
- Note that in traditional recipes, one heats the milk to 180F (82C) and then cools it to 110F (43.3C) before adding the yogurt cultures. This is to kill any other critters in the milk. I skipped this step, relying on the freshness of the milk and the cleanliness of the jars. If I’m patient enough, I’ll include this step in a future batch to see if it makes a difference, but it does take time.
- I used a modified 50W aquarium heater to maintain the temperature of the water bath, and measured it with a cooking thermometer. The heater worked very well, and temperature variations appeared to be less than +/- 1 degree F.
Results
All four samples had a thin layer of curd floating on top which was textured and slightly thicker in consistency than the rest of the yogurt.
- Sample 081001 A: (3h40m) — Much too runny. Flavor was fine, but it was really like thick milk with a yogurt taste. Should work fine in a smoothie or over granola, though.
- Sample 081001 B: (5h00m) — Good. Thin texture, but firm enough to hold up in a spoon. Light flavor.
- Sample 081001 C: (6h20m) — Very good. Firmer texture, slightly tangy flavor but still very delicate compared to the mother culture.
- Sample 081001 D: (7h40m) — Very good. The top layer of curd was somewhat thicker, and I could convince myself that the flavor was tangier than 081001 C. As a pragmatic point, it’s not clear that the extra 1h20m incubation time makes a real difference.
Commentary
Since a gallon (128 oz) of organic milk costs $6 at Safeway, and a quart (32 oz) of organic yogurt costs $4, we’ve essentially reduced our cost from $0.125 per ounce to $0.047. Assuming we use the yogurt from a previous batch as the culture mother for the next, a quart of yogurt that used to cost $4 now costs $1.50.
I liked the results, especially Sample 081001 C (6h20m incubation). Shorter incubation produced a thinner texture, longer incubation didn’t appear to make much of a difference. Skipping the lengthy “heat to 180 and cool back down” step didn’t seem to hurt the results, but might be worth trying. Ideas for future batches:
- get an insulated cooler for incubation. it will leak less heat, and I will be able to incubate six quart jars at a time.
- use “russian style” yogurt as a culture.
- use goat’s milk
- use skim milk
- use water as a base and add powdered milk. (do they make organic powdered milk? is it less expensive?)
