Archive | Incubation experiments RSS feed for this section

non-dairy yogurt, experiment no.1

17 Apr

I was invited to speak as the Yogurt Pedaler for Earth Month at Ohio University this month. My primary “appearance” was at the Vegan Cooking Workshop. I was immediately suspicious of being invited to make milk products at a vegan event, but I was assured they were enthusiastic about the Yogurt Pedaler trying to get people to care about what they eat, regardless of its origin. I was in!

In preparation, I tried to make vegan yogurt.

I honestly didn’t do too much research, but what I did suggested it would be pretty easy, following the same method as real dairy yogurt. That was wrong.

This is the failed almond milk yogurt. I was surprised I couldn’t find plain non-dairy yogurt at the grocery store. (I have my own theories that it’s because it tastes gross – I’m definitely a purist when it comes to my yogurt, so far.) The yogurt made with soy milk didn’t turn out so well either:

I’ve learned a bit about the microbiology of incubation in yogurt making over the past year, but I’m still confused about how the yogurt cultures that live on lactose can thrive and work to make yogurt in a non-dairy home that has no lactose. The “live active cultures” advertised in the soy yogurt are the same as the ones found in real dairy yogurt, but I obviously don’t know if their presence is actually the cause of the soy yogurt’s yogurt-like texture. I have my doubts, honestly. I also suspect a large part of the failure of both of these experiments is because the soy milk and almond milk I used are both very, very processed and sweetened.

Next time, I am going to try the intriguing process I found in my google adventures of fermenting my soy milk with chili pepper stems, and I am going to try it with unsweetened soy milk. If I get really ambitious, I may try to make soy milk myself from soy beans. But I wouldn’t keep your fingers crossed.

incubation experiments.14

19 Aug

It’s my first “field” yogurt incubation experience! I was excited to make yogurt from Jersey milk, the same kind of milk I learned to make yogurt with back on the farm in France. Matt pulled a half gallon of straight milk for me – not “skimmed” down to the 4.5% milkfat required in whole milk for American supermarket standards. Kilgus yogurt is drinkable – not my favorite texture of yogurt, but how could I use any other cultures and any other milk while on the farm? After some struggles with the stove, thanks to Cooper’s guidance, I got the milk on the flame and Camlin and I sat back to wait patiently.

Of course, I let the milk overflow.

Not to be discouraged, however, I let it cool down…slowly. After an hour, it was finally cool enough to inoculate. I put the pot of milk in the freezer for some of that time, but I have since learned from David that due to some strange property of air, even immersing the pot in room temperature water would cool the yogurt faster. I set up my tea light and ceramic plate in the cooler in the garage, and I headed to the fair.

The next morning, I helped milk the cows, got distracted with the goats, and left the yogurt on the heat too long. The texture turned out fine – drinkable, like the Kilgus cultures – but it’s a bit sour for my liking.

incubation experiments.12&13

12 Aug

I’m getting down to the wire. At least the last two runny batches of yogurt were …yogurt…
This time, I decided to try my new heat dissipation method, using my new terracotta flowerpot plate, and testing my new yogurt jar (the exact replacement of the one I used in the past, which was kindly shattered by Mushkilla the cat).

The result: two more jars of burnt yogurt milk.

I felt the terracotta plate with my hand, and it was actually just as hot as the pilot light surface on my stove. Granted, that means it was so hot I couldn’t keep my hand there, so it’s a pretty imprecise comparison. What it does mean is that I think I will make two changes…with a third in the wings. First, I’m going to stop using my heat blanket and go back to dish towels. Second, the tea light is going back on the ground, because there is plenty of heat coming out of that candle without me propping it up closer to my yogurt. The third adjustment waiting in the wings will be the adjustment of the cooler top – I think it’s not really necessary to close it as much as I did, although a little bit of cover probably isn’t a bad idea. The problem with this method on the road is that the temperatures and atmospheric conditions will probably vary greatly, so I’ll have to keep a better eye on ambient air temperatures than I have been. That’s what my thermometer is for, right?

An addendum:
The backstory: I was lucky to have an internship at the Exploratorium Museum of Science, Art, and Human Perception in San Francisco during the summer of 2005. (Particularly, working with Peter Richards on the Invisible Dynamics project.) It was amazing. The museum is one of the most incredible institutions I have known, encouraging exploration and experimentation and creativity and curiosity like nowhere else.
And I had a realization: the Yogurt Pedaler is a perfect example of the Exploratorium’s ideas in practice: it’s a project about science, about art, and about exploring the way people perceive their environments. Creating and experimenting and asking questions and discovering answers are all a necessary part of the process, which is (and this is where my research from 2005 is manifested) not the artistic, scientific, or any one particular process working independently, but it’s all of them at work together.

incubation experiments.10&11

10 Aug

I have two runny jars of yogurt in my fridge. One is actually being strained right now…and has the right texture of yogurt, but isn’t sour at all. I’m perplexed by this – I used the same milk (Grass Point Farms whole milk) and cultures (Fage Total) as last time, and all three batches taste and smell completely different. Time for a little research…

And so I find, in Fundamental Food Microbiology by Bibek Ray (2004), that this creaminess and sweetness is likely due to this batch of yogurt having a higher ratio of Streptococcus thermophilus to Lactobacillus bulgaricus, resulting from fermentation (incubation) happening at a lower temperature:

“If the temperature is raised above 110°F, the Lactobacillus sp. dominates, causing more acid and less flavor production; at temperatures below 110°F, growth of Streptococcus sp. is favored, forming a product containing less acid and more flavor.”

These experiments were a further development of my tea light method. I decided to experiment with whether the material of my yogurt jar made a difference in the solidification of the yogurt – I’m thinking a lot about heat dissipation these days, through ceramic vs. glass. So, bringing the experiment another step toward what it will be like on the road, I also set the containers outside in the cooler. (The air was cooler, so when I woke up in the morning I closed the lid a little bit, propping it open with my tent poles. I think I’ll do this from the beginning from now on.)

So, the method works well enough. I still want my yogurt firmer throughout, however, instead of just thick at the bottom and all watery at the top, and I suspect this may contribute to the slightly bland and watery taste of the final yogurt (in addition to my not-favorite Fage cultures being somewhat bland, in my opinion), so tonight I’m going to try a couple more tea light methods on a ceramic tile to encourage more regular and even heat dissipation, like a pilot light, which (I discovered in lifting up the top of my stove) is certainly hotter than a tea light but whose heat is deflected from the stovetop by a metal tab and a heavy enameled metal stovetop.

incubation experiments.9

8 Aug

Another failure this morning…tea light burning, again. I never expected tea lights to be SO HOT!

Perhaps I should clarify – I incubate it wrapped in the silver heat blanket you see behind the jar, but with the bottom exposed so the heat gets to the yogurt (see incubation experiment 5). Looks like tonight I’ll try again, and this time I’ll do two more experiments – another like yesterday, and I think I’m going to go back to my dish towel method of before, to see how the heat distributes when it’s enveloped in cloth instead of metal.

HOWEVER, there is some not-bad news to report on the yogurt-making front! Yesterday’s mediocre, watery yogurt is now straining, and I am hopeful! Turns out the yogurt in the bottom of the jar was much creamier and more delicious in texture than the top part. :) So it’s over a sieve with some good ol’ cheesecloth (no invisible science that challenges and frustrates me there), and hopefully in under an hour I’ll have some nice thick “Greek” yogurt.

A note on cultures: This yogurt is not as sweet and delicious as I prefer in my favorite yogurt. It actually, no surprise here, tastes like the Fage yogurt that used as cultures, which I find a little bland-tasting for my liking. — Proof of what I’ve said that the yogurt you use as culture really does influence your final product!

An update to yesterday’s heat caveat: Last night I actually used my thermometer to measure the temperature of the milk when I added the cultures. It’s supposed to be at 120°F – which is surprisingly hot! Before I had a thermometer, I always decided when to add my cultures by waiting until the milk was hot enough for me to stick my finger in it for a couple of seconds…which turns out to be closer to the “ideal” incubation temperature of 105-110°F. I’m curious how important that temperature is now, and whether it really depends on local environmental conditions just as much (or more?) than the bacterial cultures contained in your yogurt jar.

incubation experiments.7&8

7 Aug

I woke up again this morning to two more yogurt failures. This is wearing on me, but at least I have two outliers to work with on the tea light method.

Last time it was burnt, so I added some distance this time. And I did it overnight, woke up after 4 hours and it was still lit, so I switched the candle and when I woke up 4 hours later the tea light was out…I’m not sure how long it had been out, but the jar was just sort of hot, so I don’t think it had blown out too recently. The yogurt is yogurt, but really runny. So I’m trying again tonight, with the tea light a little closer to the jar (on a can of cat food). Report forthcoming…

The other method I tried was one that I’ve heard works reliably for a few other people – fill some jars with boiling water and put them in a cooler with your yogurt and cultures…I did just that, just placing the tops on the jars and not closing them so my towel wouldn’t get soaked, and I woke up this morning to warm milk. What did I do wrong, those of you who use this method regularly?

I should say – the milk was possibly a little too warm when I added the cultures, so perhaps I killed some of the cultures by scalding them…I’m not sure whether or not I hope that’s the case, but it will teach me to be patient, yet again.

incubation experiments.5&6

1 Aug

Today I did a two-fer. Steven’s suggestion of a tea light imitating the pilot light I use in my kitchen was simple, and I tried the thermos jug again, with heated water and yogurt inside.

The results: minutes after removing their UFO wrapping foils, were diverse. The thermos yogurt is definitely yogurt – smells like it, and it’s got the texture of a very, very thin yogurt. We’ll see if it firms up enough in the fridge.

The tea light yogurt was a burnt failure. There’s even a nice little browned film on top. Next time I’m going to raise it up so the tea light isn’t directly under, possibly touching the jar.

Thanks to all of you who have helped sponsor these yogurt-making adventures – the failures as well as the successes! My Kickstarter fundraising goal was met, exceeded grandly, and my time is up. Keep an eye out for future updates, and thanks again!