Archive | About RSS feed for this section

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.

i have a logo!

7 Aug

Thanks to the fantastic Alejandra Ponce de Leon and my fumbling around in Adobe Illustrator, I have a logo!  Watch for it to appear on my lessons, cards, stickers (!! inshallah), and snazzy apron.

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!

incubation experiments.4

1 Aug

Corrigan cleaned behind the counter at the bike shop the other day, and I snagged a big old thermos he was going to throw out. Instead of going through the whole yogurt making process, I filled it with hot water from the faucet, closed it up, and wrapped the whole thing in an insulation blanket I got from American Science & Surplus.


The temperature at 8:45, when I left for work, was 110°F, and when I returned home 11 hours later, at 7:45, it was at 95°F – a loss of only 15°F! I’m hopeful – today I’m going to heat some water on the stove to about 125°F and try a yogurt incubation experiment for the rest of the day. (Remember – the ideal yogurt-making temperature is 110°F.)

incubation experiments.2 & 3

30 Jul

It’s a little over 2 weeks before departure…and I have yet to successfully make yogurt outside of my kitchen.  I’m getting closer, but also more desperate.  I have a fourth experiment (no yogurt, just a temperature maintenance test) on my kitchen counter now – I’ll report back tomorrow on its success.  (It’s in a 30-year-old thermos rescued from the floor of Blackstone Bikes…so I have my doubts, but we’ll see.)

Experiment number 2 was a slight upgrade from sun experiment 1, which almost worked.  For this one, I simply stuck my yogurt jar in a black garbage bag, hoping to capture some of the sun’s heat and store it a little longer and hotter.  I sat it on the roof of Experimental Station all day long, on a consistently hot day.

At the end of the day…I had my first MISERABLE complete yogurt-making failure I can remember.  I was holding a hot jar of cream.  It smelled sweet and creamy and sour all at the same time.  I tossed it right down the drain.

Experiment number 3 was much more involved. I did some research on some awesome websites about solar ovens (I really want to make one out of an umbrella, but I don’t need to grill my yogurt, so it didn’t seem appropriate), and made one of my own.



I was excited, but also a little skeptical. Espeically of the hinge, which was screwed weakly into styrofoam. My worries turned out to be justified, because the top broke off the in wind on the way to Experimental Station.  No reflectors for me!  (I had intended to use the foil-covered roof as a reflector in the middle of the day and then close it as the sun sunk lower and cooler during the afternoon.)


In any case, this experiment definitely made yogurt, just really, really watery yogurt. I had my thermometer stuck in the top, in the shade, for the whole day, and checked it periodically. The temperature was fluctuating a LOT, so that likely had something to do with the mediocre results.

I have dreams of a fancy solar oven hooked up to solar panels and a heat storage center, with little pipes that run hot water from the super-thermos to the yogurt, like a little solar powered yogurt radiator.