From Turkish steppes to our table: Homemade yogurt

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Homemade Sous-Vide Yogurt: 2-Layered Matcha

 I'm a bit of a little food nerd, especially when it comes to researching about a dish's cultural origins. 

Take yogurt, for instance. Did you know how impressively old its origins are? Most historical accounts date them as far back as the Neolithic age, where it was probably discovered with a happy accident on the steppes of Central Asia. In those times, nomadic herdsmen stored their fresh milk in gourds made of animal stomachs or intestines. For ease of traveling, those containers where often reused. Food historians speculate that such storage practice may have encouraged the inoculation of living organisms who grew with each new milking. Combined with the warm local temperatures of the region, constant jolting camel backs, a thermophilic friendly bacteria accidentally stumbling in...and oops, what do we have here? Thick, slightly tart and tangy, fermented milk - yogurt - which, incidentally, also has better preservation capabilities than fresh milk. 

The birthplace of yogurt is often attributed to either Turkey or Bulgaria, but its origin stories are quite numerous and almost semi-mythological. There are accounts of it being consumed all throughout the Middle East, where Indian records described eating yogurt with honey as "The Food of the Gods". Further west, ancient Greeks ate something called oxygala with honey, a product believed to be similar to the Greek yogurt that we all know today (oxy meant "sour", or "vinegar", and gala meant "milk"). Finally, in cooler regions such as Northern Europe, people fermented soured milk with mesophilic bacteria to make quark.

"Yogurt"'s etymology, as we use it today, is actually Turkish - from the word yoğurt. According to my good friend Wikipedia, it can either be related to the verb yoğurmak, which means "to knead", or "to be curdled, coagulated or to thicken"; or to the word yoğun, which means "thick" or "dense". Both make sense, right? 

Homemade Sous-Vide Yogurt: Durian

So you would think that after a couple of thousand years of cumulative experience from humanity, making yogurt should be pretty foolproof. ...Nope - Well, not always. But that may be partially my fault - I decided to put durian pulp through the fermentation process along with the milk. Durian, yes, the Hulk of all Mighty Smells... I'm still questioning myself as to why I initially thought that it sounded like such a brilliant innovative idea... But all details in due time.

The biggest surprise I had while researching this was how easily it could (should) be replicated at home. Making yogurt isn't something that had ever crossed my mind as our grocery stores are chock-full of it. However, being able to play with the flavors and make something that has become one of our modern diet's staples seemed intriguing. And then, my dad dropped this little challenge bomb: "Oh, yogurt is the easiest thing to do. In Vietnam, all I had to do was drop a dollop of yogourt in a pot of milk, left the whole thing there and when I came back - tadah! Yogurt!"

 Ok, well, challenge accepted.

 So. What do we need?

  • First of all, no specialty equipment (hint: "yogurt maker"): if nomadic tribes could create this on the back of a camel, I can very damn well manage in my kitchen. Besides, very very often, my answer to "Do you have this -insert specialty tool-?" will be something along the lines of "Ehhh well no, I kind of recycle this, put this together... and manage something ghetto-style to get it to do the function I need it to do". And as far as I am concerned, it has worked up to now. So no yogurt maker. My kitchen won't be losing to sunshine and a camel's hump, nu-uh. 
  • Friendly yogurt cultures, alive: The most common bacteria used to inoculate yogurt are Streptococcus thermophilus and Lactobacillus bulgaricus. They're otherwise also known as the live probiotics touted in commercial yogurt trends. These little guys basically feed on the sugar and protein found in milk, a process known as fermentation. As a digestion exchange (by-product), they release lactic acid, which then coagulates the milk into a soft yogurt curd. 
    (Fun fact: the milk sugar these organisms like chomping on so much is also known as "lactose" - which is why lactose-intolerant people will usually have an easier time tolerating yogurt that contains live microorganisms)
    There are 2 options here: 
    1) You can use freeze-dried yogurt cultures (In Canada, I believe the brand is called "Yogourmet"). 
    2) However, I find that the simplest route is to use commercial yogurt which lists "live microorganisms" in its ingredients list. Most probiotic yogurts will have them, but check to make sure. It is important that the microorganisms are specified to be alive. 
  • A controlled 90F (32C) to 115F (46C) environment: lower than that, the cultures won't thrive, and a higher temperature might kill them. I have read at one point that going up to 120F was alright, but personally I get cold sweats the moment the mercury hits 121F. So I'll say 115F to be safe (I'm still in the baby steps of yogurt making). 
  • A trusty thermometer: Yogurt cultures aren't fastidious, but they have brittle heartbeats and, like Goldilocks, can be quite dainty about their food's temperature. Their growth conditions really need to be just right. Moreover, I find instant-read thermometers to be very handy to have around a kitchen. A low-to-moderately priced one is worth investing in.
  • Clean jars: There is nice little document on the National Center for Home Food Preservation website which explains how to sterilize glass jars. Simply fill your jars with hot water and submerge them in boiling water for 10 minutes. Now, I don't know about your experience, but each time that I do that my jars rattle like glass maracas. If you feel as much angst as I do during those 10 minutes, know that I understand and empathize. 
  • Milk: Theoretically, you should be able to make yogurt with any kind of milk, as long as they contain a decent amount of sugar and protein (especially protein). People have been creating yogurt from goat, yak, water buffalo, and even horse milk way before they discovered bovines. So go wild! (heeheh puns). Know that full fat milk will produce a thicker yogurt than skim milk. As a matter of fact, I have noticed that most 0% commercial yogurts have added gelatin in them, which I suspect serves to hold the consistency together. 

    If you use skim milk, I recommend adding 2 tablespoons of skim milk powder for each cup of milk. The extra protein will allow for more coagulation = thicker yogurt.
Homemade Sous-Vide Yogurt: 2-Layered Matcha

 As for my yogurt experiments, I have tried to make matcha (green tea powder) and durian yogurts using ChefSteps' sous-vide method. The method itself turned out to be a bigger hassle than I thought it would be. Initially, I intended to combine LadyAndPups' Sous-Vide in the Oven (works like a charm!!) with ChefSteps' homemade yogurt recipe. However, I discovered on D-Day that my oven does not have a bread proofing option, which means that it can't go lower than 200F. 

 My alternative method was to water bathe my yogurt jars in 2 giant pots and monitor the temperature every 45 minutes to 1h. According to ChefSteps, the ideal temperature should be 110F, where yogurt cultures basically reach Nirvana, but if it remained between 100F-115F I was happy.  When needed, I'd recalibrate the temperature with a cup of boiling water. 

 A little trick here: the more volume your water bath has, the more stable its temperature will be.   

 I read a bit later that another method for people who, like me, do not have a proofing option, was to simply preheat the oven up 110F, and then turn it off. If the door isn't opened too regularly, the temperature should remain stable as it is a closed environment. I will try that next time.

 On to the flavors and results!
Homemade Matcha Yogurt - All mixed up with a spoonful of honey :3

 The matcha yogurt surprisingly separated into layers, so I believe that the matcha powder sedimented during fermentation because it was too heavy. However, I'm really happy with how that flavor turned out. I didn't add any sugar to my milk mixture prior to fermenting it, so it is more sour than the commercial varieties (similar to the "Plain" versions). When the two layers are churned up and mixed with a dollop of honey, however, it tastes de-li-cious! It's also immensely satisfying to see how silky and pristine the yogurt surface is when lifting off the lid for the first time. -Insert sigh of contentment-. 
Homemade Durian Yogurt - Considerably thicker (equivalent to Greek yogurt)

 The durian yogurt... welllll. Well. I don't know how to comment on it to be honest (I think the smell knocked the words out of my mouth). It's strong. I don't want to say pungent because I have experienced so much worse (Did you ever work in a pharmacy lab? Lab technicians please back me up - reconstituting Clindamycin or Cephalexin oral suspensions was absolutely foul). That being said, I must mention that even my mom shrunk away when I popped open the jar's lid the first night the yogurt was done. Surprisingly, however, it didn't smell or taste as strong the next day. From a cultural perspective, I found it okay. In terms of mouthfeel and taste-wise, the combination of durian creaminess and the yogurt's tangy acidity is what bothered me the most - it doesn't quite go together. Furthermore, I forgot to filter out the mashed durian pulp, so my yogurt turned out thick with durian fibers. 

Here's the recipe for the matcha yogurt - which I lovedlovedloved. I think I'll also keep experimenting with other flavors that can be infused in the milk, rather than added solids. Tea leaves, coffee, spices, flower petals... Aaahh, so many possibilities! 


Homemade Sous-Vide Yogurt: 2-Layered Matcha
Look how smooth and silky they look! I feel like a proud mama. 

 Homemade Sous-Vide 2-Layers Matcha Yogurt
(ChefSteps' Sous-Vide Method: 
With subscription: https://www.chefsteps.com/activities/easy-delicious-sous-vide-yogurt 
Without subscription: https://www.youtube.com/watch?v=PMInAL7JRRo)

 I recommend watching ChefSteps' video if this is your first time making homemade yogurt. I found it to be very helpful!

 Servings: 4 x 225 ml

 Ingredients:
3 1/3 cup skim milk (800g - Use weight if you choose full-fat milk)
1/3 cup + 2 TBSP skim milk powder (Omit if you choose full-fat milk)
2 TBSP matcha powder 
4 TBSP hot water 
40 g live-cultures yogurt (2 mounded TBSP) - I used Olympic's Probiotic Yogurt
4 sterilized 250 ml glass jars (See How-to here)

 Preparation: 
1. In a small bowl, dilute matcha powder in the 4 TBSP of hot water. Combine well until you obtain a thick green paste (Do not put the matcha directly into your milk - it is not easily miscible in a big volume of liquid). Set aside. 

 2. Set or preheat your oven to 110F (Feel blessed if your oven has a proofing option).

3. On low heat, warm the milk slowly up to at least 180F (82C). As it heats, continuously run a spatula on the bottom and sides of the pot to prevent scalding (I can't stress the slow heating enough. Milk's proteins are very fragile: the faster you heat it up, the more tiny milk curds you are likely to get in your product). Midway up to 180F, add your skim milk powder if you're using it. Mix thoroughly so that no milk solids sink to the bottom. 

N.B.: Why 180F? Well, milk has 2 types of proteins: whey and casein. Most proteins are initially like knots. For yogurt making, these knots first have to be unraveled into strands. Yogurt curd is basically a matrix of milk's protein strands, interwoven together (imagine braiding a basket), which forms a gel - that's the coagulation process. Some protein "knots" unravel more easily than others. Casein protein strands will naturally coagulate to form a yogurt curd as the bacteria start feasting.  Whey, however, needs a bit of prompting. Heating the milk to 180F does that - it uncoils these additional milk proteins (whey) so that they can later participate in the coagulation fun with casein = produces thicker and smoother yogurt. End of parenthesis.

4. Once your milk has reached 180F, add the matcha paste. Combine until well incorporated. If you overshoot 180F a bit, don't worry it's alright. Your yogurt will just be thicker. However, do not let your milk reach a full boil (complete curdling alert)

5. Remove milk from a stove and transfer to an ice bath, or let it cool down at room temperature. You want it to wind up at or below 110F (43C). 110F is your bacteria's comfort zone, so see it like you're setting up their welcome home party. 

6. While the milk cools down, prepare your water bath. You are aiming for it to have a temperature of 110F (43C). 

7. Spoon your live-culture yogurt into a little bowl. Add some of the warm milk to the yogurt and mix until smooth. Add yogurt mixture to the rest of the milk and stir until combined. 

8. Carefully pour yogurt mixture into sterilized glass jars. If you want to minimize having bubbles at the surface, pour it as if you were serving beer.

9. Place your jars into the water bath, and move the whole set into your preheated oven (I would check in for the first 30 minutes to monitor temperature variations. See how often you will need to come back to recalibrate it).
IMPORTANT: Once you have set your jars, do not, under any circumstances, shake or stir them. Yogurt cultures do not like to be disturbed while they're having their private moment, and your yogurt matrix won't set as smoothly. Let them do their job. 

 10. Allow to incubate for 5-8 hours. The longer it ferments, the thicker and more sour your yogurt will be. I found 5-6h to be my sweet taste spot.

11. Once your yogurt has set, chill in the fridge for at least 2 hours - it will firm up a bit. Your matcha yogurt should have separated into 2 nice layers: a pale green top, and a dark emerald shade at the bottom. 

12. Mix it all up and enjoy with a dollop of honey :) It's like a matcha latte in yogurt-form!

Homemade Matcha Yogurt - Nom!

References:
http://downtoearth.danone.com/2013/01/31/a-brief-history-of-yogurt/
https://en.wikipedia.org/wiki/Yogurt#cite_note-toygar-25
https://www.dairygoodness.ca/yogurt/how-yogurt-is-made

About the Author

Half-baker. Half-bookworm. Full-fledged daydreamer.

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