0 Cold Start™ Yogurt Research & Testing

 Here's my experiment!
This is the data and information that I conducted while creating the Cold Start yogurt method & recipe. This data and information was collected during a three month period prior to naming and publishing my Cold Start yogurt recipe on June 22, 2019. You can find a Cold Start Yogurt FAQ post here.

110° vs Cold Start™ Experiment
I made two separate batches of Fairlife milk yogurt. I wanted to see if there was a difference in outcome with heating the milk to 110°F vs starting it cold at 42°F and letting the Instant Pot warm up the yogurt.

Batch #1: Heat to 110°
Milk Temp: 43°
Heated the milk on the boil cycle for 10 min.
The temp was 149°F, ice water bath to 110°.
Stirred in 1 Tablespoon of Walmart GV Light Greek yogurt
8 hours on the yogurt normal setting.
15 min prep.

Batch #2: - Cold Start™
Milk Temp: 44°F
stirred in 1 Tablespoon of Walmart GV Light Greek yogurt
8 hours on the yogurt normal setting.
2 min prep.

Incubation Time to Temperature - 100°-110° optimal incubation zone
Used a Thermapen digital thermometer to accurately test temperature in 3 different spots, not touching the bottom of the pot.
Time elapsed when temperature was measured in fahrenheit.

Batch A continued to increase in temp from 110° till it leveled off to a stable 107° temp at 50 minutes into incubation.
Batch B took 30 minutes to reach the optimal incubation zone for thermophilic yogurt to begin activation and begin fermenting the milk to make yogurt.

How long will it take for 2 cartons of Fairlife milk to reach incubation temp?
I tested 13 cups of 40°F water to see how long it would take for 2 bottles of Fairlife milk to come to temp in the IP Duo.
It took 23 minutes to reach 99°F
40 minutes to reach 107°, where it stayed there for the next 2 hours.

I was very surprised to see that 6.5 cups of 44°F Fairlife only took 40 min to reach 105°F and 13 cups of 40° water took 40 min to reach 107°F!

Let's take a peek!
Traditional method yogurt is typically set at the 5th-6th hour marks, so I checked the yogurt 5 hours later. The video above shows Batch (A)  at 5:15 and Batch (B) at 5:30. You can see a significant difference in firmness. You can also see Batch (A) has bubbles on the surface (from whisking to cool the milk and add the starter), whereas Batch (B) has a smooth, glossy surface.

Cold Start™Fairlife milk yogurt with the Eurocuisine strainer after 8 hours of straining. Using the OXO Good Grips digital scale
Strain or No Strain?
Straining your yogurt will give you a thicker, Greek style yogurt. The longer you strain your yogurt, the thicker it will be. Straining is a personal preference. What is thick to you may not be thick enough to another. Fairlife milk, when it is not strained, will give you a consistency somewhere between Greek and Traditional (thinner) yogurt. For your first batch of yogurt, I recommend chilling your yogurt first, then taking a spoonful of your chilled yogurt and stirring it into a bowl. If it is not thick enough for you, you will want to strain. (You can find LOTS of straining options on this post!) I like to use either coffee filters over a mesh strainer, or the Eurocuisine strainer.

See how thick and creamy this yogurt looks while pouring warm into the Eurocuisine strainer!

Fairlife milk has 50% more protein than regular dairy milk. The higher the fat and protein content, the thicker your yogurt will be. Also, if milk is heated to 180°, your yogurt will be more firm. This explains why Fairlife milk looks very set after incubation.

This video shows chilled Fairlife milk yogurt (not strained). It is very thick, but once stirred, it will thin to a consistency between Greek and traditional style yogurt.
Unstrained, chilled Fairlife Yogurt
This video shows what chilled Fairlife yogurt looks like before and after stirring. Stirring breaks the protein strands that are holding your yogurt together, allowing the whey to come through and thin your yogurt.

The video below shows the 3 finished Fairlife milk yogurts.
On the far right, chilled unstrained cold start yogurt, the middle, cold start yogurt strained with the Eurocuisine strainer, and on the far left, Heat to 110° yogurt strained with coffee filters. Both yogurts were strained overnight, for 8 hours.

Strained in the fridge for 8 hours right after incubation

Summary: Coffee filters were much better at extracting more whey, resulting in a very thick yogurt. EuroCuisine strainer yogurt is not as thick, but acceptable; it kept about 1/2 cup whey into the yogurt. Unstrained yogurt = about 50 oz (there was some yogurt stuck to the bottom, which I chose not to scrape out as it was grainy in texture).
Cost Comparison 
Fairlife Milk = $2.98 + 1 Tablespoon of WM Greek Yogurt = .04 cents 
*Does not include cost of sugar or vanilla extract.

The most expensive yogurt per oz/serving is the Fairlife yogurt that was strained very thick, using coffee filters. It had a creamy texture, and a very mild taste. The coffee filters also produced the clearest whey.

Next was the cold start Fairlife unstrained yogurt, producing a creamy texture with a moderately thick consistency, between Greek and traditional style thickness. It had a very mild taste. When compared to the 2% milk yogurt, it seemed to lack some of the depth of the traditional yogurt in taste, which is really hard to describe. If I had not compared the two yogurts, I wouldn't have noticed a difference.

The least expensive option is the regular pasteurized Costco 2% milk yogurt, using the Traditional Method,  strained with the EuroCuisine strainer, that made a reasonably thick yogurt, which is worth the cost, and 30 minutes waiting for your milk to heat and cool down. Side by side, it also won the taste test over Fairlife milk yogurt, having a slightly better taste, with depth, and flavor.

If you are lactose intolerant, your best option is to use Fairlife milk and make your yogurt, as doing this will still be less expensive than purchasing a specialty yogurt. You can use dairy milk to make a lactose free yogurt by incubating it for 15-24 hours, in which all the lactose is consumed, leaving a very tart, tangy yogurt. Using Fairlife can give you a milder yogurt that is lactose free.

Using the cold start method with Fairlife milk is a good option for those who don't want to fuss with heating/cooling/temp taking and straining their yogurt. Many moms love the fact that Fairlife milk is good for their kids as it is lower in sugar, has more protein and more calcium, a Win/Win for busy moms!


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