Saturday, August 2, 2008

Yogurt Success

As long as we're getting deliveries of fresh, whole milk and cream, I thought we should start making our own yogurt on a regular basis.

On my first attempt, I made the mistake of following instructions from a dairy cookbook, heating our unhomogenized whole milk to just 115 degrees (Fahrenheit) before inoculating is with some store-bought yogurt. I left it to incubate overnight in a cooler packed with jars of hot water. What I got was a runny, fermented sort of yogurt wanna-be. Why hadn't it firmed up?

Then I recalled our yogurt lessons from "food appreciation" classes when we had cooked the milk at 185 degrees. I went back and read the pertinent section in Harold McGee's "On Food and Cooking" and kicked myself for failing to remember that it isn't the bacteria that make the yogurt thick, it's the temperature.

Bacteria ferment the milk by noshing on lactose and making acid. That gives yogurt it's pleasant tang. The thickness occurs when the proteins in the milk are heated to a fairly high temperature. Heat concentrates the proteins and forces them to gather in thick chains. Commercial yogurt makers often add powdered milk and gelatin to achieve the thickness consumers are used to.

For this most recent batch, I mixed 3 1/2 cups whole, unhomogenized milk with 1/2 cup heavy cream and heated it slowly in a heavy saucepan to 195 degrees. I maintained that temperature for 10 minutes (according to McGee's instructions) before moving the pan to a cold water bath and lowering the temperature to 115 degrees, at which point I mixed in 3 tablespoons of our favorite commercial yogurt from Seven Stars Farm. I poured the mix into a warm quart jar and placed the jar in a cooler with a heavy pot full of hot water.

I placed an instant-read thermometer in the cooler, aiming to maintain a temperature of about 115 degrees. Turned out I didn't need to do anything further. The yogurt had firmed up after just a few hours, but I left it in the cooler overnight. The next morning it was thick and delicious. I couldn't wait to slice up a peach and smoother it in our fresh, whole-milk (with some cream) yogurt.

Without a doubt, this is the best yogurt I have ever tasted.

Note: take care not to boil or burn your milk. Use a very heavy saucepan and don't try to rush the milk to 195 degrees. Be gentle with the heat and stir frequently with a wooden spoon or heat-proof spatula to prevent the milk at the bottom of the pan from scalding.


Julia said...

Congratulations! It's always exciting to succeed at something so challenging in its precision.

frugalmom said...

I love making yogurt! I have a tutorial here that is even a bit easier than yours.

Charlotte said...

I too get gorgeous local milk from a rancher with a couple of Jersey cows, and since a gallon a week is too much for a single chick like myself, I've been making gorgeous yogurt for about a year. I use these instructions from a biology prof in Pennsylvannia:
They're bombproof -- I think I'm going to try his "basic cheese" next.

Ed Bruske said...

Julia, making yogurt is a thrill because you get to see science unfold right in your own kitchen. It's not hard to be successful making yogurt.

Frugalmom, thanks for the link. It is interesting how many different methods there are for making things like yogurt. I haven't done enough side-by-side comparisons to say which is the best. However, I would caution you about using skim milk and milk powder. I jsut finished reading "Real Food" by Nina Planck, wherein powdered milk is listed as one of the evil ingredients of the processed food world. I don't plan to use it.

Charlotte, thanks for the link. I am familiar with the professors web site and I've used it before as a reference. Good stuff. I haven't started making cheese yet. I would prefer to use raw milk.

De in D.C. said...

Thanks for this. I've been making our own yogurt off and on for a few years, and the past few months have been trying to thicken it up a bit. I've tried adding unflavored gelatin at various stages, but it just resulted in lumps. It sounds like I may just need to heat it longer - I was taking the milk to 150 then lowering to 110 and mixing in a half cup of commercial yogurt (with several strains of active cultures) then keeping it at 110 for anywhere from 12 to 24hrs. The longer time didn't result in thicker yogurt as you deducted; just tangier yogurt. I'll definitely try the higher heat next time.

Ed Bruske said...

De, heat is definitely the most important factor. This week I took my eyes off the pot for a few minutes and the tempt got up to 200 degrees. I was afraid of boiling the milk but kept it on 200 for 10 minutes making the usual adjustments (removing the pot from the electric element, etc.) It was the thickest yogurt yet. I think this is my new plan.