Robert Poor’s Weblog

Maria and I bought an insulated cooler, able to hold eight of the wide-mouth quart jars I’m using for yogurt.  That, plus the nifty 50 Watt aquarium heater I modified, will do a good job in keeping all the yogurt incubating at 110 F.

So today I’m making eight quarts.

Yogurt Batch 081906 [A-G]

• Wash 8 wide mouth quart jars in heated dishwasher to make sure they’re clean.
• Fill each jar with 800 ml of low-fat (1%) organic milk.  This batch was from Costco.
• Heat the jars, 4 at a time, to 130F in a microwave oven.  This required 15 minutes for each batch in our little Sanyo microwave.  The milk started at about 40F, and I measured a 30F rise for each 5 minutes in the microwave.
• Stand the jars in a water bath in the insulated cooler with the aquarium heater — let stabilize to 110F.
• Added the following cultures for the different samples:
  • Sample 081906 A: 4 tbsp Mountain High yogurt
  • Sample 081906 B: 4 tbsp Mountain High yogurt
  • Sample 081906 C: 3 tbsp Mountain High yogurt (I was running out)
  • Sample 081906 D: 4 tbsp Pavel’s Russian Style yogurt
  • Sample 081906 E: 4 tbsp Pavel’s Russian Style yogurt
  • Sample 081906 F: 2 tbsp Pavel’s Russian Style yogurt
  • Sample 081906 G: 3 tbsp Pavel’s Russian Style yogurt
  • Sample 081906 H: 5 tbsp Pavel’s Russian Style yogurt (“shaken, not stirred”)
• Incubated all samples for 6.5 hours at 108F except for Sample 081906 A, which was incubated for 5.5 hours (we needed some yogurt in time for breakfast).
• Placed samples in refrigerator (40F) to halt incubation.

Incubation started at 0130. Should be done at 0800. More news then.
Notes
To mix the culture into the milk base, a bit of stirring followed by vigorous shaking appears to work well.

Don’t forget to measure how much water bath is in the cooler — if I know that, it will help me stabilize the temperature of the batch more quickly.

Results

Well, all the results were good.  There was generally very little difference between batches made with the two yogurt cultures (Mountain High and Pavell’s), and the system seemed quite tolerant of different amounts of culture: there was not a strong difference between five tablespoons and two tablespoons of culture.  Perhaps the two tablespoons batch (Sample 081906 F) was a bit “wigglier” and less creamy than the five tablespoon batch (Sample 081906 H), but the main lesson is that the process tolerates large variations in the amount of culture.