Mozzarella Using Yogurt Starter - Curds Don't Knit

[SayCheese!]

Yesterday I made Mozzarella as usual (Mrs. KK recipe) but since I ran out of the C201 starter I usually use, I substituted 1/2 cup of plain Stonyfield yogurt.  I premixed the yogurt with 1 cup of milk and stirred it in as I would the C201. I did everything the same as I always do, waiting 1 hour  after adding yogurt, temp of milk kept at 90 degrees, then after the hour I added the usual 1/2 tab of vegetable rennet that I always use.  Clean break after 35 minutes, cut the curd, drained the whey several times, then let it drain overnight and waited for it to acidify.  Tested the acidity in the morning - around 5.0-5.2. Curds look good but didn't knit, and my Frankhauser stretch test failed too.  I am thinking the yogurt starter made the difference, but I am wondering why it didn't work...  Can anyone help me?  Thanks, BJ

[MrsKK]

How much milk?  If you did the five gallons that I do with that recipe, you needed 1-2/3 cups of yogurt to acidify the milk.

Don't give up on it - many times it takes up to 36 hours to be acidified enough to stretch, at room temperature.  Room temp varies quite a bit in my house, so I have to be flexible with this recipe.

[SayCheese!]

Oh, I forgot to say it was 1 gallon of milk.  (Thanks for the reply! :-))

[MrsKK]

Then you did use a good amount of yogurt.  Have you had any success in stretching it yet?

[SayCheese!]

Thanks for the response! No, it never would stretch....  I pressed it instead like a hard cheese but I don't really have any place to age it properly.  It really tastes like yogurt and is rather tart (acidic)!  I am wondering if I should have used less yogurt or combined it with a mesophilic starter? (I have packets of mesophilic starter).  Have you ever used a mesophilic starter instead of thermophilic for mozz?

[MrsKK]

No, mozzarella truly needs thermophilic starter.  Sorry it didn't work for you.