Posted by Kitty Sharkey , Friday, July 30, 2010 9:19 AM
The following quotations are from "Goats Produce Too! The Udder Real Thing Volume II - Cheese Making & more..." by Mary Jane Toth
GETTING GOOD GRADES IN YOUR HOME MILK SUPPLY
According to the USDA, milk should be cooled to 40 degrees in 30 minutes or less to meet their Grade-A Standards. Improper cooling can be the number one cause of off-flavored milk.
...milk is a perfect medium for bacteria. Unless you are doing a good job of cooling the milk to slow them down, the bacteria can be multiplying by the millions. This is true whether you pasteruize or drink the milk raw.
If you are at least a Grade-B, give yourself a pat on the back. This rating is very good for home use.
...bulk cooling tanks
This method assures milk will be at 40 degress or less within 30 minutes.
...containers small enough to place in tubs of ice water.
This method cools the milk to 48 degrees in 30 minutes, 42 degrees in 60 minutes, and 40 degrees in 90 minutes.
...small containers and placed in a sink of very cold water, with the water being changed 2 to 3 times.
This method cooled the milk to 60 degrees in 30 minutes, 52 degrees in 60 minutes, and was 50 degrees in 90 minutes.
Milk placed in freezer.
Cooled to 60 degrees in 30 minutes, 50 degrees in 60 minutes, 43 degrees in 90 minutes, finally reached 40 degrees in 105 minutes.
...placed in the refrigerator.
After 30 minutes the milk was 76 degrees, after 60 minutes it was 67 degrees, after 90 minutes it was 59 degrees, at 120 minutes 55 degrees, after 3 hours 51 degrees. Finally, after being in the refrigerator for 8 hours the milk was at 42 degrees.
So, as usual, I'm striving for perfection here at my homestead. When I read something like this, it becomes a challenge to me. How good am I doing? Can I do better without spending a ton of money or taking an excessive amount of time. I like to streamline my processes as much as possible.
Previously, I had been placing the milk into a sink with ice packs to cool it as quickly as I thought I could. But I never left it in there for 90 minutes. I had never really taken the temperature. I just waited a while (20-30 minutes?) and then put it in the refrigerator. It tasted good to me. And it made excellent cheese.
But now I had this book in hand that showed me I wasn't doing it good enough. After all my work to make my milking room and milking practices as sanitary as possible, I was defeating the purpose by not cooling my milk fast enough. My brain started working. Challenge on!
So after experimenting for a week or two with various ideas from circulating the milk in the pail while cooling to using my ice cream maker to speed the process, I think I've finally settled on the solution. Meet the contraption!
Here's the setup:
I purchased two pre-fab feet that are meant to be used for couches or chairs from the hardware store. I drilled holes into a 1/4" x 2" x 2' piece of lumber. After running the board through the handle of my trusty old mixer, I screwed the feet into the board. This placed the beaters about half way into the water. Not ideal, but good enough. Full immersion would probably be better. I'll play with heavier bottles to see if I can add more water to the sink for this purpose.
Next, the sink is filled with a couple inches of water and 4 ice packs. I leave the water to cool while I go milk my goats. When I get back in the house, the milk is approximately 90 degrees.
After straining the milk, it is placed in small jars in the sink of ice water. I use my digital themometer to first see what the temperature of the water is (48 degrees), and then place the probe in a bottle of the milk.
The beaters do a good job of circulating the cold water around the milk. This is supposed to cool the milk to whatever the water temperature is in 30 minutes or less. I'm still playing with the times. It cooled to 55 degrees in 10 minutes, but it took close to another 10 minutes to get it to 50. My guess is the water was warming up.
Once the temperature stabilizes and doesn't appear to be dropping rapidly any longer, I place the containers into the freezer. As you can see, I leave the probe in because I want to time the process.
Once I've achieved 40 degrees, the milk is transfered into quart jars and placed in the refrigerator.
And the results are in. I've used this process 3 times now.
Trial #1 - 29 minutes
Trial #2 - 40 minutes
Trial #3 - 32 minutes
Next time I'm going to try splitting the milk between 2 quart jars. This will allow me to increase the water depth. The result should be better water circulation and more surface contact. With any luck, I'll be at or under 30 minutes consistantly any day now. I just need to tweek the system a little bit more before it is perfected.
But I can tell you one thing. The milk definately tastes sweeter when it's cooled faster. Yummy and full of pro-biotic digestive goodness!