Author Topic: Making yogurt - heating milk with microwave?  (Read 375 times)

Offline awakephd

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Making yogurt - heating milk with microwave?
« on: May 30, 2014, 12:47:45 PM »
I have just added yogurt to my milk-product adventures, and initial results have been mostly fabulous. My question is how to make it more quickly and conveniently. Here's some history:

Batch 1: Made "by the book" -- carefully sterilized everything, heated whole milk (P&H) slowly to 180 degrees F and held it there for 30 minutes, cooled quickly in a cool water bath to 115 degrees, added some of the milk to about 2.5 oz. of Oikos Greek Yogurt (only plain, active-culture, no-additive yogurt I could find at the nearby store in a small quantity) and blended it. Added the mixture to the rest of the milk, and put it in the jars and the jars into the machine (Euro Cuisine YM80). I filled 4 jars, then added a smidgeon of gelatin, let it soften, stirred it in, and filled the remaining three jars. Incubated overnight, about 12 hours. Yogurt was well set, and after cooling I was amazed at the firmness of the texture of the jars without gelatin -- almost "Greek yogurt" firmness without straining! The jars with gelatin were fine, but more tendency to separate whey.

Batch 2: Decided to try a short cut -- heated milk in microwave, about 5.5 minutes total, checking temperature until reached 180 degrees. Allow to cool in the machine while I took a shower. After half an hour, still at 140 degrees or so, so I put in a cool water bath and brought down to 115. Stirred in another 2.5 oz. of Oikos and let it incubate -- only 9 hours this time. Set was okay, but not nearly as firm, and the texture seemed a bit grainy. It still tastes fabulous, and when I tried straining some, the results were excellent. But I'd really like to have the extra-firm set I achieved the first time, without straining.

So ... I did some searching here, found several descriptions by John (CH) using microwave to heat. Interestingly, his pictures seemed to show some of the same sort of graininess that I got in my microwave batch. Is this likely due to something the microwave is doing (perhaps localized over-heating)? Or is it perhaps a result of not holding at 180 degrees for 30 minutes? Or ???


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Offline awakephd

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Re: Making yogurt - heating milk with microwave?
« Reply #1 on: June 01, 2014, 07:11:38 PM »
A follow-up -- I have tried another batch using the microwave, but this time keeping the milk at (or near) 180 degrees for 30 minutes. After heating about 5.5 cups of milk to 180 degrees (took about 8 - 10 minutes in the microwave, but checking the temp along the way), I maintained the temperature by setting the power to 20 percent. (Actually, I also tried 10 percent -- not enough to keep the milk from cooling -- and 30 percent -- a bit too much.)

I then cooled it a cool water bath in the sink, poured some into some yogurt from my first batch and whisked it smooth, then combined it. Put it in the jars, and into the machine overnight, a bit less than 12 hours. The result was once again very firm -- much better than when I just heated to 180 and let it cool off without holding at temp for 30 minutes. Maybe not quite as smooth as my very first batch, made "by the book," but more than good enough -- and convenient enough -- to keep experimenting with this protocol.

Now I have a Rube Goldberg idea: constructing a plastic framework that can span over the turntable in my microwave, with a plastic paddle descending from the middle. As the turntable turns, the paddle would keep the milk stirred, making for more even heating. I can see it in my mind ... now if I can just figure out the best way to build it ...

Offline Schnecken Slayer

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Re: Making yogurt - heating milk with microwave?
« Reply #2 on: June 02, 2014, 02:21:07 PM »
That stirrer sounds like a good idea. The big problem with microwaves is hot spots.
-Bill
One day I will add something here...

Offline Hidri Mohamed

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Re: Making yogurt - heating milk with microwave?
« Reply #3 on: June 02, 2014, 03:15:55 PM »
Hi,

1-micro wave has destroyed the lactic flora
2-you can not control the temperature of milk
3-heated milk for destruction pathogenic germs and a large part of the flora trivial
4-Addition of powder skimmed milk 2-4% to increase the extract dry of milk ( yogurt more firm )

Heat treatment of milk for yoghurt production

-cow or Ewe 90-95°C during 3-5 minute or 85C° during 20 minute (recommend) or 63C° during 30 minute
-goat 90-95C° during 1 minute

incubation
-temperature 42-45°C ( 42°C= unctuous yogurt - 44°C= yogurt farm )
-acidity final 80-90°D (about 5 hours)

cooling at 4°C as soon as possible (refrigerator)

in the end you have a yogurt in 5 hours but we must follow the procedure is the international standard has prosedure

@+
Regards, Hidri

Offline awakephd

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Re: Making yogurt - heating milk with microwave?
« Reply #4 on: June 03, 2014, 03:33:06 PM »
Hi, Hidri. I am not entirely sure which questions or issues you were asking or addressing, so I apologize if my responses are off the mark.

1) My understanding is that 180 degrees for 30 minutes will destroy the lactic flora, regardless of whether the microwave is used or not -- yes?

2) In my first effort, I brought the milk up to 180 degrees, stirring and checking every minute until it got within 20 degrees, and then stirring and checking every 30 seconds. In the second effort, I brought it up to temperature, and then ran the microwave at 20% for 5 minutes at a time, stirring and checking each time. At this power setting, the temperature remained pretty constant.Obviously, there will be localized heating of the milk when the microwaves are acting on it ... I'm not sure how different this may be from the localized heating at the surface of the pan when heating on the stove with an element that cycles on and off.

3) Right, but as I understand it, the point of the heating and holding at heat is not just to kill germs; it is also to cause a change in the protein structure, resulting in a firmer set. I suspect there is also a bit of concentration of the milk happening, as some water is lost over the 30 minutes.

4) Using whole milk and holding at 180 degrees for 30 minutes, the firmness of the yogurt is remarkable, so I have not felt the need to add powdered milk.

As I reported in my second post, the second "microwave" batch that I made turned out very well indeed -- maybe just a bit less smooth in texture; I'm not entirely sure about that -- but very firmly set, and delicious. If I can make my "Rube Goldberg" stirring device, I think it will help to eliminate overly hot spots, but even without it, I am happy with this procedure, particularly in terms of its convenience.


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Offline Hidri Mohamed

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Re: Making yogurt - heating milk with microwave?
« Reply #5 on: June 03, 2014, 06:17:45 PM »
1) My understanding is that 180 degrees for 30 minutes will destroy the lactic flora, regardless of whether the microwave is used or not -- yes?

-180 °F during 30mn yes destroy the lactic flora but for 20 minutes  it is ok (recommend)

2) In my first effort, I brought the milk up to 180 degrees, stirring and checking every minute until it got within 20 degrees, and then stirring and checking every 30 seconds. In the second effort, I brought it up to temperature, and then ran the microwave at 20% for 5 minutes at a time, stirring and checking each time. At this power setting, the temperature remained pretty constant.Obviously, there will be localized heating of the milk when the microwaves are acting on it ... I'm not sure how different this may be from the localized heating at the surface of the pan when heating on the stove with an element that cycles on and off.

-the bacterium it is an alive creature, you saw a creature survi has waves of mirowave?

3) Right, but as I understand it, the point of the heating and holding at heat is not just to kill germs; it is also to cause a change in the protein structure, resulting in a firmer set. I suspect there is also a bit of concentration of the milk happening, as some water is lost over the 30 minutes.

4) Using whole milk and holding at 180 degrees for 30 minutes, the firmness of the yogurt is remarkable, so I have not felt the need to add powdered milk.

As I reported in my second post, the second "microwave" batch that I made turned out very well indeed -- maybe just a bit less smooth in texture; I'm not entirely sure about that -- but very firmly set, and delicious. If I can make my "Rube Goldberg" stirring device, I think it will help to eliminate overly hot spots, but even without it, I am happy with this procedure, particularly in terms of its convenience.

-heated milk for destruction pathogenic germs and a large part of the flora trivial only
-firmness depends on temperature incubation 42°C= unctuous yogurt - 44°C= yogurt farm
-powdered milk it is an option to have a firmer and creamy product
-milk does not lose water except has boiling 212 °F

why you leave 9 hour of incubation ?
-to reach good the aciditer 80-90°D

who acidifies milk ?
-bacteria which is present in milk and yoghurt (or or ferment yogurt)

how this acidified milk
-by the multiplication of bacteria

why it takes 9h to reach the final acidity
-because you destroyed most of the bactériequi this finds in raw milk
-because there are small quantity of bacteria (bacteria you gonna add to milk) by contribution to milk then it takes longer for multiplication

how to have a firmer yogurt
-incubation 44°C
-if it east can for your taste adds powdered milk

Tested my advisors
-you earn some time 4H
-you will have a tastier and richer yoghurt
-you will make yogurts has the scale professional



« Last Edit: June 04, 2014, 02:22:31 AM by Hidri Mohamed »
Regards, Hidri

Offline awakephd

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Re: Making yogurt - heating milk with microwave?
« Reply #6 on: June 05, 2014, 08:02:21 PM »
Hidri,

I am wondering if we are not quite communicating. There is an old saying around here: "If it ain't broke, don't fix it." For my purposes, my approach "ain't broke" -- in other words, it is working extremely well -- so I don't really want to make any changes.

Just to clarify two points: First, I have no access to raw milk, only pasteurized and homogenized. Thus, any flora in the milk before heating are not necessarily ones I want to wind up in the yogurt. In other words, killing ALL the bacteria in the heating phase is part of what I want to have happen. After I have cooled the milk back to 115 degrees F, I add in a starter with the desired active cultures.

Second, concerning water loss during the heating: water at room temperature gradually evaporates, right? The hotter the water -- or in this case, milk -- the greater the evaporation. No, it is not losing water nearly as quickly as it would if it were boiling, but yes, it is definitely losing water during 30 minutes held at 180 degrees.

Again, I am not entirely sure I have understood the direction you have in mind with your posts, so I apologize if I have responded in the wrong direction.