Valerie's Yoghurt & Yoghurt Cheese

[andiesenji]

I have been making this yogurt successfully for a while now & was wondering if I could use unpasteurised milk and not heat the milk to 80 degrees?  Any ideas?

You certainly should heat the milk to 85° C.  It is not just for pasteurization but also causes a change in the milk components that allow the yogurt cultures to convert the milk optimally during incubation. 

If you don't heat it to 85 degrees  then other bacteria, unwanted and potentially harmful, can multiply and inhibit the formation of the yogurt culture.

I know a lot of people who drink raw milk, use it in cooking and etc., but when they make cheese or yogurt they do heat it to the required temperature to allow the incubation and development of the DESIRABLE bacterial without invasion by the undesirable.

I posted the following a bit over a year ago:  It explains the specifics but includes Fahrenheit temps instead of C. 

I'm sure that in Australia you also have a dairy board that will offer the same advice. 

As I mentioned in an earlier post, as did Thermomixer, there is a chemical change in the milk after the pre-heating to a specific temperature, that allows the yogurt culture to change the structure of the milk solids - the casein proteins, of which there are four types in cow's milk. 
Without this process the culture can't "invade" the cells efficiently and there is the possibility that an undesirable organism (that is less fussy about the structure of the milk proteins) can propagate and produce what you describe as a "slimy" end result.

Pasteurization does not kill ALL the bacteria in milk.  There are always some organisms that are not exactly pathogenic but are also undesirable.   Without the heating to a high enough temp to inactivate these organisms, you will give them an opportunity to take over and actually prevent the development of the desirable bacteria.

Following is a quote from the California Milk Board:
"Yogurt is formed by the growth of two bacterial organisms in milk; Streptococcus thermophilus and Lactobacillus bulgaricus which turn the milk sugars into lactic acid. These are two separate bacteria that are active at different times during processing. Some times you will also find yogurt that contains other ""Probiotic"" cultures such as Lactobacillus acidophilus, Bifidobacterium longum, and Bifidobacterium infantis which are bacterium normally found in your intestines. Together these bacteria aid in digestion and the synthesis of vitamins. Here are the required steps. Heat milk to between 180 and 200 °F. Heating the milk is done for a few reasons. First, to sterilize/pasteurize the milk so that the yogurt bacteria/culture has a hospitable place to grow in. It is not desirable to incubate contaminating bacteria that might be present in the unsterilized milk. Heating should be done even with pasteurized milk to help make a smooth thick yogurt. Heating the milk also helps stop the whey from separating out quite as much. You must then cool milk to 115 °F and add yogurt culture. (If the milk is too hot it will kill the yogurt bacteria.) Stir in yogurt culture gently until dissolved. Hold temperature at 105 to 110 °F for approximately 8-10 hours. This allows your ""good"" bacteria to grow. The methods listed in the post are suitable for this. Finally, you must refrigerate the processed yogurt for at least two hours. Refrigeration help slow the continued bacterial growth. If yogurt is not refrigerated it will become sour."

[bigTcup]

Thankyou andiesenji, very much appreciated 

[andiesenji]

You are very welcome, bigTcup.

There was recently a bulletin issued by the L.A. County health dept. to advise anyone making homemade yogurt, cream cheese, caeso fresca, etc., to discard any that developed a pink or rosy color in the whey or the curds during incubation. 
Among the Hispanic population in one area of the county there was an outbreak of lysteria, a potentially dangerous bacteria and it can be passed by direct contact as well as in the air.  All the reported cases were from homemade product so there were no commercial recalls.

Better to be safe than sorry.

[Red Kell]

Well, I made my first ever batch of yogurt! 
It seemed to work fairly well. It isn't very thick though  ,I did read that it gets thicker each time you make using your old yogurt as a starter, so maybe there is still hope? It has a slightly gritty texture, not sure what from, but tastes wonderful with honey mixed through (I don't like natural), also with strawberries and museli. Mr 6 is onto his 3rd bowl of the day, so I think we'll get through the 2 liters OK

[jkmt]

Well done, Red Kell. It's taken me months to get my boys to eat my yoghurt - they used to go through bucketfulls of the shop stuff, so for a while we had a bit of a standoff - I wouldn't buy it, and they wouldn't eat mine!

It's possible that your yoghurt may be a bit thin because the incubation temperature hasn't been high enough. It needs to be maintained above 25 degrees for 6-12 hours. My kitchen was too cool for the Thermoserver to be effective on all but the hottest days. Now I have an electric yoghurt maker for incubation and turn out lovely thick yoghurt every time, using the same recipe.

[cathy79]

The gritty texture could be the thin skin that develops while the milk cools.  Early in my yoghurt making I didn't remove it, thinking it would blend through, but it definitely needs to be lifted off.

[Red Kell]

Thanks Cathy, that could well be it as I just stirred it through! Am due to make another batch in a day or stwo so I'll see if that makes a difference 

[Red Kell]

Well attempt two looks alot like attempt one! When it has finished doing it's thing and I take the lid off, it has separated. Most of it looks thick and yummy, but around the edges there is a really thin watery liquid. When it's all stirred through it looks and tastes like yogurt, but is fairly thin and runny. I like a much thicker yogurt Should I be trying to drain off the liquid rather than stirring it in? How can I get it thicker? HELP!!!!! 

[andiesenji]

Well attempt two looks alot like attempt one! When it has finished doing it's thing and I take the lid off, it has separated. Most of it looks thick and yummy, but around the edges there is a really thin watery liquid. When it's all stirred through it looks and tastes like yogurt, but is fairly thin and runny. I like a much thicker yogurt Should I be trying to drain off the liquid rather than stirring it in? How can I get it thicker? HELP!!!!! 

How long did you allow it to incubate?  At what temp did you incubate it?   Not enough time and too low a temperature (and a not sufficiently active culture) are the main reasons for this result. 

By all means strain it, use a coffee filter in a funnel unless you have the very fine, tightly woven cheesecloth, also called butter muslin or a muslin jelly bag. 
First try straining just a cup or so to see how it works.

[JulieO]

The liquid you talk about is the whey.  If you prefer a thicker yoghurt then drain off carefully.  Usually I drain off after refrigerating, but the other day, after removing the container from the incubator, I carefully tipped most of the whey out, put the lid back on and put into the fridge to chill. It turned out the same as when I leave it till after chilling.  

It does give a much thicker yoghurt doing this which is my preference than stirring the whey through.  

[Red Kell]

It was incubated for around 8 hours, in a thermoserver, in the oven with just the light on (I have heard this method recommended before). Next time I will try straining it and see how that goes. Mr 6 still likes it, but I like a much thicker yogurt. Mixed with homemade jam it makes great icy poles though 

[amajjika]

I have been making this yogurt successfully for a while now & was wondering if I could use unpasteurised milk and not heat the milk to 80 degrees?  Any ideas?

I just wanted to report that I have "successfully" made a large 2 litre batch of yoghurt using raw milk.
After doing a bit of online research, my criteria for "successful" was not to create the same thick consistency of pasteurised versions but that I had hoped it would indeed set.

I gently heated the milk to 42 deg C in the  using a thermometer to test the actual temperature of the milk rather than rely on the Thermomix temperature.
I added 1/4 cup of organic yoghurt (which was made from pasteurised milk) and poured it all into a pre-warmed thermoserver.  I put it into my dehydrater for 8 hours set on 40 degrees C and then put it in the fridge overnight.

It certainly set, but as other people have described there is a high degree of whey.  The resulting flavour was very mild, almost bland I would say initially but as a day passed there was more of a yoghurt taste.  They whey is fine to eat/drink as it does not really taste tart or "smelly" like when I make curds and whey from culturing raw milk.

2 litres of yoghurt is ALOT though so next time I'll try half quantities.  The excess is being successfully channelled into a plethora of fruit lassi's.

After having patiently read this thread from start to finish, and seen a great episode of Gourmet Farmer with Matthew Evans making his own ricotta... I am definitely going to work up to making cheese and ordering from the cheese culture place recommended in an early post.
Cheers and thanks everyone for your contributions to this informative thread.

[andiesenji]

I don't want to be an alarmist but, I have a word of warning.  If you do not pasteurize the milk and don't heat it to 85° C, to start the process,  do not feed it to infants or toddlers, elderly people or anyone with compromised immune systems.

Lysteria can be tolerated by healthy adults but not by any of the above and incubating the raw milk gives it an ideal growth medium.

I don't have any information about outbreaks in Australia but there was a significant outbreak in New Zealand a few years ago.  As I recall it was from fresh cheese made from raw milk.  
The life of the organism, if not given further material to expand into, will die in about 45 days so cheeses aged longer than 60 days are considered safe, as long as they have not been continually washed in raw milk (how some cheeses are processed while aging).  

Fortunately Australia has been free of Brucellosis for many years so you don't have to worry about that the way we do in the U.S., Europe and Central Asia.

[amajjika]

I don't want to be an alarmist but, I have a word of warning.  If you do not pasteurize the milk and don't heat it to 85° C, to start the process,  do not feed it to infants or toddlers, elderly people or anyone with compromised immune systems.

I don't believe you are being alarmist - people should be made aware of potential problems from eating raw dairy.  To your list of people who should not eat raw dairy I would add pregnant or lactating mothers, if this is a concern for people.  Thanks for bringing this to everyone's attention.

However, I have made a conscious decision to eat raw dairy as much as possible and have done so for many years without a problem.  Just like people have a right to smoke, the food I choose to eat is as much a political statement as it is a health choice.  I encourage everyone to do their own EXTENSIVE research and make up their own mind.  There are alot of arguements for and against.

[pippa]

The gritty texture could be the thin skin that develops while the milk cools.  Early in my yoghurt making I didn't remove it, thinking it would blend through, but it definitely needs to be lifted off.

Just clarifying - does everyone get a skin on their milk then?  I thought it was just me.  Do you just let it form and then lift it off at the end?