Questions about yoghurt
AB Yoghurt is also known as yoghurt with acidophilus (Lactobacillus acidophilus) and bifidus (Bifidobacterium bifidus). The acidophilus and bifidus cultures are special bacteria that have been isolated from the human digestive track, and it is widely claimed that they have positive health effects on the human body. Whereas most bacteria in regular yoghurt do not survive passage through the stomach and intestinal system, the acidophilus and bifidus bacteria do. This means that they continue working throughout the intestinal system. The benefits claimed by consuming these cultures include reduced flatulence, improved regularity, fewer stomach and intestinal problems caused by the positive effect on controlling harmful bacteria in the digestive system.
Subculturing is the process by which you make yoghurt by adding a small amount of already made yoghurt to milk and incubating at the required temperature. This is a popular way of making yoghurt at home, but there are a variety of problems associated with this method.
One problem is that over time the bacteria in yoghurt die out, and the older the yoghurt is, the fewer live bacteria that are left to subculture from. Connected to this is the various strains of bacteria die out at different rates, which means that after subculturing a few times the bacteria remaining in the yoghurt often get out of balance. This can cause your yoghurt to be overly runny, or have an abnormally strong flavour. It is much more reliable to add yoghurt culture directly to your milk.
You should never subculture ABT or ABY culture if you want to grow probiotics.
To make yoghurt thicker there are a couple of things that you can do. Firstly you can drain the yoghurt and get rid of some of the excess liquid that way. Another option is to add 100 grams of skim milk powder to each litre of milk, then heating to 90 degrees before cooling to make the yoghurt, which gives a thicker set due to the increased amount of protein in the milk.
Type C ABY is probably a better culture to use than type C ABT because the mixture of thermophilus and bulgaricus strain of starter bacteria gives a thicker set.
In terms of procedures, one thing that you should be aware of is that if the milk is too cool when setting the yoghurt has a tendency to go ‘stringy’. If the milk is at or below 35 degrees when it is set this is a common problem. This is more common in winter than summer, as the outside temperature is cooler.