It is the kefiran that gives your kefir a thicker
consistency. You can encourage the production of kefiran and healthy
milk kefir grains by keeping your kefir in an area close to 25 degrees
celsius, by stirring it often, by using higher fat milk, and by using
milks that have lactose as the main sugar. This is such a universal
question that I answered it more in depth in a post. Read more about
making thicker kefir.
Both Milk Kefir and Water Kefir have an effervescent
quality. They get fizzy, just like pop (soda). In fact, if you cover it
nice and tight for a second ferment, it can get so fizzy that a pressure
build up can pop a top! Milk Kefir that you buy in the store is often
like drinkable yogurt with no fizz, but that is because they use
inhibitors to stop that action. Otherwise they would be blowing tops all
over the place!
Both kefir grains and traditional milk kefir made from
heirloom grains can be frozen, and still maintain biological action
with no diminished bacterial count.