I usually have a bottle of Chinese oyster sauce in my fridge, for use in preparing various Asian dishes. Whenever I open a fresh bottle of it, it comes out with a thick consistency, similar to that of ketchup.
The bottle invariably says it should be refrigerated after opening, which I do. Within a few days I find it has become much thinner, about the thickness of table cream.
I have tried a few brands, and they all do this. Does anyone know why this happens, and what, if anything, can be done to prevent it?