the exact Defination is not know but here is what stephans curve suggests:
When an oral dose of carbohydrate is given and a plot against the oral ph is plotted against time, it results in what is called as stephans curve. There is a marked fall in ph following ingestion ofdietary carbohydrate which results in a fall of the curve.. Which gradually regains to normality in an hours time indicating rise in ph.
Repeated ingestion of dietary carbohyte is associted with fall inph for longer durations of time.(significance).