I think that "There isn't any flour in the recipe" should be accepted as this is a more correct English form.
Why doesn't אין קמח במתכון mean "there's no flour in a recipe", and אין קמח בהמתכון for "no flour in the recipe"?
In writing "in the" and "in" are identical, the prefix -ב. In speech, "in the" is pronounced "ba-" and "in" pronounced "be-".
The same thing happens to two other prefixes: -ל and -כ.