Using the brew enhancer that's all dextrose & ferment temps going too high will produce acetaldahyde in larger quantities than normal. It is one of the by products of fermentation that is eaten by the yeast cells after all the sugars are metabolized. But if too much is present,they won't eat it all,& you taste green apples.
To be precise,the Cooper's ale yeast produces non-descript fruity esters. That is to say,a fruity flavor that doesn't taste like a particular fruit. Just a general sort of fruit flavor that enhances any other fruity flavor present. Including acetaldahyde's green apple flavor.
right O thanks for the help brewers~! i went and helped a buddy brew the other day and wow nothing beats physically helping and picking his brain all day~ learned soo much!