Where does the chlorine taste in yogurt come from? My parents used to make yogurt some years ago. When they tried to make some last month, it turned out very firm and smooth in appearence, but tasted like chlorine.

The taste is so strong that even strawberries couldn't get rid of it. Since then we have not tried making yogurt anymore.

Is the chlorine taste related to some fermentation level/age? Quality of milk?

Obs.: Though the chlorine taste was very strong, it wasn't sour.
Strangely enough, I do live near Campinas (where UNICAMP belongs), where water once was contaminated by human hormones! (Note the source is not in English.) I'm noticing the local water smells very strongly of chlorine; I wonder they're adding water to milk before selling it, or if the cows are drinking the water...
I will try buying milk from different towns to test my theory.