As a general rule, I would discard any product where an unpleseant and/or bitter aroma is not exlicitly expected. Our senses of tase and smell are very good at distinguishing “good”, that is energy dense and clean, food from " bad", that is mostly rotten or contaminated, food. I have little experience with cheese making but if any doughs or yoghurts I make start to smell or taste bitter or otherwise off, it is usually because the microfauna got out of hamd and malign bacteria started overproducing.