not an answer jenny but an observation on my point. I buy 4 pint plastic bottles of milk from the supermarket, one for the fridge & one goes in the freezer. I found that my milk was going 'off' so was spilling it away but discovered that the actual milk in the bottle was fine to use but the smell was coming from the neck part of the bottle & lid where it left traces of milk. My sense of smell is acute but I then would put some milk in a cup & ad boiled water - if it split....it's off but if it didn't & smelt ok....I used it. Check temperature in your fridge like someone mentioned