How to detect tempering of a Milk Pouch

Second time in last 1 year, my wife suspected that milk supplied to us was not same as regular milk. It is easy for us to find out because we regularly remove cream from the milk and make ghee (butter). In fact, such home made ghee meets our ghee requirement and we never purchase ghee from outside. So, the reduction in quantity of cream is a direct indication of mixing of water in the milk.

Whenever she complained it our supplier, he merely said that I'm not aware - I'm just purchasing it from abc (whom we know for many years). We did not bother to cross check with abc because we don't have his contact number and he is living little far away from our place.

But one of our neighbour suggested that we purchase it from another supplier. And this is what we learnt. Here is a picture of Milk Pouch that is intact i.e., unopened before delivery to us.

Unopened Milk Pouch

Here is a picture of opened and sealed Milk Pouch. (Note: Click on the Picture to expand the view.)

Milk Pouch is opened and sealed on left hand side

So, little visual inspection is enough to find out if your supplier is mixing water in Milk Pouch or not. It is difficult to believe that this happened in spite of severe warning given to same person about 6 months back when we had suspected same mischief. And he had started supplying regular milk. But after 6 months - same mischief. What's way out? Keep on changing suppliers?