I second this. I used to buy into the organic, grass fed, all natural, no antibiotic stuff all the time. I came to realize that no matter what you do, you will slip up somewhere. GMOs are in EVERYTHING nowadays. Even organic stuff. So it's best to just eat healthy and not worry about finding the most "pure" ingredients.
As far as the OPs original concern, I noticed that too. I can only speak from experience since I'm still on the liquid pre-op diet, that I had to experiment with a ton of different things before I found what worked for me. Currently, I drink Glucerna hunger smart. It keeps me satiated for several hours and sometimes I forget to even eat. Plus, its the most palatable of the protein drinks I've tried so far. It's always a good idea to make stuff from scratch because you know what goes in it and can avoid the extra sugars and fats. But in a pinch, protein drinks and other protein sources are helpful. But I wouldn't rely to heavily on it.
Good luck 👍