Reinheitsgebot Standard, 1516

Reinheitsgebot, meaning "purity law" (and thankfully pre-dating Hitler by some 400 years), regulates that beer in Germany must contain only the following ingredients:

1. Barley. 
   
2. Hops. 
   
3. Yeast. 
   
4. Water. 

None more.  

But, hey big fella, what about:

• Rhoiso-alpha acids 
  
• Protease 
  
• Amyloglucosidase 
  
• Propylene glycol alginate 

Can't we put these bad-boys in? 

No. Fuck them.

Not even protease? 

Ok, but just protease.  That sounds sexy. 

Only, get that other shit out my beer.