I'm not going to convert C to F so I'm not sure what 55C is in Fahrenheit. You have to be careful when choosing a temperature for a proteolysis rest. English malt is high modified with Kolbach as high as 45. To employ a proteolysis rest with malt highly modified like some English malt is, will create a very stable beer, but one lacking head retention. If you use Weyermann's standard brewers malt, not their under modified, they recommend a 20 minute rest at 122F. You can look up their recipes and you'll notice that a proteolysis rest is used. The Kolbach/SNR of their standard brewer's malt ranges between 38 and 42. If you are using Dingemann's malt, a higher temp in the proteolytic range will work. Always refer to the data sheet that comes with the malt. There are a few things on it that will help a brewer to decide on what temperatures will be needed during the proteolysis rest.
German and Belgian malt aren't high protein malt. The protein levels are brewers standard 8 to 12 percent. The high protein malts are six row and wheat, 12 to 16 percent.
You are right, the beer was loaded with protein. When the protein dropped out, head retention and flavor goes with it. Only a certain kind of protein contributes to head retention. The process used doesn't create the needed protein.
The whole business about modern malt not needing a rest in the proteolytic range was put to bed in the late 70s by Gambrinus malting. The firm disproved what the grade school teacher that came up with the nonsense, said. The problem is, what the grade school teacher spewed out, somehow entered the homebrewing world and became gospel. Just because the English method makes no concession for a proteolysis rest or that the malt is modern, doesn't mean that the rest won't benefit the final product. The English method is limited to a single temperature conversion at a set length of time. The method allows a brewer to make beer quickly and cheaply, but at the cost of producing a product that is unstable with reduced shelf life.
I use a proteolysis rest in every batch I brew. I use the tri-decoction method with under modified malt. However, there was a time in the early 90s when I couldn't procure under modified malt. I had to use standard modified European malt. I still incorporated a rest at 122 to 125F in the first decoction and a temperature around 135F, the higher end of the proteolytic range in the main mash. I didn't shorten rest times. There were no issues with head retention. I began homebrewing in 1982 going from syrup and powder to the all grain English method. Within five years I had it with brewing. The method did not produce what I wanted in a beer. The method itself became about as interesting as watching grass grow. In 1987, I began learning about the tri-decoction method and stuck with it since that day. There is no way that the English method can create the quality and stability in beer that the tri-decoction or Schmitz method creates, regardless of the malt being used. It is enzymatically, chemically and nutrient wise impossible.
