One massive difference with West Germany was the absence of a Reinheitsgebot in the DDR. But it should be remembered that it had never been in force very long in this part of Germany. The law was only applied to the whole of Germany in 1906. Take out the two World Wars and you're only left with around 30 years.
Which doesn't mean all sorts of wacky ingredients were allowed. As we've already seen, sugar was only allowed in one type of beer, Doppel-Caramel. The non-Reinheitsgebot compliance was mostlu manifested through the use of unmalted grain.
"The barley rate refers to the exclusive use of barley malt. When using raw grain, this should be compared with the average amount of air-dried extract. The normal values for the air-dry extract are 75% malt, 80% rice and 65% barley. This results in the following application factors:
Rice 0.94 = 94% of the replaced amount of malt
Barley 1.15 = 115% of the replaced amount of malt.
Up to 25% of brewing malt can be replaced by raw grain, whereby the proportion is determined by instructions from the state planning commission. Rice or a milled product made from barley is understood as raw grain.
The composition of the barley brewing malts is left up to the manufacturer. Wheat malt must be used for Weissbier.
Water must comply with the requirements of § 2 of the regulation on the treatment of foodstuffs in the food trade of August 25th, 1956 (GBL.I, 1956, page 780). The manufacturer is free to decide how much cultured beer yeast to add according to the type of beer.
In the case of "Deutsches Porter", in addition to cultured beer yeast, Saccharomyces Brettanomyces is also permitted, for wheat beer, a type of cultured beer yeast and the bacterium Delbruckii. Biological acidification - mash or wort - with bacterium Delbruckii is permitted."
1960 TGL 7764, page 2.
Important there is the "Up to 25%". From evidence I've seen from a specific small brewery, it was usually no more than 20%. In posh styles like Pilsator, less than that. And a few beers intended for export - such as Wernesgrüner and Radeberger - were brewed all-malt.
I found the grains used slightly surprising. Well, one of them: rice. Which seems a bit exotic to me. Though, quickly polling a former DDR citizen (Dolores) revealed that rice was always available in the shops. She has no idea where it came from.
The final paragraph is dead interesting. Confirming the use of Brettanomyces in Porter and Lactobacillus delbruckii in Berlier Weisse. The latter also had to include wheat malt, which wasn't the case in West Berlin.
Almost forgot. Souring of the "mash or wort". That sounds like like souring and fermentation souring. Very interesting that kettle souring was specifically allowed.