This is the 12924th most frequent Swedish word.
surdeg
Sourdough.
In this sentence, 'surdeg' is used to refer to the ingredient used in baking bread, specifically sourdough.
Jag bakade ett bröd med surdeg igår.
I baked a bread with sourdough yesterday.
Here, 'surdeg' refers to the process or practice of making and maintaining sourdough culture for baking.
Att börja med surdeg kan vara utmanande, men det är roligt.
Starting with sourdough can be challenging, but it's fun.
This usage explains what 'surdeg' is, emphasizing its nature as a fermentation agent and flavor contributor.