Pliny, sometime around 50AD, wrote about lactic acid fermentation. This gives documentation to the process of fermenting vegetables to preserve them for my period of the 10th century. Crocks for fermenting vegetables and meats have been found all around the globe. So in the name of wonderful flavors and period food preparation both, I am putting boldly out into the sea of fermenting some cabbage (cheap if I foul up and must throw it out) and hoping that in a couple of weeks I will have a delicious sauerkraut. Apparently the Byzantine kitchen would have had an array of pots fermenting various vegetables and meats at any one time and every meal would have had the results as sauces, condiments and side dishes. The ancient Roman favorite Garum is the result of this sort of fermentation process.
Fermentation of cabbage seems to be found in nearly every culture. The Vikings were known to have soured cabbage, the Romans traveled with pots of it, and the peoples of Asia lifted it to amazing heights and probably were the originators of the process. For example: The Koreans make Kimchi and it is amazing! Some is only vegetable, but other types include fish. The traditional process was to cut it all up add brine and bury the closed pot in the ground for a couple months or more.
I own a crock and several heads of cabbage and sea salt. Now to put it all together!
Every tradition spices their fermentations differently. The options are amazing, the flavors stunning, and I am quite excited to be learning this ancient and marvelous practice.