Where did sourdough bread come from?

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Tags

1. #cultured
2. #leavening
3. #remained
4. #brewing
5. #bread
6. #leavened
7. #yeast
8. #middle
9. #being
10. #process
11. #usual
12. #europe
13. #until
14. #replaced
15. #northern
16. #european
17. #purpose
18. #sourdough
19. #later
20. #popular
21. #usually
22. #flour