Powdered Sour source?
Hello everyone. . .first time long time. . .
I've been going through a Polish cookbook of mine with the desire to make Polish Rye like many places here in Chicago. Just wondering if anyone has a suggested source for "powdered sour" which the author describes as "An integral ingredient that gives Rye bread its distinctive mellow, tangy, sour flavor. Powdered sour is available at any quality baking supply house or through mail order"
1) What is a good source for this either online or in Chicago? A cursory search of the internet did not help me immediatley . . which leads me to
2) Searching for "powdered sour" reveals links to "powedered sour cream" . . same thing? related?
3) I do have an active starter, would using this at any point help eliminate the need for powdered sour? Any other suggested possible recipe substitutes?