Costco shoppers divided over new 'sourdough' bread as critics say it's not the real thing

Costco's new Kirkland Signature olive and rosemary sourdough bread is a hit with many shoppers, but it's also renewed the debate about how many ingredients belong in genuine sourdough. For bread to be labeled sourdough, it should be leavened solely with a live sourdough culture, without commercial yeast or other leavening agents, and contain no additives or other ingredients like vinegar to mimic sourdough flavor or acidity, according to the Real Bread Campaign. "In 2015, Real Bread Campaign co-