Chipotle Mexican Grill revealed on Tuesday that federal prosecutors had expanded their inquiry into the company's multi-state outbreaks of food-borne illnesses, further threatening sales that declined steeply by the end of last year.

Recently, McDonald's, the world's iconic largest food service provider, has been (forgive the cliché) through the grinder. Poor performance has led to the departure of its CEO and plenty of critical attention in the business pages. Part of this story relates to the provenance, or origins, of its products: Chains that provide more upmarket "fast casual" dining such as Panera, Chipotle, and Shake Shack have brands that speak of freshness, health and trustworthy sourcing.