The two mustard brands mentioned in the crossword solutions are Guldens and Keens. Guldens is a brand of mustard that has been around since the late 1800s and is known for its spicy flavor. It is produced by Conagra Brands, Inc. and is available in both yellow and brown varieties. Keens is another popular mustard brand that has been around since the early 1900s. It is produced by the French's Food Company and is known for its mild flavor. Both brands are widely available in grocery stores and supermarkets.