Soya salad was a type of food, a salad made from soybeans.

T'Vau, a Starfleet officer aboard the USS Jefferson Randolph Smith in the 2260s, was known to request soya salad with kelp, and topped with oil and vinegar, for breakfast. Fellow officer Tatyana Trofimov was surprised by this, given the mess the dish inevitably made of the Vulcan's uniform. (TOS novel: How Much for Just the Planet)