what does this sentence translate to?
los limones, los limas y los melones son ejemplos de esta clase de comida.
You don't refer to food as being one a different class from another, you refer to them as being a different type from another. The sentence was phrased wrong in spanish to begin with. Son distintos tipos de comida, o distintos tipos de frutas, etc.
foods are classified, aren't they'
Analease, you should state "of this type of food", not class.
lemons, limes and melons are examples of this type of food.
los limones, las limas, los melones, todos son frutas
lemons, limes, and melons are examples of this class of food