If you find yourself writing like a food critic, you may be heading the wrong direction with your narrative and doing too much work.
Clients are well aware of the fact that mystery shoppers are not food critics...and many are offended when the narratives head that way. When I was an editor, I was constantly removing opinion about food items at the client's request.
If it's a high-end restaurant, chances are there's a notable chef involved who feels very confident about his creations and only needs a few pieces of information from the shopper. They mainly want to know if items are fresh, served at the right temperatures and have an appetizing visual presentation.
If the sauce spilled over the edge of the plate, the ice cream was melted when it arrived or your steak was served well done after you asked for rare, those are important points. If you were served 3 pieces of something and a neighboring table received four, that's also important. If you felt the balsamic reduction didn't pair well with a fruit topping, that's probably something you should leave out of the narrative.
I've submitted well over 1,000 high-end restaurant narratives and don't think I've ever offered more than 5 sentences about a particular food item.