Does an employee get paid for time spent taking a client to lunch?

I work as a designer for a small home construction company. I have recently changed to part time hourly. My employer, who is the owner and sales person, scheduled a meeting for me with a client to select products and finishes for her project at various supplier showrooms away from my office. These meetings often are long, sometimes lasting up to 5 hrs. The client was very hungry midway through our meeting so I took her to lunch. I paid for the meal and will be reimbursed by my employer. He will not pay me for the hour we spent at the restaurant, claiming it was my lunch hour. I contend that it is a part of doing business, and it was not my own personal time and related to a project. He has always encouraged me to take clients to lunch (when I was on salary), but I did not think he intended as my personal time. Please inform me if I have a legal claim for my wage to be paid, because this situation is likely to happen again.