Regardless of whether it is a business lunch or dinner, manners can speak volumes about you as a professional. Dining etiquette is one form of etiquette which can be critical to your career and job search success.
Employers need to see you in social situations to see how you conduct yourself. This is especially true if the job you want requires a certain standard of conduct with clients and superiors.
You could be critically evaluated on your table manners and conduct. Interviews that last for several hours often extend through mealtimes, and the employer is gracious to host breakfast, lunch and/or dinner for you. The meal is a time to visit and interact, and this is always more important than the function of eating.
Remember, etiquette is about presenting yourself with the kind of polish that shows you can be taken seriously. It is also about being comfortable around people and making them comfortable around you.