Sorry for the late reply but here's as promised.
There's two common ways to charge, first way is by day rate, let the client have choice of half day or full day. The second way is by per image or per item charge. You must decide which way you wanna go that will benefit you more. Discuss/interview the client first to find out the requirement and then decide on the way that you can profit more or rather, won't get bullied so much. For example if the client specify they got 10 dishes, 2 angle/style/crop per dish, you are probably looking at 20 pics. If it sounds like its going to take many days to shoot that 20 pics, (due to preparation by their side, availability of only certain hours, requiring the participation of other resources like location, other people, time of the day, etc) then go by day rate to maximise your profit. If it sounds like you can complete all in a day, then go by per image charge because it is easier to understand for the client.
When you plan how much you want to charge, you need to factor in worst case scenario, like what if your lights get stolen or destroyed and you need to rent? That is about $150 rent rate per day for lights, another $150 for camera plus lens. Buffer for stuff like that to ensure you still earn money for your time and efforts in case of such bad situations.
FYI, a food stylist can charge more than a photographer. Bigger jobs will have art direction from a production company, a food stylist, copywriters for the text. This is a good thing, the more professionals are involved, the better the client's management of resources will be because everyone charges for their time. Individual job responsibility are also clear cut.
A common budget rate for pro food photography is $100 to $150 per picture. If you feel confident of producing magazine quality photos, go ahead and charge at least $100 per picture and keep increasing your price till your market will bear.
Then again, if you are just not there yet, please do not enter the market and bring down the industry. No offenses meant to you truly but these threads are emerging quite too much lately. I said it before and I will say it yet again: Either do it the proper way like a pro or don't do it at all. No half way stuff. No half bucket water like so many hobby people on clubsnap charging peanuts, producing subpar visual jokes.
Good luck.