Try the International Food Service Executives Association (https://www.ifsea.org/). Their membership is incredibly broad. You can also try connecting with them on LinkedIn. The hard part is finding the first couple of executives, if you can tap into their networks, then you will find success.

Concerning email formats, use subject line: "Quick Question"

Then use a brief straight forward message:
"Dear XYZ,

I am ABC and I am trying to create a start up to help food brands. Could I ask you a few questions to learn about needs for food brands?

Sincerely,

ABC"