ACS LP Acquisition Form - Checklist input with multiple selections (check all that apply) - Concatenating selections into one field

Good afternoon! 

I am working to build a form where 1 questions is prompting the visitor to check all that apply. 

E.g. What food interests do you have? (check all that apply)

■ Pizza

■ Burger

■ Donut

If someone were to select all three, and the "name" of the checkbox were to be "name = foodinterest" then the output would read - 

"foodinterest=Pizza&foodinterest=Burger&foodinterest=Donut"

The challenge I've run into is that when I select multiple boxes, only the final input is being stored, rather than a string of all responses combined. 

Any insight on how to accomplish this in ACS?