I'd create a huge list of food manufacturers, that are not tiny (1-10 employees) and not enormous (10,000+ as these are probably public companies or something like Mars). then run Claygent to find out if they've ever been acquired by PE (I have done this at scale, DM me) and then if they have been acquired, then do another Claygent to find out what year. You could do the two things at once but i find that less effective.