Mr Johnson, who is standing on a Hard Brexit platform, visited the sausage producer’s base in North Yorkshire last week.
Advocates of staying in the European Union, however, have threatened a boycott of the firm’s sausages and accused the business of hypocrisy.
Heck has warned in the past that its workforce, over half of which is currently made up of people from Eastern Europe, would be adversely affected if freedom of movement came to an end.
The sausage firm said that it invited Mr Johnson and his rival Jeremy Hunt, who were both in York for a leadership hustings. The former responded along with the local Tory MP Rishi Sunak.
Andrew Keeble, co-founder and managing director of Heck, told The Yorkshire Post that the business was not political but it hosted Mr Johnson to seek answers on the future of many of its workers from the EU.
The visit drew ire from opponents of Brexit on social media with food critic Jay Rayner also wading in.
“I can’t think of a worse publicity stunt than associating yourself with Boris Johnson,” one Twitter user wrote.
Another responded with the Tweet: “I won’t be buying any Heck sausages in future. What a pity.”
Mr Keeble, who voted to remain in the 2016 referendum, said: “From our point of view, we have 140 people, 80 of whom are from Eastern Europe, it’s really about what’s going to happen to our staff.”
As well as seeking assurances on behalf of staff members, the firm also pressed Mr Johnson, who is favourite to become the next Prime Minister, on potential trade tariffs.
Heck is looking to increase capacity. The business will be starting to export in April to Germany and Holland, said Mr Keeble. He added that the Tory leadership hopeful’s responses to questions on trade tariffs were “very vague”.
During his visit, Mr Johnson made his own sausages called ‘Boris Bangers’ but Heck said it has made sausages for lots of people who visit.
The firm added that it “certainly” wouldn’t be selling any ‘Boris Bangers’.
Co-founder Debbie Keeble said: “We invited both candidates for leadership, to come and see us during the York Hustings.
“Indeed, we welcome anyone to look around our factory, whatever their views or political party.
“We have always said that Brexit or no Brexit, we have to make our own success, with new ranges, exporting and innovating.
“We do not specifically endorse any candidate, we want to know how Brexit will affect our business and team.
“We wanted to seize upon the chance to ask them what they are going to do to secure the long term future of our team.
“You have to work with who is going to be in power, whatever your political view. Dialogue is the only way forward.”
The winner of the Tory leadership contest will be announced later this month.
On Thursday both Mr Hunt and Mr Johnson faced questions from Tory party members at the Barbican in York.