Green Isle, Glanbia and Robert Roberts are among the companies that have purchased research by the college's food product development centre.
The products tested have included burgers, crisps and snacks - mostly products being developed with reduced sugar, fat and salt contents, the institute said.
Now there are calls in the Irish parliament for legislation to outlaw any testing that involves children.
"Schools should be places of learning, not places of research for private companies," said Olwyn Enright, speaking for Fine Gael the main opposition party.
Parent groups and teacher unions also demanded guidelines for schools to prevent such activities.
The institute said that "only half a dozen primary schools and one secondary school" had been involved, and parental consent had been sought in most cases.
While the cost of the research was recouped from the companies, she said there had been no financial gain for the schools.
She added: "Children may be asked to compare two similar examples of a product and give their views on them."