Global ID Group, a Fairfield-based firm that provides testing, certification and consulting services for the production of food products worldwide, has entered a definitive agreement to be acquired by private equity firm Paine & Partners LLC, according to a release. Terms of the agreement were not disclosed. Global ID Group serves more than 15,000 clients in more than 100 countries. In addition to Fairfield, the company has operations in Europe and South America. The company will retain its executive team, according to the release. Paine & Partners is a global private equity firm that is focused on food and agribusiness.