Equistone said its cash injection will be used to develop new products and scout out possible acquisitions to expand the business further.
Whitworths, founded in 1886, has been owned by private equity house European Capital since 2006 and is the country’s biggest supplier of dried fruit, nuts and seeds.
The company posted revenues of £157.3m in the year to April 2013.
“We are excited to work with the team at Equistone to explore new opportunities, and we are committed to continuing to deliver our exceptional product range and service to our current and prospective customers,” said Whitworths chief executive Peter Utting.
The deal is Equistone’s 14th investment from its Europe Fund IV and the firm’s latest purchase of a food company, having bought French dessert firm Charles & Alice last month.
Equistone was advised by Spayne & Lindsay, Evershed, Alvarez & Maral, Parthenon, Deloitte and Marsh. Whitworths’ management took advice from Cornerstone and EMW Legal.
Debt financing came from HSBC, Barclays and RBS.