The Norfolk-based UK arm of US firm Kettle Foods has been sold for £402.3m ($615m).
UK production of the food was set up in Bowthorpe, Norwich, in 1992. The site now employs 407 people.
A number of companies bid for the firm, previously owned by a private equity company Lion Capital, but San Francisco-based Diamond Foods won.
Diamond Foods president Michael Mendes said he welcomed their talented team of employees to his organisation.
The deal should be completed by the summer.
Kettle Foods, which makes gourmet style crisps, nuts and tortilla chips, is based in Oregon, where it was founded in 1978.
Lion Capital bought the business in 2006 for about £170m as part of a drive to become the UK's second biggest snack company behind PepsiCo.
It also owns brands such as Weetabix, Wagamama - and it has the Findus Group, the owner of the brands Findus, Young's and The Seafood Company, in its portfolio.
Diamond Foods is best known in the US for its Emerald snack nuts and Pop Secret microwave popcorn.
It is believed several companies in the North American market made bids to Lion Capital.
United Biscuits, which owns McVitie's, Jacob's and Twiglets, is thought to have offered up to £200m for the UK part of the business.
Managing director of Kettle's UK business Jeremy Bradley said Diamond's record in the snack industry made it the "ideal partner".
It gives the US company a platform for growth in the UK and Europe, he added.