There are 211 outlets, half family restaurants trading under the Black Eyed Pea brand and half Taco Bueno's, which serves Mexican fast food. Both parts will be sold together.
If successful, the cash raised should pay for Unigate's three acquisitions this year.
It paid pounds 54m for Glass Glover, the warehousing and distribution outfit, at the start of February. It has also paid pounds 17m for the milk business of the Co-operative Wholesale Society and pounds 50m for the Clifford Foods dairy, but has yet to get MMC clearance for these two deals. The ratio of debt to net assets will fall to 15 per cent from 60 per cent.
Ross Buckland, chief executive, said he expected to raise between dollars 200m ( pounds 145m) and dollars 250m ( pounds 164m). If Mr Buckland achieves his target the price will be between 11 and 12.3 times Black Eyed Pea's operating profits for the year to 31 March of pounds 13.3m.
Mr Buckland said Unigate wanted to concentrate on food distribution and manufacture. It sold its other main US operation, in cheese, last September.
It is planned to get a listing for Black Eyed Pea on the New York Stock Exchange.
Unigate's shares rose 6p to close at 373p yesterday.