Diamond Foods, the US nut maker, looks set to take a bigger bite out of the snacks market on both sides of the pond after striking a deal to buy crisp firm Kettle Foods. Upmarket snacks is a buoyant category, with, in the UK, United Biscuits and Warburtons among those launching "posh" crisps in recent months - and PepsiCo's Walkers also pushing its Red Sky brand.