Dunkin’ Donuts is expanding its coffee portfolio in the US with the addition of a dark-roast variety this month.

The dark-roast hot coffee uses a unique roasting process to extract key characteristics of different beans, creating a bold flavor and the smooth finish, said the food chain.

At least 30% of beans used in the coffee are sourced from Rainforest Alliance Certified farms.

Dunkin’ Brands’ global marketing and innovation president John Costello said: "Dark Roast represents possibly the most dramatic expansion of our coffee portfolio since we introduced espresso beverages a decade ago.

"As we continue our national expansion and introduce our brand to millions of new guests, many of whom enjoy a darker roast coffee, this new launch is a big step in our growth and reinforcing our position as a coffee leader, and the brand offering one of the largest varieties of coffee choices for busy, on-the-go people."

The new coffee comes in hot or iced forms without the bitterness associated with dark roast coffees.

It will also be available for sale for brewing at home in both packaged coffee and in K-Cup packs, for use with Keurig Brewing systems.