Mizkan Group has agreed to buy Unilever's Ragu and Bertolli pasta sauce brands for $2.15 billion as Japanese companies continue to diversify by acquiring Western assets.

The all-cash deal, which values the sauce business at 3.6 times its annual sales, boosts the Japanese condiments maker's presence in North America's grocery aisles as declining birth rates and an aging society stifle growth at home.

The companies announced the deal on Thursday after Reuters reported late Wednesday that the parties were in advanced talks, nearly a month after Unilever said it was weighing options for the sauces business and for its struggling Slim-Fast brand.