Anglo-Dutch consumer group Unilever has invited private equity bidders to submit tentative offers for its $8bn (£6.1bn) by a deadline of Oct 19, two sources close to the matter told Reuters.

The sale of the business, which makes Flora and Stork margarines, officially kicked off in late September with Unilever’s banks sending out confidential information to a series of heavyweight buyout funds which have been working on this deal since the start of the summer, the sources said.

The auction has been dominated by private equity firms which have been lured by the unit’s strong profit margins. But the valuation might prove difficult, as Western consumers cut back on bread and margarine, the sources said.

International investors have teamed up in three rival consortiums consisting of Bain Capital and Clayton Dubilier & Rice (CD&R) as part of one group, Blackstone and CVC Capital Partners as part of a rival group, and KKR joining forces with Singapore’s sovereign wealth fund GIC.

US investment fund Apollo was instead looking to bid alone, the sources said.

Industry players including US agricultural trader Archer Daniels Midland Co have decided against bidding, the sources added.

Blackstone, CD&R, Bain, CVC, KKR and Apollo declined to comment, while Unilever and GIC were not immediately available for comment.