Fans of yong tau foo say the chilli sauce can make or break the dish.

This, together with the ingredients and cooking methods, is at the heart of a legal food fight between a popular yong tau foo food shop in Tiong Bahru and operators of the Mr Bean chain.

The people behind Tiong Bahru Yong Tau Hu shop in Eng Hoon Street claim the chilli sauce, ingredients and cooking methods as their trade secret.

After setting up a joint venture, the Mr Bean chain started selling yong tau foo at its outlets using the Tiong Bahru shop's recipes.

But then things turned sour. Now the shop's operators - Mr Yeo Kee and Ms Yen Fan Ching - want a court injunction to stop the Mr Bean chain from using and disclosing their trade secrets.

They have named Mr Loh Jwee Poh and Mr Koh Thiam Soon of Bean United, Mr Simon Lim of Super Bean, Bean United and the joint venture - 118 Tiong Bahru Yong Tau Hu - as defendants.

Super Bean operates the Mr Bean chain while Bean United was set up by the company which owns the Mr Bean chain to facilitate the joint venture.

Mr Yeo and Ms Yen went into the joint venture with Bean United in 2015. As part of the agreement, Ms Yen became one of the shareholders of 118 Tiong Bahru Yong Tau Hu while Mr Yeo held the trademark of Tiong Bahru Yong Tau Hu, which he secured that same year.

Among other things, the deal meant Mr Bean would be allowed to sell yong tau foo using the pair's recipes at Mr Bean outlets.

But things went bad from December 2015.

After an initial $30,000 investment, Ms Yen says she was told the joint venture was profitable and to pump in another $90,000 to expand the business.

But Ms Yen claims she was not given substantive updates and was later told the business was making losses. She further claims that she was told she was personally liable for the losses.

She and Mr Yeo both claim the defendants knew they could not understand English well and did not have prior experience in joint ventures.

She is suing to get the $120,000 back.

As for Mr Yeo, he claims Bean United withheld royalty and technical fees meant to be paid to him. He says this was done because he did not sign over the master licence to Bean United.

The master licence would have given Bean United the rights to sell products using the Tiong Bahru Yong Tau Hu brand name.

He is demanding a true and full account of royalty and technical fees, and damages owed. He also wants an injunction to stop Bean United from using and disclosing Tiong Bahru Yong Tau Hu's trade secrets.

He claims that Mr Bean outlets were still selling his yong tau foo after the joint venture was terminated in April last year.

The defendants say Ms Yen and Mr Yeo are not entitled to any such claims.

Among other things, the defendants also deny Ms Yen's claims that the joint venture had initially exceeded profit expectations. The case has yet to be heard in court.