A British sugar producer has reached a tentative purchase agreement for Ogden-based Amalgamated Sugar with Amalgamated's parent company, Valhi Inc.

Bristar - the food division of S&W Berisford, which also owns British Sugar - has made an unsolicited offer to buy Amalgamated for an undisclosed amount, company officials said Wednesday.Dallas-based Valhi has tentatively accepted the offer, which it says will result in an after-tax gain of $185 million to the conglomerate.

The sale still must be approved by the directors of Bristar and Valhi.

Bristar has said that it intends to retain Amalgamated's current management. The sale will not result in any noticeable changes in the company's beet sugar operations, said Amalgamated President Allan M. Lipman Jr.

"I think we'll operate on our own," he said.

British Sugar is one of Europe's leading beet sugar companies. Amalgamated is among the U.S. leaders in beet sugar, accounting for 9 percent of domestic sugar production. Amalgamated, though headquartered in Ogden, mostly operates in Idaho and Oregon.

Amalgamated was founded in 1897 by David Eccles as the Ogden Sugar Co. It employs 75 workers at its Ogden operations and another 1,125 full-time and 1,600 seasonal workers, mostly in southern Idaho.

The company is finishing an anticipated record year in sales and earnings, recording $19.1 million in profits on sales of $295.6 million through the first three quarters of 1988.

Amalgamated has had an informal relationship with British Sugar dating back 40 years, and Lipman has known managers of the company for some time, he said.

British Sugar representatives approached Lipman about a possible buyout in October, he said.