By Svea Herbst-Bayliss and Abigail Summerville

NEW YORK, May 29 (Reuters) - Toms Capital Investment Management, an activist U.S. hedge fund, has built a significant stake in McCormick & Co MKC.N, according to sources familiar with the matter, at a time the U.S. food company is working on a prominent takeover deal.

Run by Benjamin Pass, Toms Capital invested in McCormick during the second quarter after the spice company announced its planned acquisition of Unilever's ULVR.L food business, said the sources who were not permitted to discuss the matter publicly.

The size of its stake and what Toms Capital intends to push for at McCormick could not immediately be learned.

Unlike some activist investors, Toms Capital prefers to stay in the background and push for changes out of the limelight, rather than launching public and noisy campaigns.

A successful takeover of Unilever's food business would create a $65 billion sauce-and-spice giant, home to brands including Hellmann's mayonnaise and French's yellow mustard. It would help Hunt Valley, Maryland-based McCormick tap London-headquartered Unilever's global scale and expertise, company executives told investors after the plans were announced in late March.

A representative for Toms Capital declined to comment, while a representative for McCormick could not be reached for comment.

Both companies' share prices have been under pressure since the deal was announced. McCormick has underperformed the State Street Consumer Staples Index XLP.P by 15% and Unilever has underperformed the MSCI Europe Consumer Staples Index by 8%.

The deal is expected to close by mid-2027, subject to regulatory and McCormick shareholder approval. Unilever shareholder approval is not required, the companies said.

McCormick has been engaging with institutional investors who have told the company they see the merits of the deal but are pushing for it to close more quickly, a separate source familiar with the discussions said.

The deal has also raised concerns about its structure and antitrust risks.

In the past, Toms Capital has owned a stake in Kenvue and pushed for a merger. The Band-Aid and Tylenol maker sold itself to Kimberly-Clark for nearly $48.7 billion last year.

More recently, the hedge fund has pressed Voya Financial, which oversees some $1.1 trillion in assets under management, to sell the entire company or sell its health insurer unit.