SAN FRANCISCO » Diamond Foods Inc. is buying Procter & Gamble Co.’s Pringles chips business in a $1.5 billion deal, the biggest in a string that have given the maker of Pop Secret popcorn and Kettle chips a steadily growing share of the snack aisle.

The deal also completes P&G’s exit from all its major food businesses. The maker of Tide and Pampers has sold off Folgers coffee, Jif peanut butter, Crisco Shortening and Sunny Delight drinks in recent years.

Diamond was known mostly for its nuts when it started out. But a series of acquisitions has steadily broadened its array of snacks. It picked up Pop Secret in 2008 and Kettle last year.

The deal is structured to create a new company under the Diamond Foods name. P&G shareholders will get about 57 percent of the combined company, while Diamond shareholders will own about 43 percent.

Diamond said Tuesday that the Pringles transaction will more than triple the size of its snack business and help bring its annual revenue to about $2.4 billion.

The San Francisco company’s stock gained $4.38, or 7.7 percent, to $61.60 in premarket trading.

"Pringles is an iconic, billion-dollar snack brand with significant global manufacturing and supply chain infrastructure," Diamond Chairman, President and CEO Michael J. Mendes said in a statement.

Diamond says the addition of Pringles will more than double its snack sales in the U.S. and U.K., which are Pringles’ two biggest markets. It will also give Diamond a greater presence in U.S. grocery, drug, mass merchandise and convenience stores.

The Pringles brand is more than four decades old and is sold in more than 140 countries, with manufacturing plants in the U.S., Europe and Asia.

The deal includes $1.5 billion in Diamond stock and the assumption of $850 million of debt. The combined business, whose headquarters will stay in San Francisco, will be led by Diamond’s Mendes.

Procter & Gamble said the Pringles deal will likely be part of a "split-off" transaction in which stockholders can choose to take part in an exchange offer, swapping Procter & Gamble shares for Diamond stock.

The debt that Diamond assumes could vary based on movements in its stock price before the deal closes. The debt amount could increase by up to $200 million or be reduced by up to $150 million based on the mechanism.

The deal will give Procter & Gamble a one-time earnings boost of about $1.5 billion, or 50 cents per share.

If the Pringles transaction closes before the end of the year, Diamond anticipates fiscal 2012 earnings per share between $3 and $3.10 per share on revenue of about $1.8 billion. The forecast excludes costs associated with the Pringles deal.

Diamond, which also makes Emerald nuts, expects about $100 million in one-time costs tied to the Pringles transaction over the next two years.

The deal, which still needs Diamond stockholder approval, is expected to close by the end of the year.