By Lisa Baertlein

LOS ANGELES (Reuters) - Cheesecake Factory Inc (CAKE.O: Quote, Profile, Research) posted lower quarterly profit on Thursday as higher food costs and the weak U.S. economy weighed on results, sending the restaurant owner's shares down nearly 10 percent.

During the quarter, sales at restaurants open at least 18 months fell 4.1 percent, the lowest level in company history, JP Morgan analyst John Ivankoe said in a client note.

The company, known for its huge portions and broad menu, said second-quarter net income was $19.1 million, or 29 cents per share, down from $23.7 million, or 33 cents per share, a year earlier.

Revenue rose 9 percent to $407.1 million from $373.2 million.

While earnings matched analysts' average estimate, revenue fell short of their $412.7 million sales target, according to Reuters Estimates.

RBC Capital Markets analyst Larry Miller said earnings quality in the quarter was low. Miller said a lower-than-expected tax rate added 1 penny to per-share earnings, while lower bonus expense added about 1.5 cents.

"Additionally, sales came in almost $5.5 million light of our estimate," Miller said.

The weakest restaurant results were from from units in California and Florida, which have been hardest hit by the U.S. mortgage meltdown, and executives noted that they are seeing a bit more weakness in Las Vegas.