SodaStream International Ltd., the Israeli maker of home soda machines, is in talks with an investment firm about taking the company private, according to people familiar with the matter.

The transaction would value the company at about $40 a share, or $828 million, or 38 percent above yesterday’s closing price, said one of the people. No final agreement has been reached and talks could still fall apart, said the people, who asked not to be identified because the discussions are private.

Several private-equity funds have been looking at SodaStream for a leveraged buyout, one of the people said.

A sale would end the rollercoaster ride that SodaStream investors have been on since the Lod, Israel-based company’s initial public offering at $20 a share in November 2010.

The stock soared to almost $78 in August 2011 after SodaStream reported back-to-back quarters of sales increasing 50 percent or more. Revenue growth slowed to below 40 percent and the company’s forecast disappointed investors, sending the stock plunging below $30 by late 2011. The stock recovered to close above $76 in the middle of last year, only to slump again as competition picked up.

SodaStream rose 3.3 percent to $29.84 at 11:20 a.m. in New York. The company doesn’t comment on rumors and speculation, Nirit Hurwitz, a SodaStream spokeswoman, said by e-mail.

SodaStream sells countertop machines and carbon dioxide cylinders that customers use in the home to make sparkling water, as well as flavorings that they can add to the soda.

Coca-Cola Co. in February agreed to buy a 10 percent stake in Keurig Green Mountain Inc., which is developing a product similar to SodaStream’s, for about $1.25 billion. PepsiCo Inc. and Green Mountain own stakes in Sliema, Malta-based Bevyz, which introduced a rival at-home beverage maker in the U.S. in March.