Kraft and Heinz products. Getty Images

Kraft Heinz recently passed on the opportunity to bid on Pinnacle Foods, a move that may shed light on its interest in Campbell Soup, sources familiar with the situation tell CNBC. The ketchup maker has often been mentioned as a logical bidder for Campbell, should it put itself up for sale. The soup giant has announced it is undertaking a critical review, stoking takeover speculation. That speculation has been fanned by the stake that activist shareholder Third Point has taken in the company. Third Point has declined to comment to CNBC about whether it has taken a stake in Campbell. Pinnacle Foods, like Campbell Soup, owns a number of brands that sit in the increasingly desolate center supermarket aisles. Those brands include Duncan Hines frosting, Vlasic pickles and Mrs. Butterworth's syrup. Unlike Campbell, though, Pinnacle also has a large frozen food business and lacks Campbell's crown jewel business, Pepperidge Farm cookies and crackers. It may also have have less room for cost-cutting than does the soup giant. According to recently filed merger documents, after a back and forth between "Company A" and Pinnacle, Company A told Pinnacle it was not interested in acquiring Pinnacle "because such an acquisition would not be a good strategic fit ... at the current valuation levels." Pinnacle ultimately sold to Conagra Brands. Company A is Kraft Heinz, sources tell CNBC. Kraft Heinz is known to be a serial looker of companies — and Pinnacle had been trading at a premium due to takeover speculation — but Kraft Heinz's disinterest in it is notable nonetheless. It implies Kraft Heinz may be looking beyond the center of the store, where growth has been a challenge across the industry. Shoppers are increasingly buying fresh food or snacks that are sold around the store perimeter. The fact it was concerned about valuations indicates it is, unsurprisingly, disciplined on price.

Those reservations may extend to Campbell, where Kraft Heinz would find significant cost savings but also a declining soup business and a challenged fresh food business. Campbell's stock in June hit a low not seen since 2012 but has traded up nearly 25 percent over the past few weeks amid takeover speculation. To be sure, dealmaking is rarely a perfect pairing, and should Campbell put itself up for sale, the opportunity to buy the soup giant may surpass potential reservations. With Kraft Heinz's cost-cutting reputation and a fumbled bid for Unilever, industry analysts wonder whether it may have difficulty finding a company to welcome it with open arms. Further, Kraft Heinz — and Heinz before it — has long been intrigued by Campbell, which could help it extract costs in Heinz's soup and beans business. But the companies and the industry in which both Campbell and Kraft Heinz operate have changed significantly over the past few years.

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