Earlier this year, Campbell Soup, which had already acquired the organic products maker Pacific Foods, closed on its $4.9 billion acquisition of Synder’s-Lance , the maker of Snyder’s of Hanover pretzels and Cape Cod potato chips. Late last year, Hershey announced plans to buy Amplify Snack Brands , the maker of SkinnyPop Popcorn and Paqui tortilla chips, for $1.6 billion, while ConAgra picked up Angie’s Boomchickapop for $250 million and Kellogg’s bought the Chicago Bar Company , maker of the RXBAR protein bar, for $600 million. In the past four years, snack sales in the United States have jumped more than 12 percent to $145 billion, according to Nielsen Retail Measurement Services. A large portion of that growth has come from consumers seeking out healthy snacks or those that are organic or have so-called clean labels — no artificial flavors, colors, preservatives or sweeteners. Sales of nuts, trail mix, and organic savory snacks in the United States jumped to nearly $9 billion last year from $7.8 billion in 2012, according to Euromonitor International.