Chocolate giants Nestlé and Barry Callebaut are expanding their offerings of ruby chocolate – a flavor that caught fire a year ago in Asia thanks mostly to social media.

       Ruby chocolate was introduced by Nestlé in Kit Kat bars in Japan last year as the “fourth chocolate” after milk, dark and white. The product immediately went viral, with young Asian consumers sharing photos of themselves enjoying it on Instagram and other social media. More than 40% of Japanese consumers are aware of ruby chocolate and 5% have tasted it, according to a poll cited by Bloomberg.

       Nestlé is bringing out a new ruby Kit Kat with dried cranberries and nuts. Meantime, Barry Callebaut, the world’s largest bulk chocolate processor, is pursuing an ambitious social-media marketing campaign. Callebaut is putting together a website that will bring together social-media mentions of ruby chocolate, detected by an algorithm, and encourage visitors to share ideas about the product.

       Ruby chocolate is not yet saleable in the U.S., pending approval by the FDA.