A growing number of wine bottles in British shops have a QR code that provides ingredients and nutritional information when scanned with a smartphone. It sounds like a welcome advance in transparency. But why do some bottles have one and others not? Does the resulting ingredients list really tell you what has gone into the wine? First, there are two different codes. The familiar striped barcode identifies a product for retailers and their tills. The square QR code usually links to an electronic label containing ingredients and nutritional information. When both appear on the back label, they are sometimes put…