Patents: Stout foam

日期:2019-03-02 09:08:04 作者:巩宀莰 阅读:

By BARRY FOX The Whitbread brewery in London and Heineken’s technical division in Amsterdam have joined forces to patent (PCT 93/15973) a solution to the age-old problem of how to make canned stout pour like draught stout. The draught drink, once poured, sports a close-knit creamy head, but this vital element is missing in a glass of the canned version. So Whitbread and Heineken plan a new type of can, with a cup-shaped plastic pod sealed to the bottom of the ring-pull lid. The pod has a small perforation in the bottom and a short tube attached to it. At the factory, the can is filled with stout, and a small dose of liquid nitrogen or solid carbon dioxide is dropped in just prior to sealing. The gas evaporates to build up a pressure of several atmospheres inside the can. When the can is opened, the bulk of the excess pressure is released into the atmosphere. But the pressure in the plastic pod stays high. The trapped gas jets down the tube and out of a small hole, into the main reservoir of stout. This shock causes mechanical shear in the stout, making it release small bubbles of gas that create foam. When the stout is poured into a glass,