Guinness Beer - Patent Information on the Smoothifier

As it happens patent no, 4,832,968 is for a very famous widget, Guinness in a can stout, "The Beer Widget."

The basics:

Inventors: Alan J. Forage & William J. Byrne

Assignee: Arthur Guinness Son & Co., Ltd. Process:

The gas pod in the can is blow molded with nitrogen (N).

A laser zaps a hole in the pod. (they experimented with holes between 0.2mm and 2.5mm finding that 0.61 mm as ideal)

Pod is inserted in the bottom of can.

Can is filled with CO2/N supersaturated stout. N is present at 1.5% v/v min up to 3.5% v/v. (FYI, vol/vol is the number of volumes of gas which are dissolved in a unit volume of beverage at 760mm of Hg & 15.6 oC) CO2 is present at between 0.8 and 1.5% v/v.

During filling, foam rises to top of can. This clears the air.

A charge of liquid N is added to the stout

Can is sealed.

As liquid N boils off in can during pasteurization (60 oC for 15-20 min), top of can pressurizes and forces the stout into the pod, thus compressing the ambient pressure N in the pod.

Equilibrium is reached at about 25 psi.

As I interpret the patent, this is what happens when the can is opened:

The can quickly depressurizes to ambient pressure. The pod thus expels the stout contained in it (about 10-15 ml) at high velocity through the orifice. This causes high local strain of the stout at the plane of the orifice. This strain exceeds the cohesive forces holding the gases in solution. As a result, the N/CO2 is liberated from the stout at the plane of the orifice. The millions of tiny N/CO2 bubbles then become the foam head. So contrary to my initial belief, while some of the N gas in the pod escapes directly into the stout, it is actually the "ripping apart" of the stout as it exits the pod which produces the bubbles, hence the creamy head.

Most beers are canned or bottled with some carbon dioxide, which provides the head when you pour the beer from the container into a glass. Guinness on tap is packaged with CO2 and Nitrogen. Nitrogen helps make the nice, foamy head you see on glasses of Guinness in a pub. But CO2 actually gets absorbed into the beer, while nitrogen does not. When you open a can or bottle of Guinness, most of the nitrogen escapes into the air before you can pour it.

The invention is a plastic ball with a small hole in it. Just before canning, they fill the ball with a little bit of nitrogen and then some beer under the same amount of pressure than the beer will be once it's canned (and the CO2 in the beer creates pressure in the can). The nitrogen stays in the widget as long as the beer can is sealed. When the can is opened, and the pressure is released, the nitrogen is released into the beer just as you pour.

Patents in the U.S. that were filed before 1995 or so last 17 years from the date of issue. (After the rules changed, it became 20 years from the date of filing). So the Guinness widget will belong to all of us in May!

Only the GWI GigaWidget noted;
PAT. NO. Title 4 6,620,444 Full-Text Two-compartment container for and method of admixing a flavour to a beverage
5 6,561,388 Full-Text Content lifting and removing container assembly and method of manufacture thereof
12 5,863,577 Full-Text Pressurized beverage package with an interior compartment for the production of foam on opening of the package, and a method of forming such a package
13 5,855,292 Full-Text Fluid storage
15 5,715,874 Full-Text Beverage packaging method and apparatus
17 5,667,832 Full-Text Method and device for foam generation by dispersion of bubbles
21 5,571,548 Full-Text Pressurized beverage package with an interior compartment for the production of foam
28 5,231,816 Full-Text Method of packaging a beverage
29 5,196,216 Full-Text Beverage package
30 5,009,901 Full-Text Method of packaging a beverage and a beverage package

Patent info on the gigawidget