Champagne and beer foams

The foaming capability and foam stability obtained from sparkling wines is usually tested by a dynamic foam stability method, as discussed in Section 2.6.2. Because these foams are evanescent and are not really very stable, at least compared with the foams found in other industries, dynamic rather than static foam tests are the most suitable. In one version of the dynamic foam test, the Mosalux method, the foam heights are automatically measured using infrared beams and sensors [66, 67]. 

The foam head created when beer is poured or dispensed is an important aspect of consumer approval of a particular beer product. Compared with champagne foams, beer foams need to have different properties and be much more stable (beer foam needs to last for about 5 min). A cryogenic electron microscope 

The traditional kinds of physicochemical characterization methods have been applied to beer foams, but potentially surface-active compounds in beer are so numerous, and their interactions are so complex that complete brewing and pour-ing/dispensing tests are still needed. There are also manyfoam stabilitytests available (see Section 2.6.2), but none has been universally accepted in this area [72]. 

Tests that employ natural pouring tend to be inconsistent, while those employing porous foam generators, or other artificial means, produce foams that are not representative of the commercial product in actual use [72]. 

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Foams Ice cream, whipped cream and toppings, bearnaise, souffles, mousses, batters and doughs, aerated icing, aerated chocolate, champagne and beer foams... 

The foam head created when beer is poured or dispensed, is an important aspect of consumer approval of a particular beer product. Compared with champagne foams, beer foams need to have different properties and be much more stable (beer foam needs to last for about five minutes). A cryogenic electron microscope image of beer foam is provided by Wilson [73]. Consumer preferences for beer foams vary, but can be characterized in terms of foam stability, quantity, lacing (adhesion to a glass surface), whiteness, creaminess (bubble texture), and concentration [852,853], As a result, much work has been done in order to be able to control these properties. 

By far, the largest technological application of liquid foams is in mineral froth flotation, and this process uses a substantial fraction of the world production of amphiphiles. Froth flotation is also used in other separation processes such as the deinking of recycled paper. Other uses of liquid foams include fire fighting, cleaning processes, drinks such as champagne or beer froth, foods such as whipped cream or egg white, and preparation of solid foams after solidification of the liquid continuous phase. 

Champagne, soda and beer heads, whipped cream, meringue Foam... 

Figure 21.3. Typically, foams can be categorized as short-lived systems where film rupture is described as a spinodal decomposition (champagne foams), or long-lived systems in which energy barriers create an activation energy and film rupture is governed by a nucieation process (robust beer foams) (from ref. (7), reproduced with permission from lOP publishing limited...

It is also important to recognize that foams and emulsions are, in an absolute sense, thermodynamically unstable however, it is often possible to classify a particular system as relatively short-lived dynamically stabilized (ca. minutes) or one that can remain stable for very long periods (ca. days or years). A champagne foam is a classic example of the former, while robust beer foams and cosmetic creams fall into the latter category (see Figure 21.3). As already mentioned, this remarkable difference in a dispersion s lifetime is... 

Because proteins are involved in beer (Evans and Sheehan, 2002) and champagne foams (Senee et ah, 1999), and these are desirable properties, ultrafiltration is not a suitable treatment for these products. Adsorbents that indiscriminately remove protein are unsuitable for the same reason. 

Adsorbents that remove proteins or polyphenols are used to treat a number of beverages to delay the onset of haze formation. Protein adsorbents include bentonite and silica. Bentonite removes protein nonspecifically (see Fig. 2.19) and so is unsuitable for stabilizing beverages where foam is desirable (beer and champagne). Silica, on the other hand, has remarkable specificity for HA proteins while virtually sparing foam-active proteins in beer (Siebert and Lynn, 1997b) (see Fig. 2.20). Silica removes approximately 80% of the HA protein from unstabilized beer, while leaving foam-active protein nearly untouched at commercial treatment levels. 

The carbon dioxide produced in this reaction causes beer to foam and provides carbon-ation for naturally fermented wines and champagnes (see > Figure 13.4). 

The carbon dioxide formed in this reaction is responsible for the foam on beer and the carbonation of naturally fermented wines and champagnes ... 

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