Fobbing is the foaming of beer during processing or dispense. Depending on when it occurs, fobbing can have either negative or positive consequences. Fobbing during wort production can contribute to oxidation that will negatively impact long-term product stability. When used in reference to beer dispense, the term “fobbing” generally refers to excess foaming while pouring draught beer. This results in product loss and subsequent loss for the pub or tavern owner (linking it to the more common layman’s definition of fobbing: to cheat or to deceive, i. e., “fob this off on someone”). Multiple factors contribute to excessive draft fobbing. These include incorrect line sizing, incorrect line pressure, uptake of carbon dioxide at the point of origin (i.e., the keg or serving vessel) during or prior to dispense, unclean beer lines, improperly cleaned and rinsed glassware, incorrect beer temperature at the point of dispense (i.e., warm beer), or defects in the beer line. See draught beer.

Fobbing during packaging, particularly bottling, is important in forcing oxygen from the bottle prior to capping. As the bottle exits the filler, foam rises to the top of the bottle, due to the drop in pressure, displacing the oxygen in the bottle’s headspace. This is known as “capping on foam.” Bottling lines will often employ liquid nitrogen or sterile water “jetters” that disrupt the surface of the beer in the bottle, causing fobbing and ensuring the beer is properly capped on foam. A similar effect can also be achieved by tapping or “knocking” the bottle on its way to the capper or by use of an ultrasonic burst that causes the beer to foam as needed.

Another use of the term “fobbing” refers to cask-conditioned beer which has undergone a secondary fermentation in the cask. Before the beer is ready to serve, the proper level of carbonation must be achieved. When the cask is first vented, it may be quite active, causing fobbing to occur through the hole in the shive. Some cellarmen will wipe away the foam and then use the frequency of its reappearance to decide when it is time to reseal the cask. See cellarmanship, art of.