In bottling plants, beverages are filled into containers in such a way that a residual gas volume remains in the headspace of the containers. This residual volume is at first filled with carbon dioxide in the case of beverages containing CO.sub.2. Since the containers are exposed to ambient air during transfer form the bottling station to the sealing station, there is a risk of oxygen entering the headspace during this transfer, which promotes germ formation in such beverages and thus greatly reduces their storage stability.
For the afore-mentioned reason, beverages are conventionally foamed during transfer from the bottling station to the sealing station by introducing a gaseous or liquid medium into the headspace onto the surface of the beverage so that the resultant foam expels the gas volume, and thus also the oxygen that has entered, from the headspace. Thus, the oxygen content in the headspace will be reduced at the moment the container is sealed.
One example of such a foaming device is disclosed in German Utility Model No. 91 16 815 U1. A jet of liquid, here in particular water, is introduced into the headspace of the filled containers at a pressure of 40 bar by means of the device described therein. The pulse of the water jet can be regulated.
It is in particular disadvantageous in such process and devices according to the prior art that after the high-pressure water injection the beverage foam has relatively large pores so that, despite large overfoam volumes (2 to 5 ml/container), the average oxygen values that can be achieved in the headspace are not better than 0.018 to 0.12 mg per liter. The disadvantageously large overfoaming results in a high waste water pollutant load and thus substantial liquid waste disposal costs; also, the large overfoam volumes are equivalent to net beverages losses which, of course, are expensive per se.
A further main disadvantage of this known foaming process resides in the fact that water, and thus foreign media, is injected into the beverage, thereby diluting it. There is danger of germs being injected into the beverage together with the water, while, to avoid this danger, special equipment for preparing germ-free water must be provided.