When filling any carbonated beverage you will soon learn that foam is your nemesis….
Foam is a necessary evil. Your customers want to experience the same carbonation level from your bottles or cans as they get when they are in your tasting room and you must give them that experience. BUT- to do so means that you must get that foaming frothy beast into that can or bottle without letting all that magic escape. In this post, I will try to break down exactly what is happening and help you understand how to keep the foaming at a minimum so that all that energy gets stored in the bottle/can and your customers can experience it. Foam, or simply put- bubbles, are just the CO2 that is dissolved in your beverage, escaping due to a sudden drop in atmospheric pressure, increase in temperature or agitation. The type of beverage determines the shape, size and characteristics of these bubbles and is what determines how it presents itself; fizzy seltzer or rich creamy head.
Carbonation:- It seems obvious, but I will mention it out of an abundance of caution; The higher your carbonation level is, the more “ANGRY” your beverage will be and the higher tendency it will have to foam. In all cases, it is best to fill with your beverage at the lowest temperature you can possibly get it chilled down to. The colder it is, the less tendency it will have to release its CO2 out into the atmosphere. Here are a few points about foaming that should help you understand it and how it effects your filling process.
First- the two most important pieces of advice with regards to bottling carbonated beverages:
- Always be as cold as possible.
- Always operate at the lowest pressures possible (read on to understand how to determine this but remember, always stay as low as you can go).
Foaming in the feed lines:- Weather you are filling from kegs or from a tank, that vessel will have to be pressurized. This pressure serves two purposes: to drive or displace the liquid from the tank and to hold the CO2 in solution. The higher your carbonation level is, and/or the warmer your liquid is- the higher this pressure will have to be to hold that CO2 in solution or “Keep the genie in the bottle”. So- because of this- the feed lines is the first place where foam can enter your process. Foam that starts in the feed lines will plague you throughout the process and must be nipped in the bud at this stage before you continue on with diagnosing your foaming problem. Foaming feed lines will always provide a place for bubbles to gather at the highest point and form a large pocket of CO2 that will cause uneven filling which deepens your headache. Once you have gotten your feed lines chilled by flushing cold beverage into them, foaming in the feed lines is remedied one of two ways. The preferred method is to lower the temperature of your liquid. If this cannot be done, then you will have to increase the pressure of the tank or keg that holds the beverage. You must increase this pressure until the foaming stops, but do not increase it anymore than necessary. You can watch the liquid in the clear lines until you see the foaming stop.
Foaming while filling:- Once you have the feed lines flowing without foam (there will always be visible bubbles here and there, just make sure you are not watching bubbles constantly forming) it is time to start filling. While you are filling you should have a thin (3/8” or so) layer of foam on top of the liquid as the level rises up. This is easy to verify with bottles but a little more difficult with cans unless you have X-Ray vision, which must be awesome for you. With cans you have to monitor how much foam is expelled into the vent lines before liquid is visible. If the foam is excessive, there is only one remedy. If you are using cans- this is where you should be glad you bought the right machine because counterpressure is the answer and many of our competitors do not use counterpressure for can filling. You need to increase counterpressure to keep that foam while filling at bay. The closer you raise your counterpressure to the pressure of the tank/keg, the slower the liquid will flow, so you will likely also have to increase fill time.
Foaming after filling:- After your containers are filled you can sometimes experience foaming before you get the bottle cap or can end on. If this is the case, it is usually caused by counterpressure or temperature too high. Remember, always be as cold as possible (you’re getting that right? colder is better). So, the solution here is to lower counterpressure- but wait, you say you had to raise it to where it is so you can control foaming while filling…. Well sometimes it is a very delicate balancing act. This is where that second piece of advice comes in- always use the lowest pressures possible; if you can lower that keg/tank pressure a couple PSI without starting a foaming problem, you can lower your counterpressure the same amount. Or perhaps you can lower your counterpressure and live with a little bit more foam while you’re filling, and if you can do either or both of these- you may just eliminate that little “POP” you get when you raise your fill heads and that can eliminate your foaming problem after filling. Another trick- if all else fails, is to just wait a few seconds before you lift the heads. Usually, your counterpressure will slowly leak down a bit which means a more gentle transition to atmospheric pressure. For some beverages you might have to develop a habit of counting to 10 or whatever works for you, before lifting the heads. In an absolute worst case- where you cannot get it under control even after lowering temperature and pressures as low as you can, you could very slowly open the drain valve on the counterpressure tank and allow it to slowly drop to atmospheric pressure before raising the heads. Although certainly not ideal, with a little practice, this will not be a bad tradeoff for being able to package a particularly “ANGRY” beverage.
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