HOW TO MINIMIZING DO PICKUP
Few topics are as important to the Micro-Canning community as dissolved oxygen pickup in the packaging process.
Cans are 100% hermetically sealed so (unlike bottles) once the packaging process is completed, the Total Packaged Oxygen (TPO) in the can is locked in for the life of that can.
That is why it is so important to ensure that the air that makes it into your final product is as absolutely minimal as possible so the flavours you have crafted are delivered to your customers as fresh as they day they were brewed.
- Dissolved Oxygen (DO): dissolved oxygen is the amount of oxygen that is dissolved in your beer.
- Total Packaged Oxygen (TPO): all of the oxygen in the package including, any oxygen in the headspace and any dissolved oxygen in the liquid. By definition, TPO will always be greater than or equal to DO.
- Inline canning systems: inline canning systems are just that – “in-a-line” or a linear process along a conveyor without any axially rotating equipment. Inline canning systems typically fill cans in an open environment at atmospheric pressure. Cask invented inline canning for the craft beer industry and all of our 4 canning systems are inline.
- Fob: Foam On Beer. This refers to the foam “cap” on top of a well filled can.
Minimizing Your Dissolved Oxygen Content
Keeping minimal dissolved oxygen levels day in and day out requires proper training and a thorough understanding of the factors that influence oxygen pickup.
We have customers who are very diligent in monitoring their oxygen content and can consistently achieve DO pickup as low as 6 to 15ppb (yes, that’s parts per billion) with our Automated Canning System (ACS V4.2) and ACX X2.
Note that we quote 6 to 15ppb as the oxygen pickup through the canning system as measured by the difference from brite tank to a well shaken can measured immediately after seaming, as oxygen pickup in brite tanks or during filtration is a function of a given brewery’s specific process (for example, use of filtration and brite tank purging procedure) and not a function of packaging process or technology.
The following variables can all influence your dissolved oxygen pickup.
- Beer Temperature
For smooth canning operation, beer must be supplied from brite tank to the canning machine between 0 – 2C (32 – 35.6F). This is essential to allow our canning system to precisely control foam creation during the filling process.
As beer increases in temperature, its normal tendency is to have more foam breakout which makes it harder for us to control foam creation. Warmer beer is also able to physically dissolve more oxygen into solution in the liquid so keeping your beer as cold as possible assists on multiple fronts.
- Infeed beer hose length and diameter
If your hose length between your brite tank and canning system is too long, the beer will warm up as it travels through a hose that is surrounded by ambient temperature. The beer might well be within specification of 0 – 2C in the bright tank but flowing through a long, uninsulated beer hose can quickly increase temperature.
If your beer hose diameter is too small, additional (and unnecessary) friction is created as your beer flows through the line between your brite tank and canning system will have difficulty creating consistent foam volumes at the fill head. This additional friction will also decrease the pressure of the beer at your fill head which results in slower filling and more time for your beer to interact with atmospheric oxygen.
For example, if your brite tank pressure is 20 psi and you are losing 8psi in friction while your beer flows to the canning machine, your fill head is only operating with 12psi pressure instead of the 20psi you are reading in the tank.
Cask recommends using a minimum of a 1 ½” diameter beer hose that is as short as possible, preferably right beside your brite tank.
- Infeed beer hose insulation
We realize that the layout of your brewery might not allow your canning machine to be installed directly beside your brite tank. Regardless of the length of your hose run, we recommend that you use insulated hose to minimize temperature increase while beer is flowing to your canning system.
- CO2 Pre-Purge Pressures
The bottom up pre-purging of the empty can is one of two key distinguishing feature of our inline canning systems that allow us to achieve DO pickup as low as 6 – 15ppb. The piston like displacement of air from the can bottom ensures nil air remains in purged cans.
One of the most valuable learnings from our nearly two decades of experience in Micro-Canning has been CO2 regulator set pressures. It is absolute imperative that CO2 pre-purge and under lid gassing occur with laminar or smooth, steady CO2 flow instead of turbulent flow.
To achieve laminar CO2 flow, our recommended settings are as follows:
CO2 Can Pre-Purge Regulator: 8 – 12psi
- This pressure is the ideal balance between minimizing time required to pre-purge cans while maintaining smooth, laminar CO2 flow for effective air displacement.
- CO2 is heavier than air and fills the can from the bottom up, displacing all air out the top of the can.
- Turbulent flow will result if your regulator pressure is set too high which will cause CO2 eddies to draw air into the can and increase the oxygen content in your purged can in the same way a turbulent river will bubble with air.
CO2 Under Lid Gassing: 1-2psi
- As CO2 is heavier than air, a small, smooth flow of CO2 cascading down underneath the lid at the same time as the lid is placed on top of the can further displaces any oxygen near your beer immediately prior to seaming.
- Foam Fob Creation
If there is one critical element of minimizing DO pickup during packaging, this is it.
Fill and foam creation technology varies amongst inline system manufactures and should be a key point of consideration and comparison prior to any canning system purchase.
Our fill technology leads the Micro-Canning market in minimizing oxygen pickup, specifically because of our foam creation process and CO2 under lid purging effectively eliminates head space oxygen.
The “Foam Timer” on our ACS is a single input that controls the operation of our foam valves down to the millisecond to allow precision control of foam creation and foam volume. All beer has more breakout at startup so we recommend starting with a Foam Timer of 0 seconds (i.e. foam valves off) to begin with and adjust by monitoring actual foam levels. You should be prepared to increase Foam Timer right away once you are up and running at steady state.
An example of a great foam fob courtesy of our friends at Perrin Brewing
Cask recommends a foam level at least to the top of the can edge to eliminate head space in the can itself. This ensures enough foam for adequate protection of beer from air but not so much that lids are “floating” on the foam which can lead to off center lids jamming in the seamer in extreme cases.
As shown in the clear cans below, the fob is present during the entire fill process. Combined with the CO2 pre-purge volume, this creates two barriers between your beer and atmospheric air during the fill process.
Foam doesn’t just protect your beer when the can is full – it is present right from the beginning of the fill
- Top Up Timer
The last element of minimizing your oxygen pickup is appropriately setting your Top Up timer. Cask recommends to start with 0 second and to increase as required once your canning run is at steady state.
If the fill tubes are lifted out of the can without Top Up enabled, the level of the beer and foam can actually drop down and in severe cases, the can may collect additional air (depending on the height your level sensors are set at).
With Top Up on, the fill cycle is extended for a very brief period (typically 0.1 to 0.5 seconds) while the fill head is being retracted which keeps the height of the beer and foam constant while the fill tubes are withdrawn from the can.
Note: Top Up cannot continue once fill tubes are out of beer or additional air will be introduced.