OXYGEN LIMITING METHODS

Certain beverages are adversely affected by oxygen.  The most common are beer and wine although this category also includes some types of enzyme containing health food drinks.  SMB Technik provides a variety of means and processes to limit beverage contact with oxygen during filling and closing.  Each technology has its own advantages/disadvantages and costs both capital and ongoing.  The selection of an oxygen limiting system should consider all factors.  There are frequently several ways that arrive at the same net result.  So one of the important considerations when selecting an oxygen limiting system is with what technology is the customer familiar and has confidence in.

It is very difficult to specify a period for product "shelf life" based upon the exposure to oxygen.  Shelf life depends not only upon oxygen exposure alone, but the type of product, the presence or absence of antioxidants, how the individual flavor components respond to oxygen, and the opinion of the observer.  There are no shelf life figures estimated here.  It is the customer's responsibility to measure oxygen contact, not only during filling but throughout his processing and correlate it with the results of product degradation. 

It is also important to understand a little of the dynamics of flavor and the importance of oxygen limiting.  Sensory determination of flavor is not linear with concentration.  Concentration of flavor increases greatly to produce a corresponding linear increase in perceived flavor.  Each beverage and flavor has its own unique characteristics but typical functions that relate perceived linear increase in flavor to concentration are logarithmic or power of 2 functions.  The important bit of information to glean from all this is as follows: 

At the point in time you can detect a linear decrease in flavor quality, then the actual concentration of flavoring materials in the beverage have decreased a substantial portion of their original total concentration. 

Oxygen contact during filling is not a single step process.  It can occur in several places.  Broadly, the areas of contact can be divided into two stages.  The first is what happens between the beverage entering the filler to the time the bottle is filled and secondly, how is the head-space oxygen content limited between filling and closing.  The main process which occurs during the first stage is solubility and during the second stage, it is oxygen capture in the head-space.  Some of the factors which determine oxygen contact during the first stage are the area of the liquid in the bowl, the oxygen content of the atmosphere in the bowl, residence time of the liquid in the bowl, agitation during liquid dispensing, and oxygen content of the atmosphere in the container prior to filling. The second stage of contact is limited by how effectively the atmosphere in the head-space is removed or replaced with inert gas.  All factors effect the total package air and all must be considered.  Establishing a good quality, low oxygen contact filling process without consideration of head-space is futile.

Measurement of Oxygen

There are two common measuring systems used to determine oxygen contact.  They are direct measurement of oxygen in the beverage using a membrane interfaced detector and by the Zahm & Nagel total package gas.  The two different tests measure two different things and the results are absolutely not inter-convertible.

A direct oxygen measuring instrument (d.o. meter) has a sensor that is either placed in the beverage or has a system to force liquid passed the sensor.  The instrument measures the amount of oxygen that is dissolved in the liquid.  It is a highly accurate device for measuring the oxygen dissolved into the beverage across the filling section of the machine.  It can be used to make a good estimate of total package oxygen but additional variables need to be known (temperature, head space volume, liquid volume) in order to do this.  The mathematics are hairy and it's best to use a table.

The Zahm & Nagel system measures the total volume of non-caustic soluble dissolved gases.  For all practical purposes, this is oxygen and nitrogen.  It does NOT measure AIR.  If the Zahm & Nagel measured air, then it would be inter-convertible with d.o.  The greatest deviations between "air" and what Zahm & Nagel measures occurs at the lower levels of measure.  This is because oxygen and nitrogen dissolve into liquids in relative proportions different than their concentration in air.  Nitrogen is more soluble.  At low levels of measurement, Zahm & Nagel tends to have higher values than the volume of air calculated from a total package d.o. measurement.

Direct oxygen measure has the greatest accuracy but it is expensive.  The advantage of Zahm & Nagel is low price and simple operation.

Bowl Design

SMB Technik filler bowls tend to be small in cross sectional area and to have small volumes.  This limits the exposure of the beverage to oxygen both by area and by limiting the average residence time of the beverage in the bowl.  It also has the advantage that liquid losses from start up and shut down volumes are limited.

Long tube compared to short tube

Short tube filling valves direct the liquid to the sides of the container to be filled.  Liquid cascades down the side of the container.  This flow pattern maximizes the interaction between the liquid and the atmosphere within the container.

Long tube filling valves dispense the liquid near the bottom of the container.  Liquid quickly covers the pipe exit.  So the area of interaction between liquid and atmosphere within the bottle is limited to the cross sectional area of the bottle.

The typical oxygen pick up during filling of a long tube valve is 10 - 15% that of a short tube filling valve given equal conditions of atmosphere in the container to start with.

SMB Technik makes both short tube and long tube valves.  Slightly different versions of each valve can be used for still or carbonated beverages.

A long tube filler with no other oxygen limiting system, typically, has an oxygen pick up across the filling section of approximately 140 - 180 ppb for a 12 oz beer bottle.  Although higher than other systems, it is still a very respectably low contact.  This is the best compromise of limiting oxygen pick up and mechanical simplicity.  It is our observation that such a value represents approximately 1/4th to 1/3rd of the total package oxygen when operated together with a good system for removing oxygen from the head-space.

Sparging (flushing) prior to filling

This can be done in two ways.  A separate machine can be installed in front of the filler to inject inert gas into the container prior to the container entering the filler.  Alternatively, SMB Technik manufactures a long tube valve which can inject inert gas into the container through the long tube as the container is lifted up to the filling valve.

Pre-evacuation and flow-through

Pre-evacuation is a system of pulling a vacuum on a bottle and then pressurizing the bottle with gas from the filler bowl or from an external source of inert gas.  The process is not very efficient so it is typically done twice.  It is easy to repeat this process as many times as the customer requires.  Each additional cycle reduces the time available for filling.

SMB Technik valves use 100% inert gas from an external source.  This is superior to using bowl gas which is, typically, contaminated with oxygen from the vent gas of previously filled bottles.

SMB Technik offers pre-evacuation systems with either short tube or long tube valves.  The net oxygen pick up across the filling process is about the same using a short tube, double pre-evacuation systems compared to a long tube filler in combination with single pre-evacuation.  A 12 oz. beer fill typically picks up about 30 - 50 ppb across the filler with either system.

Flow-through is a system that opens the vacuum and the inert gas simultaneously so there is a very high velocity flow through the bottle. It is a diluting process that uses relatively high quantities of inert gas to achieve good results.  It'd main application is with plastic bottles that cannot withstand vacuum.

Head-space

Reducing the oxygen content of the head-space can be accomplished in a variety of ways depending upon the beverage bottled.  For beer, SMB Technik supplies a jetter nozzle and control assembly.  For wine, SMB Technik cork closures come standard with vacuum plates. 

There are other systems which we can supply such as inert gas injection into the head space prior to closing.