A variety of brewing apparatus have been developed to combine heated water with a brewing substance such as ground coffee or tea material in order to infuse the material and produce a brewed beverage.  There are many ways to combine the water with the brewing substance.  One way is to place the substance in a filter device such as a disposable filter paper and place the filter paper and brewing substance in a brewing funnel or basket.  The water is mixed with the brewing substance in the filter thereby allowing the brewed substance to filter through the paper leaving the saturated brewing substance in the filter paper.  The saturated substance and used filter paper can be thrown away. 
Another way of brewing beverage is to encapsulate the brewing substance in a filter material.  The brewing substance in the filter material provides a convenient package for handling a predetermined quantity of brewing substance.  The filter material provides a package or container for the brewing substance.  This package allows the brewing substance to be handled prior to brewing and after brewing without complication or mess. 
Such brewing substances pre-packaged in filter material are referred to as “pods” or “sachets.”  Pods can be compressed while packaging in the filter material or left in a generally loose condition.  Pods are generally shaped in a circular shape having a generally flattened configuration.  The pods often are provided in the shape of a disc or puck.  Pods generally range in a size from approximately 45-60 mm and contain approximately 9-10 grams of brewing substance.  The typical pod is used to produce approximately 8 ounces of brewed beverage. 
It is desirable to improve the flavor and extraction of the flavors and other components of the coffee or other brewing substances.  When brewing a beverage it is desirable to saturate, penetrate, agitate and otherwise engage all of the particles of the brewing substance so as to thoroughly wash from the brewing substance all of the desirable flavor characteristics and substances for incorporation into the brewed beverage. 
One method of determining the flavor of coffee or any other brewed beverage is by taste.  One way of more objectively determining the characteristics is by use of an extraction test.  The extraction test requires brewed beverage to be placed in a refractometer which calculates the percentage of solubles.  The refractometer produces a number which can then be compared to an established scale calibrated to various characteristics.  Another technique for objectively determining the characteristics of a beverage is to perform a uniformity of extraction test.  In theory, a properly brewed beverage will uniformly extract solubles, particles and other flavor characteristics from all of the particles of the brewing substance in a generally uniform manner.  In practice, extraction generally does not occur in a uniform manner across all regions of the pod.  In other words, some areas of the brewing substance will be extracted to a desired level, some may be extracted below a desired level and some areas may be over extracted.  This variety of extraction levels in different areas of the brewing substance may occur with brewing devices and methods which employ a pod of brewing substance.  The pod retains the brewing substance in a generally confined area.  As such, the brewing material may not freely agitate within the confinement of the filter material.  As a result the water may tend to pass directly from the top of the pod, collecting solubles as it passes through the pod and exiting through the bottom of the pod in a generally vertical path.  This flow pattern through the pod may result in some areas being over extracted and other areas being under extracted.  Generally, it is acknowledged that pod brewing may produce non-uniform extraction. 
It would be desirable to improve the uniformity of extraction and extraction characteristics of a pod brewing system.