Coffee beans quickly lose their freshness if they are exposed to oxygen; so roasted beans are packaged and sealed in carbon dioxide, sometimes with other gases present too. However, roasted beans absorb carbon dioxide in a process referred to as drawdown, which is why coffee often appears to have been vacuum-packed.
Gas suppliers will provide a certificate of conformance stating that the composition is within the acceptable limits, and packaging machinery will be regularly tested to ensure that it is functioning correctly. But many in the industry believe that testing is necessary in order to be certain that coffee is packed in the correct atmosphere.
At this particular US coffee producer, a number of packs of coffee are sampled per thousand produced and the oxygen concentration is checked. This is done by using a probe that consists of a hypodermic needle, the tip of which is surrounded by a foam pad that prevents the ingress of gases from the working environment.
The needle tip pierces the pack and a small volume of gas is extracted by the analyser's internal pump (an inline filter ensures only gases are drawn into the measurement cell). In cases where drawdown has reduced the free gas, multiple samples can be taken to provide sufficient sample volume for the analyser - though the manufacturer claims that the 574 analyser can operate with as little as 2.5ml of gas.
A portable instrument can be used across several different production lines, but one of the main attractions of the 574 is its size; often the gas analyser will be vying for benchtop space with other quality assurance (QA) equipment such as weighing scales. A portable instrument can also be carried back to a QA laboratory for recalibration if required, or the Servomex 574 can be easily recalibrated in the production environment using nitrogen and/or air to maintain its accuracy of 0.2 per cent oxygen with a repeatability of +/-0.1 per cent oxygen.
A further advantage of the 574 analyser is that it uses non-depleting paramagnetic technology in the sensing cell, which according to Servomex means that the operator can be certain that it will always function correctly. The company claims that in contrast, other sensing technologies can degrade, giving no indication that the readings are misleading.
Servomex' gas analysis solutions are used worldwide to improve plant efficiency, increase product quality and maintain plant and process safety. The company is also involved in helping companies to comply with environmental legislation.