The food industry continuously changes based on consumer demand and economic realities. Most recently, the industry’s focus has been on food safety, quality, and shelf life. One of the responses to these concerns within the food industry has been the increased use of Modified Atmosphere Packaging (MAP).
Explore this issueAugust/September 2007
Exposure of food products to the atmosphere causes oxidation of the product, resulting in decreased shelf live, loss of flavor, and discoloration. MAP reduces the amount of oxygen to which the product is exposed. This is accomplished by flushing the package with nitrogen or CO2 prior to sealing, creating an internal package environment of less than 0.5% oxygen. In order for a MAP package to meet the objective, there must be good packaging materials with oxygen barriers, a good flush of the package before sealing, and a good seal for package integrity.
While the development and evaluation of packages and packaging materials has been going on for centuries, real-time monitoring of MAP processes is now available. One method is through the MAP 1000 System, developed by OxySense, Inc. Earlier the OxySense 4000B system allowed packaging laboratories to monitor oxygen levels inside the package without having to destroy the package to do so. The newer systems also allow the operator to have real-time, noninvasive monitoring, control, and documentation of the flush cycle.
Oxygen in packages is typically monitored by extracting a sample of the atmosphere from the package or flush chamber, which is then taken to an instrument that makes the measurement. The sample is extracted automatically using a vacuum system with long hoses/tubes. The drawback to this type of system is that it does not provide real-time information, is intrusive and does not provide documentation of the flush cycle. The vacuum system can easily break down, or the sampling tube can easily be clogged, leading to unreliable data readings and resulting in stoppages of the packaging line.
New technologies provide noninvasive, real time, passive, in-situ monitoring of the flush chamber/packages. With this system, there is no sample extraction, no vacuums or hoses. One such system, the OxySense MAP 1000, has two components—the Master Controller (the box) and the OxySentry Sensor—and no moving parts, meaning limited maintenance. Oxygen is measured directly in the chamber or package using the solid state optical sensor.
Optical sensing allows measurements without disturbing the environment in which they are being made. The act of sensing does not consume the oxygen. This is different from the conventional sensors as they consume the oxygen during measurement and alter the environment in which they are being used.
Based on Fluorescence Quenching of Dye
The optical oxygen sensing method used in one of the new technologies the OxySense MAP 1000 is based on the fluorescence quenching of a dye immobilized in a gas permeable hydrophobic polymer (a patented formulation that can stand high temperatures, oils, and other harsh environments).
The dye absorbs light in the blue region of the spectrum and fluoresces in the red region of the spectrum. The presence of oxygen quenches the fluorescent light from the dye, resulting in a change in the emitted intensity as well as its lifetime as function of oxygen concentration. The change in the lifetime can be calibrated to provide very accurate oxygen measurements. The change in the oxygen concentration can be calibrated resulting in a very accurate oxygen sensor, which is totally passive (does not consume oxygen to make the measurement). The fluorescence decay curves for various oxygen concentrations are shown.
The accuracy of measurements made by this optical sensing method has been compared with measurements made by a gas chromatograph and show a high degree of correlation. These tests were independently conducted and show better than 99% correlation with GC in light and dark conditions.
Simple, Reliable Measurements
The MAP 1000’s instrument box contains all the electronics and is, in effect, the controller. The separate OxySentry sensor can be configured and customized to the individual production lines such as machines with flush chambers, form fill and seal machines.