There are many different approaches to food preservation for extending the lifetimes of perishable goods. From pickling, salting, canning or jellying, all of these approaches have different effects on the properties of the preserved produce and are suitable for different types of food. Two of the most widely used methods for food preservation are freezing and dried food storage.
The low temperatures involved in freezing food kill and prevent the growth of bacteria and other microorganisms and help to reduce nutrient loss. Drying foods, on the other hand, achieve bacterial growth inhibition by removing moisture from the food and slows down the enzyme activity alongside this.
As well as the atmospheric conditions during the freezing or drying process being important for maximizing the quality of the produce, the relative ratios of different atmospheric gases and humidity is also crucial during the storage of preserved foods. For dried products such as flour or cereals, ‘modified atmospheric conditions’, or storage of the food in specific, controlled mixture of gases, can extend shelf life by up to three times by inhibiting chemical reactions that lead to degradation and spoilage.
Modified atmospheric conditions are now commonplace in the packaging, storage, and transport of all kinds of food products, from fresh to frozen produce. High carbon dioxide and reduced oxygen levels can be beneficial for killing invasive insect species or microorganisms that would otherwise grow on and spoil the food as it was stored. High nitrogen concentrations can be used as a humidity control for keeping dried foods as it can help preserve food quality while extending food lifetimes.
By using gas mixtures to replace insecticides and the addition of preservatives such as nitrites to meats, modified atmospheric package, and controlled atmosphere storage offer a versatile and effective way to preserve foods without the need to add additional chemicals or processing stages.
The main gases of interest for modified atmosphere storage are carbon dioxide, oxygen, and nitrogen. However, controlling and maintaining the concentrations of these gases, particularly for dried food storage can be challenging. Optimum conditions often require very precise levels of control, with gas concentration ranges needing to be within 1 % of a given value. The other challenge for foods such as cereals is that they continue to produce and release gases such as carbon dioxide and carbon monoxide so the atmospheric conditions require constant adjustment. Monitoring gas levels is advantageous not just for maintaining optimum storage conditions, but also as increased carbon dioxide production can be an early indicator of food spoilage.
Frozen and Dried Food Storage
Gas monitoring for frozen and dried food comes with a particular set of challenges. Often, the freezing process is performed using carbon dioxide as a cryogen. The carbon dioxide is normally used in its solid form, known as ‘dry ice’, which has a temperature of – 79◦C. This allows rapid cooling of the food to help reduce risk of contamination and preserve food quality.
However, the National Institute for Occupational Health and Safety indicating that CO2 levels of 40 000 ppm (4%) are immediately dangerous to life and health with 10-hour workplace exposure limits being set at much lower limits. Foods may also be kept in similar cryogenic conditions during transportation and before use to reduce food wastage so reliable gas monitoring during the freezing and storage process is an essential part of health and safety.
For dried foods, even dried fruits produce not insignificant levels of carbon dioxide over time so for storage of large volumes of dried fruits, such as in grain barges, carbon dioxide monitoring is key for both food preservation and worker safety.
For frozen and dried food storage, real-time gas monitoring and logging can help prevent unnecessary wastage while keeping produce in its optimal conditions. To achieve this requires gas detectors capable of constant, online analysis and with rapid response times and good accuracy.
Edinburgh Sensors are one of the market leaders in the development and production of non-dispersive infrared sensors (NDIR). As many hydrocarbon gases and molecules like carbon dioxide absorb infrared light very efficiently, NDIR sensors offer a very sensitive approach to detecting even small concentrations of such molecules.
Some of the NDIR sensors offered by Edinburgh Sensors include the Gascard, the Guardian NG, and the GasCheck. All of these devices have minimal need for recalibration and long device lifetimes and are capable of self-correcting measurements over a range of humidity conditions (0 – 95 %) ensuring they always achieve the best accuracy and reliability.
All of Edinburgh Sensors’s products can be interfaced with networking data logging systems or more complex control software if setting up feedback systems to maintain active control over modified atmospheric conditions is desirable. In the case of the Gascard, this can be done with on-board R323 connections but the Boxed Gascard version of this instrument can also be quickly connected via USB for immediate use.
With accuracies for carbon dioxide monitoring typically in the ± 2 % range, Edinburgh Sensors has a variety of solutions for gas monitoring even in challenging environmental conditions and offer full pre- and post-purchase technical sales advice.