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From farm to plate, food usually has a long and arduous journey before it reaches us. In the United States, it is estimated that the typical distance that food travels from the farms where it is produced to the dinner table where it is ultimately consumed as food is between 1500 and 2500 miles1. Even fruits and vegetables that we may think of as ‘fresh’ could have been in storage or traveling for much longer than we think, potentially up to four weeks in the case of lettuce.2
Although locally-sourced produce has reduced food miles, it is still important for these suppliers to ensure the best quality and freshness for their produce. If food is not properly stored and transported, the vitamin content can deteriorate3 along with the appearance of the produce, making it less attractive and more difficult to sell to consumers.
One approach that has been particularly successful in preserving food quality during transportation and storage is incorporating gaseous microenvironments in food packaging and storage, known as modified atmospheric packaging (MAP), or atmospherically modified package (AMP).
In this approach the containers that foods are packed in have an environment with carefully-controlled gas concentrations.4 MAP has been used with a huge number of the foods we buy to enhance their freshness and lengthen shelf lives without the addition of preservatives or modification of the food itself in any way.
A Fresh Environment
Regardless of whether it’s by land, air or sea, fruit and vegetables are usually transported under refrigerated conditions, typically around 5°C with carefully controlled humidity. 5 The low temperature slows the growth of any microorganisms and extends the lifetime of the food, when used alongside MAP.
MAP is undoubtedly effective in preserving produce quality6, but the gas mixture to achieve optimum freshness varies from produce to produce. For example, using a small amount of O2 in the atmosphere helps most plant-based produce to respire, but this has to be balanced with increased CO2 concentrations to decrease the rate of respiration sufficiently to improve the lifetime of the produce.7, 8
This gas concertation can also vary slightly between different types of fruit and vegetables. Citric fruits, for example, can only tolerate a lower limit of a 5% O2 concentration, whereas apples and pears can stand O2 concentrations down to 1%.9
Such precise margins in the environmental conditions for optimum fruit and vegetable preservation during transportation, requires highly-sensitive gas sensors that can distinguish the slightest variation in gas concentration. These gas sensors must be able to monitor the gases typically used in MAP for fresh fruit and vegetable preservation: CO2, O2 and sometimes N2.
Precision for Freshness
Edinburgh Sensors offers a range of gas monitoring systems, ideal for ensuring optimum gas conditions during fresh food transportation. In particular, the range of CO2 online monitoring sensors includes the Guardian NG10, Gascard NG11, the IRgaskiT12 and the Gascheck13. These devices will meet the needs of most customers for food transport applications.
Where low-cost, highly-robust gas monitors are desirable, the Gascheck is an ideal option. Capable of detecting CO2 concentrations in the 0-3000 ppm range, with a zero-stability of ± 3% over 12-months and an accuracy of ± 3% over the full detection range. Depending on the particular version of the Gascheck, the response time can be as low as 30 seconds, with an initial warm-up time of 5 minutes.
Where higher accuracy is desirable, the Guardian NG comes in a range of options with an accuracy of ± 2%. The Guardian NG also has a convenient interface which displays true volume % readout over a wide range of pressures as well as being capable of displaying historical graphical information over a user-defined period. If necessary, there are built-in alarm systems to warn if gas concentrations deviate too much or the possibility to connect and interfacing with external logging devices.
The Gascard NG now comes in two versions, either as the stand-alone card, or as the Boxed Gascard14 to minimize installation and set-up time. The Gascard is capable of detecting CO2 concentrations in the range of 0–5000 ppm and, like the other Edinburgh Sensors products, can also operate in humidity conditions spanning 0 – 95%. By using RS232 communications the Gascard can be integrated with other control or data logging devices, also with the option for on-board LAN support where required.
The full range of instruments from Edinburgh Sensors comes with both pre- and post-sales technical support and these devices build on their nearly 40 years of expertise in a range of gas sensor technologies. Most of these products are based upon infra-red detection, which facilitates their very high sensitivities for gases such as CO2 or other hydrocarbon species like methane and in systems like the Boxed Gascard, the infrared source is field-replaceable.
Online monitoring of gas concentrations for MAP applications allows maintenance of optimum conditions for fresh fruit and vegetable preservation, which is highly beneficial not just for ensuring better quality produce, but also ensuring less food spoilage and wastage and the cost-savings associated with this.
References and Further Reading
- B. Halweil, Home Grown: The Case for Local Food in a Global Market, World Watch Institute, 2002
- How old are the ‘fresh’ fruit and vegetables we eat, https://www.theguardian.com/lifeandstyle/2003/jul/13/foodanddrink.features18, (accessed February 2019)
- M. I. Gil, F. Ferreres and F. A. Tomás-Barberán, J. Agric. Food Chem., 1999, 47, 2213–2217.
- B. Ooraikul, Modified Atmosphere Packaging of Food, Springer, 1991
- Packing Fresh Fruit and Vegetables, https://www.modifiedatmospherepackaging.com/~/media/Modifiedatmospherepackaging/Pictures/Guide%20%20%20Packaging%20of%20Fresh%20Fruit%20and%20Vegetables%20%20%20PDF%20file.ashx, (accessed February 2019)
- E. M. Yahia , Modified and Controlled Atmospheres for the Storage, Transportation, and Packaging of Horticultural Commodities, Taylor and Francis Group, USA, 2009
- Modified Atmospheric Packaging Poster, https://modifiedatmospherepackaging.com/~/media/Modifiedatmospherepackaging/Brochures/MAP-Poster-Guide-2014.ashx, (accessed February 2019)
- S. Mangaraj and T. K. Goswami, Fresh Prod., 2009, 3, 1–33.
- A. A. Kader, D. Zagory and E. L. Kerbel, Crit. Rev. Food Sci. Nutr., 1989, 28, 1–28.
- Guardian NG, https://edinburghsensors.com/products/gas-monitors/guardian-ng/, (accessed February 2019)
- Gascard NG, https://edinburghsensors.com/products/oem/gascard-ng/, (accessed February 2019)
- IRgaskiT, https://edinburghsensors.com/products/oem/irgaskit/, (accessed February 2019)
- Gascheck, https://edinburghsensors.com/products/oem/gascheck/, (accessed February 2019)
- Boxed Gascard, https://edinburghsensors.com/products/oem/boxed-gascard/, (accessed February 2019)
This information has been sourced, reviewed and adapted from materials provided by Edinburgh Sensors.
For more information on this source, please visit Edinburgh Sensors.