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It is becoming increasingly difficult to meet the food requirements of a growing global population. In spite of the need for additional food, it has been estimated that 50-60% of grain is lost after harvesting, at a cost of about $1 trillion per year.1
One of the major reasons for lost grain is spoilage due to insect or mold infestation during storage.2 A constant supply of grain is provided all through the year by keeping the grains in long term storage after they are harvested. It is crucial to maintain the quality of stored grain in order to prevent economic losses for Farmers and also to ensure the quality of the final food products.
Molds and insects can grow in stored grain, and their potential to flourish depends on the moisture and temperature of the stored grain. Molds are considered to be the most common cause of grain spoilage and can bring about changes in the quality and appearance of stored grains. Some molds are capable of releasing toxic chemicals called mycotoxins, which can reduce nutrient absorption, suppress the immune system, cause cancer and also be lethal in high doses. It is thus crucially important to prevent the existence of mycotoxins in food products.2
Monitoring Stored Grain
Farmers are advised to conduct a weekly check on their stored grain in order to look out for signs of spoilage.3 Grains are traditionally checked both visually and by odor. Grain sampling can permit earlier detection of molds and insects, but these methods can be time-consuming and tiresome. Simple, rapid methods are required for early detection of spoilage and to prevent grain losses.2
When molds and insects grow and respire, they produce CO2, heat and moisture. Temperature sensors detect increases in temperature caused by insect infestation or mold growth, thus indicating the existence of grain spoilage. However, they are not able to detect temperature increases brought about by infestation unless the infestation is within a few meters of the sensors. CO2 sensors are capable of detecting the CO2 produced by insects and molds during respiration. As the CO2 gas moves with air currents, CO2 sensors will be able detect infestations that are located far away from the sensor than temperature sensors. CO2 measurements are thus considered to an important part of the toolkit needed to monitor stored grain quality.2
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Using CO2 Measurements to Detect Spoilage
CO2 monitoring can be employed for monitoring the quality of stored grains, and for early detection of spoilage in stored grains. Safe grain storage generally results in CO2 concentrations below 600 ppm, while concentrations of 600-1500 ppm indicate the onset of mold growth. Severe infestations are indicated by CO2 concentrations more than 1500 ppm, and these concentrations can also represent the presence of mycotoxins.4
CO2 measurements can be performed in a rapid and effortless manner and can detect infestations 3-5 weeks earlier than temperature monitoring. After spoilage has been detected, the Manager of the storage facility will address the problem by aerating, selling, or turning the grain. Additionally, CO2 measurements can help in deciding which storage structure should be unloaded first.2
Research published by Purdue University and Kansas State University has established that increased CO2 levels detected by portable and stationary devices are linked with elevated levels of spoilage and the existence of mycotoxins.4,5 In addition, they compared the potential of temperature sensors and CO2 sensors in a storage unit filled with grain, to identify the presence of a simulated ‘hot spot’ developed using a water drip in order to promote mold growth.
The CO2 concentration in the headspace of the storage unit displayed a strong correlation with the temperature at the core of the hot spot, and the CO2 sensors were, thus, capable of detecting biological activity. The temperature sensors were unable to identify the mold growth, even though they were placed within 0.3-1 m of the hotspot.6
Accurate, simple and reliable use of CO2 detectors will help in efficient monitoring of grain spoilage. Gascard NG Gas Detector from Edinburgh Sensors offer precise CO2 measurements together with atmospheric data, thus allowing grain storage Managers to make decisions with confidence.7
A proprietary dual wavelength infrared sensor is used by the Gascard NG Gas Detector to enable the long term, reliable measurement of CO2 over different concentrations and in temperatures ranging from 0-45 °C. Measurements are not affected by humidity (0-95% relative humidity), and real-time environmental compensation is provided by the onboard pressure and temperature sensors, resulting in the most accurate CO2 concentration readings.
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Easy, accurate and fast CO2 concentration monitoring during grain storage can offer early detection of grain spoilage, resulting in higher quality stored grain, reduced grain losses and lower mycotoxin levels. CO2 monitoring is capable of saving millions of dollars every year in the grain production industry.4
References and Further Reading
- Kumar D, Kalita P, Reducing Postharvest Losses during Storage of Grain Crops to Strengthen Food Security in Developing Countries. Foods 6 (1):8, 2017.
- Monitoring CO2 in stored grain - World Grain, Accessed May 25th, 2017.
- HGCA Grain storage guide for cereals and oilseeds, third edition, Accessed May 25th, 2017.
- Maier DE, Channaiah LH, Martinez-Kawas, A, Lawrence JS, Chaves EV, Coradi PC, Fromme GA, Monitoring carbon dioxide concentration for early detection of spoilage in stored grain. Proceedings of the 10th International Working Conference on Stored Product Protection, 425, 2010.
- Maier DE, Hulasare R, Qian B, Armstrong P, Monitoring carbon dioxide levels for early detection of spoilage and pests in stored grain. Proceedings of the 9th International Working Conference on Stored Product Protection PS10-6160, 2006.
- Ileleji KE, Maier DE, Bhat C, Woloshuk CP, Detection of a Developing Hot Spot in Stored Corn with a CO2 Sensor. Applied Engineering in Agriculture 22(2):275-289, 2006.
- https://edinburghsensors.com/products/oem/gascard-ng/ Accessed May 25th, 2017.
This information has been sourced, reviewed and adapted from materials provided by Edinburgh Sensors.
For more information on this source, please visit Edinburgh Sensors.