Fruits and vegetables stay fresh longer thanks to controlled atmosphere

To offer seasonal fruits and vegetables throughout the year, they must be kept in controlled atmosphere (CA) storage areas for several months. Humidity, temperature and CO₂-sensors are critical to ensure challenging conditions in these spaces. 

To ensure that fruit retains its consistency, ingredients, color and flavor for as long as possible, it is stored in cold rooms at consistently low temperatures and high humidity. In addition, the composition of the storage atmosphere also has a major influence on storage capacity. The ideal composition of the atmosphere in CA storage depends on the specific fruit or vegetable type. Typical storage conditions are usually in the following ranges: < 2% O₂ ; 0.5 - 5 °C; 0-5% CO₂ and up to 98% RH. 

DCA storage

DCA storage technology, where DCA stands for Dynamic Controlled Atmosphere, is an improvement over conventional CA storage. It takes into account the fact that the stored fruit continuously produces heat, water, carbon dioxide and ethylene (C₂H₄) released to the ambient air by cellular respiration, changing the composition of the storage atmosphere. Therefore, in DCA storage, oxygen content and ethylene and carbon dioxide concentrations are continuously monitored and dynamically controlled. The goal is to achieve the lowest possible oxygen content, just above the anaerobic compensation point (ACP), or the critical oxygen concentration at which fermentation occurs in the fruit metabolism process.

Oxygen content

In so-called Ultra Low Oxygen (ULO) or Extreme Low Oxygen (XLO) storage facilities, oxygen levels are gradually reduced to about 0.7 to 1%. This puts the stored fruit into a kind of "coma" and reduces fruit metabolism to the absolute minimum. Varietal-specific O₂- and CO₂-values must not be exceeded or exceeded in this process, otherwise the fruit will be damaged by lack of oxygen or excessive CO₂-concentration.  

Accurate sensors 

To ensure ideal storage conditions, CA / DCA storage rooms are equipped with a wide range of technical systems for cooling, air conditioning, humidification and gas management. A prerequisite for precise control of storage conditions is continuous monitoring of the relevant climate parameters using appropriate sensors. Reliable measuring devices that provide exact readings are of great importance in this regard. 

To measure is to know

Humidity, temperature and CO₂ are among the most important parameters to be monitored in CA / DCA storage. Due to the challenging conditions in storage rooms, the following requirements arise for the sensors: high measurement accuracy (<2% RH) and long-term stability under conditions of high humidity, a contamination-resistant measurement principle, ideally with automatic calibration, resistance to chemical contamination, condensation-resistant, robust housing with protection class IP65 or higher and easy maintenance and sensor replacement in case of service. 

EE211 and EE872 

CaTeC bv offers Humidity, temperature and CO₂-sensors from E+E Elektronik that are specially designed for use in demanding conditions. For example, consider the EE211 and the EE872. For example, the EE211 is humidity and temperature sensor equipped with a heated humidity probe and a replaceable temperature sensor. The combination of sealed electronics and unique E+E sensor coating ensures high measurement accuracy even under challenging environmental conditions. The EE872 CO₂-probe with heated, easily replaceable sensor module is particularly suitable for environments with high humidity and condensation. CO₂measurement is based on the pollution-resistant NDIR dual wavelength principle and automatically compensates for aging effects.