Controlled Atmosphere Equipment
Controlled Atmosphere (CA)
UKCA Ltd has years of experience and a wealth of knowledge in this specialised field. Whether you are installing a new storage facility, upgrading an old one, or seeking to get the best possible performance out of an existing facility, we can help you.
The first commercial CA store was in the UK in 1929 carried out by Spencer and Mount in Canterbury, Kent.
Controlled Atmosphere storage is an area in which the atmosphere is modified to that of the normal air, in respect to CO2 and O2 levels, with the aim of extending the storage life of perishable products. The storage of fresh produce requires the store to be sealed and as air tight as possible, with constant monitoring of the adjusted CO2 and O2 levels. A variable such as fruit and vegetable respiration and leakage of gases though the doors and walls will require the gas mixtures to be observed and changed accordingly.
The most common way to achieve the correct levels of gases combines the natural respiration of the product with the use of CO2 adsorber and nitrogen generator. Sometimes the addition of an ethylene scrubber is beneficial. Along with the modified atmosphere, fresh produces also requires low temperatures to achieve an extended storage life.
A number of probes will be installed in each storage area. These may be spread throughout the store, at different heights, and even inside containers, to accurately monitor the temperature across the storage area. This gives a much more accurate picture of the store conditions than the single sensor attached to the refrigeration unit, enabling you to control the conditions precisely, simultaneously keeping your fruit in good condition and potentially making savings in refrigeration costs.
The signals from several stores may be fed back to a single control location, where variations in conditions may be automatically logged. Depending on the system, it may be possible to monitor the system from another location (even another country) remotely via the internet.
Most systems provide the facility to raise an alarm if the temperature rises or falls beyond pre-determined limits. Some of the more modern systems are able to trigger a text alert via mobile phone, thus ensuring an immediate response to a malfunction in the refrigeration plant or elsewhere.
Despite being in a "dormant" state as a result of being cold and deprived of Oxygen, the fruit will continue to breathe (albeit at a reduced rate) and will continue to produce Carbon Dioxide (CO2). Allowed to build up unchecked, high concentrations of CO2 will cause damage to the fruit. It is therefore essential to monitor levels, and to take action to remove excess levels of CO2 as they occur.
The CO2 Adsorber (or scrubber) draws air from the store and filters out CO2 before pumping it back into the store. By circulating the air in this way, the air returned to the store maintains the important low oxygen conditions.
The Adsorber works by passing the air through a bed of carbon, which attracts and holds the CO2 molecules. Periodically, the machine flushes out the carbon bed by pumping air through it in a reverse direction and venting to the outside, thus there is very little expense in terms of consumables or costly maintenance.
Generally, one Adsorber will be connected to a number of stores, treating each one in rotation via a series of valves. The operation of the machine is controlled by an internal or external analyser, which samples air regularly from each store.
Around 78% of the air that we breathe is made up of Nitrogen, so there is no need to make any more. What this machine does is to filter out the Oxygen from the atmosphere, along with CO2, small amounts of other gases and water vapour, to create a supply of virtually pure Nitrogen.
Using an injection system this is then pumped into the store, gradually displacing the normal air until the desired level is reached. Air from the store is regularly analysed to ensure that the atmosphere is maintained within set parameters.
Recirculation (VSA) systems are also available which take air from the store, remove the Oxygen and return to the store, thus providing a potentially more efficient reduction in Store Oxygen levels
Ethylene is both a product of and a catalyst to ripening, being given off as fruit starts to ripen, and then acting as a trigger to the process. It is therefore essential to swiftly extract the gas before this vicious cycle can become established.
The Ethylene scrubber overcomes these drawbacks by eliminating the need for chemical treatment. Air from the store is passed through a chamber either containing a hot precious metal catalyst or a relatively high Ozone concentration. Both systems process the returning air so that it is fit and ready to rte-introduce to the storage area.
An important benefit of both of our Ethylene systems is the destruction of airborne bacteria, thus also reducing mould and rotting on the surface of fruits and vegetables.
A fully Integrated Control System can simultaneously achieve significant savings in time, whilst helping you to maintain a high degree of control over your storage conditions.
A single unit will receive output from sensors measuring temperature, O2 / CO2 levels, providing clear and regular updates about the storage conditions in several stores at one location. Data may be logged continuously, and arrangements made to trigger an alert if conditions vary outside given parameters.
Various levels of sophistication are available allowing operators to remotely monitor and control storage complexes via an internet link, or relay of alarm conditions to a mobile phone.
Whilst such a sophisticated system does not replace the need for human vigilance, it will provide the information that you need to maintain effective control, and a prompt alert to any potential problems.
We can also supply Portable Analysers, which may be used where fully integrated control is not possible, as an independent check, or as the main control system for smaller installations.
Dynamic Controlled Atmosphere
Dynamic Controlled Atmosphere (DCA)
DCA is a step on from standard CA storage. With DCA we are lowering the oxygen down further, and use the Harvest watch sensor to detect stress induced in the fruit or vegetable being stored
Benefits include better respiration control providing improved long term storage without the use of chemicals
The first large scale DCA installation was completed in the UK in 2013, by UKCA Ltd in conjunction with the Italian manufacturer Isolcell. The system uses sensors called F.I.R.M. (Fluorescence Interactive Response Monitor) to dynamically control the atmosphere allowing the storage of fresh produce at its lowest respiration rate.
The optimum level will vary considerably according to a variety of factors, including;
- The Cultivar
- Growing conditions before harvest
- The state of maturity of the fruit at harvest
- The temperature at which fruit is stored
Guidance concerning recommended "safe" levels will be provided to achieve the optimum conditions. In doing so, the storage life of the crop can be extended significantly. Additional benefits have identified that postharvest chemicals such as 1-MCP are no longer essential to maintain the quality of produce. DCA provides this security whilst also protecting against storage disorders such as superficial scald and internal browning.
Commercially DCA is achieved using three techniques. The easiest, safest and most proven way is using Chlorophyll Fluorescence sensor, the alternative options are detecting the Respiration Quotient or the Fermentation Quotient.
UKCA are the sole suppliers of Isolcells DCA system. If you wish to discuss the viability of Dynamic Control, please contact us for an initial discussion and arrange a site visit.
UKCA Ltd supply Isolcells DCA system due to the vast experience and continual global scientific research being carried out on this technology.
Basics of Chlorophyll Fluorescence principle involves light entering the plant and being absorbed by the Chloroplast. Most of the light is used in the process of photochemistry to create sugar. A small amount is released in a non-photochemical process as heat with some re-emitted as fluoresced (red light) from the plant at a longer wavelength.
This system uses sensors called F.I.R.M. (Fluorescence Interactive Response Monitor) to detect the re-emitted fluoresced light. The F.I.R.M. typically emits up to 10,000 times every 180 secs per cycle thus giving you an average fluorescence (Fα) after each scanned period.
As the oxygen decreases you will reach the LOL where the sensor will detect an increase (Spike) in Fα. This point highlights the transition of the fruit from aerobic to anaerobic metabolism (also known as the Anaerobic Compensation Point -ACP). Maintaining oxygen at 0.1%-0.2% above the LOL allows produce to be stored at the lowest and safest possible O2 level whilst achieving the maximum quality retention. Other stress effects can also be identified using Fα such as; increased carbon dioxide, low temperature and ammonia gas.
To achieve successful DCA storage levels, the CA room and control equipment must be completely air tight to achieve and maintain <0.5% Oxygen.