Ethelyne meets the needs of potato and onion storage

Greenvale AP are just finishing their 7th year of prepack potato storage using the Restrain ethylene system. The Restrain generators built by International Controlled Atmospheres (ICA Ltd ) at their new factory in Paddock Wood have proved robust, simple and reliable in commercial store situations. “The fact that they are easily portable being light enough to pick up & carry makes the system very flexible. We run 60,000 tonnes of potato storage and can move the Restrain systems round as we empty early stores and move them in to long term stores” reports Paul Coleman Technical Director of Greenvale AP. The Restrain generators simply plug in to a single phase socket with a sensor on a 20m long cable. They convert alcohol to ethylene (+ some water) which means there is no need for expensive explosive monitoring systems which are required when ethylene gas cylinders are used.

Sprout suppression has been very reliable but the Restrain Company has continued to invest in ethylene research at the BPC's Sutton Bridge Experimental Station. This research identified important criteria for the slow introduction of ethylene which is now fully automated in the Restrain Generator controls. Research also focused on the interaction between high CO2 levels and ethylene. CO2 has been overlooked by the prepack industry unlike the processing industry which manages CO2 in potato stores as a routine. CO2 is low in many stores due to natural air leakage into the building but some build types need management by flushing fresh air especially new or brick/block built coldstores stores.

Both CO2 and ethylene temporarily increase the respiration rate of the potato. “It is important that growers keep CO2 low when using ethylene as high respiration rates are not desirable. I also recommend growers continually move the air in the store during the first 3 weeks of ethylene introduction. This prevents any localised CO2 build up in the middle of the boxes or in “dead” areas of the store” says Paul Coleman.

From Greenvales own experience of ethylene in prepack potatoes we are very happy and it avoids residues which result when other chemical sprout suppression are used.

Ethylene is now also becoming established in onions to prevent sprouting in store. This is being driven by the onion packing companies including Stour Garden , Bedfordshire Growers and Moulton Bulb Company which between them supply most of the major retailers. “I have not had a lot of close contact with the use in onion stores but the feedback is very positive and I am aware the number of onion stores with Restrain continue to increase year on year. Some packers are using it to replace maleic hydrazide which is the only sprout suppression available for onions and has to be applied to the growing crop while others are using it in combination with maleic hydrazide or CA storage to extend the storage season and reduce the need for imported southern hemisphere onions..

The larger onion producers report that ethylene offers management flexibility not previously available. It is not possible to be sure about which onions are the best quality for long term storage until after they are harvested and cured in store. As a result maleic hydrazide used to be applied to most of the growing crops even though some may be marketed quite early from store when MH need not have been used. The Restrain ethylene system allows growers to avoid having to make the decision about sprout suppression until the onions are safely loaded, cured and the long term storage crops identified. The Restrain generator is simply placed in the appropriate store whether bulk or box and switched on.

Ethylene is currently progressing through Annex 1 registration supported by a consortium of companies including fruit companies as well as Restrain Company Limited. Restrain has also completed several years of efficacy work on potatoes, seed potatoes and onions which will be required for individual country registration post Annex 1. Annex 1 approval is expected in the next 2-3 years. The Restrain Company has patented the use of ethylene in onions as well as the equipment design.