Feasibility of automatic ventilation technology for sea freight of Protea cut flower products
Advances in cold storage and transport technologies have seen the development of automatic ventilation technology and dynamic controlled atmosphere (DCA). Instead of using the commonly used fixed, open air exchange ventilation (AirEx) at 15,000 L fresh air h-1 during shipping of Proteaceae stems, the new technologies restrict ventilation to gas concentrations that are near the set limits. Ventilation only occurs at O2 levels near the lower O2 limit (LOL) and at levels below the CO2 toxicity limit of the products. The gas exchange dynamics and ventilation requirements of sea freighted Protea cut flowers from South Africa (SA) are largely unknown, which has been a limiting factor to the introduction of automatic ventilation as an alternative within sea freight shipping. Furthermore, the suitability of current sea freight technology for Proteaceae cut flowers that are shipped from SA to Europe is under question due to inconsistencies in product quality upon arrival at their markets. The low storage temperature, AirEx ventilation and lengthy cold storage period have been identified as possible causes of quality loss during sea freight. The feasibility of the use of automatic ventilation technology during exports to distant markets was evaluated by determining the LOL values of the Protea cut flower products when stored at low O2 concentration and assessing the toxicity tolerance in high CO2 atmosphere. Determination of the LOL was done using a fluorescence interactive response monitor (FIRM) sensor attached to a DCA system. High CO2 tolerance was tested by increasing the CO2 concentration stepwise from 5 to 15% CO2 atmospheric concentration (5-10-15% CO2). The LOL values of the products ranged from 0.08-0.25% O2. AirEx atmosphere led to higher moisture loss than high CO2 atmosphere, with insignificant differences between AirEx and low O2 atmosphere. The products stored in AirEx and high CO2 atmospheres had comparable flower head and leaf quality. The flower head and leaf quality of products stored in low O2 was better than that of products stored in AirEx atmosphere.
Matsikidze, S.N., Botes, W.J., Huysamer, M. and Hoffman, E.W. (2018). Feasibility of automatic ventilation technology for sea freight of Protea cut flower products. Acta Hortic. 1201, 455-462
Cape Flora, automatic ventilation technology, long term cold storage, CO2 toxicity, lower O2 limit, Proteaceae