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Microclimate tools to monitor quality changes in stored onions

Islam, Md. N., Wang, A., Skov Pedersen, J., Edelenbos, M.
Acta horticulturae 2017 no.1154 pp. 229-234
cooling, cultivars, disease incidence, harvesting, microclimate, monitoring, onions, organic production, relative humidity, spoilage, sprouting, storage temperature, storage time
Losses of onion are caused by spoilage from microbial infection, sprouting and mass loss. Pre-harvest factors such as cultivar, climate and growing conditions, as well as harvesting, curing, storage duration, temperature and relative humidity during storage, influence losses. The optimal storage conditions for onions are 0°C and 65‑75% relative humidity (RH); however, it is costly to store onions at this low temperature for long periods. It can also be challenging to maintain low RH at low storage temperature. The aims of the present study were: 1) to test the applicability of a HortiSens® sensor to monitor temperature and RH under experimental conditions and to evaluate the effects of 2) conventional and pulse cooling, and 3) low and high RH during storage on the quality of conventionally and organically grown onions. We found that online microclimate monitoring using the novel wireless HortiSens® sensor gave similar results as data from other sensors. Onions had higher basal root sprouting with pulse cooling and after storage in high RH. There was a higher incidence of disease at high RH, but lower mass losses. Organically grown onions had higher incidence of root sprouting and diseases than conventionally grown onions, especially during storage at high RH.