Firstly, thanks very much for the newsletters we receive from your institution. It’s really inspiring reading. We would appreciate very much if you could respond to the following question.
We are evaluating our practice of transport and storage of our produce. We are looking at your “Compatible Fresh Fruits and Vegetables During 7 Day Storage” (Thompson & Kader, UC Davis 1999) chart. Dry onions are placed in group 3, 55 – 65 °F, even though the optimal temperature is set to be 32 °F. Can you please explain the reason for the placement of the dry onions in group 3? (A.B.)
You are correct, the recommended long term storage conditions for onions are 0°C and 65 to 70% relative humidity. However onions generally have a long shelf life compared with most produce and decay caused by high relative humidity or condensation is a key source of postharvest loss. Cold rooms in retail stores and home refrigerators usually have high humidities, above the recommended levels, so we recommend short term storage in warm, unrefrigerated areas that usually have low relative humidities.
Our recommendations in the seven-day storage chart not only consider optimum produce storage conditions but also the compromises that must be made in the less than optimum options we have in retail distribution and home storage. –Jim Thompson