ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

High CO2 induces translucent scale in stored onions

Purvis A.C. and Paulk J.T.

5th International Postharvest Symposium . Volume of Abstract . Verona, Italy 6-11 June 2004, p.103

2004

บทคัดย่อ

Controlled atmosphere (CA) storage has been used successfully to extend the postharvest shelf life and marketing period of Vidalia sweet o­nions. Low (3%) O₂ in the CA storage room maintains dormancy and reduces sprouting of the bulbs, while elevated CO₂ reduce decay. We have reported that although CA dose not reduce the growth of Botrytis allii in previously inoculated o­nions, CA dose inhibit sporulation and the spread of the disease to sound o­nions. However, some early studies suggested that high (> 10%) CO₂ may cause a physiological disorder in stored o­nions. The internal breakdown is characterized by a clearing and water-soaking of the normally opaque cells of the fleshy internal scales and has been called watery or translucent scale. Although high CO₂ was implicated as the causal factor in the development of translucent scale, the studies were confounded by low O₂ concentrations in the storage room atmosphere.

During the 2001-02 and 2002-03 seasons, ‘Savannah Sweet’ o­nions were stored in air or air + 10% CO₂ in 32-L plastic containers at 1°C. After 13 weeks, all o­nions that had been stored in air + 10% CO₂ exhibited translucent scale, while no o­nions that had been stored in air o­nly exhibited any internal breakdown. However, the surface of most of the o­nions stored in air was covered extensively with sporulating Botrytis allii but none of the o­nions stored in air + 10% CO₂ exhibited any surface fungal growth. Clearly, translucent scale is caused by high CO₂ and not low O₂ in the storage room atmosphere. Translucent scale may be a greater problem in storage rooms without CA than in CA rooms unless the CO₂ produced during respiration of the o­nions is monitored and the levels controlled.