Impact of Ethanol Treatment on the Chemical Properties of Cell Walls and Their Influence on Toughness of White Asparagus (Asparagus officinalis L.) Spears

Toughening is the most important postharvest factor that negatively affects quality of fresh white asparagus (Asparagus officinalis L.) spears. It is assumed to result from wounding-induced or developmentally regulated cell wall thickening and increased lignification of sclerenchyma sheath cells and of vascular bundle elements. Postharvest application of ethanol has been shown to be an effective disinfectant of white asparagus spears; it is also known to delay or inhibit plant development. The latter was tested for its potential efficacy to reduce undesired spear toughening. In this context, effects of ethanol treatment on changes in cell wall properties were investigated. Practically relevant short-term washing of spears in 50 % ethanol solution (v/v) at 10 A degrees C for 30 and 90 s reduced toughening of fresh white asparagus spears during 4 days of storage at approx. 20 A degrees C. The treatment inhibited the biosynthesis of secondary cell wall structural carbohydrates (hemicellulose and cellulose) and of lignins, although to a lesser extent. Cell wall contents of pectic substances were also less affected, while the content of cell wall proteins was pronouncedly reduced by ethanol exposure. As a conclusion, practically relevant short-term washing with ethanol solution seems to be a promising approach to improve quality maintenance and safety of fresh white asparagus spears.