TEXTURAL PROPERTIES AND CELL WALL METABOLISM OF WHITE ASPARAGUS SPEARS (ASPARAGUS OFFICINALIS L.) DURING POSTHARVEST

Texture is one of the predominant quality requirements for fresh asparagus spears and serves as an indicator of product quality and acceptability. The dynamics and interaction between mechanical characteristics of textural properties, water status and cell wall compounds were investigated in white asparagus spears during short-time storage at different storage temperatures. The apparent elastic modulus E and dynamic stiffness S, both describing the elastic properties of asparagus spears, showed similar patterns for all temperatures. Both parameters declined at storage temperatures of 0°C and 20°C, whereas they remained almost constant at 5°C and 10°C. These changes were found to be associated with the pressure potential, which tended to increase during storage at the lower temperatures. Moreover, these changes were accompanied by an increase in water insoluble pectic substances. Cutting force (N), which reflects tissue strength of asparagus spears, declined at all storage temperatures. However, the decline was more pronounced after four days of storage at 0°C and 5°C. The decline in firmness correlated with the increasing water potential and with a decrease in the EDTA soluble pectin fraction. These results may indicate a loss of tissue integrity (Ca is released from the pectin bridges) which might have led to a lower tissue strength accompanied by a highly turgescent tissue in asparagus spears during short-time storage.