Mechanical properties of green asparagus

The mechanical properties of three sections (upper, middle and lower) of the spears of green asparagus ( Asparagus officinalis ) were investigated as affected by storage and cooking. A range of methods based on cutting, compression and puncture was employed to measure mechanical properties of spear sections. A transverse puncture test was the most suitable for measuring mechanical properties of fresh and cooked spear sections, and it was observed that strength increased along the spear from the upper to the lower section of fresh asparagus. Postharvest storage resulted in strengthening, mainly located in the last portion of the stem. A softening phenomenon was detected in every section as a consequence of cooking. The results of a tensile test on two different tissue types separated from the middle and lower portions of the stem showed that the external tissues were stronger and stiffer than the internal tissues, and both increased in strength and stiffness after 3 days of storage. However, the effect of cooking was different: while the external tissues decreased in stiffness and strength, as expected, a significant increase was observed for the internal tissues of the stem.