Towards a freshness test for asparagus: spear tip asparagine content is strongly related to post-harvest accumulated heat-units

The shelf-life of asparagus (Asparagus officinalis L.) is strongly related to the post-harvest accumulated heat-units; the greater the number of accumulated heat-units (degree-h > 0 degrees C) experienced by the spears the lower the residual shelf-life. The potential of using asparagine and/or amino acid content as markers of freshness for asparagus spears was assessed by determining the relationship between the concentrations of these metabolites in the spear tips of two cultivars ('Limbras 10' and 'Jersey Giant') and the past-harvest age of the spears in terms of accumulated heat-units. There was a strong quadratic relationship between spear tip asparagine content and degree-h (R-2 = 0.878) that was independent of cultivar (P = 0.16). Free amino acid content was also correlated quadratically with degree-h (R-2 = 0.788 and 0.813 for 'Limbras 10' and 'Jersey Giant', respectively) but this was cultivar dependent (P = 0.002). Spear tip asparagine concentration has potential as a marker of freshness for asparagus but requires the development of an asparagine assay suitable for use in packhouses or by exporters. (C) 1998 Elsevier Science Ltd. All rights reserved.