Kazuhide Kawada

Seasonal changes of asparagus spears in relation to enzyme activities and carbohydrate content

Seasonal changes in the activities of acid invertase, sucrose synthase (SS) and sucrose phosphate synthase (SPS) along with the sugar content were studied in asparagus spears (Asparagus officinalis L. cvs. E414 and Welcome) grown in the greenhouse. The primary objective of this study was to understand the effect of long-term harvesting on the quality of green asparagus spears. Both soluble and cell wall-bound acid invertase increased in activity until June after which they changed very little. Similarly, SS activity increased to a maximum in June and changed little after this time. SPS activity changed little throughout the season. Sucrose concentration declined from March to a minimum in June and increased again in October. On the other hand glucose and fructose concentrations increased to a maximum in June and thereafter changed little except for a possible decline in October. A highly significant negative correlation was found between acid invertase and SS activities and sucrose content accounting well for the relation between the substrate and the activity. There were no significant differences between the cultivars.

Changes in Acid Invertase and Fructanase Activities and Sugar Distribution in Asparagus Spears Harvested in Three Different Seasons

Changes in acid invertase (EC3.2.1.26), fructanase (EC3.2.1.7) activities and sugar distribution were investigated in the different portions of asparagus (Asparagus officinalis. L. cv. E414, HC, WC and S-235, grown in greenhouse) spears harvested in “Spring harvest (2nd and 3rd of March)”, “Middle harvest (27th and 29th of May)” and “Summer harvest (27th of August)”. The weight of “Middle harvest” asparagus was apt to be higher than “Spring harvest” and “Summer harvest”. In soluble and cell wall-bound fractions, the acid invertase and fructanase activities of the two spears increased in the “Middle harvest” concurrent with the most rapid increased in reducing sugar content but with a lower sucrose and fructane contents. In the top portion of ‘HC’, substrate of sucrose was negatively correlated with acid invertase activity in soluble fraction and accounted well for the relation between the substrate and the activity. Due to the existence of fructane in the spear, fructose content was considered to be higher than glucose content. The best harvest time was in the “Middle harvest” since the total sugar content and fresh weight were adequate.