Influence of pre-harvest calcium applications on table olive characteristics during Spanish-style elaboration process

Abstract

Calcium is largely used in the agri-food industry thanks to its positive effects, such as its preserving activity or its protection against pathogens. Post-harvest spraying of calcium chloride (CaCl2) solutions has demonstrated an increase in firmness and phenolic content. The aim of this research was to investigate the effects of pre-harvest applications of two CaCl2 concentrations (Ca 0.5% and Ca 1.0%) during the Spanish-style elaboration process at the beginning, middle, and end of the fermentation process. The analysis focussed on the Ca concentration in the whole fruit and in the different tissues (pulp, pit, and seed), as well as on the firmness, phenolic content, and antioxidant activity in the ‘Ascolana tenera’ table olive. An increased Ca concentration in the pulp (20.2 and 55.1%) and seed (13.4 and 36.5%) was observed during a monitoring period in which 0.5% and 1.0% CaCl2 concentrations, respectively, were compared with Ca 0% (water). No significant Ca increase was found in the pit. The fruit firmness was higher following the Ca treatments (22.8% and 68.3%, respectively), and a decrease in the contents of hydroxytyrosol, tyrosol, and verbascoside was observed during the elaboration process. The highest content of these phenols was found on the first date of monitoring for a 1.0% CaCl2 concentration. Hydroxytyrosol, oleuropein, and PB1 showed a significant difference on different monitoring dates. The antioxidant activity during the fermentation period rose between 63.3 and 87.2% compared with the Control (Ca 0%). A similar increasing trend was registered for the phenolic compounds. Our results are useful for the table olive sector to improve the handling in post-harvest processing and to increase the final quality of the olives.