Pre-harvest calcium application increases biomass and delays senescence of broccoli microgreens

• The effect of preharvest calcium application on postharvest quality and shelf-life of broccoli microgreens was studied.
• Preharvest spray with calcium chloride increased the microgreen biomass and the calcium content.
• Calcium-treated microgreens exhibited higher superoxide dismutase and peroxidase activities.
• Calcium treatment improved overall visual quality, and reduced microbial growth during storage.
• Calcium treatment significantly affected expression of the senescence-associated genes.

Microgreen consumption has been steadily increasing in recent years due to consumer awareness of their unique color, rich flavor, and concentrated bioactive compounds. However, industrial production and marketing is limited by their short shelf-life associated with rapid deterioration in product quality. This study investigated the effect of pre-harvest calcium application on the post-harvest quality and shelf-life of broccoli microgreens. Broccoli microgreen seedlings were sprayed daily with calcium chloride at concentrations of 1, 10 and 20 mM, or water (control) for 10 days. The fresh-cut microgreens were packaged in sealed polyethylene film bags. Package headspace atmospheric conditions, overall visual quality and tissue membrane integrity were evaluated on days 0, 7, 14, and 21, during 5 °C storage. Results indicated that the 10 mM calcium chloride treatment increased the biomass by more than 50%, and tripled the calcium content as compared to the water-treated controls. Microgreens treated with 10 mM calcium chloride spray exhibited higher superoxide dismutase and peroxidase activities, lower tissue electrolyte leakage, improved overall visual quality, and reduced microbial growth during storage. Furthermore, calcium treatment significantly affected expression of the senescence-associated genes BoSAG12, BoGPX6, BoCAT3 and BoSAG12. These results provide important information for commercial growers to enhance productivity and improve postharvest quality and shelf-life, potentially enabling a broadening of the retail marketing of broccoli microgreens.