Coconut coir media sterilization method for growing Chinese kale microgreens

Abstract

Sterile media provide seeds a good head start during the germination process. 'Bang Bua Thong 35' Chinese kale seeds (20 g tray-1) were sown in coconut coir medium that was either boiled or steamed initially for 15 min followed by another evaluation for an extended period of 30 min. At harvest time, roots were longer and seedling growth was more uniform due to less incidence of disease (6%) in seedlings grown in boiled coco coir medium for 15 min. Shoot length of microgreens grown in the 15 min boiled medium was similar to the control. Weight losses in the microgreens after 9 days of storage at 4°C was minimal and similar among treatments. The total bacterial population was slightly less in microgreen harvested from boiled medium (15 min) for up to 3 days. A longer sterilization period for 30 min showed a distinct reduction of bacterial load in coconut coir but not in the microgreens assessed at day 14. FRAP and total phenolic content, weight loss and overall visual quality were not affected by the sterilization method. DPPH radical scavenging activity varied only on day 14. A longer treatment time of 30 min resulted in significantly lower total plate count in the medium relative to the control while that of the microgreens were similar to the control, indicating need for sterilization of seed and sanitation during microgreen production.