How harvesting time affects the phytochemical profiles and microbial load of brassica microgreens: Balancing health and safety

ABSTRACT Cress and rocket microgreens are widely consumed for their excellent sources of health-promoting phytonutrients and their spicy sensory attributes, yet the role of harvesting time as a determinant of yield, functional quality and microbial safety remains unknown. This study investigates how different harvesting times impact the phytochemical content, antioxidant capacity, and microbial load of cress and rocket microgreens. Harvesting time significantly impacted plant and shoot height, leaf area, and fresh and dry biomass, with rocket microgreens yielding higher values than cress microgreens. Species-specific responses to harvesting time were observed in phytochemicals, antioxidant capacity, and microbial load. Extending the harvesting time from Day 7 to Day 19 in rocket microgreens enhanced the accumulation of chlorophyll, carotenoids, phenolics, flavonoids, and anthocyanins, as well as antioxidant activity, and simultaneously reduced the microbial load. In contrast, cress microgreens showed a more limited phytochemical response, with extended harvesting time mainly associated with higher chlorophyll and anthocyanin contents. Although chlorophyll concentration increased in both species, extended harvesting time was associated with a decline in visual quality; however, these plants remained a good source of phytochemicals, highlighting their potential as functional ingredients rather than fresh-market products. This study reveals that harvesting time, as a key factor in yield, phytochemicals, and microbial safety, offers a practical approach to optimising microgreens as safe, sustainable, and high-value functional foods.