Quantification of Postharvest Respiration Rates for Specialty Cut Greens

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Microgreens are 7-10 day old seedlings of various vegetable crops. At harvest, seedlings are cut at root level and the product is packaged as young shoots, including only cotyledons and 3-cm long hypocotyls. Very little information is available describing the postharvest characteristics of this high value specialty crop.  To expand markets of this perishable product, respiration rates must be quantified and controlled to extend shelf life. Postharvest respiration rates and visual quality were evaluated for three cool-season vegetable crop species: arugula (Eruca sativa), radish (Raphanus sativus ‘China Rose’), and red cabbage (Brassica oleracea var. capitata f. rubra) at 4^oC (control) and 10^oC. Respiration rates were measured at harvest, and every seven days thereafter, for a total of three weeks.  Rates were quantified using a modified conifer chamber and a portable gas exchange system (LI-6400 Lincoln, NE).  In addition, product quality was evaluated and quantified visually each week. Based on visual analysis, shelf-life averaged fourteen days for arugula and red cabbage, and twenty-one days for radish when stored at 4^oC. However, shelf life was reduced to seven days when stored at 10^oC for red cabbage and arugula. Mean respiration rates were significantly lower at 4^oC than at 10^oC for all three crops. Radish mean respiration rates were 110 µg CO₂ g^-1·h^-1 at 4^oC and 255 at 10^oC at harvest; one week later mean respiration rates were 83 and 141, respectively. Arugula mean respiration rates were 101 µg CO₂ g^-1·h^-1 at 4^oC and 189 at 10^oC at harvest; one week later mean respiration rates were 83 and 167, respectively. Red cabbage mean respiration rates 110 µg CO₂ g^-1·h^-1 at 4^oC and 189 at 10^oC at harvest; one week later mean respiration rates were 35 and 141, respectively. However, beginning in week two there was a spike in respiration rates, possibly due to decay organisms, which also corresponded to a decrease in the visual quality rating of the crop.  This study provides a benchmark data set for future microgreens postharvest experiments designed to lower respiration rates and increase shelf life.