Shelf Life of Greenhouse- and Garden-grown Kale in Nitrogen-enriched and Nonenriched Packaging

Over half of global food waste occurs in retail and households, highlighting the importance of improving shelf life. Many factors affect shelf life, including storage temperature, harvest time, processing method, and packaging. Modified atmosphere packaging (MAP), such as nitrogen (N2), has been used to improve the shelf life of produce. This study aimed to determine the effect of nitrogen-enriched packaging on the shelf life of greenhouse- and garden-grown kale in raised beds outdoors. Five kale cultivars (Black Magic, Darkibor, Lacinato, Red Russian, and Westlander) were grown in the greenhouse, and four cultivars (Curly Roja, Dwarf Green Curled, Meadowlark, and Vates) outdoors in raised beds, harvested and stored in nitrogen-enriched or nonenriched bags for 6 days. Leaf water content, water activity, color, visual score, and texture were measured for each replicate. Nitrogen-enriched packaging did not affect the kale shelf life. Garden-grown kale exhibited significantly lower water activity (0.979 vs. 0.999) and noticeably lower water content (88.6 vs. 90.6%) than greenhouse-grown kale. The cultivars were significant for all factors tested except for texture on day 4 and change in light to dark (Δ L*) and blue to yellow (Δ b*) color ratios. At the end of the study, cultivars Darkibor and Curly Roja had the highest visual score (4.4) and texture (305 g), respectively. The high performance of ‘Darkibor’ and ‘Curly Roja’ in visual score and texture may be due to decreased (Δ L*) and (Δ b*) values and decreased water content and water activity values. Future breeding efforts focused on the shelf life of kale should use the top-performing cultivars identified in this study and a diverse genetic population tested in a range of environments to develop cultivars with a longer shelf life.