Karin Albornoz (Dept. Plant Sciences, UC Davis, Davis CA 95616) and Marita Cantwell (Dept. Plant Sciences, UC Davis, Davis CA 95616)
Kale (Brassica oleracea var. Acephala) is a very nutritious leafy vegetable and its consumption in fresh cut salads has increased in recent years. Kale leaves may be harvested at different stages of maturity, resulting in a heterogeneity that may be detrimental to fresh-cut salad quality and shelf-life. Changes in composition and visual parameters were investigated in fresh-cut kale leaves (var. Lacinato) harvested at three maturity stages used commercially and based on leaf position and size (immature, mature, overmature), two temperatures (0 and 5 degrees C) and five periods of storage (0, 14, 21, and 28d; up to 42d at 0 degrees C). Product was cut manually into 2cm strips, washed in chlorinated water, manually centrifuged and packaged in unsealed LDPE bags. Total chlorophyll content decreased during storage, with the lowest concentrations found in pieces from ‘overmature’ leaves at 5 degrees C, while the total carotenoid content did not vary among the conditions studied. Ammonia content, an indicator of membrane degradation and senescence, remained low for pieces from all maturity stages stored at 0 degrees C up to 42 days, was intermediate in immature cut leaves at 5 degrees C, and increased dramatically in pieces from mature and overmature leaves at 5 degrees C between 21 and 28 days. Objective color (L*, a* and b* values) as well as marketability indicators (off-odors, overall visual quality, yellowing, decay, cut-end browning) exhibited significant differences in response to the postharvest conditions studied. In general, the loss of composition and visual quality of fresh-cut kale leaves increased with increasing temperature, days of storage, and leaf maturity.