Tesis Magíster
Postharvest Characterization of Kale (Brassica oleracea L. var acephala DC.): A Study of the Impact of Leaf Maturity, Fresh-Cut Preparation and Storage Conditions
Fecha
2014Autor
Cantwell, Marita, I.
UNIVERSITY OF CALIFORNIA- DAVIS
Institución
Resumen
Kale (Brassica oleracea L. var acephala DC.) is a leafy vegetable that has experienced a dramatic increase in consumption in the U.S. market recently due to its nutritional content and health-associate benefits. Currently it is consumed as intact leaves as well as fresh-cut processed. Kale is harvested several times from the same plant and leaves may be harvested at different stages of maturity. To determine the potential impact of leaf maturity in combination with fresh-cut processing and storage temperature on the postharvest performance of kale, intact or fresh-cut leaves at different stages of maturity were evaluated at a range of temperatures (0 to 20°C) in air or modified atmospheres. Kale leaves were obtained from two cultivars (‘Winterbor’ and ‘Lacinato’) and different commercial sources. Product was evaluated for marketable quality attributes (visual quality, yellowing, decay, discoloration, off-odors), for color by destructive and non-destructive techniques (pigment extraction, reflectance colorimeter, reflectance spectrophotometer, SPAD), respiration, and chemical composition (ammonia, malondialdehyde, antioxidants and pigment extraction). Immature leaves had the highest antioxidant capacity and the lowest contents of ammonia and malondialdehyde over time, as well as the highest marketable quality scores. Overmature leaves had the highest rates of deterioration, the highest total ammonia and malondialdehyde contents and the lowest marketable quality scores over time. Total chlorophyll and carotenoid content were slightly affected by leaf maturity and processing over time at storage temperatures lower than 5°C. Respiration rates were higher in immature than in mature and overmature leaves. Objective color was not affected by leaf maturity but was influenced by storage temperature and fresh-cut processing over time. Fresh-cut processing and temperature hastened the senescence process by increasing the rate of overall deterioration and compositional degradation, as well as respiration rates. Mature fresh-cut leaves stored at 5°C in air + 15% CO2 atmosphere for 24 days had the highest marketable quality and compositional attributes, except for off-odors and total ammonia content, respectively, compared to leaves stored in air or air + 7.5% CO2. Control fresh-cut leaves had the lowest postharvest performance.