Effect of hot air treatments on senescence and quality parameters of harvested broccoli (Brassica oleracea L var Italica) heads

Treatments with hot air were applied to broccoli (Brassica oleracea L) florets to investigate the effect on several quality and senescence parameters. To select the optimum treatment, florets were treated with different combinations of time/temperature ranging from 1 to 3 h and 37 to 50 degrees C and then placed in darkness at 20 degrees C. Most treatments delayed yellowing and loss of chlorophylls, except those performed at 37 degrees C, which accelerated senescence. Treatment at 48 degrees C for 3h caused the highest delay in chlorophyll loss and was chosen to analyse its effect on quality and senescence. Non-treated florets showed yellowing and reduced their chlorophyll content during storage. Heat treatment delayed the onset of chlorophyll catabolism by 1 day and slowed down the rate of degradation. Treated florets also showed lower losses of total sugars and proteins and an inhibition of protein solubilisation. Control heads showed an increment in CO2 production, which was not detected in heat-treated florets. Total antioxidants decreased and thiobarbituric acid-reactive substances (TBARS) increased during storage. The treatment delayed the decrease in antioxidant content and inhibited the increment in TBARS. In conclusion, treatment at 48 degrees C for 3 h delayed broccoli senescence at 20 degrees C and contributed to maintaining an overall better quality of the product. (c) 2005 Society of Chemical Industry.