Addition of sorbitol with KMnO4 improves broccoli quality retention in modified atmosphere packages

The objective of this study was to determine if the addition of sorbitol (a water absorbent) to packages containing potassium permanganate (KMnO4) on an inert carrier (a volatile adsorber) could be used to enhance the removal of volatiles associated with off-odors in broccoli (Brassica oleracea L., Italica group) during storage in modified atmosphere packaging (MAP). Broccoli heads were held in PD-961EZ bags (five per bag), to allow CO2 to accumulate above the recommended 5-10%. Six treatments within MAP were investigated: (1) control - 0-g sorbitol + 0 g-KMnO4; (2) 0-g sorbitol + 20.0-g KMnO4; (3) 2.5-g sorbitol + 20.0-g KMnO4; (4) 5.0-g sorbitol + 20.0-g KMnO4; (5) 10.0-g sorbitol + 20.0-g KMnO4; and (6) 20.0-g sorbitol + 20.0-g KMnO4. Broccoli heads in MAP with sorbitol had better appearance, firmness and odor ratings after 29 days of storage at 0-1C, compared to the controls. Furthermore, the odor rating was higher (less off-odor) as the amount of sorbitol was increased (1.9 control versus 3.9 for 20-g sorbitol). Slight increases in weight loss (<= 1.3%) of the broccoli were also noted with the addition of sorbitol, although not near an amount that would affect marketability. Acetaldehyde concentrations were higher in the control bags with no sorbitol or KMnO4 after 29 days of storage at 0-1C (0.21 versus 0.00-0.02 mu L/L with KMnO4 and/or sorbitol), while ethanol content was greater in both control bags and those with only KMnO4 (0.12-0.13 versus 0.00-0.06 mu L/L with sorbitol). Chlorophyll fluorescence (Phi(PSII)) began to decrease more rapidly in the control broccoli, as the ethanol and acetaldehyde began to accumulate. Overall, the use of sorbitol (>= 2.5 g) with KMnO4 in MAP could enhance the removal of volatiles that are responsible for off-odors and off-flavors in broccoli, and thus maintain the quality and marketability longer.