Antimicrobial packaging system for optimization of electron beam irradiation of fresh produce

摘要

This study evaluated the potential use of an antimicrobial packaging system incombination with electron beam irradiation to enhance quality of fresh produce.Irradiated romaine lettuce up to 3.2 kGy showed negligible (p > 0.05) changes in color,but texture and sensory attributes were less acceptable with increased dose.We established the antimicrobial effectiveness of various active compoundsincorporated into the low-density polyethylene (LDPE)/polyamide films to increaseradiation sensitivity of surrogate bacteria (Listeria innocua and Escherichia coli). Allfilms showed inhibition zones in an agar diffusion test. In the liquid culture test, theactive compounds reduced the specific growth rate and decreased final cell concentrationof strains. Films incorporated with active compounds increased the radiation sensitivityof the tested strains, demonstrating their potential to reduce the dose required to controlmicrobial contamination using electron beam technology. The active compoundsmaintained their antimicrobial activity by exposure to ionizing radiation up to 3 kGy. Antimicrobial activity of LDPE/polyamide films incorporated with transcinnamaldehydewas tested with fresh-cut romaine lettuce. Total aerobic plate counts(APC) and yeast and mold counts (YMC) were determined as a function of dose (0, 0.5,and 1.0 kGy) for 14 days of storage at 4????C. Irradiation exposure significantly loweredAPCs of lettuce samples by 1-log CFU/g compared to the non-irradiated controls;however, it only slightly reduced YMCs. The effectiveness of using irradiation withantimicrobial films was enhanced with increased radiation dose and transcinnamaldehydeconcentration.Electron beam irradiation up to 20 kGy did not affect the tensile strength andtoughness of the polymeric films. The film??????s flexibility and barrier properties weresignificantly improved by exposure to 20 kGy. The addition of an active compound didnot affect the tensile strength and barrier properties of the films, but decreased thepercent elongation-at-break and toughness, making them slightly more brittle.Ionizing radiation affected the release kinetics of the antimicrobial agent from thepackaging material into a model food system. Irradiated films exhibited slower releaserates than non-irradiated film by 69%. In addition, release rate was lower at 4????C by62.6% than at 21-35????C. The pH of the simulant solution affected release rate with pH 4yielding higher rates than pH 7 and 10.