A treatment combining hydrogen peroxide and ultra-violet (UV-C) irradiation was assessed for reduction of microbial contamination in pre-formed food packaging cartons. There was a synergistic effect between low concentrations (0 – 5% wt/vol) of hydrogen peroxide and UV-C irradiation (10 s) on spores of Bacillus subtilis, the maximum lethality occurring between 0.5 and 1% peroxide. A combined treatment using 1% hydrogen peroxide and 10 s of UV-C irradiation was also effective against a variety of other organisms (spores and vegetative cells). The efficiency of the treatment was dependent on the type of inner surface of the carton. A greater lethal effect was obtained against B. subtilis spores in polyethylene-lined cartons than in aluminium/polyethylene laminate-lined cartons (5.1 and 3.5 decimal reductions in numbers respectively, using a combined treatment with 1% peroxide and 10 s of UV-C).
Reflectivity, smoothness and geometry of several types of food packaging board were studied in relation to the effectiveness of decontamination treatments involving ultraviolet (UV-C, 254 nm) irradiation. Surfaces containing aluminum in the laminate reflected more light in the 325 to 550 nm range and showed a lower lethal effect when Bacillus subtilis spores were irradiated. Visible light of wavelengths between 325 and 550 nm is known to cause photoreactivation of UV damage in vegetative cells. It was suggested that a similar phenomenon might occur in spores on reflective surfaces. Smoothness of the board surface was not an important factor in the extent or the variability of the lethal effect. The geometry of the irradiated surface was shown to be important for aluminum/polyethylene laminatelined surfaces only, as more spores were killed on board normal to incident UV-C irradiation than in cartons with reflective angles. Spores on the inner sides of this type of carton may have received more reflected light of photoreactivation wavelengths.
A comparative assessment has been made of the performance of minerals modified glutamate medium (MMGM), lauryl sulphate tryptose broth (LST), MacConkey broth (MAC) and brilliant green bile broth (BGBB) in the enumeration of coliform organisms present in soft cheese, cooked meat and p2te. The medium MMGM was superior in sensitivity to the other three media and compared favourably with them in specificity; BGBB was inferior to the other media tested.
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