After irradiation of chickens to a dose of 2.5 kGy, the decrease in the standard plate count (SPC) was similar in air and in vacuum-packaged chickens. During storage at 4°C for 15 d, the SPC increased progressively in both types of packaged chickens. At the end of the storage period, the SPC was higher in air-packaged chicken than in vacuum-packaged chickens. In irradiated chickens, Listeria monocytogenes was only recovered from the vacuum-packaged chickens after 7 d cold storage. In unirradiated chickens, L. monocytogenes proliferated similarly in both air- and vacuum-packaged chickens.
As the standard technique for sulfite analysis, the Monier-Williams distillation, is time consuming and relatively insensitive, many alternative methods have been developed. Three of these methods were tested for their suitability for the routine determination of residual sulfite in prawns: i) a rapid steam distillation; ii) high performance liquid chromatography (HPLC), and iii) an enzyme-based procedure. Testing of the three selected methods involved analyses of standard sulfite solutions, prawns of known sulfite levels and prawns of unknown sulfite levels and comparison of results with those determined by the Monier-Williams procedure. Statistical analysis showed that the sulfite levels determined on standard solutions by rapid distillation were in close agreement with those obtained by the Monier-Williams distillation. However, a correction factor had to be introduced when analyzing prawns by the rapid distillation method to obtain comparable results with those produced by the Monier-Williams distillation. The same statistical analysis performed on levels determined by HPLC and the Monier-Williams distillation gave close agreement for both standard solutions and prawns. The enzyme test, after promising results for the standard solutions, proved to be unsatisfactory for analysis of sulfite in prawns.