Effect of packaging conditions on the growth of micro-organisms and the quality characteristics of fresh mushrooms (Agaricus bisporus) stored at inadequate temperatures

Mushrooms were packed in two polymeric films (perforated and non-perforated PVC) and stored at 17 degreesC and 25 degreesC. The carbon dioxide and oxy gen content inside the packages, aerobic mesophiles, Pseudomonas spp., faec al coliforms, Escherichia coli, anaerobic spores and major sensory factors (colour, texture, development stage and presence of moulds) were determined . The non-perforated packages had the highest contents of CO2 (6-7%), the l owest contents of O-2 (0.013-0.17%) and the most desirable quality paramete rs (texture, development stage and absence of moulds). Pseudomonas spp. cou nts were around 1 logarithmic unit lower in mushrooms packaged in non-perfo rated film as the O-2 concentrations were lower than in perforated film. Th e mushrooms themselves were inoculated with an enterotoxin A-producing stra in of Staphylococcus aureus, packaged in overwrapped trays and stored at 17 and 25 degreesC. Staphylococcus aureus did not grow in the samples stored at 17 degreesC. Only slight growth was observed in mushrooms packaged with non-perforated film after 1 day at 25 degreesC. No enterotoxin was detected in any package. Faecal coliform counts were <2 log cfu g(-1). Escherichia coli was not isolated in any of the samples. At 25 degreesC, counts of anae robic spores of around 2 log cfu g(-1) were detected in those mushrooms pac kaged in non-perforated film.