Summary The effect of modified atmospheres, generated by using different packaging films, on the quality of sliced mushrooms was evaluated. The carbon dioxide and oxygen content inside the packages as well as the colour, texture, weight loss, sensory attributes, mesophiles, psychrotrophs, Pseudomonas fluorescens, faecal coliforms, Escherichia coli and anaerobic spores were determined. Modified atmospheres containing 2.5% CO2 and 10–20% O2 reduced the microbial counts and improved the mushrooms’ appearance when compared with an air atmosphere. Modified atmospheres containing 15% CO2 and <0.1% O2 inhibited mushroom development and toughening and reduced microbial growth. Although these atmospheres had no effect on colour, they did allow the development of off odours and anaerobic spores were detected. No differences in microbial growth or mushroom spoilage were observed under the different moisture contents generated in the packages at 4 °C. Aerobic bacteria counts were considered very high even at the beginning.

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Aims: The aim of this study was to evaluate the potential of Listeria monocytogenes to grow in mushrooms packaged in two different types of PVC ®lms when stored at 4°C and 10°C. Methods and Results: Mushrooms were packed in two polymeric ®lms (perforated and nonperforated PVC) and stored at 4°C and 10°C. The carbon dioxide and oxygen content inside the packages, aerobic mesophiles, psychrotrophs, Pseudomonas spp., Listeria monocytogenes, faecal coliforms, Escherichia coli, anaerobic spores and major sensory factors were determined. The mushrooms packaged in nonperforated ®lm and stored at 4°C had the most desirable quality parameters (texture, development stage and absence of moulds). Listeria monocytogenes was able to grow at 4°C and 10°C in inoculated mushrooms packaged in perforated and nonperforated ®lms between 1 and 2 log units during the ®rst 48 h. After 10 d of storage, the populations of L. monocytogenes were higher in mushrooms packaged in nonperforated ®lm and stored at 10°C. Conclusions: MAP followed by storage at 4°C or 10°C extends the shelf life by maintaining an acceptable appearance, but allows the growth and survival of L. monocytogenes. Signi®cance and Impact of the Study: According to this study additional hurdles must be studied in order to prevent the growth of L. monocytogenes.

We evaluate the microbiological quality and physicochemical and sensorial characteristics of white asparagus washed with and without chlorine and packaged in 2 different types of film (perforated polyvinyl chloride [PVC] and P-Plus 160) when stored at 4°C for up 15 d. Dehydration was the main cause of quality losses. Asparagus packaged in P-Plus maintained their fresh appearance better than those packaged in perforated PVC. The total sugar and ascorbic acid content decreased about 9% and 41% after 15 d, respectively. Peeled white asparagus packaged in perforated PVC or P-Plus kept a reasonable sensorial quality after storage at 4°C for 15 d, although mesophile and psycrotroph counts of about 9 log CFU/g were reached in asparagus washed with water. The effect of washing and type of film on different microbial groups is discussed.

Mushrooms were packed in two polymeric films (perforated and non‐perforated PVC) and stored at 17 °C and 25 °C. The carbon dioxide and oxygen content inside the packages, aerobic mesophiles, Pseudomonas spp., faecal 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 lowest contents of O2 (0·013–0·17%) and the most desirable quality parameters (texture, development stage and absence of moulds). Pseudomonas spp. counts were around 1 logarithmic unit lower in mushrooms packaged in non‐perforated film as the O2 concentrations were lower than in perforated film. The mushrooms themselves were inoculated with an enterotoxin A‐producing strain of Staphylococcus aureus, packaged in overwrapped trays and stored at 17 and 25 °C. Staphylococcus aureus did not grow in the samples stored at 17 °C. Only slight growth was observed in mushrooms packaged with non‐perforated film after 1 day at 25 °C. 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 °C, counts of anaerobic spores of around 2 log cfu g−1 were detected in those mushrooms packaged in non‐perforated film.