CHANGES IN MICROBIAL-POPULATIONS ON FRESH CUT SPINACH

The microbial populations found on fresh-cut spinach leaves that were stored in gas permeable bags at 10 degrees C for 12 days were examined and identified. The microorganisms consisted of mesophilic aerobic ba cteria, psychrotrophic bacteria, Pseudomonadaceae, Enterobacteriaceae, Micrococcaceae, lactic acid bacteria and yeasts. Populations of mesop hiles, psychrotrophs, Pseudomonadaceae and Enterobacteriaceae increase d sharply during the storage period. The initial populations were 10(7 ), 10(6), 10(6) and 10(4) CFU . g(-1) respectively. Populations reache d 10(10) for the mesophiles, psychrotrophs and Pseudomonadaceae and 10 (7) CFU . g(-1) for Enterobacteriaceae after 12 days of storage. Micro coccaceae, lactic acid bacteria and yeasts remained constant (10(3)-10 (4) CFU . g(-1)). The majority of the bacterial isolates were identifi ed as Pseudomonas fluorescens, Aeromonas caviae and Staphylococcus xyl osus. The yeasts, which were most frequently isolated, were classified in the genus Cryptococcus. No pathogens such as Listeria monocytogene s and Salmonella were detected. Observations with low temperature scan ning electron microscopy (LTSEM) indicated that the microoganisms were not present on the surface of healthy unbroken leaves. Alternatively, they were found in areas where the cuticle was broken and could be se en infecting the internal palisade parenchyma.