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Changes in microbial populations on fresh cut spinach
1Horticultural Crops Quality Laboratory, Agricultural Research Service, United States Department of Agriculture, Beltsville, MD 20705-2350, USA.
International Journal of Food Microbiology
|August 1, 1996
Summary
Microbial growth on fresh-cut spinach stored for 12 days showed significant increases in mesophilic and psychrotrophic bacteria, including Pseudomonadaceae and Enterobacteriaceae. Pathogens were not detected, but microorganisms were found in damaged leaf areas.
Area of Science:
- Food Microbiology
- Microbial Ecology
- Plant Pathology
Background:
- Fresh-cut produce is susceptible to microbial spoilage during storage.
- Understanding microbial dynamics is crucial for food safety and shelf-life extension.
Purpose of the Study:
- To identify and quantify microbial populations on fresh-cut spinach during refrigerated storage.
- To investigate the location and potential damage caused by microorganisms on spinach leaves.
Main Methods:
- Microbial enumeration of various bacterial groups and yeasts.
- Identification of dominant bacterial and yeast isolates.
- Low-temperature scanning electron microscopy (LTSEM) for visualizing microbial colonization.
Main Results:
- Mesophilic aerobic bacteria, psychrotrophic bacteria, Pseudomonadaceae, and Enterobacteriaceae populations increased significantly, reaching up to 10(10) CFU/g.
- Micrococcaceae, lactic acid bacteria, and yeasts remained relatively constant.
- Pseudomonas fluorescens, Aeromonas caviae, Staphylococcus xylosus, and Cryptococcus yeasts were the most common isolates.
- Microorganisms were found in damaged leaf cuticle areas, not on healthy surfaces.
Conclusions:
- Refrigerated storage of fresh-cut spinach supports the growth of spoilage microorganisms.
- Microbial contamination is associated with physical damage to the spinach leaf cuticle.
- Absence of Listeria monocytogenes and Salmonella suggests low risk of specific pathogens under these conditions.
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