The microflora of fresh vegetables

Plant material, including edible vegetables, serves as the natural habitat for a wide variety of microorganisms (Table 7-2). The endogenous or epiphytic flora consist of yeast, fungi, and both Gram positive and Gram negative bacteria. The plant environment is exposed to the air and the surfaces of plant tissue have a high Eh. Thus, aerobic organisms, such as Pseudomonas, Flavobacterium, Bacillus, and various mold species, would be expected to dominate freshly harvested material, as is indeed the case.

However, facultative anaerobes, including Enterobacter, Escherichia coli, Klebsiella, and other enteric bacteria, as well as sporeforming clostridia, are also part of the resident flora. Various yeasts, including Candida, Saccharomyces, Hansenula, Pichia, and Rhodotorula, may also be present. Lactic acid bacteria, mainly species belonging to the genera Lactobacillus, Pedio-coccus, Streptococcus, and Enterococcus, are ordinarily present, but at surprisingly low numbers. In fact, whereas the total population of Pseudomonas, Flavobacterium, Escherichia, and Bacillus may well reach levels as high as 107 cells per gram, lactic acid bacteria are nor-

Table 7.2. Representative microflora of vegetables.

Organisms

Log CFU/g

Aerobic bacteria

4 — 6

Pseudomonas

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