Protozoa of significance in food
Fruits and vegetables can become contaminated with free living Protozoa through contact direct with soil, irrigation water, air, rain, insects, and during industrial produce‐washing.
Amoebae have been recovered from mushrooms and vegetables such as carrots, cauliflower, lettuce, radishes, scallions, spinach, and tomatoes.
Flagellates were found on spinach, Romaine lettuce, and butterhead lettuce.
Ciliates were recovered from mushroom surfaces.
The number of Protozoa on leafy vegetables can be high, with flagellates being more abundant than amoebae and ciliates.
Washing or rinsing lettuce leaves followed by spin‐drying in a household salad spinner reduced the protozoan number only by a maximum 1 log unit (90%).
Protozoa have also been recovered from ready‐to‐eat lettuce, which suggests that they are able to survive mild treatments such as industrial washing.
The following table summarises research conducted over many years into the various species of Protozoa found on particular vegetables – this can be useful when undertaking a HACCP hazard analysis.
|Lettuce, scallions, radishes||Amoebae||A. rhysodes, A. palestinensis, Naegleria gruberi||Ciurea‐Van Saanen (1981)|
|Mushrooms (Agaricus bisporus)||Amoebae||Acanthamoeba spp., Hartmannella spp., Vannella spp.||Napolitano (1982)|
|Ciliates||Colpoda sp., holotrichs, hypotrichs|
|Oak leaf lettuce, Boston lettuce||Amoebae||Acanthamoeba spp., Hartmannella spp.||Napolitano and Colletti‐Eggolt (1984)|
|Carrots, radishes, tomatoes, mushrooms, cauliflowers, spinach||Amoebae||A. polyphaga, A. rhysodes, A. castellanii||Rude and others (1984)|
|Carrots||Amoebae||A. culbertsoni, A. rhysodes, H. vermiformis||Sharma and others (2004)|
|Romaine lettuce||Amoebae||A. palestinensis||Gourabathini and others (2008)|
|Butterhead lettuce||Amoebae||Cochliopodium sp., Mayorella vespertiloides, Ripella platyopodia, Ripella platyopodia, Vannella simplex, H. vermiformis, Saccamoeba sp., Vahlkampfia sp.||Vaerewijck and others (2011)|
|Flagellates||Goniomonas truncata, Bodo saltans, Bodo sp., Cercomonas spp., Notosolenus sp., Peranema trichophorum, Petalomonas sp., Rhynchomonas nasuta, Allantion tachyploon, Spumella spp.|
|Ciliates||Aspidisca lynceus, Cinetochilum margaritaceum, Chilodonella uncinata, C. steinii, Colpoda sp., Cyclidium glaucoma, Glaucoma scintillans, Glaucoma sp., Paramecium putrinium, Platyophrya sp., Tachysoma pellionellum, Trachelophyllum sp., Vorticella convallaria complex, Vorticella sp.|
|Ready‐to‐eat lettuce (butterhead lettuce)||Flagellates||Bodo saltans, Cercomonas spp., Spumella cylindrica, Spumella‐like flagellates||Vaerewijck and others (2011)|
The prevalence of Protozoa in meat and fish has not been established through research: however, it is reasonable to accept that if good hygiene practices are not followed, there can be cross contamination during processing.
The most significant Protozoa for causing illness in humans are Giardia and Cryptospiridia. Both can cause significant illness, especially in children.