Heat resistance of Listeria monocytogenes in vegetables: evaluation of blanching processes.
The heat resistance of a Listeria monocytogenes composite (serotypes 1/2a, 1/2b, and 4b) was determined in fresh broccoli florets, sweet green peppers, onions, mushrooms, and peas using an end-point procedure in polyester pouches. The heat resistance of L. monocytogenes was higher in peas (D(60 degrees C) = 1.0 min) and mushrooms (D(60 degrees C) = 0.7 min) than in other vegetables tested (D(60 degrees C) in onions = 0.2 min) and was highest when cells were subjected to starvation before the thermal death time experiments (D(60 degrees C) of starved L. monocytogenes in mushrooms = 1.6 min). The results showed that blanching can be used as an antilisterial treatment (inactivation of 5 logs of L. monocytogenes) when the cold spot of vegetables is treated for at least 10 s at 75 degrees C or instantaneously (<1 s) at temperatures above 82 degrees C.
Center for the Development of Research Policy & New Technologies, National Food Processors Association, Washington, DC 20005, USA. amazzotta@pillsbury.com
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Mazzotta
D005511:Food Handling / Q000379:methods*; D006358:Hot Temperature; D008089:Listeria monocytogenes / Q000502:physiology*; D013997:Time Factors; D014675:Vegetables / Q000382:microbiology*