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 pou ches. The heat resistance of L. monocytogenes was higher in peas (D-60 degr eesC - 1.0 min) and mushrooms (D-60 degreesC = 0.7 min) than in other veget ables tested (D-60 degreesC in onions = 0.2 min) and was highest when cells were subjected to starvation before the thermal death time experiments. (D -60 degreesC Of starved L. monocytogenes in mushrooms = 1.6 min). The resul ts showed that blanching can be used as an antilisterial treatment (inactiv ation of 5 logs of L. moncytogenes) when the cold spot of vegetables is tre ated for at least 10 s at 75 degreesC or instantaneously (<1 s) at temperat ures above 82<degrees>C.