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Title: Heat transfer and microbial kinetics modeling to determine the location of microorganisms within cucumber fruit

item MATTOS, F
item FASINA, O
item REINA, L
item Breidt, Frederick
item PASSOS, F

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2005
Publication Date: 6/1/2005
Citation: Mattos, F.R., Fasina, O.O., Reina, L.R., Fleming, H.P., Breidt, F., Damasceno, G.S., Passos, F. 2005. Heat transfer and microbial kinetics modeling to determine the location of microorganisms within cucumber fruit. Journal of Food Science. 50(5):E324-E330.

Interpretive Summary: This manuscript describes a novel method for determining the location of microorganisms on and within cucumber fruit. Currently, brief blanching treatments (which do not alter the sensory properties or quality of the intact fruit) are being considered for a variety of fruits and melons as an alternative to washing procedures. The washing procedures now in use are not efficient at removing subsurface bacteria, which can make up a large part of the bacteria associated with these foods and can include disease-causing microorganisms. In this manuscript we describe a technique that involves combining an engineering model for heat penetration into fruit with a microbiology model for heat killing of bacteria. Using the combined model, it is possible to predict at what depth into the fruit most of the bacteria are located. The experiments used to validate the model have shown that most bacteria in and on cucumbers are located within a few millimeters of the surface, as the model predicted. The utility of this model is two-fold. It can give researchers a clear picture of how bacteria contaminate cucumbers and selected fruits, and the model has the potential to be used to predict the minimum blanching times needed for killing bacteria on and in a variety of melons and other fruit.

Technical Abstract: Microbiological and modeling (combined heat transfer and microbial kinetic equations ' HTMK model) approaches were used to determine the location of microorganisms within cucumber. The total number of aerobes found on cucumbers varied from 105 to 107 CFU/g. The highest and the least amount of microflora were respectively found at the blossom end and middle part of the cucumbers and are within the first 6 mm of the cucumber surface. A comparison of the calculated thermal death time from the HTMK model with the values obtained from experimental data showed that total aerobic microorganisms are located within 0.65 mm of the fruit surface.