Efficacy of Surface Pasteurization Process Using Hot Water Immersion on Salmonella Poona Populationsa on Inoculated Cantaloupesb

Treatmentc

Storage temperature

2 h control 24 h control 76° C for 3min

Room temperature wash for 3 min

3.66 ± 0.43 5.54 ± 0.09 0.16 ± 0.08d 5.08 ±0.20

a S. Poona populations were selectively isolated on XLT4 agar medium, and reported as log CFU/cm2 rind.

b Data are reported as the mean ± standard deviation for three separate cantaloupes. c Cantaloupes were dip inoculated with S. Poona for 5 min, allowed to air dry under biosafety cabinet for 2h, and were stored at either room temperature or 4°C for 24 h prior to washing treatments.

d Although two of three cantaloupes tested showed no survivors, 0.1 log CFU/cm2 (minimum detection level) was used in place of no survivors for determining the mean and standard deviation.

treated oranges. These adverse effects can be controlled by limiting treatment temperatures and times. Since individual commodities have different thermal tolerances, the hot water immersion treatment should be tailored to each commodity. While the rind of a cantaloupe [2] and the peel of an orange [18] effectively insulate the flesh from thermal damage at temperatures above 70° C, the peel of an apple does not protect the flesh from thermal damage at temperatures above 60°C [7]. Accordingly, the tolerance to hot water immersion over a range of temperatures must be determined for individual commodities at different maturity stages [15].

Following hot water immersion, produce should be rapidly cooled to reduce the risk of heat damage to the commodity [2]. This cooling process must be carefully controlled, for it is known to induce infiltration of the cooling solution, including any possible contaminating microorganisms, into the commodity [20-23]. Therefore, the cooling water to be used for this purpose should be free of human pathogens and spoilage microorganisms. A forced cold air tunnel could be used for rapid cooling of the commodity. The use of sanitizing agents during washing treatments, which includes a hot water wash, is recommended to reduce the microbial load in the washing solution. This prevents possible cross contamination in the washing tank, which could result in internalization during the subsequent cooling treatment.

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