54F-22 |
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O. RODRIGUEZ, M. E. Castell-Perez, and R. G. Moreira. Dept. of Biological and Agricultural Engineering, Texas A&M Univ., 233-C Scoates Hall, College Station, TX 77843-2117 The sugar content of fruits, a measure of their quality, may also promote the growth of pathogens. There is not enough information on the effects of fruit composition due to maturity on the efficacy of electron beam irradiation treatments. Our goal was to determine whether irradiation of fruits at different maturity levels (sugar content) and storage temperature affects the resistance/recovery of pathogens. We prepared models of the Early Ripe (ER), Moderately Ripe (MR) and Ripe (R) stages of fruits such as melons by mixing unflavored gelatin (10%w/v) with sugars (fructose, glucose and sucrose) at different ratios (1.5:1.5:0, 1:1:1 and 0.5:0.5:2) and levels (3%, 5.5%, 8%), respectively. We inoculated the gels with 106-107 CFU/ml of E. coli K-12 MG1655, a good surrogate of E. coli, Listeria and Salmonella, in Petri dishes, irradiated them at 1.0kGy using a 2MeV Van de Graaff linear accelerator, stored at 4º C, melted and platted for 3 days. We also stored MR gels at 10º C and 20º C to study the effect of temperature. All gels stored at 4° C had 1.3-1.4-log reduction in the microbial populations by day 1. When stored at 10° C and 20° C, the MR gels had only a 1-log reduction. This suggests a potential recovery due to higher temperature. By day 2, the ER gels had an additional 0.6-log reduction, while no further growth occurred in the other gels at 4° C. By day 3, the Ripe (R) gels showed additional growth (0.6-log) while the ER gels had an additional 0.5-log reduction. No growth occurred in the irradiated MR gels stored at 10º C. At 20º C, however, these gels showed a 1.3-log increase by day 2. These results suggest that 1.0kGy irradiation of early ripe fruits and low temperature storage (4° C) may be the most effective treatment to inhibit the growth of pathogens in fruits.
Session 54F, Nonthermal Processing: General I
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |