The effects of electron beam (e-beam) irradiation and sanitizers in the reduction
of Escherichia coli O157:H7 and Salmonella counts and attachment prevention on
spinach was studied. Survival of these pathogens in spinach was observed at multiple
times and temperatures. Inoculated spinach was examined by confocal microscopy to
determine attachment sites and internalization of these pathogens. To determine the
effectiveness of sanitizers in reducing pathogen numbers, inoculated spinach was treated
with L-lactic acid, peroxyacetic acid, calcium hypochlorite, ozone, and chlorine dioxide.
Inoculated spinach was exposed to e-beam irradiation and tested for counts of both
pathogens immediately after irradiation treatment to determine bacterial reduction, and
at 2 day intervals over 8 days to determine effects of ionizing irradiation on pathogen
survival. Respiration rates were measured on spinach exposed to e-beam. The
effectiveness of e-beam irradiation on the microbiological and sensory characteristics of
spinach was studied. For spinach samples stored at 4�C and 10�C for 8 days, E. coli
O157:H7 survived and grew significantly in samples stored at 21�C for 24 h. Confocal microscopy images provided valuable information on the attachment sites and
internalization of the pathogens on spinach. The greatest reduction by a chemical
sanitizer was 55�C L-lactic acid with a 2.7 log CFU/g reduction for E. coli O157:H7 and
2.3 log CFU/g reduction for Salmonella. Each dose of e-beam irradiation significantly
reduced populations of both pathogens. Respiration rates of spinach increased as
irradiation treatment doses increased. Total aerobic plate counts were reduced by 2.6 and
3.2 log CFU/g at 0.7 and 1.4 kGy, respectively. Lactic acid bacteria were reduced at both
doses but grew slowly over the 35 day period. Yeasts and molds were not reduced in
samples exposed to 0.7 kGy whereas 1.4 kGy had significantly reduced counts. Gas
compositions for samples receiving 0.7 and 1.4 kGy were significantly different than
controls. Irradiation did not affect the objective color or basic taste, aromatic or
mouthfeel attributes of spinach. These results suggest that low dose e-beam irradiation
may be a viable tool for reducing microbial populations or eliminating E. coli O157:H7
and Salmonella from spinach with minimal product damage.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-289 |
| Date | 2009 May 1900 |
| Creators | Neal, Jack A. |
| Contributors | Castillo, Alejandro |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
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