15D-13 |
Destruction of Listeria monocytogenes during drying and storage of peaches treated with acid or sodium metabisulfite solutions |
P. A. DIPERSIO1, P. A. Kendall1, M. Calicioglu2, and J. N. Sofos2. (1) Food Science and Human Nutrition, Colorado State University, Room 200 Gifford Building, Fort Collins, CO 80523-1571, (2) Animal Sciences, Colorado State University, Fort Collins, CO 80523-1171
The increased incidence of foodborne illness associated with dried foods has prompted the need for research on home food drying. There is little research on the effectiveness of home drying to
destroy Listeria monocytogenes on fruits.
The objective of this study was to evaluate the destruction of L. monocytogenes on inoculated peach slices during drying and to determine whether pre-treating inoculated slices with acid or metabisulfite solutions altered destruction during dehydration and storage.Inoculated (five strain mixture, 7.8 log CFU/g) peach
slices were subjected to pre-drying treatments, dried for 6 h at 60°C, and stored aerobically
at 25°C for 30 d. Pre-drying treatments included: (1) no
treatment; or 10 min immersion in: (2) sterile water, (3) 3.4% ascorbic acid,
(4) 0.21% citric acid, or (5) 4.18% sodium metabisulfite solutions. Samples were plated on tryptic soy agar with
0.1% pyruvate (TSA) and PALCAM agar for enumeration of surviving bacteria.
Immersion
in water reduced bacterial populations on peach slices by 0.7 log CFU/g (TSA
and PALCAM). Acidic treatments reduced
populations by 0.5-0.8 log CFU/g, while immersion in the sodium metabisulfite
solution reduced populations by 1.5 (TSA) and 2.0 (PALCAM) log CFU/g. After 6 h of dehydration, bacterial
populations on untreated or immersed in water slices were reduced by 3.2 (TSA)
and 3.3-3.4 (PALCAM) log CFU/g. In
contrast, after 6 h drying, populations on slices treated with citric acid,
sodium metabisulfite, and ascorbic acid were reduced by 4.3, 4.5 and 5.1 log
CFU/g on TSA and by 5.3, 5.4 and 6.2 log CFU/g on PALCAM agar,
respectively. Populations decreased
below the detection limit (1.1 log CFU/g) by 21 d of storage in all treatments.
Results suggest that acid or sodium metabisulfite solutions may serve as effective pre-treatments to enhance destruction of L. monocytogenes during home-type drying of peach slices.
Session 15D, Food Microbiology: Fruits and vegetables
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