Influence of blanching treatments on Salmonella during home-type dehydration and storage of potato slices

Recommended drying treatments may not enhance destruction of pathogens that could be present on home-dried foods. In this study, the effects of traditional and modified treatments on Salmonella were evaluated during preparation, home-type dehydration (60 degrees C for 6 h), and storage of potato slices. Potato slices inoculated with five strains of Salmonella (8.4 log CFU/g) were left untreated or were treated by steam blanching (88 degrees C for 10 min), water blanching (88 degrees C for 4 min), 0.105% citric acid blanching (88 degrees C for 4 min), or 0.210% citric acid blanching (88 degrees C for 4 min). Slices were then dried (6 h for 60 degrees C) and aerobically stored for up to 30 days at 25 +/- 3 degrees C. Cells were enumerated on tryptic soy agar with 0.1% pyruvate (TSAP) and on xylose lysine deoxycholate agar. Salmonella populations were reduced by 4.5 to 4.8 CFU/g and by >5.4 log CFU/g immediately following steam and water blanching, respectively. Populations were below the detection limit (0.80 log CFU/g) immediately following acid blanching, except for samples blanched in 0.105% citric acid and recovered on TSAP. After dehydration (6 h for 60 degrees C), Salmonella reductions on blanched potato slices (5.3 to 5.6 log CFU/g) were significantly greater (P < 0.05) than those on untreated samples (1.9 to 2.7 log CFU/g). Populations on all samples continued to decrease throughout 30 days of storage but still were 3.1 to 3.9 log CFU/g on untreated samples. In comparison, bacterial populations on blanched samples were undetectable by direct plating following 30 days of storage (regardless of blanching method). Blanching treatments used in this study improved the effectiveness of drying for inactivating Salmonella inoculated onto potato slices and, therefore, may enhance the safety of the product.