Survival of Salmonella During Apple Dehydration as Affected by Apple Cultivar and Antimicrobial Pretreatment.

Dehydrated fruit, including dried coconut and dried apple slices, have been the subject of manufacturer recalls due to contamination with Salmonella . A study was conducted to determine the survival of Salmonella on six cultivars of apple slices after dehydration as well as survival following treatment with antimicrobial solutions (0.5%, wt./wt.)  and dehydration. Six apple cultivars (Envy, Gala, Red Delicious, Fuji, Pink Lady, Granny Smith) were cored and sliced into 0.4 cm rings, halved, inoculated with a five-strain composite of desiccation-resistant Salmonella and dehydrated at 60°C for 5 h.  Subsequently, Gala apple slices were treated in 0.5% solutions of one of eight antimicrobial rinses for two min and then dehydrated at 60°C for 5 h.  Antimicrobial solutions were potassium sorbate (PS), sodium benzoate (SB), ascorbic acid (AA), propionic acid (PA), lactic acid (LA), citric acid (CA), fumaric acid (FA), and sodium bisulfate (SBS). Reduction of Salmonella populations varied according to apple cultivar.  Survival on were Envy, Gala, Red Delicious, Fuji, Pink Lady, and Granny Smith were 5.92, 5.58, 4.83, 4.68, 4.45, and 3.84 log CFU, respectively.  Greater numbers of Salmonella ( p <0.05) were inactivated on Granny Smith, Pink Lady and Fuji apples than on Gala and Envy apples.  Survival of Salmonella on Gala apple slices (log CFU) following antimicrobial treatments and dehydration were 5.58, 4.76, 3.90, 3.29, 3.13, 2.89, 2.83, 2.64, and 0.0 for untreated control, PS, SB, AA, PA, LA, CA, FA, and SBS, respectively.  Lower survival was obtained by pre-treating apple slices with either FA or SBS before dehydration when compared to all other antimicrobial treatments. Lower apple pH was statistically correlated ( p <0.05) with decreasing survival of Salmonella following dehydration.  These results may provide methodology applicable to the food industry for increasing the inactivation of Salmonella during the dehydration of apple slices.