Survival of Salmonella during Apple Dehydration as Affected by Apple Cultivar and Antimicrobial Pretreatment
Joshua B Gurtler1,2, Susanne E Keller3, Xuetong Fan1
1U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038-8551.
Abstract:
Dehydrated fruits, including dried coconut (Cocos nucifera) and dried apple (Malus sp.) slices, have been the subject of manufacturer recalls due to contamination with Salmonella. A study was conducted to determine the survival of Salmonella on apple slices of six apple cultivars after dehydration and also following treatment with antimicrobial solutions (0.5%, w/w) and dehydration. Samples of 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 2 min and then dehydrated at 60°C for 5 h. Antimicrobial solutions used were potassium sorbate, sodium benzoate, ascorbic acid, propionic acid, lactic acid, citric acid, fumaric acid, and sodium bisulfate. Reduction of Salmonella populations varied according to apple cultivar. Salmonella survival on Envy, Gala, Red Delicious, Fuji, Pink Lady, and Granny Smith was 5.92, 5.58, 4.83, 4.68, 4.45, and 3.84 log CFU, respectively. There was significantly greater (P < 0.05) Salmonella inactivation on Granny Smith, Pink Lady, and Fuji apples than on Gala and Envy. Survival of Salmonella on Gala apple slices following dehydration was 5.58 log CFU for the untreated control and 4.76, 3.90, 3.29, 3.13, 2.89, 2.83, 2.64, and 0.0 log CFU for those treated with potassium sorbate, sodium benzoate, ascorbic acid, propionic acid, lactic acid, citric acid, fumaric acid, and sodium bisulfate, respectively. Pretreatment of apple slices with either fumaric acid or sodium bisulfate before dehydration led to lower Salmonella survival than pretreatment with 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.
