Inactivation of Salmonella during Drying and Storage of Apple Slices Treated with Acidic or Sodium Metabisulfite Solutions

Abstract

This study was undertaken to determine whether pretreating inoculated Gala apple slices with metabisulfite or acidic solutions enhanced the inactivation of Salmonella during dehydration and storage. Apple slices inoculated with a five-strain mixture of Salmonella (7.6 log CFU/g) were pretreated, dried for 6 h at 60 degrees C, and stored aerobically at 25 degrees C for 28 days. Predrying treatments included (i) no treatment, (ii) 10 min of immersion in sterile water, (iii) 10 min of immersion in a 4.18% sodium metabisulfite solution, (iv) 10 min of immersion in a 3.40% ascorbic acid solution, and (v) 10 min of immersion in a 0.21% citric acid solution. Samples were plated on tryptic soy agar with 0.1% pyruvate (TSAP), brilliant green sulfa (BGS) agar, and xylose lysine tergitol 4 (XLT4) agar for the enumeration of bacteria. Populations were not significantly (P > 0.05) reduced by immersion in water but were reduced by 0.7 to 1.1 log CFU/g by immersion in acidic solutions. Immersion in the sodium metabisulfite solution reduced populations by 0.4, 1.3, and 5.4 log CFU/g on TSAP, BGS agar, and XLT4 agar, respectively. After 6 h of dehydration at 60 degrees C, populations on untreated and water-treated slices were reduced by 2.7 to 2.8, 2.7 to 2.9, and 4.0 to 4.2 log CFU/g as determined with TSAP, BGS agar, and XLT4 agar, respectively. In contrast, populations on slices treated with sodium metabisulfite, ascorbic acid, and citric acid were reduced after 6 h of dehydration by 4.3, 5.2, and 3.8 log CFU/g, respectively, as determined with TSAP; by 4.7, 5.5, and 3.9 log CFU/g, respectively, as determined with BGS agar; and by 5.5, 5.7, and 5.6 log CFU/g, respectively, as determined with XLT4 agar. Bacteria were still detectable by direct plating after 28 days except on slices treated with ascorbic acid. Immersion in metabisulfite or acidic solutions prior to dehydration should enhance the inactivation of Salmonella during the dehydration and storage of Gala apple slices.

Effect of Desiccation on Tolerance of Salmonella enterica to Multiple Stresses

“…Interestingly, acid-adapted cells did not mount tolerance to desiccation and, in fact, were more susceptible to this stress. Likewise, exposure of Salmonella-contaminated tomato or apple slices to acids (ascorbic and citric acids) also reduced Salmonella survival following dehydration (15,52). Thus, prechallenge to a single stress does not necessarily result in the development of tolerance to another stress.…”

Effect of Sodium Metabisulphite and Storage Temperature on the Survival of Vibrio cholerae on Prawns (Penaeus monodon)

“…Although sodium metabisulphite is also a known antimicrobial (DiPersio et al 2003) it is not equally active against all microorganisms (Barnett 1985), in all foods (DiPersio et al 2003) or under all storage conditions . Although this compound is used to treat blackspot in cholera-endemic countries, no information on its effect on the survival of V. cholerae or prawn safety is readily available.…”

Sensory Evaluation of Home Dried Fruit Prepared Using Treatments That Enhance Destruction of Pathogenic Bacteria

“…In the spring of 2001, we conducted a survey of home‐fruit drying recommendations made by the CES. Information was gathered from 27 states (DiPersio et al. 2003).…”

“…Recent studies evaluating the various recommended drying methods have shown that treating with an ascorbic or citric acid solution also enhances inactivation of pathogenic bacteria during dehydration and storage (Burnham et al. 2001; DiPersio et al. 2003; Derrickson‐Tharrington et al.…”