title: Removal of Salmonella enterica Enteritidis and Escherichia coli from green peppers and melons by ultrasound and organic acids.
abstract: The aim of this study was to evaluate the effectiveness of ultrasound treatment combined with organic acids in the decontamination step for green peppers and melons. The influence of the surface roughness of the peppers and melons on bacterial adhesion was evaluated, as measured using a profilometer. The adhesion of Salmonella enterica serovar Enteritidis and Escherichia coli to the green pepper and melon surfaces was also evaluated by measuring the hydrophobicity of the microorganisms and the surfaces. The bacteria that adhered to the surface of green peppers and melons was quantified by plate count and visualized by scanning electron microscopy. In addition, the efficiency of ultrasound and organic acids to remove bacteria from the pepper and melon surfaces was examined. The average roughness (Ra) of the green peppers (13.0±2.7 nm) was significantly different (p>0.05) from the melons (33.5±7.9 nm). Adherence of S. Enteritidis and E. coli are thermodynamically unfavorable for both surfaces studied (∆G(adhesion)>0). Despite these data, good adhesion occurred on both surfaces. The number of bacteria on green pepper slices was 7.3 and 7.0 log CFU/cm(2) for E. coli and S. enterica Enteritidis, respectively. For melon surfaces, the number of bacteria was 7.0 and 6.9 log CFU/cm(2) for E. coli and S. Enteritidis, respectively. The greater adherence of both bacteria on the green peppers can be explained by its hydrophobic surface; the hydrophilic surfaces of melons resulted in lower adherence. These results suggest that the adhesion observed in this experiment is a multifactorial process. Among the treatments evaluated for green peppers, a higher removal of pathogens was observed after use of a combination of ultrasound and 1% lactic acid; this treatment reduced E. coli and Salmonella by 2.9 and 2.8 log CFU/cm(2), respectively. For melons, the combination of ultrasound and lactic acid showed a reduction of 2.5 and 3.1 log CFU/cm(2) for E. coli and S. Enteritidis, respectively. These results indicate that it is possible to replace the chlorinated compounds that are commonly used to sanitize fruits and vegetables. These results confirm that ultrasound, an emerging technology for food processing applications, could enhance the microbial safety of fresh produce.
authors.affiliation: Federal University of Espírito Santo, CEP 29043-910 Vitória, ES, Brazil. Electronic address: jackline.jose@ufes.br.
authors.forename: Jackline Freitas Brilhante de São
authors.initials: JF
authors.lastname: José
authors.affiliation: Department of Food Technology, Federal University of Viçosa, CEP 36570-000 Viçosa, MG, Brazil.
authors.forename: Hiasmyne Silva
authors.initials: HS
authors.lastname: de Medeiros
authors.affiliation: Federal University of Espírito Santo, CEP 29500-000, Alegre, ES, Brazil.
authors.forename: Patrícia Campos
authors.initials: PC
authors.lastname: Bernardes
authors.affiliation: Department of Food Technology, Federal University of Viçosa, CEP 36570-000 Viçosa, MG, Brazil.
authors.forename: Nélio José
authors.initials: NJ
authors.lastname: de Andrade
mesh_terms: D001422:Bacterial Adhesion / Q000187:drug effects* / Q000528:radiation effects; D002212:Capsicum / Q000382:microbiology*; D002264:Carboxylic Acids / Q000494:pharmacology*; D015169:Colony Count, Microbial; D019662:Cucurbitaceae / Q000382:microbiology*; D004926:Escherichia coli / Q000502:physiology*; D005516:Food Microbiology / Q000379:methods*; D005638:Fruit / Q000382:microbiology; D012477:Salmonella enteritidis / Q000502:physiology*; D014675:Vegetables / Q000382:microbiology
chemical_list: D002264:Carboxylic Acids
keywords: Bacterial adhesion; Fruits; Organic acids; Roughness; Ultrasound; Vegetables