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Foodborne Pathogen Survival in Commercial Alorena de Malaga Table Olive Packaging.

ABSTRACT: This study presents an approach to determine the survival of diverse foodborne pathogens (Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella enterica) in three Aloreña de Málaga table olive commercial presentations (fresh green, traditional, and cured olives). The microbial survival in this green natural table olive speciality was fit using a log-linear regression model implemented in GInaFIT. The contents of sugars, phenolic compounds, additives, salt, pH, and levels of autochthonous microorganisms differed among presentations and affected the survival of microorganisms. The inoculated initial populations of pathogens (7-8 log₁₀ CFU/mL brine) decreased rapidly and, 48 h after inoculation, their counts were always below the detection limit (<1.3 log₁₀ CFU/mL), except for S. aureus in the fresh green presentation which was ∼ 5.0 log₁₀ CFU/mL. The highest maximum death rates (k_max ) and lowest periods for 4 log₁₀ reductions (4Dr) were observed in cured olives but decreased and increased, respectively, from the traditional to the fresh green presentations. L. monocytogenes and S. aureus were the most resistant species. The multivariate analysis showed that high concentrations of compounds released from the olives (sugars and phenols) were positively associated to 4Dr and negatively to k_max . Conversely, the presence of preservatives reduced 4Dr. This study, executed in commercial products, pointed out that packaged table olives are adverse habitats for foodborne pathogens with their effects being presentation dependent. The survival of S. aureus was particularly long in green fresh Aloreña de Málaga table olives packaged without preservatives; therefore, its changes in this presentation still requires further in-deep research.

SUBMITTER: Romero-Gil V

PROVIDER: S-EPMC6234914 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Nowadays, our knowledge of the fungal biodiversity in fermented vegetables is limited although these microorganisms could have a great influence on the quality and safety of this kind of food. This work uses a metagenetic approach to obtain basic knowledge of the fungal community ecology during the course of fermentation of natural Aloreña de Málaga table olives, from reception of raw material to edible fruits. For this purpose, samples of brines and fruits were collected from two industries in Guadalhorce Valley (Málaga, Spain) at different moments of fermentation (0, 7, 30 and 120 days). The physicochemical and microbial counts performed during fermentation showed the typical evolution of this type of processes, mainly dominated by yeasts in apparent absence of Enterobacteriaceae and Lactobacillaceae. High-throughput barcoded pyrosequencing analysis of ITS1-5.8S-ITS2 region showed a low biodiversity of the fungal community, with the presence at 97% identity of 29 different fungal genera included in 105 operational taxonomic units (OTUs). The most important genera in the raw material at the moment of reception in the industry were Penicillium, Cladosporium, Malassezia, and Candida, whilst after 4 months of fermentation in brines Zygotorulaspora and Pichia were predominant, whereas in fruits were Candida, Penicillium, Debaryomyces and Saccharomyces. The fungal genera Penicillium, Pichia, and Zygotorulaspora were shared among the three types of substrates during all the course of fermentation, representing the core fungal population for this table olive specialty. A phylogenetic analysis of the ITS sequences allowed a more accurate assignment of diverse OTUs to Pichia manshurica, Candida parapsilosis/C. tropicalis, Candida diddensiae, and Citeromyces nyonensis clades. This study highlights the existence of a complex fungal consortium in olive fermentations including phytopathogenic, saprofitic, spoilage and fermentative genera. Insights into the ecology, identification and quantification of fungi species in olive fermentation will facilitate the design of new strategies to improve the quality and safety of this fermented vegetable.

Project description:Olives from the Sigoise, Verdale, and Sevillana cultivars were elaborated as Spanish-style table olives by four Algerian factories, and the quality and food safety of the industrial table olives have been studied by the analysis of physicochemical and microbiological parameters. Differences were observed between the treatments carried out by the different factories throughout the manufacturing process, especially during the washing stage, but no significant differences were found between the analyzed samples for the concentration of sugars and polyphenols. The final pH values reached at the end of fermentation ranged between 5.04 and 4.27, and the titratable acidity was above 0.4% for all samples. Lactic and acetic acids were produced in mean concentrations of 0.68% and 0.21% as a result of lactic acid bacteria (LAB) and yeast metabolism, respectively. However, the presence of butyric, isobutyric, and propionic acids was also detected, and was related to the growth of undesirable spoilage microorganisms, responsible for secondary fermentations. The high-throughput sequencing of bacterial DNA suggested the dominance of LAB species belonging to genera Lactiplantibacillus, Leuconostoc, Pediococcus, Oenococcus, or Enterococcus. The Enterobacteriaceae family was detected during the first days of brining and in only one sample after 120 days of fermentation. Other spoilage microorganisms were found, such as Lentilactobacillus buchneri or the Pectinatus and Acetobacter genera, capable of consuming lactic acid and these played an essential role in the onset of spoilage. The Clostridium and Enterobacter genera, producers of butyric and propionic acids, were responsible for the malodorous fermentation present in the industrial samples that were analyzed. The study concluded that the safety of the table olives analyzed was compromised by the presence of undesirable microorganisms and microbial stability was not guaranteed. The elaboration process can be improved by reducing the washing steps and the time should be reduced to avoid the loss of fermentable matter, with the goal of reaching a pH < 4.0 after the fermentation and preventing the possibility of the growth of spoilage microorganisms and foodborne pathogens.

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Foodborne Pathogen Survival in Commercial Alorena de Malaga Table Olive Packaging.

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