Isolation, Characterization, and Selection of Molds Associated to Fermented Black Table Olives.

Simona L Bavaro,Jens C Frisvad,Antonia Susca,Agathi Chytiri,Gianluca Bleve,Maria Tufariello,Giancarlo Perrone,Giovanni Mita,Antonio F Logrieco

doi:10.3389/fmicb.2017.01356

Abstract

Table olives are one of the most important fermented food in the Mediterranean countries. Apart from lactic acid bacteria and yeasts that mainly conduct the olive fermentation, molds can develop on the brine surface, and can have either deleterious or useful effects on this process. From the food safety point of view, occurring molds could also produce mycotoxins, so, it is important to monitor and control them. In this respect, identification of molds associated to two Italian and two Greek fermented black table olives cultivars, was carried out. Sixty strains were isolated and molecularly identified as Penicillium crustosum (21), P. roqueforti (29), P. paneum (1), P. expansum (6), P. polonicum (2), P. commune (1). A group of 20 selected isolates was subjected to technological (beta-glucosidase, cellulolytic, ligninolytic, pectolytic, and xylanolytic activities; proteolytic enzymes) and safety (biogenic amines and secondary metabolites, including mycotoxins) characterization. Combining both technological (presence of desired and absence of undesired enzymatic activities) and safety aspects (no or low production of biogenic amines and regulated mycotoxins), it was possible to select six strains with biotechnological interest. These are putative candidates for future studies as autochthonous co-starters with yeasts and lactic acid bacteria for black table olive production.

Highlights

During fermentation of table olives, molds can develop on the brine surface and produce a thick layer on the top
Molds were collected during fermentation from different lab- and industrial-scale table olive fermentations performed in Italy and Greece and from different Italian and Greek commercial products belonging to the four cultivars Leccino, Cellina di Nardò, Kalamàta, and Conservolea
The analysis revealed 21 Penicillium crustosum isolates from all the cultivars

Summary

Introduction

During fermentation of table olives, molds can develop on the brine surface and produce a thick layer on the top. Mold growth during storage in the market can result in appearance of visible mycelia. They are generally considered spoilage microorganisms responsible for product alterations, such as flesh softening and development of moldy taste, flavor, and appearance. The most representative identified mold genera are Aspergillus and Penicillium (Fernandez et al, 1997). Their presence reduces product acceptance by the consumers, and it is of relevant interest for the safety of table olives, since they can be responsible for mycotoxin production. The occurrence of Penicillium citrinum and P. verrucosum during fermentation, in particular in black olives, was linked to the production of ochratoxin A (OTA) and citrinin, while the contamination by aflatoxin B1 (AFB) is mainly related to Aspergillus flavus on damaged olives during drying and storage (El Adlouni et al, 2006; Ghitakou et al, 2006; Heperkan et al, 2006, 2009)

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Conclusion