We studied the fermentation of black olives during yearlong spontaneous fermentations, from fresh harvested fruits to fermented olives. The study was done in partnership with a local and artisanal producer. We studied the microbial ecology and dynamics of Nyons table olives, using complementary and innovative microbiological methods. The fresh olives fruits, the salt implemented for the brine as well as the process environment were analysed to decipher the origin of the microbes and their potential role during fermentation.

Four different Nyons table olive fermentations were monitored using culture-dependent and -independent analyses. What we found:

• Unlike other fermented table olives, Nyons table olive fermentations mainly rely on yeasts but not on lactic acid bacteria. Lactic acid bacteria are only detected in fresh olive fruits in some fermentations.
• At the start of fermentation, the microbial population is mainly constituted by yeasts, originated from soil and olive fresh fruits. Then this flora is replaced by different yeast species, which follow each other in a precise order: Wickerhamomyces anomalus, Citeromyces nyonsensis, Zygotorulasporamrakii, Pichia membranifaciens and Candida boidinii.
• These five yeast species constitute the core microbiota of Nyons olive fermentation, and are very resilient, as there were found in all the fermentations monitored over the past 4 years.
• For the first time, Nyons table olive aroma profile was deciphered and its evolution during fermentation correlated to yeast dynamics.

 
 Analysis of the yeast species present in brine during a complete olives fermentation, from the firts day (D1) to the end of fermentation (Day 365). The yeasts were identified by metagenomic analysis. For each day, the analysis were performed in triplicate (for each day of analysis each column corresponds to a sample). 

 
We deciphered for the first time the core microbiota of the famous Nyons table olives. This microbiota is mainly constituted by yeasts species. The role of each yeast remains to be precisely elucidated. Finally, as a result of this work, we isolated numerous yeast strains representative of the nyons table olive fermentations, that are conserved in microorganism collection, for further studies.

Collaborations

• Monika Coton & Jérôme Mounier - Université de Bretagne Occidentale - LUBEM

Read more

Marine Penland, Jérôme Mounier, Audrey Pawtowski, Sylvie Tréguer, Stéphanie-Marie Deutsch, Monika Coton (2021-06). Use of metabarcoding and source tracking to identify desirable or spoilage autochthonous microorganism sources during black olive fermentations. Food Research International, 144, 110344, https://hal.inrae.fr/hal-03205178

Marine Penland, Stéphanie-Marie Deutsch, Hélène Falentin, Audrey Pawtowski, Elisabeth Poirier, Giorgia Visenti, Christophe Le Meur, Marie-Bernadette Maillard, Anne Thierry, Jérôme Mounier, Monika Coton (2020-10-08). Deciphering Microbial Community Dynamics and Biochemical Changes During Nyons Black Olive Natural Fermentations. Frontiers in Microbiology, https://hal.inrae.fr/hal-02961412

Financial support

PROMEDFOODS is a project funded through the ARIMNet2 2017 Call by the following funding agencies: ANR, ELGO-DEMETER, MESRS, MIPAF, INIA and MHESR. ARIMNet2 (2014-2017) has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement n° 618127.

Contacts

Stéphanie Deutsch • stephanie-marie.deutsch@inrae.deutsch

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