Current Status, Recent Advances, and Main Challenges on Table Olive Fermentation: The Present Meets the Future

Abstract

Table olives are among the most well-known fermented foods, being a vital part of the Mediterranean pyramid diet. They constitute a noteworthy economic factor for the producing countries since both their production and consumption are exponentially increasing year by year, worldwide. Despite its significance, olive’s processing is still craft based, not changed since antiquity, leading to the production of an unstable final product with potential risk concerns, especially related to deterioration. However, based on industrial needs and market demands for reproducible, safe, and healthy products, the modernization of olive fermentation processing is the most important challenge of the current decade. In this sense, the reduction of sodium content and more importantly the use of suitable starter cultures, exhibiting both technological and potential probiotic features, to drive the process may extremely contribute to this need. Prior, to achieve in this effort, the full understanding of table olive microbial ecology during fermentation, including an in-depth determination of microbiota presence and/or dominance and its functionality (genes responsible for metabolite production) that shape the sensorial characteristics of the final product, is a pre-requisite. The advent of meta-omics technology could provide a thorough study of this complex ecosystem, opening in parallel new insights in the field, such as the concept of microbial terroir. Herein, we provide an updated overview in the field of olive fermentation, pointing out some important challenges/perspectives that could be the key to the olive sector’s advancement and modernization.

Fermented table olives from Cyprus: Microbiota profile of three varieties from different regions through metabarcoding sequencing

“…Successful fermentation and thus, the production of high-quality table olives is strongly dependent on the prevalence; against other microorganisms; of Lactic Acid Bacteria (LAB) and/or yeasts, the role of which is of great importance for an appropriate fermentation process, that will lead to the production of well-accepted final products ( Perpetuini et al, 2020 ). Table olive fermentation involves complex associations among the members of the microbial ecosystem and is a non-stable procedure that takes place spontaneously until nowadays ( Anagnostopoulos and Tsaltas, 2022 ). Even though there are different types of olives production, such as the Spanish-style, the Greek style, the Californian style, and other local-based methods ( Perpetuini et al, 2020 ), in all cases the fermentation process occurs spontaneously, led exclusively by the indigenous microbiota coming from the raw materials (olive variety, salt, water; Heperkan, 2013 ; Anagnostopoulos et al, 2020a ) or by contaminants during the processing stage (fermenters, tanks, patios, etc.)…”

“…This means that the microbial communities from the micro-environment where olives are cultivated, as well as olive’s cultivar., have significant roles in the microbiota formation during the fermentation process and consequently in the final product qualitative characteristics formation. Therefore, a potential geographical-dependent significance that is not well-defined until today is proposed ( Anagnostopoulos and Tsaltas, 2022 ). This hypothesis is also reinforced by some indications that support the claim of “environmental selection,” which means that different environments are constituted by specific microbial communities that are transferred and participate in the spontaneous fermentation of several foods ( Martiny et al, 2006 ; Argyri et al, 2020 ).…”

“…Since then, a limited number of scientific research related to those aspects (comparison of different varieties and/or from different regions) has been published, such as a work performed by Kazou et al (2020) on the microbiota of natural Black Kalamata cultivar from different regions of Greece, or the study by Argyri et al (2020) dealing with the microbial diversity of fermented olives of two varieties from different regions in the Greek territory. As it is clearly observed, the number of works applied until now is very low, making the knowledge about those aspects very limited, even though such kind of concepts deserves more attention from the scientific community ( Anagnostopoulos and Tsaltas, 2022 ). Connecting the microbiota composition of a fermented olive variety with a specific region may potentially lead to its promotion a as Protected Designation of Origin (PDO) or Protected Geographical Indication (PGI) product and thus, increase its added value, a fact with major economic benefits for the producers ( Anagnostopoulos and Tsaltas, 2022 ).…”

“…As it is clearly observed, the number of works applied until now is very low, making the knowledge about those aspects very limited, even though such kind of concepts deserves more attention from the scientific community ( Anagnostopoulos and Tsaltas, 2022 ). Connecting the microbiota composition of a fermented olive variety with a specific region may potentially lead to its promotion a as Protected Designation of Origin (PDO) or Protected Geographical Indication (PGI) product and thus, increase its added value, a fact with major economic benefits for the producers ( Anagnostopoulos and Tsaltas, 2022 ).…”

A Preliminary Approach to Define the Microbiological Profile of Naturally Fermented Peranzana Alta Daunia Table Olives

“…The biota of table olives is complex and variable, since it can be affected by several factors, such as pH, water activity, sugar availability, concentration of phenolic compounds, temperature, oxygen availability, salt, etc. [ 5 , 6 ]. However, lactic acid bacteria (LAB) and yeasts can be considered the dominant microbial groups: the first are the main players of fermentation through acidification of the brine and consequent inhibition of other undesirable microbial groups (which are not able to tolerate low pHs), and the latter give a precious contribution to sensorial quality improvement (in terms of taste, odor and flavor) due to their capacity to produce volatile organic compounds [ 7 , 8 ].…”