Treatment of table olives with 1-methylcyclopropene, heat shock, and dimethyl dicarbonate impacts the microbial fermentation profile and composition of the fruit biofilm

In this study, we used an experimental design to assess the influence of 1-methylcyclopropene (1-MCP), a mild heat shock, and dimethyl dicarbonate (DMDC) on microbial evolution in brines and the biofilm composition of Spanish-style and naturally fermented table olives. Data were statistically analyzed using classical and compositional data analysis (CoDA). In the brines, the natural processing style raised the presence of yeast/fungi, while heat shock increased the populations of lactic acid bacteria populations. The interaction among heat shock, natural fermentation, and DMDC favored the survival of Enterobacteriaceae. Concerning biofilms, the metataxonomic analysis showed that the five most frequently detected bacterial genera were Lactiplantibacillus (66.79%), Secundilactobacillus (15.12%), Pediococcus (7.50%), Marinilactibacillus (4.92%), and Enterobacter (3.88%), while most common fungal genera were Saccharomyces (63.13%), Bannoa (11.49%), Candida (8.34%), Wickerhamomyces (4.15%), and Kluyveromyces (2.04%). Treatments also affected microbial diversity in biofilms. Adding DMDC significantly reduced the number of bacterial taxa compared to untreated olives. Additionally, the Spanish-style processing resulted in lower bacterial diversity. In contrast, fungi displayed an opposite trend, with the highest similarity found in naturally processed olives. CoDA revealed that the bacterial genera Marinilactibacillus and Lactiplantibacillus were characteristic of Spanish-style olives, while Secundilactobacillus and Pediococcus were associated with naturally processed olives. For fungi, Saccharomyces was related to both Spanish-style and naturally processed olives. The results indicate that the treatments influenced bacterial and fungal populations in brines and olive biofilms and their relationships. These effects may help modulate/control the microbial evolution during olive fermentation. • 1-MCP and heat shock promote LAB in brine; natural processing enhances yeast/fungi. • Spanish-style processing promotes Lactiplantibacillus development in brines. • Natural process enhances the presence of Secundilactobacillus and Saccharomyces. • Adding DMDC reduces bacterial diversity in olive biofilms, mainly in Spanish style.