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In the present study, a dose-response model was used to investigate the susceptibility (NIC) and resistance (MIC) of the lactic acid bacteria and yeast populations with respect to five chemical preservatives (fumaric and pyruvic acids, cinnamaldehyde, sodium metabisulphite and natamycin) with potential application in table olives. Results were compared with respect to potassium sorbate, a well-known preservative habitually used in olive packaging. Sodium metabisulphite was the most efficient preservative to control lactic acid bacteria growth (MIC, 50 ppm), followed by cinnamaldehyde (1060 ppm) while pyruvic acid required higher concentrations (3211 ppm). Natamycin (25 ppm) was highly efficient against yeasts, followed by cinnamaldehyde (125 ppm), potassium sorbate (553 ppm), sodium metabisulphite (772 ppm) and pyruvic acid (3038 ppm). Fumaric acid, in the range assayed (0–2000 ppm), did not show any inhibitory effect against these two microbial groups. This survey presents for the first time a comparative study of the efficiency of potential preservatives to control the growth of table olive related microorganisms. Further studies should be performed to validate their effects and interactions in the food matrix. [ABSTRACT FROM AUTHOR]

After moisture, fat is the major constituent of table olives. However, scarce studies have been carried out to determine the influence of microorganisms and type of processing on the modification of their quality indexes. The present survey studies the influence of lipolytic ( Candida boidinii TOMC Y5 and Wickerhamomyces anomalus TOMC Y10) and nonlipolytic ( Debaryomyces etchellsii TOMC Y9 and Pichia galeiformis TOMC Y27) yeasts on the oil quality indexes of Manzanilla and Hojiblanca green fruits processed as directly brined and lye-treated table olives. Overall, the inocula scarcely used available sugars, except the lipolytic C. boidinii strain in lye-treated olives. Acetic acid production was limited in all conditions, except for the D. etchellsii strain in directly brined Manzanilla fruits. Ethanol formation was also reduced, although the W. anomalus (in both types of elaboration) and the C. boidinii (in lye-treated olives) strains produced significantly higher proportions. Apparently, changes in the oil quality indexes of processed olives were not related to the presence of yeasts, and hence, could have been caused by the endogenous activity of the fruits. A principal component analysis using the microbiological, physicochemical, and oil quality data supported this hypothesis, grouping treatments according to olive variety and type of elaboration, while segregation due to yeast inocula was not observed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]