Impact of lactic acid bacteria inoculation on fungal diversity during Spanish-style green table olive fermentations

This study delved into the evolution of fungal population during the fermentation of Spanish-style green table olives (Manzanilla cultivar), determining the influence of different factors such as fermentation matrix (brine or fruit) or the use of a lactic acid bacteria inoculum, on its distribution. The samples (n = 24) were directly obtained from industrial fermentation vessels with approximately 10.000 kg of fruits and 6.000 L of brines. Our findings showcased a synchronized uptick in lactic acid bacteria counts alongside fungi proliferation. Metataxonomic analysis of the Internal Transcribed Spacer (ITS) region unearthed noteworthy disparities across different fermentation time points (0, 24, and 83 days). Statistical analysis pinpointed two Amplicon Sequence Variants (ASV), Candida and Aureobasidium, as accountable for the observed variances among the different fermentation time samples. Notably, Candida exhibited a marked increase during 83 days of fermentation, opposite to Aureobasidium, which demonstrated a decline. Fungal biodiversity was slightly higher in brines than in fruits, whilst no effect of inoculation was noticed. At the onset of fermentation, prominently detected genera were also Mycosphaerella (19.82 %) and Apohysomyces (16.31 %), hitherto unreported in the context of table olive processing. However, their prevalence dwindled to nearly negligible levels from 24th day fermentation onwards (<2 %). On the contrary, they were replaced by the fermentative yeasts Saccharomyces and Isstachenkia. Results obtained in this work will be useful for designing new strategies for better control of table olive fermentations.

Functional features of the exopolysaccharide extracts produced by Lactiplantibacillus strains isolated from table olives

This study evaluates the functional characteristics of the exopolysaccharide (EPS) extracts produced by various strains of Lactiplantibacillus pentosus (LPG1, 119, 13B4, and Lp13) and Lactiplantibacillus plantarum (Lp15) isolated from table olives. None of the EPS crude extracts showed cytotoxicity when administered to THP-1 human macrophage cells at dosages ranging from 6.25 to 50 μg mL-1. Many exhibited anti-inflammatory properties (reduction of pro-inflammatory cytokines TNF-α and IL-6 production) and antioxidant activity (reduction of ROS%) when macrophages were stimulated with Escherichia coli lipopolysaccharide. Notably, the EPS extract produced by the L. pentosus LPG1 strain had the best results corroborated by western blot immune analysis for differential expression of COX-2, Nrf-2, and HO-1 proteins, with the most significant antioxidant and anti-inflammatory response observed at a dosage of 50 μg mL-1. Chemical analysis revealed that the EPS extract produced by this strain contains a heteropolymer composed of mannose (35.45%), glucose (32.99%), arabinose (17.93%), xylose (7.48%), galactose (4.03%), rhamnose (1.34%), and fucose (0.77%). Finally, we conducted response surface methodology to model the EPS extract production by L. pentosus LPG1 considering pH (3.48-8.52), temperature (16.59-33.41 °C) and salt concentration (0.03-8.77% NaCl) as independent variables. The model identified linear effects of salt and pH and quadratic effects of salt as significant terms. The maximum EPS extract production (566 mg L-1) in a synthetic culture medium (MRS) was achieved at pH 7.5, salt 7.0%, and a temperature of 20 °C. These findings suggest the potential for novel applications for the EPS produced by L. pentosus LPG1 as nutraceutical candidates for use in human diets.

Delving into the bacterial diversity of spoiled green Manzanilla Spanish-style table olive fermentations

This work applies metataxonomic, standard statistics, and compositional data (CoDa) techniques to study the bacterial diversity of spoiled and normal Spanish-style table olive fermentations, analysing a total of 10-tons of industrial fermentation containers from two processing yards. Forty percent were affected by butyric, sulfidic, or putrid spoilage, while 60% followed the ordinary fermentation course. The samples were obtained at 30 days of fermentation, determining their 16S rRNA gene Amplicon Sequence Variant compositions (ASVs). The butyric containers showed a bacterial profile strongly associated with the genera Enterococcus, Leuconostoc, and Atlantibacter, but also with Lactiplantibacillus and Melissococcus, and less confident to Raoultella, Enterobacter, Serratia, and Celerinatantimonas. The sulfidic fermentation was linked to Alkalibacterium and, to a lesser extent, Marinilactibacillus and the absence of Lactiplantibacillus. Putrid spoilage was mainly related to Halolactibacillus and Alkalibacterium. Sulfidic/putrid (together) differed from butyric spoilage by the presence of Alkalibacterium/Marinilactibacillus as well as by Halomonas/Halanaerobium. Lactiplantibacillus dominated normal fermentations, but Vibrio was also frequently found (0-46%), apparently not causing any alteration. These results contribute to a better microbial characterisation of non-zapatera spoiled table olive fermentations. They also suggest using several statistical techniques to discriminate normal vs spoiled fermentations adequately.

Exploring bacteria diversity in commercialized table olive biofilms by metataxonomic and compositional data analysis

In this work, a total of 72 samples of non-thermally treated commercial table olives were obtained from different markets of the world. Then, prokaryotic diversity in olive biofilms was investigated by metataxonomic analysis. A total of 660 different OTUs were obtained, belonging to Archaea (2.12%) and Bacteria domains (97.88%). From these, 41 OTUs with a proportion of sequences ≥ 0.01% were studied by compositional data analysis. Only two genera were found in all samples, Lactobacillus, which was the predominant bacteria in the biofilm consortium (median 54.99%), and Pediococcus (26.09%). Celerinatantimonas, Leuconostoc, Alkalibacterium, Pseudomonas, Marinilactibacillus, Weissella, and the family Enterobacteriaceae were also present in at least 80% of samples. Regarding foodborne pathogens, only Enterobacteriaceae, Vibrio, and Staphylococcus were detected in at least 91.66%, 75.00%, and 54.10% of samples, respectively, but their median values were always below 0.15%. Compositional data analysis allowed discriminating between lye treated and natural olive samples, as well as between olives packaged in glass, PET and plastic bags. Leuconostoc, Celerinatantimonas, and Alkalibacterium were the bacteria genera with a higher discriminant power among samples. These results expand our knowledge of the bacteria diversity in olive biofilms, providing information about the sanitary and hygienic status of this ready-to-eat fermented vegetable.

Influence of Acid Adaptation on the Probability of Germination of Clostridium sporogenes Spores Against pH, NaCl and Time

The Clostridium sp. is a large group of spore-forming, facultative or strictly anaerobic, Gram-positive bacteria that can produce food poisoning. The table olive industry is demanding alternative formulations to respond to market demand for the reduction of acidity and salt contents in final products. while maintaining the appearance of freshness of fruits. In this work, logistic regression models for non-adapted and acid-adapted Clostridium sp. strains were developed in laboratory medium to study the influence of pH, NaCl (%) and time on the probability of germination of their spores. A Clostridium sporogenes cocktail was not able to germinate at pH < 5.0, although the adaptation of the strains produced an increase in the probability of germination at 5.0-5.5 pH levels and 6% NaCl concentration. At acidic pH values (5.0), the adapted strains germinated after 10 days of incubation, while those which were non-adapted required 15 days. At pH 5.75 and with 4% NaCl, germination of the adapted strains took place before 7 days, while several replicates of the non-adapted strains did not germinate after 42 days of storage. The model was validated in natural green olive brines with good results (>81.7% correct prediction cases). The information will be useful for the industry and administration to assess the safety risk in the formulation of new processing conditions in table olives and other fermented vegetables.

Shelf-life of traditionally-seasoned

Few studies have been carried out to determine the shelf-life of the Aloreña de Málaga table olive packaging from a physicochemical, microbiological and sensorial point of view. This study showed that under the current packaging conditions, commercial products were free from Enterobacteriaceae, the initial yeast population was progressively inhibited, and only lactic acid bacteria grew during shelf-life. Among the physicochemical characteristics, pH decreased, lactic acid was formed while citric acid and mannitol were consumed. These changes resulted in gradual olive texture degradation and green color fading during packaging. A multivariate analysis showed that the packaged olives with storage time between 6 and 42 days enjoyed the highest acceptance; while after the 74th day, they were progressively losing acceptability, which was mainly evident at the 131st day of packaging (willingness-to-buy attribute was reduced to 50%). A complete microbiological stabilization would require the use of alternative preservatives since thermal treatment is not convenient for this type of olive speciality.

Reduction of the Bitter Taste in Packaged Natural Black Manzanilla Olives by Zinc Chloride

The work assays the use of various concentrations of ZnCl2 (0.0-0.1%, w/v) in packaged natural black Manzanilla table olives. The transformations were followed for 4 months. The presence of Zn modified the leaching of total sugars (sucrose, glucose, fructose, and mannitol) into the brine, which decreased as the ZnCl2 content increased. Over the study, sucrose and glucose were exhausted while fructose, although consumed, left some final residues and the use of mannitol was limited. Titratable acidity was always gradually formed causing the subsequent pH decrease, which stabilized at ≈3.5. Acetic and mainly lactic acid were also formed during the assay, reaching the highest level of lactic acid in the 0.050% ZnCl2 treatment, followed by the Control. The acids were formed by lactic acid bacteria (LAB) (Lactobacillus pentosus, 39%, and Lactobacillus plantarum, 61%). However, the most outstanding Zn effect was found on the olive sensory characteristics: its presence markedly reduced the bitter notes, increased the overall appreciation, and the treatment containing 0.075% ZnCl2 had the highest scores in hardness, crunchiness, and overall appreciation. Therefore, the addition of ZnCl2 into packaged natural table olives may lead to healthy products with desirable sensory characteristics which, in turn, could promote consumption.

Foodborne Pathogen Survival in Commercial Aloreña de Málaga Table Olive Packaging

This study presents an approach to determine the survival of diverse foodborne pathogens (Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella enterica) in three Aloreña de Málaga table olive commercial presentations (fresh green, traditional, and cured olives). The microbial survival in this green natural table olive speciality was fit using a log-linear regression model implemented in GInaFIT. The contents of sugars, phenolic compounds, additives, salt, pH, and levels of autochthonous microorganisms differed among presentations and affected the survival of microorganisms. The inoculated initial populations of pathogens (7–8 log₁₀ CFU/mL brine) decreased rapidly and, 48 h after inoculation, their counts were always below the detection limit (<1.3 log₁₀ CFU/mL), except for S. aureus in the fresh green presentation which was ∼ 5.0 log₁₀ CFU/mL. The highest maximum death rates (k_max) and lowest periods for 4 log₁₀ reductions (4Dr) were observed in cured olives but decreased and increased, respectively, from the traditional to the fresh green presentations. L. monocytogenes and S. aureus were the most resistant species. The multivariate analysis showed that high concentrations of compounds released from the olives (sugars and phenols) were positively associated to 4Dr and negatively to k_max. Conversely, the presence of preservatives reduced 4Dr. This study, executed in commercial products, pointed out that packaged table olives are adverse habitats for foodborne pathogens with their effects being presentation dependent. The survival of S. aureus was particularly long in green fresh Aloreña de Málaga table olives packaged without preservatives; therefore, its changes in this presentation still requires further in-deep research.

Microbiological and Physicochemical Changes in Natural Green Heat-Shocked Aloreña de Málaga Table Olives

Preserving the highly appreciated natural freshness of Aloreña de Málaga table olives and preventing their progressive darkening during processing is a major challenge. In this work, heat-shocked (60°C, 5 min) fruits were processed according to the three denominations referred to in the Protected Designation of Origen (cured, fresh green, and traditional) and their characteristics compared with those that followed the habitual industrial process (controls). The results revealed that the effects of the heat treatment on the evolution of pH, titratable acidity, salt, sugar, organic acid, ethanol content, texture, and color of fruits as well as on microbial populations (yeasts and lactic acid bacteria) were slight in the case of the fresh green and cured presentations. However, the differences between heat-shocked and its control were remarkable in the traditional process. Notably, the heat treatment favored lactic acid fermentation, retention of the green appearance of the fruits, stability during packaging, and led to the highest sensory evaluation. The metagenomic analysis carried out at the end of the fermentation revealed the presence in all samples of three genera (Lactobacillus, Pediococcus, and Celerinatantimonas) which encompassed most of the sequences. The number of Lactobacillus sequences was statistically higher (p ≥ 0.05) in the case of traditional heat-shocked fruits than in its control.

Assessing the Challenges in the Application of Potential Probiotic Lactic Acid Bacteria in the Large-Scale Fermentation of Spanish-Style Table Olives

This work studies the inoculation conditions for allowing the survival/predominance of a potential probiotic strain (Lactobacillus pentosus TOMC-LAB2) when used as a starter culture in large-scale fermentations of green Spanish-style olives. The study was performed in two successive seasons (2011/2012 and 2012/2013), using about 150 tons of olives. Inoculation immediately after brining (to prevent wild initial microbiota growth) followed by re-inoculation 24 h later (to improve competitiveness) was essential for inoculum predominance. Processing early in the season (September) showed a favorable effect on fermentation and strain predominance on olives (particularly when using acidified brines containing 25 L HCl/vessel) but caused the disappearance of the target strain from both brines and olives during the storage phase. On the contrary, processing in October slightly reduced the target strain predominance on olives (70–90%) but allowed longer survival. The type of inoculum used (laboratory vs. industry pre-adapted) never had significant effects. Thus, this investigation discloses key issues for the survival and predominance of starter cultures in large-scale industrial fermentations of green Spanish-style olives. Results can be of interest for producing probiotic table olives and open new research challenges on the causes of inoculum vanishing during the storage phase.

In silico Logistic Model for Table Olive Related Microorganisms As a Function of Sodium Metabisulphite, Cinnamaldehyde, pH, and Type of Acidifying Agent

A probabilistic/logistic model, based on binary data (growth/no growth), was used to assess the effects of sodium metabisulphite (SM) and cinnamaldehyde (CIN; 0-1000 mg/L) against the main microbial groups found in table olive environment [lactic acid bacteria (LAB), yeasts, and Enterobacteriaceae], according to pH (range 3.5-5.0), and type of acidifying agent (HCl or pyruvic acid). The inhibitory effect of SM depended on the pH while that of CIN was scarcely influenced by it (except for LAB). LAB were more sensitive to SM, while yeasts were to CIN. The use of pyruvic acid for correction of pH always produced a reduction (compared to HCl) of the inhibitory power of both preservatives. The in silico models for HCl showed that, at pH 4.0, and growth probability 0.01, the LAB population might be inhibited by the presence in the medium of 150 mg/L SM or 1000 mg/L CIN, while in the case of yeasts, 450 mg/L SM, or 150 mg/L CIN are required. No growth of Enterobacteriaceae was observed at this (or lower) pH level. The results obtained may contribute to the stabilization of non-thermally treated table olive packaging.

Assessment of the bacterial community in directly brined Aloreña de Málaga table olive fermentations by metagenetic analysis

This study uses an "omics" approach to evaluate the bacterial biodiversity changes during fermentation process of natural green cracked Aloreña de Málaga table olives, from raw material to fermented fruit. For this purpose, two industries separated by almost 20km in Guadalhorce Valley (Málaga, Spain) were analysed for obtaining both brines and fruit samples at different moments of fermentation (0, 7, 30 and 120days). Physicochemical and microbial counts during fermentation showed the typical evolution of this type of processes, apparently dominated by yeasts. However, high-throughput barcoded pyrosequencing analysis of V2-V3 hypervariable region of the bacterial 16S rRNA gene showed at 97% identity the presence of 131 bacterial genera included in 357 operational taxonomic units, not detected by the conventional approach. The bacterial biodiversity was clearly higher in the olives at the moment of reception in the industry and during the first days of fermentation, while decreased considerably as elapse the fermentation process. The presence of Enterobacteriaceae and Lactobacillaceae species was scarce during the four months of study. On the contrary, the most important genus at the end of fermentation was Celerinatantimonas in both brine (95.3% of frequency) and fruit (89.4%) samples, while the presence of well-known spoilage microorganisms (Pseudomonas and Propionibacterium) and halophilic bacteria (Modestobacter, Rhodovibrio, Salinibacter) was also common during the course of fermentation. Among the most important bacterial pathogens related to food, only Staphylococcus genus was found at low frequencies (<0.02% of total sequences). Results show the need of this type of studies to enhance our knowledge of the microbiology of table olive fermentations. It is also necessary to determine the role played by these species not previously detected in table olives on the quality and safety of this fermented vegetable.

Survival of foodborne pathogens in natural cracked olive brines

This work reports the survival (challenge tests) of foodborne pathogen species (Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella enterica) in Aloreña de Málaga table olive brines. The inhibitions were fit using a log-linear model with tail implemented in GInaFIT excel software. The olive brine had a considerable inhibitory effect on the pathogens. The residual (final) populations (Fp) after 24 h was below detection limit (<1.30 log10 cfu/mL) for all species assayed. The maximum death rate (kmax) was 9.98, 51.37, 38.35 and 53.01 h(-1), while the time for 4 log10 reductions (4Dr) was 0.96, 0.36, 0.36 and 0.24 h for E. coli, S. aureus, L. monocytogenes and S. enterica, respectively. Brine dilutions increased Fp and 4Dr, while decreased kmax. A cluster analysis showed that E. coli had an overall quite different behaviour being the most resistant species, but the others bacteria behaved similarly, especially S. aureus and S. enterica. Partial Least Squares regression showed that the most influential phenols on microbial survival were EDA (dialdehydic form of decarboxymethyl elenolic acid), HyEDA (EDA linked to hydroxytyrosol), hydroxytyrosol 4-glucoside, tyrosol, and oleoside 11-methyl ester. Results confirm the adverse habitats of table olives for foodborne pathogenic microorganisms.

Effect of green Spanish-style Manzanilla packaging conditions on the prevalence of the putative probiotic bacteria Lactobacillus pentosus TOMC-LAB2

This work focuses on the persistence of the putative probiotic bacteria Lactobacillus pentosus TOMC‐LAB2 on green Spanish‐style Manzanilla olives according to different packaging conditions and storage temperatures. The lactic acid bacteria population decreased with time but the highest survival counts (and lowest yeasts) at the end of storage (8 months) were observed in plastic pouches under nitrogen atmosphere and glass jars with brine stored at 20°C. Molecular techniques showed a 100% presence of the putative probiotic bacteria in biofilms adhered to olive epidermis, while it was absent in PPB (plastic pouches with brine) and in olives stored at 7°C. No changes in NaCl, pH or combined acidity were observed during the storage except for a slight increase in titratable acidity at 20°C. The color of the fruits was stable but degraded at 20°C for olives in plastic pouches with brine.

Effect of zinc formulations, sodium chloride, and hydroxytyrosol on the growth/no-growth boundaries of table olive related yeasts

This study uses a mathematical approach to assessing the inhibitory effect of Zn(2)(+)(0-10 mM, obtained from ZnCl2 and ZnSO4) in presence of NaCl (0-8%) and hydroxytyrosol (0-2588 mg/L), on a yeast cocktail formed by species Pichia galeiformis, Pichia kudriavzevii, Pichia manshurica and Candida thaimueangensis obtained from spoilt green olive packages. The logistic/probabilistic models were built in laboratory medium using a total of 1980 responses (1188 for NaCl and 792 for hydroxytyrosol). ZnCl2 showed significantly higher inhibitory effect than ZnSO4 in the presence of both NaCl (p < 0.033) and hydroxytyrosol (p < 0.009). NaCl did not interfere the effect of Zn(2)(+)while hydroxytyrosol, at high levels, had a slight antagonistic effect. According to models, Zn(2)(+)inhibits (p = 0.01) the yeast cocktail in the range 4.5-5.0 mM for ZnCl2, or 8.5-9.5 mM for ZnSO4. Therefore, this work confirms the fungicidal activity of zinc compounds (mainly ZnCl2) in synthetic medium, and also shows that the loss of zinc effectiveness in real green Spanish-style olive packaging is not due to the presence of NaCl or hydroxytyrosol, two of the most abundant chemical compounds in the product.

The effect of ZnCl2 on green Spanish-style table olive packaging, a presentation style dependent behaviour

BACKGROUND

Zinc chloride has been used previously as a preservative in directly brined olives with promising results. However, this is the first time that the effects of ZnCl2 addition (0-1 g L(-1) ) on green Spanish-style table olive (cv. Manzanilla) packaging has been studied.

RESULTS

The presence of ZnCl2 affected the physico-chemical characteristics of the products; the presence of the Zn led to lower pH values (particularly just after packaging) and titratable and combined acidity values than the control but did not produce clear trends in the colour parameters. No Enterobacteriaceae were found in any of the treatments evaluated. At the highest ZnCl2 concentrations, the lactic acid bacteria were inhibited while, unexpectedly, its presence showed a lower effect than potassium sorbate against the yeast population. Regardless of the use of potassium sorbate or ZnCl2 , the packages had a reduced microbial biodiversity because only Lactobacillus pentosus and Pichia galeiformis were found at the end of the shelf life. With respect to organoleptic characteristics, the presentations containing ZnCl2 were not differentiated from the traditional product.

CONCLUSION

Zinc chloride was less efficient than potassium sorbate as a yeast inhibitor in green Spanish-style olives, showing clear presentation style dependent behaviour for this property. Its presence produced significant changes in chemical parameters but scarcely affected colour or sensory characteristics.

Survival of pathogenic and lactobacilli species of fermented olives during simulated human digestion

The present survey uses a dynamic gastric and small intestinal model to assess the survival of one pathogenic (Escherichia coli O157:H7 EDL 933) and three lactobacilli bacteria with probiotic potential (Lactobacillus rhamnosus GG, L. pentosus TOMC-LAB2, and L. pentosus TOMC-LAB4) during their passage through the human gastrointestinal tract using fermented olives as the food matrix. The data showed that the survival of the E. coli strain in the stomach and duodenum was very low, while its transit through the distal parts (jejunum and ileum) resulted in an increase in the pathogen population. The production of Shiga toxins by this enterohemorrhagic microorganism in the ileal effluents of the in vitro system was too low to be detected by ELISA assays. On the contrary, the three lactobacilli species assayed showed a considerable resistance to the gastric digestion, but not to the intestinal one, which affected their survival, and was especially evident in the case of both L. pentosus strains. In spite of this, high population levels for all assayed microorganisms were recovered at the end of the gastrointestinal passage. The results obtained in the present study show the potential use of table olives as a vehicle of beneficial microorganisms to the human body, as well as the need for good hygienic practices on the part of olive manufacturers in order to avoid the possibility of contamination by food-borne pathogens.

Fortification of table olive packing with the potential probiotic bacteria Lactobacillus pentosus TOMC-LAB2

Dairy products are currently the main carriers of probiotic microorganisms to the human body. However, the development of new matrices for probiotic delivery is convenient for intolerant to milk (or its derivatives) and those requiring low-cholesterol diet consumers. The present work focused on the fortification of previously fermented green Spanish style olives with the autochthonous putative probiotic bacteria Lactobacillus pentosus TOMC-LAB2. The fortification was carried out by inoculating the bacteria into the packing brines using Manzanilla fruits from three different processes: (i) spontaneously fermented (F1), (ii) fermented using L. pentosus TOMC-LAB2 as starter (F2), and (iii) spontaneously fermented and then thermally treated (F3). Data showed that all inoculated treatments had higher population levels (5.49, 4.41, and 6.77 log₁₀ cfu/cm²) than their respective controls (1.66, 4.33, and 0.0 log₁₀ cfu/cm², for F1, F2, and F3 treatments, respectively). The presence of L. pentosus TOMC-LAB2 on olive surface was confirmed by rep-PCR, with a recovery frequency at the end of the shelf life (200 days) of 52.6, 57.9, and 100.0% for F1, F2, and F3 treatments, respectively. Thus, results obtained in this work show the ability of this microorganism to survive under packing conditions for long period of times as well as to colonize the olive surface which is the food finally ingested by consumers. This opens the possibility for the development of a new and simply probiotic fortified olive product.

Microbial stability and quality of seasoned cracked green Aloreña table olives packed in diverse chloride salt mixtures

This work was conducted to determine the effect of the partial replacement of NaCl by KCl and CaCl2 (expressed as percentages, wt/vol) on the microbial stability and physicochemical characteristics of seasoned cracked olives using a simplex centroid mixture design. Neither Enterobacteriaceae nor lactic acid bacteria were found during the 50 days that olive packages were monitored. Therefore, microbial instability was considered due to the growth of yeasts, which were the only detected microorganisms; Saccharomyces cerevisiae and Pichia membranifaciens were the most relevant species. Yeasts decreased during the first 21 to 30 days after packing, but their populations rose to 3.5 log CFU/ml by the end of the storage period, clearly causing product deterioration. The partial substitution of NaCl with the other chloride salts slightly altered the phase of microbial inhibition and regrowth. Most of the quality characteristics were not affected by the use of the alternative salt mixtures, but the pH values and Cl(-) concentrations in brine decreased as the CaCl2 concentration increased. Hence, seasoned cracked table olives can be produced using a lower proportion of NaCl without causing significant changes in the shelf life and product quality, although further detailed studies are necessary to guarantee the stability of products packed with specific salt mixtures.

Evaluating the individual effects of temperature and salt on table olive related microorganisms

Statistical modelling techniques were used in the present study to assess the individual effects of temperature and NaCl concentration on the growth of 10 lactic acid bacteria and 6 yeast strains mostly isolated from different forms of table olive processing and belonging to the species Lactobacillus pentosus, Lactobacillus plantarum, Saccharomyces cerevisiae, Wickerhamomyces anomalus and Candida boidinii. The mathematical models obtained in synthetic laboratory media show that yeasts, except for C. boidinii, were more resistant to a high salt concentration than lactic acid bacteria, with an MIC value ranging from 163.5 (S. cerevisiae) to 166.9 g/L (W. anomalus); while for L. pentosus and L. plantarum this parameter ranged from 110.6 to 117.6 g/L, respectively. With regards to temperature, lactic acid bacteria showed a slight trend towards supporting higher temperature values than yeasts, with the exception of S. cerevisiae. The maximum temperatures for growth of L. pentosus and L. plantarum were 41.9 and 43.0 °C, respectively; while for W. anomalus and C. boidinii they were 38.2 and 36.5 °C. The optimum temperatures for growth were also higher for L. pentosus and L. plantarum (35.5 and 32.9 °C), compared to W. anomalus and C. boidinii (29.3 and 26.9 °C, respectively). Additional experiments carried out in natural olive brines confirmed previous results, showing that high NaCl concentrations clearly favoured yeast growth and that at high temperatures LAB slightly overcame yeasts. Results obtained in this paper could be useful for industry for a better control of both table olive fermentation and packaging.

Yeasts in table olive processing: desirable or spoilage microorganisms?

Yeasts are unicellular eukaryotic microorganisms isolated from many foods, and are commonly found in table olive processing where they can play a double role. On one hand, these microorganisms can produce spoilage of fruits due to the production of bad odours and flavours, the accumulation of CO(2) leading to swollen containers, the clouding of brines, the softening of fruits and the degradation of lactic acid, which is especially harmful during table olive storage and packaging. But on the other hand, fortunately, yeasts also possess desirable biochemical activities (lipase, esterase, β-glucosidase, catalase, production of killer factors, etc.) with important technological applications in this fermented vegetable. Recently, the probiotic potential of olive yeasts has begun to be evaluated because many species are able to resist the passage through the gastrointestinal tract and show beneficial effects on the host. In this way, yeasts may improve consumers' health by decreasing cholesterol levels, inhibiting pathogens, degrading non assimilated compounds, producing antioxidants and vitamins, adhering to intestinal cells or by maintaining epithelial barrier integrity. Many yeast species, usually also found in table olive processing, such as Wicherhamomyces anomalus, Saccharomyces cerevisiae, Pichia membranifaciens and Kluyveromyces lactis, have been reported to exhibit some of these properties. Thus, the selection of the most appropriate strains to be used as starters, alone or in combination with lactic acid bacteria, is a promising research line to develop in a near future which might improve the added value of the commercialized product.

Formation of lactic acid bacteria-yeasts communities on the olive surface during Spanish-style Manzanilla fermentations

This work examines the formation of poly-microbial communities adhered to the surface of Manzanilla olive fruits processed according to the Spanish style. The experimental design consisted of four pilot fermenters inoculated with four Lactobacillus pentosus strains, plus another fermenter which was not inoculated and fermented spontaneously. Lactic acid bacteria and yeasts were analysed in depth on olive epidermis throughout fermentation by plate count, molecular techniques and scanning electron microscopy. Data show that in all cases high population levels (above 8 log(10) CFU per olive) were reached for both groups of microorganisms at the second week of fermentation and that these counts never fell below 6 log(10) CFU per olive during the 3 months that fermenters were monitored. In situ observation of olive epidermis slices revealed a strong aggregation and adhesion between bacteria and yeasts by the formation of a matrix which embedded the microorganisms. Geotrichum candidum, Pichia galeiformis and Candida sorbosa were the main yeast species isolated from these biofilms at the end of fermentation (confirmed by RFLP analysis of the 5.8S-ITS region), while molecular characterization of lactobacilli isolates by means of RAPD-PCR with primer OPL(5) showed in many cases a high similarity in their banding profiles with the inoculated strains. Results obtained in this survey show the importance of studying the olive epidermis throughout fermentation, because ultimately, olives are ingested by consumers.

Potential benefits of the application of yeast starters in table olive processing

The classification of high-throughput sequencing data of protein-encoding genes is not as well established as for 16S rRNA. The objective of this work was to develop a simple and accurate method of classifying large datasets of pmoA sequences, a common marker for methanotrophic bacteria. A taxonomic system for pmoA was developed based on a phylogenetic analysis of available sequences. The taxonomy incorporates the known diversity of pmoA present in public databases, including both sequences from cultivated and uncultivated organisms. Representative sequences from closely related genes, such as those encoding the bacterial ammonia monooxygenase, were also included in the pmoA taxonomy. In total, 53 low-level taxa (genus-level) are included. Using previously published datasets of high-throughput pmoA amplicon sequence data, we tested two approaches for classifying pmoA: a naïve Bayesian classifier and BLAST. Classification of pmoA sequences based on BLAST analyses was performed using the lowest common ancestor (LCA) algorithm in MEGAN, a software program commonly used for the analysis of metagenomic data. Both the naïve Bayesian and BLAST methods were able to classify pmoA sequences and provided similar classifications; however, the naïve Bayesian classifier was prone to misclassifying contaminant sequences present in the datasets. Another advantage of the BLAST/LCA method was that it provided a user-interpretable output and enabled novelty detection at various levels, from highly divergent pmoA sequences to genus-level novelty.

Evaluating the effects of zinc chloride as a preservative in cracked table olive packing

This survey studies the influence of different zinc chloride concentrations (0.050, 0.075, and 0.100%, wt/vol) on the shelf life of "Aceituna Aloreña de Málaga" table olives. The Enterobacteriaceae population significantly (P ≤ 0.05) decreased in treatments containing 0.050 and 0.100% ZnCl(2), and those with 0.075% ZnCl(2) had also lower average counts than those observed under the usual packaging conditions (0.12% potassium sorbate). Lactic acid bacteria increased for treatments with 0.050 and 0.075% ZnCl(2), but in the presence of 0.100% they practically disappeared at the end of the shelf life period (∼3 months). With respect to yeasts, populations of these microorganisms significantly decreased with the first two concentrations (0.050 and 0.075%) but showed a slight increase in the presence of 0.100% of ZnCl(2), although remaining markedly below populations observed with potassium sorbate packing. The use of this chloride salt also led to products with higher concentrations of sugars in brine because of its selective microbial inhibition. Finally, olives treated with 0.075% ZnCl(2) showed an improved sensory profile.