Table Olive Fermentation Research Articles

Starter Cultures for the Production of Fermented Table Olives: Current Status and Future Perspectives

Starter Cultures for the Production of Fermented Table Olives: Current Status and Future Perspectives

Impact of lactic acid bacteria starter inoculation on the Physico-chemical, microbiological, volatiles and sensory properties of natural black Gemlik (Olea europaea L., cv.) table olives

Traditionally, the fermentation of Gemlik table olives takes place spontaneously by the endogenous microbiota in Turkey, but the uncontrolled process during fermentation can result in the formation of off-flavours and a low sensory quality of the final product. In this research, the effects of inoculating naturally black Gemlik olives with Lactiplantibacillus pentosus and Lactiplantibacillus plantarum starter cultures on lactic fermentation development, volatile compounds, and sensory properties were investigated. Changes in spontaneous and culture inoculated olives were monitored during fermentation. Compared to spontaneous fermentation, rapid acidification, and sugar depletion were achieved with the use of starter cultures. Extra lactic acid bacteria and total yeast growth were detected in the inoculated trials during fermentation compared to the control trial. Volatile compounds in olives were extracted by the Purge and Trap method. 46 volatile compounds from 10 chemical groups have been identified in olives. In all three trials, volatile acids were the group of volatile compounds found in the top amount in olives, higher alcohols, phenols, aldehydes/ketones, and terpenes followed the volatile acids. Phenyl ethyl alcohol, α-farnesen, (Z)-3-hexene-1-ol and 2-hexanol, which give pleasant flavors, were determined to be in more quantity in olives with inoculated starter cultures. This study reveals that the use of starter culture provides advantages in the production of Gemlik variety table olives, positively affects aroma development, and improves sensory properties.

Identifying the sensory profiles of naturally fermented table olives and their application to industrially processed cultivars

The study examines the sensory profile of industrially processed, naturally fermented table olives. A detailed set of descriptors crunchiness, hardness, bitter, fibrousness, saltiness, chewiness, sourness, green fruit, ripe fruit, flesh/stone separation, piquant, and musty was developed for green and turning colour Manzanilla and Gordal products, using Quantitative Descriptive Analysis (QDA). Green Gordal (GG) was characterised by higher than average chewiness (scores 7.0–7.1), crunchiness (7.5–8.2), hardness (scores 7.7–8.0) and fibrousness (6.2–6.4). In contrast, turning colour Gordal was lower than average in bitter (2.9–3.4), crunchiness (4.1–4.9), hardness (4.5–5.1) and fibrousness (4.4–4.7). Initially, the green Manzanilla was characterised by higher than average levels of bitter (6.5–7.1), crunchiness (7.2–7.4), hardness (6.9–7.0), and saltiness (3.2–3.3). However, they diminished to about average levels by the end of the fermentation process. The turning colour Manzanilla was initially associated with elevated bitter (5.6–5.9) and lower-than-average final crunchiness (4.6–4.9), hardness (5.1–5.7) and fibrousness (4.5-4.6). However, the final product resulting from this treatment had relatively high significant values for acetic/vinegar (3.5), astringent (3.5), musty (2.0), piquant (2.5), rancid (1.8) and ripe fruit flavour (3.3). The Hotelling T2 test, PCA, and the correlation circle reinforced the specific sensory profile associated with cultivars and maturation stages. Minimal changes were observed over time. PLS-R revealed associations between physicochemical characteristics and sensory profiles such as bitter with phenol content (standardised coefficient; 0.881) and texture (0.755) or ripe fruit with bitter index (0.475), among others.

Inoculated fermentation of cv. Conservolea natural black olives with multifunctional starter cultures in reduced‐sodium brines

SummaryThe purpose of this research was to investigate the fermentation of Conservolea variety natural black olives using two lactic acid bacteria (LAB) with multifunctional potential as starter cultures. Moreover, the effect of 50% substitution of NaCl by KCl in the brines was examined to produce a reduced‐sodium product with multifunctional potential. For this purpose, Lactiplantibacillus pentosus B363 and Lactiplantibacillus plantarum B380, previously isolated from table olive fermentations and characterised for technological and probiotic potential, were inoculated at the onset of fermentation in 6% (w/v) NaCl and 3% (w/v) NaCl/3% (w/v) KCl salt brines. The microbial populations (LAB, yeasts, and Enterobacteriaceae), pH, acidity, salt content, organic acids, and ethanol were measured in the brine for 146 days. Additionally, the recovery of each starter culture from the olive drupes at the beginning (5 days) and final (146 days) stages of fermentation was determined by plating, genotyping, and identification through RAPD‐PCR and 16S region amplicon sequencing, respectively, and subsequent strain differentiation through rep‐GTG5 fingerprint analysis. The results revealed the dominance of LAB in populations from 5.5 to 8.1 log CFU/mL. The final recovery rate of L. pentosus B363 on the olives was approximately 80% in both 6% (w/v) NaCl and reduced (3% (w/v) NaCl/3% (w/v) KCl) salt brines. Similarly, L. plantarum B380 recovery rates were 89% and 85%, respectively, for the same fermentations. Yeasts coexisted with LAB in counts ranging from 2.3 to 5.8 log CFU/mL, whereas no enterobacteria were enumerated in the brines and olives at the end of fermentation. The obtained fermentation profile and the sensory analysis of the olives revealed a typical lactic acid fermentation in both control and reduced‐sodium brines. The current results support the feasibility of the production of reduced‐sodium natural black olives with probiotic potential. The proposed fermentation process, including the selected starters, can be readily employed by the table olive industry to meet consumers' needs for low‐sodium dietary intake while enhancing the functional potential of table olives.

Study of the effects of pasteurization and selected microbial starters on functional traits of fermented table olives

Table olives are one of the most known fruit consumed as fermented food, being a fundamental component of the Mediterranean diet. Their production and consumption continue to increase globally and represent an important economic source for the producing countries. One of the most stimulating challenges for the future is the modernization of olive fermentation process. Besides the demand for more reproducible and safer production methods that could be able to reduce product losses and potential risks, producers and consumers are increasingly attracted by the final product characteristics and properties on human health.In this study, the contribution of microbial starters to table olives was fully described in terms of specific enzymatic and microbiological profiles, nutrient components, fermentation-derived compounds, and content of bioactive compounds. The use of microbial starters from different sources was tested considering their technological features and potential ability to improve the functional traits of fermented black table olives.For each fermentation assay, the effects of controlled temperature (kept at 20 °C constantly) versus not controlled environmental conditions (oscillating between 7 and 17 °C), as well as the consequences of the pasteurization treatment were tested on the final products. Starter-driven fermentation strategies seemed to increase both total phenolic content and total antioxidant activity. Herein, among all the tested microbial starters, we provide data indicating that two bacterial strains (Leuconostoc mesenteroides KT 5-1 and Lactiplantibacillus plantarum BC T3-35), and two yeast strains (Saccharomyces cerevisiae 10A and Debaryomyces hansenii A15-44) were the better ones related to enzyme activities, total phenolic content and antioxidant activity. We also demonstrated that the fermentation of black table olives under not controlled environmental temperature conditions was more promising than the controlled level of 20 °C constantly in terms of technological and functional properties considered in this study. Moreover, we confirmed that the pasteurization process had a role in enhancing the levels of antioxidant compounds.

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.

Impact of 1-Methylcyclopropene in Combination with Heat Shock and Dimethyl Dicarbonate on the Physicochemical Profiles of Table Olive Fermentations

AbstractTable olives are the most important fermented vegetable in the Mediterranean countries. In a continuous effort to improve the quality of this food, this work applies an experimental design with four variables to study the use of 1-methylcyclopropene (1-MCP, 2.85 µL/L) in combination with a light heat shock (65 °C, 5 min) and dimethyl dicarbonate (DMDC, 83 mg/L), during the processing of Spanish style and natural table olives. Fruits processed in the Spanish style exhibited higher moisture levels, luminance, and combined acidity. On the contrary, natural olives contained more sugars, had a firmer texture, and displayed a greener colour. Our results show that applying 1-MCP, heat shock, and DMDC can positively impact the processing of Spanish style and natural table olives and influence their physicochemical characteristics. Adding DMDC to the initial brine caused colour degradation but lowered the pH. Using 1-MCP with a light heat shock improved the sugar content and luminance of olives and increased the titratable acidity in the brine. Applying 1-MCP to the Spanish style enhanced the luminosity (brightness) and, when combined with DMDC, led to the lowest pH levels. Further research at an industrial scale is necessary to validate these results and study their influence on microorganisms. These treatments could have applications in developing new table olive processing methods that allow for more predictable products.

Effect of Growing Regions on Discrimination of Turkish-Style Black Table Olives from Gemlik Cultivar.

Gemlik is a cultivar that grows in a distinct region of Turkiye and is ideal for brine fermentation of brine black table olives. Bursa Protected Designated Origin (PDO) and Izmir non-PDO Gemlik table olives have high levels of oleic acid (74%), total phenol (190 mg/kg), and dry matter (57%), while being low in linoleic acid (8%). The pH values and salt contents were observed to be in the range of 4.1 to 4.3 and 3.9% to 4.8%, respectively. During the fermentation of Gemlik table olives, a mass transfer occurred, resulting in a reduction in reducing sugar and total sugar contents as well as an increase in the salt content of the olives. Despite the reduction of phenolic content in both Gemlik PDO and non-PDO table olives, their antioxidant capacity remains high after fermentation. The oil content, antioxidant activity, phenolic contents, palmitic, palmitoleic, oleic, and linoleic acids were all found to be significant variables in distinguishing between Gemlik PDO and non-PDO table olives using PLS-DA analysis. There is a statistically significant correlation between the phenolic content and oleic (0.588) and linoleic (-0.659) acids (p < 0.05). Bursa PDO and Izmir non-PDO exhibit enhanced nutritional quality and antioxidant activity, unequivocally differentiating them from Hatay and Mersin non-PDO Gemlik table olives with 98% accuracy through discriminant analysis (p < 0.05). PLS-DA and DA can effectively identify variations in the quality of Turkish-style black table olives preserved in brine, originating from PDO and non-PDO growing areas.

LP309 a new strain of Lactiplantibacillus pentosus that improves the lactic fermentation of Spanish-style table olives.

Different varieties of table olives have suitable morphological characteristics that allow them to be processed as Spanish-style green table olives. However, the Campiñesa cultivar presents difficulties when submitted to a lactic fermentation, in spite of being inoculated with dedicated starter cultures such as OleicaStarter. The strategy followed in this study to facilitate the start of lactic fermentation was to reinforce the OleicaStarter culture with the use of the Lactoplantibacillus pentosus Lp309 a strain that enhanced the survival of lactic acid bacteria (LAB) at the beginning of fermentation, reaching final pH values (4.08±0.01), free acidity (1.00±0.01g/100mL of brine), LAB population (6.17±0.09 logCFU/mL), nutrient depletion (0.80±0.09g/kg of pulp), and lactic acid production (11.85±0.72g/L). These values allowed stabilization of the final product, thus complying with the quality and food safety standards established by the Codex Alimentarius for table olives.

Application of technological protocols on an industrial scale to improve Seville-style table olive production in Italy and Spain

Improving the fermentation performance of starter strains used in the fermentation of table olives is a biotechnological solution of current interest to improve the quality characteristics of the final product. The aim of this study was to evaluate the use of Lactiplantibacillus pentosus OM13 as a starter culture for the fermentation of Seville-type table olives in two different production areas: Italy and Spain. The starter strain L. pentosus OM13 was inoculated into two different table olive varieties: Nocellara del Belice in Italy and Manzanilla in Spain. Lactiplantibacillus plantarum Vege-Start 60 was used as a commercial control, while an additional control production was carried out by spontaneous fermentation. The industrial productions consisted of three different protocols, differing in the type of nutrient and the presence/absence of acclimatisation of the starter strain. All trials were subjected to microbiological monitoring, evaluation of acidification dynamics and sensory analysis of the final product. After 90 days, the pH reached values below 5 in the different treatments. The LAB reached microbial loads varying between 6.5 and 8.7 log CFU/mL throughout the monitoring period. The microbial populations of spoilage and/or potential pathogenic microorganisms were variable depending on the microbial group monitored. However, after 12 days of fermentation, Enterobacteriaceae showed values below the detection limit. In contrast, a fluctuating trend was observed for yeasts, Pseudomonadaceae and Staphylococcaceae. Sensory analyses showed variable differences depending on the technological protocol used. Table olives obtained with L. pentosus OM13 in the presence of nutrient, activator and acclimatisation period achieved higher overall acceptability values compared to the other trials. The use of adjuvants (nutrients and activators) is a strategy used in the production of table olives fermented with L. pentosus OM13 to improve the sensory characteristics of table olives.

Understanding the transcriptomic response of Lactiplantibacillus pentosus LPG1 during Spanish-style green table olive fermentations.

Lactiplantibacillus pentosus (Lbp. pentosus) is a species of lactic acid bacteria with a great relevance during the table olive fermentation process, with ability to form non-pathogenic biofilms on olive epidermis. The objective of this work is to deepen into the genetic mechanisms of adaptation of Lpb. pentosus LPG1 during Spanish-style green table olive fermentations, as well as to obtain a better understanding of the mechanisms of adherence of this species to the fruit surface. For this purpose, we have carried out a transcriptomic analysis of the differential gene expression of this bacterium during 60 days of fermentation in both brine and biofilms ecosystems. In brines, it was noticed that a total of 235 genes from Lpb. pentosus LPG1 were differentially expressed during course of fermentation and grouped into 9 clusters according to time-course analysis. Transport and metabolism of carbohydrates and amino acids, energy production, lactic acid and exopolysaccharide synthesis genes increased their expression in the planktonic cells during course of fermentation. On the other hand, expression of genes associated to stress response, bacteriocin synthesis and membrane protein decreased. A total of 127 genes showed significant differential expression between Lpb. pentosus LPG1 planktonic (brine) and sessile (biofilms) cells at the end of fermentation process (60 days). Among the 64 upregulated genes in biofilms, we found genes involved in adhesion (strA), exopolysaccharide production (ywqD, ywqE, and wbnH), cell shape and elongation (MreB), and well as prophage excision. Deeping into the genetic bases of beneficial biofilm formation by Lpb. pentosus strains with probiotic potential will help to turn this fermented vegetable into a carrier of beneficial microorganisms to the final consumers.

Brine Volatilome Changes Along the Spontaneous Fermentation of Spanish-Style cv. Chalkidiki Green Olives Under High and Low NaCl Conditions

Table olives are essential components of the Mediterranean diet. Yet, their contribution to salt intake has prompted efforts to reformulate traditional products via safe interventions, mainly focused on the fermentation step. The volatilomics approach is an important tool to assess the complex table olives fermentation. However, extensive data related to monitoring of volatile organic compounds (VOCs) in manufacturing process of Spanish-style cv. Chalkidiki green table olives are scarce in the literature. The present work systematically examines VOCs profile in brines during spontaneous fermentation of cv. Chalkidiki olives under high (8% w/v) and 50% lower NaCl content using selected combinations of chloride salts (NaCl, KCl, CaCl2) in pilot scale for two consecutive periods. VOCs were determined by headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry. Changes in the population of the dominant microbial groups, pH, and titratable acidity values were also investigated. A total of 56 VOCs were identified, including acids, alcohols, carbonyls, esters, and phenols. Multivariate data analysis explored the links between volatile metabolites, microbial groups, and fermentation stages under different NaCl conditions. The evolution of propanoic acid and 2-butanol was intriguing for monitoring a fermentation dominated by lactic acid bacteria under low NaCl conditions, while 3-methyl-1-butanol was indicative of yeast prevalence arising from seasonal variation and/or high NaCl processing. Τhe important contribution of acetic acid to the overall VOCs profile at a late fermentation stage was typical in low NaCl brines. The complete results could be beneficial for marker-assisted monitoring of the fermentation processes in the future.

Innovative Device for Automated Monitoring of Table Olive Fermentation Parameters: First Experimental Results

The table olive sector is highly important to the Italian agri-food industry. To produce quality table olives without defects in appearance, flavors, or aroma and to meet consumer expectations, special precautions must be taken to limit side effects associated with transformation and storage processes. During these processes, essential to debitter and stabilize the final product, drupes may undergo undesirable fermentations due to changes in the olive-to-brine ratio, temperature changes, and alteration of the brine’s chemico–physical parameters, thus decreasing their commercial and nutritional value. An innovative user-friendly system, equipped with low-cost digital and sensorized devices, has been engineered and realized for step-by-step batch monitoring of table olive storage brines. The main fermentation parameters (i.e., temperature, pH, salinity, free acidity, volatile acidity, and residual sodium hydroxide) of virgin, compliant, and altered brines were analyzed with both the automated prototype and Official reference methods, with the aim of testing the functionality of the prototype device and verifying the reliability and repeatability of the measurements. Good linearity was observed for all parameters examined, with a relatively low mean deviation between the two approaches. It is therefore possible to constantly monitor brine conformity automatically during the processing stages, benefiting product quality and environmental, energy, and economic sustainability.

Effect of Glucose and Inactivated Yeast Additions on the Fermentation Performances of Lactiplantibacillus pentosus OM13 during the Production of Nocellara del Belice Table Olives

The use of selected strains of lactic acid bacteria is necessary to produce fermented table olives with high hygiene and quality standards at the industrial level. A current tendency is the use of fermentation adjuvants (nutrients and activators) that can satisfy the nutritional needs of starter strains. In this study, five experimental protocols, different for nutrient and activator presence and addition of Lactiplantibacillus pentosus OM13 in freeze-dried form and after acclimatisation, were tested with the aim of improving the fermentation performances of the commercial starter. The trial inoculated with the starter strain acclimatised in the presence of nutrients and activator showed the most rapid acidification during the first phase of fermentation (third to ninth day), registering a pH loss of 3.40 units. The addition of adjuvants positively influences starter dominance (&gt;89%) and rapid colonisation (&gt;7 Log CFU/mL from third d) by indirectly limiting the presence of undesirable microorganisms. The analysis of volatile organic compounds revealed the presence of 32 chemicals distributed differently in each trial. Sensory evaluation showed that table olives produced with the different treatments were characterised by low bitterness, acidity, and absence of unpleasant odours/flavours. Control production showed slower acidification kinetics and lower sensory pleasantness than the other trials.

Concentration of phenolic compounds from olive washing wastewater by forward osmosis using table olive fermentation brine as draw solution

The olive industry has a considerable amount of process water consumption. As a result of the process, a large volume of oil mill wastewater (OMW) and table olive wastewater (TOW), both of them with high concentrations of organic matter, phenolic compounds and conductivity, are released. The appropriate management of these wastewaters is of paramount importance due to their toxic impacts on the environment. In this work, forward osmosis (FO) process is presented as an option to concentrate phenolic compounds for their further recovery. Two membranes, OsmoF2OTM (FTS, USA) and HFFO.6 (Aquaporin, Denmark) were evaluated with NaCl as draw solution (DS) and olive oil washing wastewater (OOWW) filtered at 5μm (5F) as feed solution (FS). Both membranes were able to concentrate the phenolic compounds with acceptable volume reduction (VR) values. The HFFO.6 membrane, which presented the lowest passage of phenolic compounds (TPhC) to the DS, was tested with fermentation brine from table olive processing (FTOP) as DS. As FS the same 5F-OOWW as well as an OOWW ultrafiltration permeate (UF-OOWW) were considered. Interestingly, greater percentages of TPhC concentration were observed compared to the tests with NaCl as DS (74.13–76.93% versus 62.6%, respectively). Although the tests with UF-OOWW presented greater flux, the recovery percentages of TPhC were similar, even slightly lower than those obtained with 5F-OOWW. Therefore, FO appears as a promising option to concentrate TPhC from OOWW and as well as to dilute FTOP. Thus both wastewaters from the olive industry could be treated at the same time.

Comparing Spanish-Style and Natural Fermentation Methods to Valorise Carolea, Nocellara Messinese and Leccino as Table Olives

This paper presents the results of the transformation into table olives of drupes belonging to three Italian cultivars: Carolea, Leccino and Nocellara Messinese, widely used for virgin olive oil production, by using the two most common methods to produce fermented table olives: the Spanish-style method (SS) and the natural fermentation (NF). The most suitable drupes as table olives due to their flesh-to-pit ratio and high-weight fruits were Nocellara Messinese olives. From the results obtained, it was highlighted that fermentation must be improved by using a selected starter culture that can drive the fermentation by rapid acidification. In fact, the long time required by NF results in a lower pH close to the hygienic safety limit but not low enough to be considered as a stable product, while the fast fermentation obtained by treating the olives with lye solution resulted in pH values that were too high. The sugar content in all table olives was almost null, and the sensory evaluation showed that SS olives were less bitter than NF olives. Moreover, NF olive-flesh samples showed a higher amount of healthy phenolic compounds than SS olives, whose phenolic content was drastically affected by the alkaline treatment and the successive washing steps.

Microbial community and volatilome changes in brines along the spontaneous fermentation of Spanish-style and natural-style green table olives (Manzanilla cultivar)

Microbial community and volatilome of brines were monitored during the spontaneous fermentations of Spanish-style and Natural-style green table olives from Manzanilla cultivar. Fermentation of olives in the Spanish style was carried out by lactic acid bacteria (LAB) and yeasts, whereas halophilic Gram-negative bacteria and archaea, along with yeasts, drove the fermentation in the Natural style. Clear differences between the two olive fermentations regarding physicochemical and biochemical features were found. Lactobacillus, Pichia, and Saccharomyces were the dominant microbial communities in the Spanish style, whereas Allidiomarina, Halomonas, Saccharomyces, Pichia, and Nakazawaea predominated in the Natural style. Numerous qualitative and quantitative differences in individual volatiles between both fermentations were found. The final products mainly differed in total amounts of volatile acids and carbonyl compounds. In addition, in each olive style, strong positive correlations were found between the dominant microbial communities and various volatile compounds, some of them previously reported as aroma-active compounds in table olives. The findings from this study provide a better understanding of each fermentation process and may help the development of controlled fermentations using starter cultures of bacteria and/or yeasts for the production of high-quality green table olives from Manzanilla cultivar.

Evaluating the Probiotic Potential of Lactic Acid Bacteria Implicated in Natural Fermentation of Table Olives, cv. Cobrançosa.

The probiotic features of Lactiplantibacillus (L.) pentosus and L. paraplantarum strains, endogenous in Cobrançosa table olives from northeast Portugal, were assessed in terms of functional properties and health benefits. Fourteen lactic acid bacteria strains were compared with Lacticaseibacillus casei from a commercial brand of probiotic yoghurt and L. pentosus B281 from Greek probiotic table olives, in attempts to select strains with higher probiotic performances than those references. For functional properties, the i53 and i106 strains, respectively, exhibited: 22.2 ± 2.2% and 23.0 ± 2.2% for Caco-2 cell adhesion capacity; 21.6 ± 7.8% and 21.5 ± 1.4% for hydrophobicity; 93.0 ± 3.0% and 88.5 ± 4.5% for autoaggregation ability by 24 h of incubation; and ability to co-aggregate with selected pathogens-from 29 to 40% to Gram+ (e.g., Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212); and from 16 to 44% for Gram- (e.g., Escherichia coli ATCC 25922 and Salmonella enteritidis ATCC 25928). The strains proved to be resistant (i.e., halo zone ≤14 mm) to some antibiotics (e.g., vancomycin, ofloxacin, and streptomycin), but susceptible (i.e., halo zone ≥ 20 mm) to others (e.g., ampicillin and cephalothin). The strains exhibited health-beneficial enzymatic activity (such as acid phosphatase and naphthol-AS-BI-phosphohydrolase), but not health-harmful enzymatic activity (such as β-glucuronidase and N-acetyl-β-glucosaminidase). Additionally, the antioxidant activity and cholesterol assimilation features, respectively, of the strains were 19.6 ± 2.8% and 77.5 ± 0.5% for i53, and 19.6 ± 1.8% and 72.2 ± 0.9% for i106. This study indicated that the addition of L. pentosus strains i53 and/or i106 to Cobrançosa table olives is likely to enhance the added value of the final product, in view of the associated potential benefits upon human health.

Quantitative PCR Assay as a Tool for the Detection of Lactobacilli in Sicilian Table Olives Produced at an Industrial Scale

Table olives are an important fermented product of the Mediterranean area consumed all over the world. In our era, the food industry requires a safe and stable final product with desirable characteristics for the consumer. In the present study, two different experimental fermentations (L, with Lactiplantibacillus plantarum strains, and LY, with L. plantarum strains and Wickerhamomyces anomalus strain) were conducted and monitored up to 180 days and compared with a spontaneous fermentation, used as control (C). The safety and stability of table olives were determined by applying a plate count and quantitative real-time PCR (qPCR) approach. Compared with the control sample (C), experimental fermentations showed a faster acidification and a good inhibition rate of spoilage bacteria, indicating the safety of the process. Quantitative PCR data confirmed the abundance of the Lactobacillus group in both experimental table olives, confirming the importance of the starter cultures for the stability of the final product. In conclusion, the use of starter cultures ensures the safety of industrially produced table olives, and the application of qPCR seems to be a promising tool to detect and quantify lactobacilli as a positive biomarker of table olive fermentation.

Delving into the study of lactic acid bacteria and yeasts distribution in table olive biofilms using a non-destructive procedure

To turn table olives into appropriate carriers of beneficial bacteria and yeasts to consumers, it is essential to have reliable methods for analysing microorganisms in biofilms. This work validates the application of a non-destructive procedure to study the lactic acid bacteria and yeasts distribution in fruits during Spanish-style green table olive fermentations. Laboratory-scale fermentations were inoculated simultaneously with three Lactiplantibacillus pentosus strains (LPG1, 119, and 13B4) and two yeasts (Wickerhamomyces anomalus Y12 and Saccharomyces cerevisiae Y30), all of them natives of table olive fermentations. Data showed that L. pentosus LPG1 and yeasts W. anomalus Y12 were quite prone to colonise olive biofilms, but only the Lactiplantibacillus strain also can penetrate the epidermis of the fruit and colonise the flesh. Applying a non-destructive treatment consisting in shelling the fruits with glass beads led to obtaining similar lactic acid bacteria and yeast recovery than the classical stomacher destructive method. However, the glass bead procedure improved the quality of the metagenomics analysis (especially when using 16 S rRNA gene-based sequencing). Results show the great utility of procedures that do not destroy the fruit for studying fermented vegetable biofilms.