Effect of Spanish-style processing steps and inoculation with Lactobacillus pentosus starter culture on the volatile composition of cv. Manzanilla green olives

Chemical changes of potential probiotic Lactiplantibacillus plantarum and Lactobacillus pentosus starter cultures in natural Gemlik type black olive fermentation

The aim of this study was to determine the ability of probiotic Lactiplantibacillus plantarum and Lactobacillus pentosus starter cultures to maintain Olea europaea L. cv. Gemlik fermentation and some chemical changes occurred by HPLC. It was observed that starter cultures decreased the pH by increasing the acidity of the fermentation medium. In addition, it was determined that the number of yeast-mold (Y-M) and aerobic mesophilic bacteria (AMB) were lower than the number of lactic acid bacteria (LAB) in the samples with starter cultures. As the fermentation period progressed, it was observed that the amount and variety of phenolic substances increased, albeit slightly, in the brined olive samples to which the starter culture was added. Alcohols, biogenic amines, sugars and organic acids increased or decreased in all samples. During the fermentation gallic acid, apigenin, kaempferol, curcumin, vanillin, caffeic acid, salicylic acid, putrescine, triamine, spermidine and maleic acid could not be detected.

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 ± 0.01 g/100 mL of brine), LAB population (6.17 ± 0.09 log CFU/mL), nutrient depletion (0.80 ± 0.09 g/kg of pulp), and lactic acid production (11.85 ± 0.72 g/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.

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.

Microbial and Chemical Characterization of Natural-Style Green Table Olives from the Gordal, Hojiblanca and Manzanilla Cultivars

Microbial and biochemical changes in the brine during the spontaneous fermentation of Gordal, Hojiblanca and Manzanilla olive cultivars processed according to the natural style were monitored. The microbial composition was assessed through a metagenomic study. Sugars, ethanol, glycerol, organic acids and phenolic compounds were quantified by standard methods. In addition, the volatile profiles, contents of phenolic compounds in the olives and quality parameters of the final products were compared. Fermentation in Gordal brines was conducted by lactic acid bacteria (mainly Lactobacillus and Pediococcus) and yeasts (mainly Candida boidinii, Candida tropicalis and Wickerhamomyces anomalus). In Hojiblanca and Manzanilla brines, halophilic Gram-negative bacteria (e.g., Halomonas, Allidiomarina and Marinobacter) along with yeasts (mainly, Saccharomyces) were responsible for the fermentation. Higher acidity and lower pH values were reached in Gordal brines compared to Hojiblanca and Manzanilla. After 30 days of fermentation, no sugars were detected in Gordal brine, but residual amounts were found in the brines from Hojiblanca (<0.2 g/L glucose) and Manzanilla (2.9 g/L glucose and 0.2 g/L fructose). Lactic acid was the main acid product in Gordal fermentation, whereas citric acid was the predominant organic acid in the Hojiblanca and Manzanilla brines. Manzanilla brine samples showed a greater concentration of phenolic compounds than Hojiblanca and Gordal brines. After a 6-month fermentation, Gordal olives were superior compared to the Hojiblanca and Manzanilla varieties regarding product safety (lower final pH and absence of Enterobacteriaceae), content of volatile compounds (richer aroma), content of bitter phenolics (lower content of oleuropein, which resulted in less perceived bitterness) and color parameters (more yellow and lighter color, indicating a higher visual appraisal). The results of the present study will contribute to a better understanding of each fermentation process and could help to promote natural-style elaborations using the above-mentioned olive cultivars.

Metagenetic and Volatilomic Approaches to Elucidate the Effect of Lactiplantibacillus plantarum Starter Cultures on Sicilian Table Olives

The present study aimed to evaluate the effect of selected Lactiplantibacillus plantarum strains on both microbiota composition and volatile organic compound profile of Sicilian table olives. Two mixed cultures, named O1 and O2, were set up for pilot-plan scale fermentations at 5% of NaCl. Uninoculated table olives at 5 and 8% (C5 and C8) of salt were used as control. The fermentation process was monitored until 80 days through a dual approach, which included both classical microbiological and 16S amplicon-based sequencing and volatilomics analyses. Compared with control samples (C5 and C8), experimental samples, inoculated with starter cultures (O1 and O2), exhibited a faster acidification with a more pronounced drop in pH. Metagenetics data revealed significant differences of microbiota composition among samples, highlighting the dominance of lactobacilli in both experimental samples; a high occurrence of Enterobacter genus only in control samples with 5% of NaCl; and the presence of Bacteroides, Faecalibacterium, Klebsiella, and Raoultella genera only in control samples with 8% of NaCl. Furthermore, microbiota composition dynamics, through the fermentation process, significantly affected the volatile organic compounds of the final products, whereas no compounds involved in off-odors metabolites were detected in all samples investigated. In conclusion, the addition of the proposed starter cultures and the use of low concentrations of sodium chloride positively affected the microbiota and volatile organic compounds, ensuring the microbiological safety and the pleasant flavors of the final product.

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

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.

Industrial Processing of Algerian Table Olive Cultivars Elaborated as Spanish Style

Olives from the Sigoise, Verdale, and Sevillana cultivars were elaborated as Spanish-style table olives by four Algerian factories, and the quality and food safety of the industrial table olives have been studied by the analysis of physicochemical and microbiological parameters. Differences were observed between the treatments carried out by the different factories throughout the manufacturing process, especially during the washing stage, but no significant differences were found between the analyzed samples for the concentration of sugars and polyphenols. The final pH values reached at the end of fermentation ranged between 5.04 and 4.27, and the titratable acidity was above 0.4% for all samples. Lactic and acetic acids were produced in mean concentrations of 0.68% and 0.21% as a result of lactic acid bacteria (LAB) and yeast metabolism, respectively. However, the presence of butyric, isobutyric, and propionic acids was also detected, and was related to the growth of undesirable spoilage microorganisms, responsible for secondary fermentations. The high-throughput sequencing of bacterial DNA suggested the dominance of LAB species belonging to genera Lactiplantibacillus, Leuconostoc, Pediococcus, Oenococcus, or Enterococcus. The Enterobacteriaceae family was detected during the first days of brining and in only one sample after 120 days of fermentation. Other spoilage microorganisms were found, such as Lentilactobacillus buchneri or the Pectinatus and Acetobacter genera, capable of consuming lactic acid and these played an essential role in the onset of spoilage. The Clostridium and Enterobacter genera, producers of butyric and propionic acids, were responsible for the malodorous fermentation present in the industrial samples that were analyzed. The study concluded that the safety of the table olives analyzed was compromised by the presence of undesirable microorganisms and microbial stability was not guaranteed. The elaboration process can be improved by reducing the washing steps and the time should be reduced to avoid the loss of fermentable matter, with the goal of reaching a pH < 4.0 after the fermentation and preventing the possibility of the growth of spoilage microorganisms and foodborne pathogens.

Multi-Statistical Approach for the Study of Volatile Compounds of Industrial Spoiled Manzanilla Spanish-Style Table Olive Fermentations

Table olives can suffer different types of spoilage during fermentation. In this work, a multi-statistical approach (standard and compositional data analysis) was used for the study of the volatile organic compounds (VOCs) associated with altered (butyric, sulfidic, and putrid) and non-altered (normal) Manzanilla Spanish-style table olive fermentations. Samples were collected from two industrial fermentation yards in Seville (Spain) in the 2019/2020 season. The VOC profiles of altered (n = 4) and non-altered (n = 6) samples were obtained by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Ninety-one VOCs were identified and grouped into alcohols (30), esters (21), carbonyl compounds (12), acids (10), terpenes (6), phenols (6), sulfur compounds (2), and others (4). The association of the VOCs with spoilage samples depended on the standard or compositional statistical methodology used. However, butyric spoilage was strongly linked by several techniques to methyl butanoate, ethyl butanoate, and butanoic acid; sulfidic spoilage with 2-propyl-1-pentanol, dimethyl sulfide, methanol, 2-methylbutanal, 2-methyl-2-butenal, ethanol, 2-methyl-3-buten-2-ol, and isopentanol, while putrid was mainly related to D-limonene and 2-pentanol. Our data contribute to a better characterisation of non-zapatera spoiled table olive fermentations and show the convenience of using diverse statistical techniques for a most robust selection of spoilage VOC markers.

Volatile Composition of Industrially Fermented Table Olives from Greece

Table olives represent one of the most important fermented products in Greece. Their highly appreciated flavor is directly associated with the volatile composition. However, extensive data on the volatile profile of table olives from Greek cultivars are scarce in the literature. For this reason, the volatile components of industrially fermented table olives from Kalamata, Conservolea and Halkidiki cultivars grown in different geographical areas within Greece were determined using headspace solid-phase microextraction combined with gas chromatography–mass spectrometry. More than 100 volatile compounds were identified and distributed over different chemical classes. All samples were rich in esters, alcohols and acids, whereas the samples of cv. Halkidiki were also characterized by increased levels of volatile phenols. Both qualitative and quantitative differences were observed, which resulted in the discrimination of the table olives according to olive cultivar and growing location. To the best of our knowledge, this is the first systematic study on the volatile profiles of table olives from Greek cultivars that also highlights the pronounced effect of olives’ growing location.

FoodOmics as a new frontier to reveal microbial community and metabolic processes occurring on table olives fermentation

Table olives are considered the most widespread fermented food in the Mediterranean area and their consumption is expanding all over the world. This fermented vegetable can be considered as a natural functional food thanks to their high nutritional value and high content of bioactive compounds that contribute to the health and well-being of consumers. The presence of bioactive compounds is strongly influenced by a complex microbial consortium, traditionally exploited through culture-dependent approaches. Recently, the rapid spread of omics technologies has represented an important challenge to better understand the function, the adaptation and the exploitation of microbial diversity in different complex ecosystems, such as table olives. This review provides an overview of the potentiality of omics technologies to in depth investigate the microbial composition and the metabolic processes that drive the table olives fermentation, affecting both sensorial profile and safety properties of the final product. Finally, the review points out the role of omics approaches to raise at higher sophisticated level the investigations on microbial, gene, protein, and metabolite, with huge potential for the integration of table olives composition with functional assessments.

Influence of Alkaline Treatment on Structural Modifications of Chlorophyll Pigments in NaOH-Treated Table Olives Preserved without Fermentation

Alkaline treatment is a key stage in the production of green table olives and its main aim is rapid debittering of the fruit. Its action is complex, with structural changes in both the skin and the pulp, and loss of bioactive components in addition to the bitter glycoside oleuropein. One of the components seriously affected are chlorophylls, which are located mainly in the skin of the fresh fruit. Chlorophyll pigments are responsible for the highly-valued green color typical of table olive specialties not preserved by fermentation. Subsequently, the effect on chlorophylls of nine processes, differentiated by NaOH concentration and/or treatment time, after one year of fruit preservation under refrigeration conditions, was investigated. A direct relationship was found between the intensity of the alkali treatment and the degree of chlorophyll degradation, with losses of more than 60% being recorded when NaOH concentration of 4% or greater were used. Oxidation with opening of the isocyclic ring was the main structural change, followed by pheophytinization and degradation to colorless products. To a lesser extent, decarbomethoxylation and dephytylation reactions were detected. An increase in NaOH from 2% to 5% reduced the treatment time from 7 to 4 h, but fostered greater formation of allomerized derivatives, and caused a significant decrease in the chlorophyll content of the olives. However, NaOH concentrations between 6% and 10% did not lead to further time reductions, which remained at 3 h, nor to a significant increase in oxidized compounds, though the proportion of isochlorin e₄-type derivatives was modified. Chlorophyll compounds of series b were more prone to oxidation and degradation reactions to colorless products than those of series a. However, the latter showed a higher degree of pheophytinization, and, exclusively, decarbomethoxylation and dephytylation reactions.

Table Olives: An Overview on Effects of Processing on Nutritional and Sensory Quality

Table olives are a pickled food product obtained by a partial/total debittering and subsequent fermentation of drupes. Their peculiar sensory properties have led to a their widespread use, especially in Europe, as an appetizer or an ingredient for culinary use. The most relevant literature of the last twenty years has been analyzed in this review with the aim of giving an up-to-date overview of the processing and storage effects on the nutritional and sensory properties of table olives. Analysis of the literature has revealed that the nutritional properties of table olives are mainly influenced by the processing method used, even if preharvest-factors such as irrigation and fruit ripening stage may have a certain weight. Data revealed that the nutritional value of table olives depends mostly on the balanced profile of polyunsaturated and monounsaturated fatty acids and the contents of health-promoting phenolic compounds, which are best retained in natural table olives. Studies on the use of low salt brines and of selected starter cultures have shown the possibility of producing table olives with an improved nutritional profile. Sensory characteristics are mostly process-dependent, and a relevant contribute is achieved by starters, not only for reducing the bitterness of fruits, but also for imparting new and typical taste to table olives. Findings reported in this review confirm, in conclusion, that table olives surely constitute an important food source for their balanced nutritional profile and unique sensory characteristics.

Table Olives More than a Fermented Food

Table olives are one of the oldest vegetable fermented foods in the Mediterranean area. Beside their economic impact, fermented table olives represent also an important healthy food in the Mediterranean diet, because of their high content of bioactive and health-promoting compounds. However, olive fermentation is still craft-based following traditional processes, which can lead to a not fully predictable final product with the risk of spontaneous alterations. Nowadays, food industries have to face consumer demands for safe and healthy products. This review offers an overview about the main technologies used for olive fermentation and the role of lactic acid bacteria and yeasts characterizing this niche during the fermentation. Particular attention is offered to the selection and use of microorganisms as starter cultures to fasten and improve the safety of table olives. The development and implementation of multifunctional starter cultures in order to obtain heath-oriented table olives is also discussed.

Lactobacillus pentosus SMB718 as a probiotic starter producing allyl mercaptan in garlic and onion-enriched fermentation

Lactobacillus pentosus SMB718 has the properties of being a beneficial probiotic for human health and is a desirable starter for better flavor in fermented allium species plants.

Aroma profile and volatile composition of black ripe olives (Manzanilla and Hojiblanca cultivars)

The aroma profile and volatile composition of 8 samples of black ripe olives from Manzanilla and Hojiblanca cultivars were analyzed with the aim to characterize this type of table olive. The aroma of samples was described by a sensory panel using quantitative descriptive analysis (QDA), whereas the volatiles were analyzed by headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). Eleven odor descriptors (briny, sautéed mushroom, earthy/soil-like, oak barrel, nutty, artificial fruity/floral, natural fruity/floral, vinegary, alcohol, fishy/ocean-like, and cheesy) were evaluated, of which only one descriptor (briny) showed a significant difference between cultivars. A total of 74 volatile compounds were identified in the headspace of samples, of which 12 were identified as significant volatiles contributing to the discrimination between Manzanilla and Hojiblanca black ripe olives. Partial least squares (PLS) regression was able to predict one odor descriptor (nutty) with sufficient accuracy and allowed identifying the volatiles that highly contributed to three odor descriptors of black ripe olives (nutty, natural fruity/floral, and cheesy).

Lactic Acid Bacteria and Yeast Inocula Modulate the Volatile Profile of Spanish-Style Green Table Olive Fermentations

In this work, Manzanilla Spanish-style green table olive fermentations were inoculated with Lactobacillus pentosus LPG1, Lactobacillus pentosus Lp13, Lactobacillus plantarum Lpl15, the yeast Wickerhanomyces anomalus Y12 and a mixed culture of all them. After fermentation (65 days), their volatile profiles in brines were determined by gas chromatography-mass spectrometry analysis. A total of 131 volatile compounds were found, but only 71 showed statistical differences between at least, two fermentation processes. The major chemical groups were alcohols (32), ketones (14), aldehydes (nine), and volatile phenols (nine). Results showed that inoculation with Lactobacillus strains, especially L. pentosus Lp13, reduced the formation of volatile compounds. On the contrary, inoculation with W. anomalus Y12 increased their concentrations with respect to the spontaneous process, mainly of 1-butanol, 2-phenylethyl acetate, ethanol, and 2-methyl-1-butanol. Furthermore, biplot and biclustering analyses segregated fermentations inoculated with Lp13 and Y12 from the rest of the processes. The use of sequential lactic acid bacteria and yeasts inocula, or their mixture, in Spanish-style green table olive fermentation could be advisable practice for producing differentiated and high-quality products with improved aromatic profile.

Changes in volatile composition during the processing and storage of black ripe olives

The present study revealed the effects of each step of black ripe olive processing (preservation, darkening, packing + sterilization) and storage on the volatile composition of two olive cultivars (Manzanilla and Hojiblanca). The preservation step enriched the volatile profile of the olives, mainly in ethyl acetate, methyl acetate, and ethanol. The darkening step produced the total or partial elimination of 55-65% of the volatiles identified before this step. Around 70% of the volatiles in the final products corresponded to compounds that were formed or increased significantly as a result of the sterilization treatment at 121 °C. Although differences in the volatile compositions and contents between Manzanilla and Hojiblanca were found, the dominant volatiles in both cultivars were benzaldehyde, dimethyl sulfide and ethyl acetate. Storage for 8 months had little influence on their volatile profiles, although the stability of individual volatiles in Manzanilla was better than that in the Hojiblanca cultivar.

Phytochemical profile, mineral content, and antioxidant activity of Olea europaea L. cv. Cornezuelo table olives. Influence of in vitro simulated gastrointestinal digestion

The main goals of this study were to determine the phenolic composition and antioxidant activity of table olives from Olea europaea L. cv. Cornezuelo, as well as the effect caused by a simulated in vitro digestion to evaluate compounds bioavailability. High-performance liquid chromatography with diode-array and mass spectrometry detection (HPLC-DAD-MSⁿ) was used to evaluate the phytochemical profile, whereas conventional spectrophotometric methods (ABTS·⁺ and DPPH) were used to determine the antioxidant activity. The mineral content was also quantified by inductively coupled plasma - mass spectrometry. Thirty compounds were identified, mainly polyphenols, quantifying the major compounds by HPLC-DAD. After the simulated digestion, the phenolic content suffered an important decrease - more than 50% - reaching losses of up to 75% for oleuropein and comselogoside isomers. This decrease also resulted in a loss of antioxidant activity, observing significant differences for all parameters. However, the analyzed extracts still retained considerable antioxidant potential.

Perilla frutescens Britton: A Comprehensive Study on Flavor/Taste and Chemical Properties During the Roasting Process

This study investigated changes of volatile compounds, sniffing test-assisted sensory properties, taste associated-constituent and free amino acid compositions, taste description by electronic-tongue, and chemical characteristics in Perilla frutescens Britton var. acuta Kudo after roasting at 150 °C for 0–8 min. A total of 142 volatile compounds were identified, among which methyl benzoate and limonene were predominant, regardless of roasting time, and these were also detected as the major compounds in the sniffing test by GC-olfactometry. For constituent amino acids analyzed by the acid hydrolysis method using hydrochloric acid (HCl), the concentration of glutamic acid, aspartic acid, and leucine showed an increase pattern with increased roasting time, which results in umami taste, sour taste, and bitter taste, respectively. For free amino acids, valine and hydroxylysine eliciting bitter and bitter and sweet tastes, respectively, also tend to increase by roasting. The pattern of amino acid concentration by roasting was readily matched to the taste description by electronic-tongue but that of sweetness and sourness by electronic-tongue did not coincide with the amino acid composition. For the chemical properties, total phenolic content, antioxidative capacity, and browning intensity tend to increase with roasting but decreased by 8 min. The results of this study provide fundamental information on perilla in both the food industry and cooking environment for the sake of increasing the utilization of perilla as a food source and ingredient.

Microbiota and Metabolite Profiling of Spoiled Spanish-Style Green Table Olives

The aim of the present study was to assess the malodorous spoilages of Spanish-style green table olives through microbial and metabolite composition using current measuring techniques (e.g., high-throughput DNA sequencing, headspace solid-phase microextraction combined with gas chromatography-mass spectrometry). Under different alkaline and washing conditions, the spoilage fermentations were reproduced with Gordal and Manzanilla olive cultivars using a low salt concentration (71 g L⁻¹ NaCl) in the initial brine. The degradation of lactic acid and significant increases in volatile fatty acids and phenols were found in all the spoiled samples in comparison with the unspoiled control samples. According to high-throughput DNA sequencing, Cardiobacteriaceae and Ruminococcus were the dominant bacteria in the spoiled samples. PLS regression and Pearson’s correlation coefficient analyses revealed positive and negative correlations among microbial communities, metabolites, and sensory spoilage descriptors. Notably, the “zapatera” descriptor was significantly associated with Propionibacterium, which was positively correlated with acetic acid, propionic acid, succinic acid, and methyl propanoate; while the “butyric” descriptor exhibited a significant positive relationship with the genus Ruminococcus, which gave an almost significant correlation with propionic and butyric acids.