Natural Table Olives Research Articles

Human α-glucosidase inhibition and phytochemical profile of natural and shinzuke treated olives: implications from the processing method

Olive (Olea europaea) phytochemicals are associated with a reduced risk of type 2 diabetes. Table olives typically have higher phytochemical concentrations than olive oil, but their impact on human intestinal α-glucosidase is largely unknown. Shinzuke, the most common trade preparation in Japan, are alkali-treated non-fermented green olives. In contrast, natural olives are debittered by brining, which may enhance phytochemical retention. We evaluated the α-glucosidase inhibitory effect of Shinzuke and natural green olives produced in-house and compared them with commercial table olives. Eight types of table olives were tested against human intestinal α-glucosidase. Shinzuke Mission was the least effective (IC50 0.710 ± 0.058 mg/mL), while Natural green olives showed double to triple activity, with a non-competitive mechanism. Natural table olives retained more phytochemicals than shinzuke and other treated olives, and are good inhibitors of human α-glucosidase in vitro, exhibiting potential as a functional food for the management of postprandial glycaemia.Graphical

Comparative study of Spanish-style and natural cv. Chalkidiki green olives throughout industrial-scale spontaneous fermentation and 12-month storage: safety, nutritional and quality aspects

Table olives are among the most popular fermented foods and cv. Chalkidiki green table olives are particularly popular in both Greek and international markets. This work aimed at comparatively investigating the effect of processing method on the production of Spanish-style and natural cv. Chalkidiki green olives during fermentation and 12-month storage in brines with different chloride salts composition (NaCl, KCl, CaCl2) at industrial scale. All delivered products were safe with satisfactory color and texture characteristics. Employment of UPLC-HRMS revealed differences in metabolites’ profile of polar extracts from olives and brines between the processing methods. Τhe application of alkali treatment drastically decreased the content of hydroxytyrosol and tyrosol in drupes, still an essential amount (1037–2012 and 385–885 mg/kg dry flesh, respectively) of these health-promoting phenolic compounds was retained in all products, even after storage. Noteworthy, fermentation of natural olives in brine (5 % NaCl) yielded in products with significantly lower Na levels in olive flesh (1.7 g/100 g), followed by Spanish-style olives fermented in low (4 %) and high (8 %) NaCl brines (2.7 and 5.2 g Na/100 g, respectively), supporting the efforts toward the establishment of table olives as functional food. Moreover, maslinic and oleanolic acids content was 1.5–2-fold higher in the natural table olives compared to the Spanish-style ones owing to the detrimental effect of alkali treatments. The processing method did not exert a differential effect on α-tocopherol content of olives. Sensory analysis indicated that all the final products were acceptable by consumers, with a slight preference for Spanish-style green olives fermented in brines with 50 % lower NaCl content. Present findings could be beneficial to the ongoing endeavor directed for the establishment of table olives as a source of bioactive compounds that concerns both industrial and scientific communities.

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.

“Table Olive Flours”: An Ingredient Rich in Bioactive Compounds?

The aim of this study was to produce different “table olive flours” from fruits at different maturation stages. “Table olive flour” is here presented as an innovative product that can gain importance as a bioactive rich ingredient. Three types of natural table olives from cv. Cobrançosa, i.e., green, turning color, and black olives, were soaked, freeze-dried and ground to obtain three different flours. Their physical and nutritional characterization, lipid fraction (fatty acids and tocopherols profiles), phenolic profile, and antioxidant activity (total reducing capacity, radical scavenging activities of DPPH and ABTS●+) were analyzed. “Table olive flours” with different colors and different characteristics were obtained. The “green table olive flour” had the lowest fat content and energy. On the contrary, it showed the highest protein, carbohydrate contents, percentages of oleic acid (C18:1), and MUFA, as well as total tocopherols. It also showed the highest antioxidant activity. The “black table olive flour” was the one with the highest percentages of palmitic acid (C16:0), SFA, and total reducing capacity. In the three types of developed “flours”, nine phenolic compounds were detected, hydroxy-tyrosol being the major, followed by tyrosol, and luteolin. In conclusion, from natural table olives of cv. Cobrançosa, different “table olive flours” with distinct properties and high amounts of health-promoting compounds can be produced.

Chemical parameters and antioxidant activity of turning color natural-style table olives of the Sigoise cultivar

A chemical characterization of turning color table olives of the Sigoise variety was made through their processing as natural-style. Polyphenols, sugars, tocopherols, fatty acids, and antioxidant activity in the olives were monitored throughout the elaboration process. Oleuropein, salidroside, hydroxytyrosol 4-glucoside, rutin, ligustroside and verbascoside showed a decrease of 16.90-83.34%, while hydroxytyrosol increased during the first months of brining. Glucose was consumed by 90% due to the metabolism of the fermentative microbiota. The tocopherol content remained stable during the process and only the α-tocopherol decreased. The fatty acids were not affected. The loss in antioxidant compounds resulted in a decrease in the percentage of DPPH radical inhibition from 75.91% in the raw fruit to 44.20% after 150 days of brining. Therefore, the turning color natural table olives of the Sigoise variety are a good source of bioactive compounds.

Inoculation with acetic acid bacteria improves the quality of natural green table olives

This study aims to develop a method for the preparation of natural table olives using locally selected microorganisms and without resorting to the usual techniques which employ lye treatment and acids. The effects of parameters, such as lye treatment, inoculation with yeasts, substitution of organic acids with vinegar and/or acetic acid bacteria, and finally alternating aeration have been assessed. Four different combinations were applied to the “Picholine marocaine” olive variety using indigenous strains, namely Lactobacillus plantarum S1, Saccharomyces cerevisiae LD01 and Acetobacter pasteurianus KU710511 (CV01) isolated respectively from olive brine, Bouslikhen dates and Cactus. Two control tests, referring to traditional and industrial processes, were used as references. Microbial and physicochemical tests showed that the L3V combination (inoculated with A. pasteurianus KU710511 and L. plantarum S1 under the optimal growth conditions of the Acetic Acid Bacteria (AAB) strain with 6% NaCl) was found to be favorable for the growth of the Lactic Acid Bacteria (LAB) strain which plays the key role in olive fermentation. This result was confirmed by sensory evaluation, placing L3V at the top of the evaluated samples, surpassing the industrial one where a chemical debittering treatment with lye was used. In addition, alternating aeration served to increase the microbial biomass of both AAB and LAB strains along with Saccharomyces cerevisiae LD01 strain, but also to use lower concentration of NaCl and to reduce the deterioration of olives compared to the anaerobic fermentation process. Finally, a mixed starter containing the three strains was prepared in a 10-L Lab-fermenter from the L3V sample in order to improve it in subsequent studies. The prepared starter mixture could be suitable for use as a parental strain to prepare table olives for artisan and industrial application in Morocco.

Fluorescence Study of Four Olive Varieties Paste According to Sampling Dates and the Control in the Elaboration of Table Olives of “Ascolana tenera”

A fluorescence method combined with chemometric algorithms has been developed for the fruit characterization of four olive varieties (“Arbequina,” “Piantone di Falerone,” “Piantone di Mogliano,” and “Maurino”) cultivated in Marche (Italy) according to sampling dates. The score values obtained by parallel factor analysis (PARAFAC) were correlated with the hydroxytyrosol and oleuropein concentrations quantified by liquid chromatographic. The analysis of excitation-emission matrices by PARAFAC and unfolding partial least squares, using the three component score values, allowed to differentiate between varieties. The use of the scores of oleuropein and hydroxytyrosol, which were represented each other, allowed to highlight differences between the three sampling dates. Furthermore, a good discrimination of fresh olive, lye table olives, and natural table olives was also achieved in “Ascolana tenera,” another typical olive variety of Marche. Results can be explained by the changes of concentration of tyrosol and oleuropein due to the elaboration method characteristics.

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.

Chemical hydrolysis of oleuropein affected by the type of organic acid

The debittering of natural table olives is a very slow process. The effect of acetic, lactic and citric acids on the hydrolysis rate of oleuropein was studied in vitro and at pilot plant scale. The acid hydrolysis of oleuropein was faster with lactic and citric acids than acetic acid, running the experiments at the same pH of 3.8–4.0 units. The temperature exerted a high effect of the hydrolysis of oleuropein in a range of 10–30 °C and the concentration of the organic acid did not show a significant trend. Moreover, the in vitro results were confirmed with three lots of olives that presented a higher content of oleuropein after 3–7 months of preservation when they were processed with acetic acid rather than lactic acid and the opposite for hydroxytyrosol. These results open the possibility of accelerating the debittering of natural olives by preserving them with lactic acid instead of acetic acid.

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.

Optimization of the natural debittering of table olives

Olives can debitter naturally without the use of NaOH but it is a very slow process. The purpose of this work was to evaluate the influence of both temperature and chemical characteristics of brine on the oleuropein hydrolysis rate in natural table olives. Two different phases were established for natural debittering. During the first 1–2 months of brining, a low concentration of NaCl (60 g/L) and acetic acid (2 g/L) together with a low storage temperature (10 °C) were the processing conditions that promoted a rapid hydrolysis of the bitter phenol because these mild conditions facilitated the action of endogenous enzymes (β-glucosidase and esterase). Thereafter, higher concentrations and temperature of storage (140 g/L NaCl, 16 g/L acetic acid and 40 °C) favored the chemical hydrolysis of oleuropein during long term (a few months) storage. These results will contribute to the knowledge of the natural debittering of table olives and they will help processors to accelerate their elaboration methods.

Sensory analysis of natural table olives: Relationship between appearance of defect and gustatory-kinaesthetic sensation changes

Abstract In the present study, we evaluated sensory characteristics of table olives of the Italian double-aptitude olive cultivar ( Olea europaea L. cv. Itrana) processed as green ( Oliva Bianca di Itri ) and black ( Oliva di Gaeta ) table olives, according to the Method for the sensory analysis of table olives of International Olive Council. The sensory attributes evaluated were: a) negative sensations or defects (abnormal fermentations and other defects as butyric, putrid and zapateria, winey-vinegary, soapy, metallic, cooking effects, rancid, musty and earthy defects); b) gustatory sensations (salty, bitter, acid) and c) kinaesthetic sensations (hardness, fibrousness, crunchiness). Multivariate statistical analysis has been used to identify similarities and differences between defected and un-defected samples. We carried out the Principal Component Analysis on two data sets: the first data-set included all sensory parameters (data-set A), while the second data-set did not include abnormal fermentation and other defects (data-set B). The occurrence of negative sensations have a negative impact on gustative and kinaesthetic attributes. The samples classified as “Extra or Fancy” but with intensity of defect >1.0 are more similar to defected samples, also not considering the defects as discriminant parameters.

Evaluation of a single strain starter culture, a selected inoculum enrichment, and natural microflora in the processing of Tonda di Cagliari natural table olives: Impact on chemical, microbiological, sensory and texture quality

The processing of natural table olives is still empirical and far to be controlled. Taking natural fermentation (NF) as control, the performances of a single strain LAB starter culture (SSL) and a selected inoculum enrichment (SIE) were compared. The results showed that the SIE was more efficient in controlling spoiling microflora (Enterobacteriaceae spp.) compared to SSL and NF. Indeed, Enterobacteriaceae in SIE samples were not detectable starting from 10 days, while in SSL and NF samples starting from 30 days. Both starters rapidly acidified the brine, lowering the pH to safety levels (<4.0) after 12 days, while NF samples reached pH 4.3 after 45 days, and these values were kept constant up to 150 days. Moreover, both starters showed debittering activity, as stated through sensory analyses and HPLC analysis of phenols. Compared to NF samples, SIE and SSL extracts retained more hydroxytyrosol at the end of the process, and this could partially account for their higher scavenging activity. Texture profile analysis (TPA) showed that olives processed with SIE inoculum were firmer and more elastic, compared to SSL inoculated olives, thus resulting more similar to NF samples.

Endogenous enzymes involved in the transformation of oleuropein in Spanish table olive varieties.

The main Spanish table olive varieties supplied by different olive cooperatives were investigated for their polyphenol compositions and the endogenous enzymes involved in their transformations during two growing seasons. Olives of the Manzanilla variety had the highest concentration in total polyphenols, followed by the Hojiblanca and Gordal varieties. The Gordal and Manzanilla cultivars showed the highest polyphenol oxidase activities. The Gordal cultivar presented a greater β-glucosidase and esterase activity than the others. An important influence of pH and temperature on the optimal activity of these enzymes was also observed. The polyphenol oxidase activity increased with temperature, and peroxidase activity was optimal at 35 °C. The β-glucosidase and esterase activities were at their maximum at 30 and 55 °C, respectively. The oxidase and β-glucosidase activities were at their maximum at the pH of the raw fruit. These results will contribute to the knowledge of the enzyme transformation of oleuropein in natural table olives.

3,4-Dihydroxyphenylglycol (DHPG): An Important Phenolic Compound Present in Natural Table Olives

The presence of 3,4-dihydroxyphenylglycol (DHPG) was studied in 32 samples and 10 different cultivars of natural table olives, using an accurate method to avoid wrong quantification. Hydroxytyrosol (HT), tyrosol, and verbascoside were also quantified, as these four compounds comprise the majority of the chromatographic profile. Analyses were carried out by HPLC-DAD-UV after extraction of all phenolics, and hydroxytyrosol was the major component in nearly all samples. High levels of DHPG (up to 368 mg/kg of dry weight) were found in the pulp of natural black olives independent of cultivar and processing method, similar to its concentration in the brine in almost all of the samples. The presented data for this antioxidant indicate that natural table olives are a rich source of DHPG and hydroxytyrosol, compounds with interesting nutritional and antioxidant properties.