Deriving valorization of phenolic compounds from olive oil by-products for food applications through microencapsulation approaches: a comprehensive review

Exploring the Bioactive Content of Liquid Waste and Byproducts Produced by Two-Phase Olive Mills in Laconia (Greece): Is There a Prospect for Added-Value Applications?

The use of a two-phase decanter (TwPD) for olive-oil extraction produces wastes and byproducts (a small volume of water from oil washing, olive leaves from the defoliator, and a high moisture pomace which can be destoned) that contain valuable bioactive compounds, such as phenolics and/or triterpenic acids. So far, there is no (water) or limited information (leaves and the destoned pomace fraction) on their content of bioactives, especially triterpenic acids. To contribute to the characterization of such streams from cultivars of international interest, in the present study, samples obtained from five mills from the region of Laconia (from one or two harvests) in Greece, where Koroneiki cv dominates, were screened for phenols and/or triterpenic acids. The leaves and pomace were dried at two temperatures (70 °C and/or 140 °C), and the pomace was also destoned before analysis. The liquid wastes contained low amounts of total (TPC) phenols (<140 mg gallic acid/L), hydroxytyrosol (<44 mg/L), and tyrosol (<33 mg/L). The olive leaves varied widely in TPC (12.8-57.4 mg gallic acid/g dry leaf) and oleuropein (0.4-56.8 mg/g dry leaf) but contained an appreciable amount of triterpenic acids, mainly oleanolic acid (~12.5-31 mg/g dry leaf, respectively). A higher drying temperature (140 vs. 70 °C) affected rather positively the TPC/oleuropein content, whereas triterpenic acids were unaffected. The destoned pomace TPC was 15.5-22.0 mg gallic acid/g dw, hydroxytyrosol 3.9-5.6 mg/g dw, and maslinic 5.5-19.3 mg/g dw. Drying at 140 °C preserved better its bioactive phenols, whereas triterpenic acids were not influenced. The present findings indicate that TwPD streams may have a prospect as a source of bioactives for added-value applications. Material handling, including drying conditions, may be critical but only for phenols.

Utilization of industrial hemp by-product defatted seed flour: effect of its incorporation on the properties and quality characteristics of 'tsoureki', a rich-dough baked Greek product

BACKGROUND

A rich-dough baked Greek product named 'tsoureki' was prepared using non-gluten hemp seed flour at ratios of 0:100, 10:90, 30:70, and 50:50. The effects of hemp flour addition on the properties of 'tsoureki', including physicochemical properties (moisture content, water activity, sorption phenomena), structural properties, textural properties, total phenolic content, antioxidant activity, and sensorial characteristics, as well as the macroscopic structure and morphological characteristics, were studied.

RESULTS

Hemp flour addition affected dough rheology, showing tan δ values < 1, a decrease in both G' and G″ values, while both flow behavior and consistency indices were also significantly affected, which might have an influence on the final baked goods. The Guggenheim-Anderson-de Boer model satisfactorily described sorption data, while both hemp addition and temperature had a significant effect. A significantly higher hardness of 11.55 N, a lower specific volume of 2.65 cm³  g^-1 , and a lower porosity of 0.676 were observed at high hemp additions. The hemp flour level influenced the color of the crumb and crust, and the total color difference (ΔE) increased significantly with the increase in hemp flour. Hemp flour additions were detectable by the naked eye, with an obvious color difference between control and hemp-containing samples. Moreover, the phenolic content and antioxidant capacity were increased, as were some organoleptic characteristics, such as the bitter aftertaste. Concurrently, overall acceptability decreased significantly.

CONCLUSION

Overall, the incorporation of gluten-free defatted hemp seed flour in 'tsoureki' formulations seems to be a promising alternative for improving quality of such rich-dough baked products. © 2022 Society of Chemical Industry.

Materials Derived from Olive Pomace as Effective Bioadsorbents for the Process of Removing Total Phenols from Oil Mill Effluents

This work investigates olive pomace from olive mill factories as an adsorbent for the removal of total phenols from olive mill effluent (OME). This pathway of valorization of olive pomace reduces the environmental impact of OME while providing a sustainable and cost-effective wastewater treatment approach for the olive oil industry. Olive pomace was pretreated with water washing, drying (60 °C) and sieving (<2 mm) to obtain the raw olive pomace (OPR) adsorbent material. Olive pomace biochar (OPB) was obtained via carbonization of OPR at 450 °C in a muffle furnace. The adsorbent materials OPR and OPB were characterized using several basic analyzes (Scanning Electron Microscopy-Energy-Dispersive X-ray SEM/EDX, X-ray Diffraction XRD, thermal analysis DTA and TGA, Fourier transform infrared FTIR and Brunauer, Emmett and Teller surface BET). The materials were subsequently tested in a series of experimental tests to optimize the sorption of polyphenols from OME, investigating the effects of pH and adsorbent dose. Adsorption kinetics showed good correlation with a pseudo-second-order kinetic model as well as Langmuir isotherms. Maximum adsorption capacities amounted to 21.27 mg·g-1 for OPR and 66.67 mg·g-1 for OPB, respectively. Thermodynamic simulations indicated spontaneous and exothermic reaction. The rates of total phenol removal were within the range of 10-90% following 24 h batch adsorption in OME diluted at 100 mg/L total phenols, with the highest removal rates observed at pH = 10. Furthermore, solvent regeneration with 70% ethanol solution yielded partial regeneration of OPR at 14% and of OPB at 45% following the adsorption, implying a significant rate of recovery of phenols in the solvent. The results of this study suggest that adsorbents derived from olive pomace may be used as economical materials for the treatment and potential capture of total phenols from OME, also suggesting potential further applications for pollutants in industrial wastewaters, which can have significant implications in the field of environmental technologies.

Exploring Olive Pomace for Skincare Applications: A Review

The cosmetic industry is continuously searching for new active ingredients in an effort to attend to consumer demands which, in recent years, are focused on more natural and environmentally friendly products, obtained from sustainable resources. Nevertheless, they are required to provide cosmetologically appealing skincare products, ultimately with the purpose of improving skin appearance. The olive oil industry generates a large amount of liquid and semi-solid by-products such as olive pomace. Their phytotoxicity impairs safe disposal, so valorization strategies that promote by-product reuse are needed, which may include skincare products. Hydroxytyrosol is the main phenolic compound present in olive pomace and possesses biological effects that make it a desirable active compound for cosmetic formulations such as antioxidant and anti-aging activities as well as photoprotector, depigmenting, antimicrobial and anti-inflammatory actions. Other compounds present in olive pomace can also have functional properties and skin-related benefits. However, the application of this by-product can be a challenge in terms of formulation’s design, stability, and proven efficacy, so appropriate methodologies should be used to validate its incorporation and may include extraction and further encapsulation of bioactive compounds in order to achieve effective and aesthetic appealing skincare products.

Response Surface Modeling and Optimization of the Extraction of Phenolic Antioxidants from Olive Mill Pomace

Bioactive compounds from olive mill pomace (OMP) were extracted through a two-step solid-liquid extraction procedure considering four factors at five levels of a central composite rotatable response surface design. The influence of the process variables time of the primary extraction (2.0-4.0 h), solvent-to-sample ratio during the primary extraction (5.0-10.0 mL/g), time of the secondary extraction (1.0-2.0 h), and the solvent-to-sample ratio during the secondary extraction (3.0-5.0 mL/g) were examined. The content of bioactive compounds was determined spectrophotometrically, and the individual phenolic compounds were evaluated by reserved-phase high-performance liquid chromatography (RP-HPLC). The Derringer's function was used to optimize the extraction process, and the best conditions were found to be 3.2 h for the primary extraction, 10.0 mL/g for the solvent-to-sample ratio and 1.3 h for the secondary extraction associated with a solvent-to-sample ratio of 3.0 mL/g, obtaining a total phenolic content of 50.0 (expressed as mg gallic acid equivalents (GAE)/g dry weight (dw). The response surface methodology proved to be a great alternative for reducing the number of tests, allowing the optimization of the extraction of phenolic antioxidants from OMP with a reduced number of experiments, promoting reductions in cost and analysis time.

Virgin coconut oil: A comprehensive review of antioxidant activity and mechanisms contributed by phenolic compounds

Virgin coconut oil (VCO) is obtained by processing mature coconut cores with mechanical or natural methods. In recent years, VCO has been widely used in the food, pharmaceutical, and cosmetic industries because of its excellent functional activities. VCO has biological functions such as antioxidant, anti-inflammatory, antibacterial, and antiviral, and also has potential therapeutic effects on many chronic degenerative diseases. Among these functions, the antioxidant is the most basic and important function, which is mainly determined by phenolic compounds and medium-chain fatty acids (MCFAs). This review aims to elucidate the antioxidant functions of each phenolic compound in VCO, and discuss the antioxidant mechanisms of VCO in terms of the role of phenolic compounds with fat, intestinal microorganisms, and various organs. Besides, the composition of VCO and its application in various industries are summarized, and the biological functions of VCO are generalized, which should lay a foundation for further research on the antioxidant activity of VCO and provide a theoretical basis for the development of food additives with antioxidant activity.

Potential of Halophilic Penicillium chrysogenum Isolated from Algerian Saline Soil to Produce Laccase on Olive Oil Wastes

Enzymes from halophilic fungi offer interesting biotechnological applications, which lead us to explore novel producing strains. 23 fungi were isolated from Algerian saline soil. Among the three strains presenting laccase activities, one exhibited the high decolourising capacity of olive mill wastewaters. Identification showed that the efficient isolate GS15 belongs to Penicillium chrysogenum. This strain achieves optimal growth at 15% NaCl, 25 °C, pH 5, dark, aerobic and static conditions. The selected fungus is capable of producing extracellular enzymes as follows: caseinase, tannase, esterase and lipase. The laccase activities produced by P. chrysogenum on raw olive wastes are being reported here for the first time. GS15 produced 183.0 and 203.0 U/L of laccase activities in 10% and 20% unsupplemented olive mill wastewaters, respectively. The significant enzymatic activities can be correlated to the high ability of GS15 to decolourise industrial wastewater from the olive oil extraction. In these conditions no pre-treatment of olive wastewaters was needed. On the untreated grinded and non-grinded olive pomace, the laccase activity was 5.78 U/g and 5.36 U/g, respectively. Because the halophilic fungus has basic requirement for growth, this fungal strain is promising for saline biotechnological applications.

A Potential Valorization Strategy of Wine Industry by-Products and Their Application in Cosmetics-Case Study: Grape Pomace and Grapeseed

Grape pomace and grapeseed are agro-industrial by-products, whose inadequate treatment generates socioeconomic and environmental concerns. Nevertheless, it is possible to valorize them by extracting their bioactive compounds, such as antioxidants (phenolic compounds), vitamin E and fatty acids. The bioactive compounds were extracted using solid-liquid extraction. The yields for phenolic compounds were 18.4 ± 0.4% for grape pomace, and 17.4 ± 0.4%, for grapeseed. For the oil, the yields were 13.3 ± 0.2% and 14.5 ± 0.3% for grape pomace and grapeseed. Antioxidant capacity was assessed by the assay with 2,2-diphenyl-1-picrylhydrazyl (DPPH), and showed that phenolic extract has higher antioxidant capacity than the oils. Grape pomace and grapeseed extracts exhibit, correspondingly, values of 90.8 ± 0.8 and 87.5 ± 0.5 of DPPH inhibition and IC₅₀ of 48.9 ± 0.5 and 55.9 ± 0.7 μg_extract·mL_DPPH⁻¹. The antimicrobial capacity was assessed by the disk diffusion test, and revealed that, phenolic extracts inhibit the growth of Staphylococcus aureus and Staphylococcus epidermidis. The obtained extracts were incorporated in 10 face cream formulations, with slight modifications in quantities of formulation stabilizers. Their stability was studied for 35 days, and this revealed the possibility of incorporating extracts and oils obtained from by-products as antioxidants in cosmetics, and replacing synthetic ones. As a future recommendation, microencapsulation of the extracts should be performed, in order to increase their stability.

Influence of the extraction method on the recovery of bioactive phenolic compounds from food industry by-products

Agro-foodindustries generate colossal amounts of non-edible waste and by-products, easily accessible as raw materials for up-cycling active phytochemicals. Phenolic compounds are particularly relevant in this field given their abundance in plant residues and the market interest of their functionalities (e.g. natural antioxidant activity) as part of nutraceutical, cosmetological and biomedical formulations. In "bench-to-bedside" achievements, sample extraction is essential because valorization benefits from matrix desorption and solubilization of targeted phytocompounds. Specifically, the composition and polarity of the extractant, the optimal sample particle size and sample:solvent ratio, as well as pH, pressure and temperature are strategic for the release and stability of mobilized species. On the other hand, current green chemistry environmental rules require extraction approaches that eliminate polluting consumables and reduce energy needs. Thus, the following pages provide an update on advanced technologies for the sustainable and efficient recovery of phenolics from plant matrices.

Antimicrobial Properties of Lyophilized Extracts of Olive Fruit, Pomegranate and Orange Peel Extracts against Foodborne Pathogenic and Spoilage Bacteria and Fungi In Vitro and in Food Matrices

Several novel antimicrobials with different concentrations of olive, pomegranate, and orange fruit pulp extracts were produced from agricultural byproducts and, after lyophilization, their antimicrobial activity and potential synergistic effects were evaluated in vitro and in food samples against foodborne pathogenic and spoilage bacteria and fungi. The Minimum Inhibitory of the tested bacteria was 7.5% or 10%, while fungi were inhibited at a concentration of 10% or above. The optical density of bacterial and yeast cultures was reduced to a different extent with all tested antimicrobial powders, compared to a control without antimicrobials, and mycelium growth of fungi was also restricted with extracts containing at least 90% olive extract. In food samples with inoculated pathogens and spoilage bacteria and fungi, the 100% olive extract was most inhibitory against E. coli, S. typhimurium, and L. monocytogenes in fresh burger and cheese spread samples (by 0.6 to 1.8 log cfu/g), except that S. typhimurium was better inhibited by a 90% olive and 10% pomegranate extract in burgers. The latter extract was also the most effective in controlling the growth of inoculated fungi (Aspergillus niger, Penicillium italicum, Rhodotorula mucilaginosa) in both yogurt and tomato juice samples, where it reduced fungal growth by 1–2.2 log cfu/g at the end of storage period. The results demonstrate that these novel encapsulated extracts could serve as natural antimicrobials of wide spectrum, in order to replace synthetic preservatives in foods and cosmetics.

Alginate-based microparticles structured with different biopolymers and enriched with a phenolic-rich olive leaves extract: A physico-chemical characterization

Encapsulation of olive leaves extracts (OLE), rich of healthy components like Oleuropein, Hydroxytyrosol and Verbascoside, represents a new challenge to improve stability and nutritional value of food as well as a way to recover value added compounds from by-products, contributing to a more sustainable food system. In this context, OLE-loaded microbeads of Na alginate alone or in combination with Pectin, Na Caseinate or Whey protein isolates, were produced by emulsification internal ionotropic gelation. Encapsulation efficiency of the main phenolic compounds (Oleuropein, Hydroxytyrosol, Verbascoside) was carried out along with microparticles morphological characterization by scanning electron microscopy (SEM), thermal properties by differential scanning calorimetry (DSC) and color. Encapsulation efficiency resulted higher for Alginate/Pectin, whilst Alginate/Caseinate was the less performing system, probably due to the lower interaction with polyphenols. SEM revealed collapsed structures and continuous smooth surfaces for Alginate and Alginate/Pectin microbeads while more regular structures and porous surfaces were observed for Alginate/Caseinate and Alginate/Whey proteins. Higher hue angle and lower chroma values were observed for all the beads with respect to the pure extract, indicating a reduction of the yellow/brown color. DSC highlighted higher thermal stability for the microbeads in comparison to the original ingredients, showing also new thermal transitions related to bonds formation between polymers and OLE.

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Verbascoside showed higher encapsulation efficiency compared to Oleuropein.

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Alginate/Pectin was the most efficient system for encapsulation purposes.

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Microstructural traits were linked to the encapsulation efficiency.

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Thermal analysis revealed increased thermal stability of encapsulated polyphenols.

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Encapsulation allowed a mitigation of the color properties of the olive leaf extract.

Developing an Olive Biorefinery in Slovenia: Analysis of Phenolic Compounds Found in Olive Mill Pomace and Wastewater

The valorization of olive pomace through the extraction of phenolic compounds at an industrial scale is influenced by several factors that can have a significant impact on the feasibility of this approach. These include the types and levels of phenolic compounds that are present, the impact that seasonal variation and cultivar type have on the phenolic compound content in both olive pomace and mill effluents and the technological approach used to process the olive crop. Chemical analysis of phenolic compounds was performed using an HPLC-diode-array detector (DAD)-qTOF system, resulting in the identification of 45 compounds in olive mill wastewater and pomace, where secoiridoids comprised 50–60% of the total phenolic content. This study examined three different factors that could impact the phenolic compound content of these processing streams, including cultivar types typically grown on local farms in Slovenia, the type of downstream processing used and seasonality effects. Olive crop varieties sourced from local farms showed high variability, and the highest phenolic content was associated with the local variety “Istrska Belica”. During processing, the phenolic content was on average approximately 50% higher during two-phase decanting compared to three-phase decanting and the type of compound present significantly different. An investigation into the seasonal effects revealed that the phenolic content was 20% higher during the 2019 growing season compared to 2018. A larger sample size over additional growing seasons is required to fully understand the annual variation in phenolic compound content. The methods and results used in this study provide a basis for further analysis of phenolic compounds present in the European Union’s olive crop processing residues and will inform techno-economic modelling for the development of olive biorefineries in Slovenia.

Olive Tree Leaves—A Source of Valuable Active Compounds

The agricultural and processing activities of olive crops generate a substantial amount of food by-products, particularly olive leaves, which are mostly underexploited, representing a significant threat to the environment. Olive leaves are endowed with endogenous bioactive compounds. Their beneficial/health-promoting potential, together with environmental protection and circular economy, merit their exploitation to recover and reuse natural components that are potentially safer alternatives to synthetic counterparts. These biomass residues have great potential for extended industrial applications in food/dietary systems but have had limited commercial uses so far. In this regard, many researchers have endeavoured to determine a green/sustainable means to replace the conventional/inefficient methods currently used. This is not an easy task as a sustainable bio-processing approach entails careful designing to maximise the liberation of compounds with minimum use of (i) processing time, (ii) toxic solvent (iii) fossil fuel energy, and (iv) overall cost. Thus, it is necessary to device viable strategies to (i) optimise the extraction of valuable biomolecules from olive leaves and enable their conversion into high added-value products, and (ii) minimise generation of agro-industrial waste streams. This review provides an insight to the principal bioactive components naturally present in olive leaves, and an overview of the existing/proposed methods associated with their analysis, extraction, applications, and stability.

New insights in the in vitro release of phenolic antioxidants: The case study of the release behavior of tyrosol from tyrosol-loaded ethylcellulose microparticles during the in vitro gastrointestinal digestion

In this study, tyrosol - a phenolic antioxidant that present in olive oil and olive mill wastes - was embedded in ethylcellulose microparticles by double emulsion solvent evaporation technique. The effect of loading content (5 % w/w and 10 % w/w) on the release behavior and bioaccessibility of tyrosol was evaluated. The polymer endowed efficient protection to tyrosol during the in vitro gastrointestinal digestion of loaded microparticles as the maximum release of tyrosol was observed during the simulated intestinal digestion, and the releases were kept outstanding low during the simulated salivary and gastric digestions. The bioaccessibility of tyrosol was improved when encapsulated. The best-fitting models of the release profiles of tyrosol were the first, and the zero-order models for formulations considering a loading of 5% w/w and 10 % w/w, respectively. The results of this study bring new perspectives for the design of loaded microparticles that will be further submitted to gastrointestinal digestion.

Characterization and Bio-Accessibility Evaluation of Olive Leaf Extract-Enriched "Taralli"

Olive leaves are rich in many compounds precious for human health. Due to this property, the current study was aimed to valorize the extract from this by-product in a cereal-based food, very popular all around the world, the "taralli". To this aim, ultrasound-assisted extraction was applied to dried olive leaves to obtain the extract, used as "taralli" ingredient, instead of white wine. The "taralli" with and without extract was subjected to in vitro digestion to assess the quantity of polyphenolic compounds released in the gastrointestinal tract to become available for absorption. Total content of phenols and flavonoids, as well as the antioxidant capacity, was measured on both cooked and uncooked samples, before and after digestion. In addition, High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD) of the three most abundant polyphenols present in olive leaf extracts, such as oleuropein, hydroxytyrosol, and verbascoside, was carried out at the three stages of the digestion process. The results showed that the substitution of white wine with olive leaf extract increased the total content of polyphenols and flavonoids and the antioxidant capacity. Bio-accessibility of the main phenolic compounds demonstrated that oleuropein resisted slightly after gastric digestion but was almost completely degraded in the intestinal phase, while hydroxytyrosol and verbascoside were not resistant to the digestion process from the gastric phase.