Enrichment of table olives with polyphenols extracted from olive leaves

Investigation into the Reduction of Palm Oil in Foods by Blended Vegetable Oils through Response Surface Methodology and Oxidative Stability Tests

Recently, there has been a significant transition in the dietary preferences of consumers toward foods containing health-promoting compounds. In addition, as people's environmental awareness increases, they are increasingly looking for sustainable solutions. Palm oil, an oil used extensively by the food industry, does not fit these criteria. This study investigated the development of a complex oil blend consisting of commonly used vegetable oils such as corn, rapeseed, sunflower, and palm oil. The aim was to find the optimal blended oil and compare this combination with palm oil in terms of its oxidative stability, antioxidant capacity, and the composition of bioactive compounds (i.e., fatty acids, tocopherols, and carotenoids). Palm oil was found to have greater oxidative stability as a result of its increased concentration of saturated fatty acids. The optimal blended oil, which consisted of corn and rapeseed oil at a ratio of 4:3 w/w, inhibited the superior antioxidant activity, showing a ~33% increase in DPPH• inhibition activity. ATR-FTIR spectra further verified the existence of a significant quantity of saturated fatty acids in palm oil and unsaturated fatty acids in the blended oil. Finally, several correlation analyses revealed interesting connections between oil samples and investigated parameters. This work has the potential to establish a basis for the mass production of oil blends that possess high concentrations of antioxidant compounds and reduce the use of palm oil.

Effects of Enriched-in-Oleuropein Olive Leaf Extract Dietary Supplementation on Egg Quality and Antioxidant Parameters in Laying Hens

The objective of the present study was to evaluate the effects of an olive leaf extract obtained with an up-to-date laboratory method, when supplemented at different levels in laying hens' diets, on egg quality, egg yolk antioxidant parameters, fatty acid content, and liver pathology characteristics. Thus, 96 laying hens of the ISA-Brown breed were allocated to 48 experimental cages with two hens in each cage, resulting in 12 replicates per treatment. Treatments were: T1 (Control: basal diet); T2 (1% olive leaf extract); T3 (2.5% olive leaf extract); T4 (Positive control: 0.1% encapsulated oregano oil). Eggshell weight and thickness were improved in all treatments compared to the control, with T2 being significantly higher till the end of the experiment (p < 0.001). Egg yolk MDA content was lower for the T2 and T4 groups, while total phenol content and Haugh units were greater in the T2. The most improved fatty acid profile was the one of T3 yolks. The α-tocopherol yolk content was higher in all groups compared to T1. No effect was observed on cholesterol content at any treatment. Based on the findings, it can be inferred that the inclusion of olive leaf extract at a concentration of 1% in the diet leads to enhancements in specific egg quality attributes, accompanied by an augmentation of the antioxidant capacity.

Development of Enriched Oil with Polyphenols Extracted from Olive Mill Wastewater

The extraction of olive oil produces significant residual olive-mill wastewater (OMW). The composition of OMW varies according to the type of olive, the fruit's ripeness level, and the extraction method (traditional one-pressing system or continuous systems based on centrifugation of the olive pulp). In olive-producing countries, OMW is important for the environment and the economy and is also a low-cost source of polyphenolic compounds with high antioxidant properties. Olive oil's properties, such as its anti-atherogenic, anti-inflammatory, anti-aging, and immunological modulator effects, have been attributed to its polyphenols. In this study, the cloud point extraction (CPE) method was used to recover polyphenolic compounds from OMW. The total micellar phase of the three recoveries was 24.2% and the total polyphenols (after sonication) was 504 mg GAE/Kg. Furthermore, the addition of polyphenols recovered from OMW enhanced the olive oil and extended its shelf life without changing its organoleptic properties. There was a 42.2% change in polyphenols after 0.5% enrichment of micellar dispersions. Thus, it is suggested that the CPE method could lead to better waste management in the olive oil industry and improve the nutritional quality of food products.

Evaluation of the Efficacy and Synergistic Effect of α- and δ-Tocopherol as Natural Antioxidants in the Stabilization of Sunflower Oil and Olive Pomace Oil during Storage Conditions

Tocopherols are natural bioactive compounds with several health benefits. This study evaluated the effect of different ratios of α- and δ- tocopherol homologs to protect sunflower oil (SO) and olive pomace oil (OPO) against oxidation. A synergistic effect was recorded when the two tocopherols were combined at a ratio of 7:1 (α-T/δ-T). The oil samples were exposed to accelerated oxidation conditions using a Rancimat (90 °C and airflow of 15 L/h for 24 h) and protection from tocopherols was compared with that from butylated hydroxytoluene (BHT). Assessment of oil stability was examined using well-known parameters such as peroxide value (PV), thiobarbituric acid reactive substances (TBARS), p-anisidine value (p-AV), conjugated dienes (CD) and trienes (CT), and total oxidation (Totox) value, which were all significantly reduced when tocopherols were added at a ratio of 7:1 α-T/δ-T. Primary oxidative compounds measured according to PV were only reduced in SO samples (6.11%). Off-flavor compounds measured via TBARS assay in SO samples were reduced by above 20%, while p-AV was also reduced. CDvalue was correlated with PV in SO samples, while the 7:1 mixture was more effective than BHT for CTvalue. Total oxidation values in SO samples and OPO samples were reduced by 6.02% and 12.62%, respectively. These values in SO samples also provided a remarkable correlation (R2 > 0.95) with incubation time. Moreover, the synergistic effect was not only effective in reducing the oxidation values of oil samples, but also in lowering the degradation rate of tocopherols. Protective effects from tocopherols were mainly observed in SO samples, as OPO samples were more resistant to oxidation processes. This effect was even observed in fatty acid analysis, where the 7:1 mixture provided better results than BHT-spiked samples. Thus, it is suggested that tocopherol mixtures might be used as a natural preservative in the food industry to restrain lipid oxidation processes.

Evaluation of Tunisian Olive Leaf Extracts to Reduce the Bioavailability of Acrylamide in Californian-Style Black Olives

The aim of this work was analyzing the use of olive leaf extracts (OLE) obtained from two local Tunisian olive tree cultivars 'Chemlali' and 'Sayali' to reduce the acrylamide in Californian-style black olives. The phenol profile, antioxidant, and antibacterial activity of the two OLE extracts were evaluated. The principal phenols found were hydroxytyrosol (1809.6 ± 25.3 mg 100 g^-1), oleuropein (2662.2 ± 38 mg 100 g^-1) and luteolin-7-O-glucoside (438.4 ± 38 mg 100 g^-1) presented higher levels in 'Sayali' variety. Small differences were observed between the two kinds of extracts used; the greatest activity of OLE was observed against S. choleraesuis, with values up to 50% inhibition. The extract of 'Chemlali' cultivar was added to the Californian-style table olive, improving its phenol content and its antioxidant characteristics without negatively affecting its sensorial characteristics; these olives showed the highest firmness and proper quality characteristics. The gastrointestinal activity on the acrylamide concentration showed a partial degradation of this compound through the digestion, although the addition of the extract does not seem influence in its gastrointestinal digestion. These findings prove the usefulness of by-products to generate a high-quality added-value product, and this would also be relevant as a step towards a more sustainable, circular economy model.

Olive Oil Produced from Olives Stored under CO2 Atmosphere: Volatile and Physicochemical Characterization

In this study, an alternative debittering technique for olives, invented and patented by Prof. Vassilis Dourtoglou, was employed. Olive fruits (Olea europaea cv. Megaritiki) were stored under CO2 atmosphere immediately after harvest for a period of 15 days. After the treatment, a sensory evaluation between the olives stored under CO2 and those stored under regular atmospheric conditions (control) was performed. Additionally, the CO2-treated olives were used for the cold press of olive oil production. The volatile profile of the olive oil produced was analyzed using headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to mass spectrometry (GC-MS). A total of thirty different volatile compounds were detected. The volatile characteristics of olive oil are attributed, among others, to aldehydes, alcohols, esters, hydrocarbons, alkanes, and terpenes. The volatile compounds' analysis showed many differences between the two treatments. In order to compare the volatile profile, commercial olive oil was also used (produced from olives from the same olive grove with a conventional process in an industrial olive mill). The antioxidant activity, the content of bioactive compounds (polyphenols, α-tocopherol, carotenoids, and chlorophylls), and the fatty acids' profile were also determined. The results showed that the oil produced from CO2-treated olives contains different volatile components, which bestow a unique flavor and aroma to the oil. Moreover, this oil was found comparable to extra virgin olive oil, according to its physicochemical characteristics. Finally, the enhanced content in antioxidant compounds (i.e., polyphenols) not only rendered the oil more stable against oxidation but also better for human health. The overall quality of the olive oil was enhanced and, as such, this procedure holds great promise for future developments.

Valorizing the usage of olive leaves, bioactive compounds, biological activities, and food applications: A comprehensive review

Olive oil production is a significant source of economic profit for Mediterranean nations, accounting for around 98 percent of global output. Olive oil usage has increased dramatically in recent years, owing to its organoleptic characteristics and rising knowledge of its health advantages. The culture of olive trees and the manufacture of industrial and table olive oil produces enormous volumes of solid waste and dark liquid effluents, involving olive leaves, pomace, and olive oil mill wastewaters. These by-products cause an economic issue for manufacturers and pose major environmental concerns. As a result, partial reuse, like other agronomical production wastes, is a goal to be achieved. Because these by-products are high in bioactive chemicals, which, if isolated, might denote components with significant added value for the food, cosmetic, and nutraceutical sectors, indeed, they include significant amounts of beneficial organic acids, carbohydrates, proteins, fibers, and phenolic materials, which are distributed differently between the various wastes depending on the olive oil production method and table olive agronomical techniques. However, the extraction and recovery of bioactive materials from chosen by-products is a significant problem of their reasonable value, and rigorous detection and quantification are required. The primary aims of this review in this context are to outline the vital bioactive chemicals in olive by-products, evaluate the main developments in extraction, purification, and identification, and study their uses in food packaging systems and safety problems.

Oxidative and Microbial Stability of a Traditional Appetizer: Aubergine Salad

An eggplant-based salad, called aubergine salad (AS), is a traditional appetizer and as such, is quite popular in the Mediterranean area. It is widely produced either on a home scale or on an industrial scale and widely consumed. However, there are cases where preservatives (such as sodium benzoate and potassium sorbate) are added in order to extend the shelf life of the product. In the present study, the stability of this delicatessen against oxidation and microbial spoilage was evaluated, with or without preservatives. The physicochemical properties of the salad were evaluated, along with the tocopherol content, resistance to oxidation, and microbial count. According to the results, it is evident that the induction period of AS is 16% (in the case that preservatives were used) and 26% (in the case without preservatives) increased, compared to a control sample (plain soybean oil). This can be attributed to the increased content in tocopherols, and more specifically to α-tocopherol. Furthermore, the addition of preservatives resulted in increased storage days and a reduction of microorganisms. However, in both cases, the AS-prepared salad exhibited a self-stabilization ability after 13 days, negating the need for preservatives.

Effect of High Hydrostatic Pressure in the Storage of Spanish-Style Table Olive Fermented with Olive Leaf Extract and Saccharomyces cerevisiae

Olives treated according to the Spanish-style are firstly treated with caustic soda and then fermented in brine to reduce phenols. Next, olives are packed and subjected to pasteurization. The effect of different high hydrostatic pressure treatments (400 MPa, 4 and 6 min) was evaluated in Spanish-style table olives fermented with olive leaf extract (OLE) and S. cerevisiae compared with thermal pasteurization (P) at 80 °C for 15 min. HHP and P led to a significant reduction in yeast and aerobic mesophiles after the conservation treatment and during storage (300 days). The physical-chemical properties changed slightly during storage, except for olive hardness; olives treated with HHP presented a higher hardness than pasteurized ones. The CIELAB parameter L* decreased until day 300 in most of the treatments, as well as phenols. The HHP treatment led to significantly higher contents of phenolics (even during storage) than olives submitted to P. Some sensory attributes (colour, aspect, hardness, and overall evaluation) decreased during storage. P treatment caused a decrease in appearance, aroma, hardness, and overall evaluation compared to olives treated with HHP. Thus, the application of HHP in table olives to increase the shelf-life can be considered a valid alternative to P.

Comparative Analysis of Fatty Acid Profile and Fat-Soluble Vitamin Content in Sheep and Goat Milk of Organic and Conventional Origin

Consumers tend to perceive organic foods as more nutritious and safer in comparison to conventional, due to the perception that organic food is eco- and animal-friendly. Since fatty acids and fat-soluble vitamins in dairy produce are important nutrients, this study aims to assess possible differences in the amount of these components included in organic and conventional ewes and goat raw milk in Greece, while identifying the potential determining factors. A total of 48 samples were collected from organic and conventional sheep and goat farms in Greece (Thessaly) during the lactation period. A standardized questionnaire, including information about the farming system, and a sampling protocol were completed. Samples were studied for the fat-soluble vitamins (all-trans-retinol and α-tocopherol) and the fatty acids profile, while the outcomes were statistically analyzed to explore any associations with the questionnaire data for potential factors affecting the results. According to the obtained results there are slight differences in milk fatty acid content, which indicates that organic and conventional sheep and goat milk in Greece do not have any substantial differences in terms of feeding strategies. Regarding the content of fat-soluble vitamins, the organic milk is generally found to contain a higher amount than the conventional one.

Phenolic content, antioxidant, cytotoxic and antiproliferative effects of fractions of Vigna subterraenea (L.) verdc from Mpumalanga, South Africa

Consistent intake of legumes has been correlated with decreased possibility of developing colorectal cancer (CRC) due to the content of some phytochemicals like polyphenols. Bambara groundnut (BGN) is an underutilized crop with a rich nutritional profile, but have not been exploited for its nutraceutical and medicinal benefits. In this study, total polyphenol, flavonoid (flavonol and flavanol) content, antioxidant activity and cytotoxicity/antiproliferative properties of 70% ethanolic extracts of whole BGN, cotyledon and seed coat on Caco-2 and HT-29 colon cancer cells were evaluated. Seed coat had a significantly (p < 0.05) higher composition of total polyphenol, flavonol and flavan-3-ol (flavanol) compared to whole seed and cotyledon. Antioxidant activity determined with ferric reducing antioxidant power (FRAP), 2,2- azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and oxygen radical absorbance capacity (ORAC) assays, showed that seed coat with higher polyphenolic content had significantly (p < 0.05) greater antioxidant activity. BGN fractions demonstrated cytotoxic and antiproliferative effects against HT-29 and Caco-2 colon cancer cells in a dose-dependent manner, with seed coat and whole seed exhibiting greater cytotoxicity and higher antiproliferative activity and colon cancer cell inhibition. Extracts of the cotyledon also showed cytotoxic activity and hindered cancer cell growth/division but to a significantly (p < 0.05) lower magnitude. BGN parts indicated a greater cytotoxic effect and potential to slow down Caco-2 colon cancer cell growth and division over HT-29. This result provides new knowledge on the possible health benefits of BGN, as well as the potential for product development and may influence its consumption and utilisation.

Optimization of Pulsed Electric Field as Standalone "Green" Extraction Procedure for the Recovery of High Value-Added Compounds from Fresh Olive Leaves

Olive leaves (OLL) are reported as a source of valuable antioxidants and as an agricultural by-product/waste. Thus, a twofold objective with multi-level cost and environmental benefits arises for a "green" standalone extraction technology. This study evaluates the OLL waste valorization through maximizing OLL extracts polyphenol concentration utilizing an emerging "green" non-thermal technology, Pulsed Electric Field (PEF). It also provides further insight into the PEF assistance span for static solid-liquid extraction of OLL by choosing and fine-tuning important PEF parameters such as the extraction chamber geometry, electric field strength, pulse duration, pulse period (and frequency), and extraction duration. The produced extracts were evaluated via comparison amongst them and against extracts obtained without the application of PEF. The Folin-Ciocalteu method, high-performance liquid chromatography, and differential scanning calorimetry were used to determine the extraction efficiency. The optimal PEF contribution on the total polyphenols extractability (38% increase with a 117% increase for specific metabolites) was presented for rectangular extraction chamber, 25% v/v ethanol:water solvent, pulse duration (tpulse) 2 μs, electric field strength (E) 0.85 kV cm-1, 100 μs period (Τ), and 15 min extraction duration (textraction), ascertaining a significant dependence of PEF assisting extraction performance to the parameters chosen.

Assessment of the Efficacy of Olive Leaf (Olea europaea L.) Extracts in the Treatment of Colorectal Cancer and Prostate Cancer Using In Vitro Cell Models

Cancer is one of the most serious public health issues worldwide, ranking second only to cardiovascular diseases as a cause of death. Numerous plant extracts have extraordinary health benefits and have been used for centuries to treat a variety of ailments with few side effects. Olive leaves have a long history of medicinal and therapeutic use. In this study, the anti-cancer properties of an olive leaf extract were investigated in vitro using colorectal and prostate cancer cell lines (HT29 and PC3, respectively). A high-performance liquid chromatography analysis showed that the olive leaf extract contained a high chlorogenic acid content. Accordingly, chlorogenic acid may be related to the observed effects of the aqueous extract on cancer cells, including increased inhibition of cancer cell growth, migration, DNA fragmentation, cell cycle arrest at the S phase, reactive oxygen species (ROS) production, and altered gene expression. The effects of the extracts were greater in HT29 than in PC3 cells. These results suggest that chlorogenic acid, the main constituent in the olive extract, is a promising new anti-cancer agent. Further analyses should focus on its in vivo effects on colorectal tumor models, both alone and in combination with established agents.

Use of Pulsed Electric Field as a Low-Temperature and High-Performance “Green” Extraction Technique for the Recovery of High Added Value Compounds from Olive Leaves

Olive leaves (OLL), an agricultural waste by-product, are considered a significant bioresource of polyphenols, known as bioactive compounds. This study evaluates the pulsed electric field (PEF) technique for the extraction of polyphenols from OLL. The study parameters included a series of “green” solvents (ethanol, water as well as mixtures of them at a 25% step gradient) and different input values for the pulse duration of PEF. The phytochemical extraction degree was evaluated using total phenol concentration (Folin–Ciocalteu method) and high-performance liquid chromatography (HPLC) analyses, while the antioxidant activity was assessed using differential scanning calorimetry (DSC). The results obtained from the PEF extracts were compared with those of the extracts produced without the PEF application. The highest PEF effect was observed for aqueous ethanol, 25% v/v, using a pulse duration of 10 μs. The increase in the total polyphenols reached 31.85%, while the increase in the specific metabolites reached 265.67%. The recovery in polyphenols was found to depend on the solvent, the pulse duration of treatment and the structure of the metabolites extracted.

The challenge of exploiting polyphenols from olive leaves: addition to foods to improve their shelf-life and nutritional value

Olive leaves represent a waste from the olive oil industry which can be reused as source of polyphenols. The most representative phenolic compound of olive leaves is the secoiridoid oleuropein, followed by verbascoside, apigenin-7-O-glucoside, luteolin-7-O-glucoside, and simple phenols. The attention towards these compounds derives above all from the large number of studies demonstrating their beneficial effect on health, in fact olive leaves have been widely used in folk medicine in the Mediterranean regions. Moreover, the growing demand from consumers to replace the synthetic antioxidants, led researchers to conduct studies on the addition of plant bioactives in foods to improve their shelf-life and/or to obtain functional products. The current study overviews the findings on the addition of polyphenol-rich olive leaf extract (OLE) to foods. In particular, the effect of OLE addition on the antioxidant, microbiological and nutritional properties of different foods is examined. Most studies have highlighted the antioxidant effect of OLE in different food matrices, such as oils, meat, baked goods, vegetables, and dairy products. Furthermore, the antimicrobial activity of OLE has been observed in meat and vegetable foods, highlighting the potential of OLE as a replacer of synthetic preservatives. Finally, several authors studied the effect of OLE addition with the aim of improving the nutritional properties of vegetable products, tea, milk, meat and biscuits. Advantages and drawbacks of the different use of OLE were reported and discussed. © 2020 Society of Chemical Industry.

Functional compounds from olive pomace to obtain high-added value foods - a review

Olive pomace, the solid by-product from virgin olive oil extraction, constitutes a remarkable source of functional compounds and has been exploited by several authors to formulate high value-added foods and, consequently, to foster the sustainability of the olive-oil chain. In this framework, the aim of the present review was to summarize the results on the application of functional compounds from olive pomace in food products. Phenolic-rich extracts from olive pomace were added to vegetable oils, fish burgers, fermented milk, and in the edible coating of fruit, to take advantage of their antioxidant and antimicrobial effects. Olive pomace was also used directly in the formulation of pasta and baked goods, by exploiting polyunsaturated fatty acids, phenolic compounds, and dietary fiber to obtain high value-added healthy foods and / or to extend their shelf-life. With the same scope, olive pomace was also added to animal feeds, providing healthy, improved animal products. Different authors used olive pomace to produce biodegradable materials and / or active packaging able to increase the content of bioactive compounds and the oxidative stability of foods. Overall, the results highlighted, in most cases, the effectiveness of the addition of olive pomace-derived functional compounds in improving nutritional value, quality, and / or the shelf-life of foods. However, the direct addition of olive pomace was found to be more challenging, especially due to alterations in the sensory and textural features of food. © 2020 Society of Chemical Industry.

Application of Hydroxytyrosol in the Functional Foods Field: From Ingredient to Dietary Supplements

Hydroxytyrosol (HT) is an amphipathic functional phenol found in the olive tree, both in its leaves and fruits, in free or bound forms, as well as in olive oil and by-products of olive oil manufacture. The European Food Safety Authority recommends regular consumption of HT due to its several beneficial effects on human health, which are closely associated to its antioxidant activity. These reasons make HT an excellent candidate for application as a functional ingredient in the design of novel food products. Patents already exist for methodologies of extraction, purification, and application of HT in supplements and food products. The present review discusses the impact of HT incorporation on food properties and its effects on consumers, based on relevant data related to the use of HT as a functional ingredient, both as a pure compound or in the form of HT-rich extracts, in various food products, namely in edible oils, beverages, bakery products, as well animal-based foods such as meat, fishery and dairy products.

Enrichment of Olive Fruits in Antioxidant Content by Pre-Harvest Salicylic Acid Treatment

We here study the effect of the pre-harvest application of salicylic acid at two different concentrations on the olive phenolic composition. Influence of the cultivar and harvesting day were considered. As a result, the total phenol content increased significantly, particularly when using 200 mg mL⁻¹ of salicylic acid. However, the free radical scavenging activity was cultivar dependent. For instance, when the olives were harvested on day 3 and treated with 200 mg mL⁻¹ of salicylic acid, the antioxidant activity decreased from 161 to 278 µg mL⁻¹ for Arbequina, whereas it increased from 397 to 258 µg mL⁻¹ for Picual. Generally speaking, oleuropein and hydroxytyrosol contents enhanced with the application of 200 mg mL⁻¹ of salicylic acid. The results found suggest that exogenous salicylic acid is an interesting agronomic practice to enrich olive fruits in antioxidants.

Effect of olive leaf extract combined with Saccharomyces cerevisiae in the fermentation process of table olives

Yeasts have a great importance in the table olives quality and have been proved more and more as starter cultures. Moreover, the addition of olive leaf extract (OLE) could enhance the nutritional value of table olives, but there are no studies in which added OLE has been combined with yeasts during fermentation. The aim of this work was to determine if the quality and functional value of table olives increases when OLE and a yeast starter are used during a Spanish-style olive fermentation process. Several combinations were used: (1) fermentations trials with OLE combined with a strain of Saccharomyces cerevisiae; (2) fermentations with OLE; (3) control fermentations, with no extract or starter culture. During fermentation performed with the addition of OLE and yeasts, the yeast number remained stable for most of the time, resulting in a slight decrease of yeasts by the end of the process. The phenolic profile of olive flesh and brines of the trials was analysed during the fermentation. The addition of OLE increased the concentration of phenols in olive flesh and brines at the end of the fermentation; in these fermentations, hydroxytyrosol was the most abundant, at around 1700 mg/kg in olive flesh and 3500 mg/L in brines olive flesh, whereas in the control fermentation the concentrations were around 900 mg/kg and 2500 mg/L, respectively. In spite of adding OLE, the fermentation resulted in olives without bitterness. We can conclude that yeast inoculation combined with OLE improves safety, nutritional value and other properties of the final product, without affecting its sensorial qualities.

Physico-Chemical, Microbiological and Sensory Evaluation of Ready-to-Use Vegetable Pâté Added with Olive Leaf Extract

The shelf-life extension implicates the reduction of food waste. Plant polyphenols can have a crucial role in the shelf-life extension of foods. Olive leaf extract (OLE) is rich in phenolic compounds such as oleuropein, which is well-known for its antioxidant properties. Physico-chemical, microbiological and sensory aspects of non-thermally stabilized olive-based pâté fortified with OLE at concentrations of 0.5 (EX0.5) and 1 mg kg⁻¹ (EX1) were investigated. These samples were compared with olive-based pâté fortified with the synthetic antioxidant BHT (butylated hydroxytoluene) and with a control sample (CTR) without antioxidants. No sensory defects were perceived in all samples, even if a more intense typical olive flavour was perceived in samples containing OLE compared to those containing BHT and CTR. This result was confirmed by significantly higher levels of 2-methylbutanal and 3-methylbutanal in samples containing OLE compared to CTR and BHT. Moreover, the main microbial groups registered a significant loss of 0.5–1 logarithmic cycles in samples containing OLE, especially in EX1. The results of the present study indicate the potentiality of using OLE as natural preservatives in non-thermally stabilized olive-based pâté, since some spoilage-related microbial groups were negatively affected by the addition of OLE at the highest concentration.

Monitoring of acrylamide and phenolic compounds in table olive after high hydrostatic pressure and cooking treatments

Acrylamide and phenolic compounds on both fresh and cooked olives were monitored by HPLC/MS-MS and reversed-phase-HPLC methods along different procedures: elaboration process, high hydrostatic pressure (HHP), cooking treatment and bioavailability evaluation. Acrylamide was not detected during the elaboration process and after HHP treatment. Hydroxytyrosol, tyrosol, oleuropein and verbascoside were the most important phenols after HHP treatment. The frying and baking processes on olives enhanced the formation of acrylamide and a significant reduction in the phenolic compounds. The frying process produced lower acrylamide concentration and less reduction of phenolic compounds than the baking process, while in the gastrointestinal digestion these compounds were slightly reduced if compared to the initial stage. As a conclusion, the best way to ingest high quantities of phenols and reduce acrylamide consumption is by ingesting the olives when they are fresh. In case the olives need to be cooked, specific time and temperature conditions shall be applied.

Olive Leaves Extract from Algerian Oleaster (Olea europaea var. sylvestris) on Microbiological Safety and Shelf-life Stability of Raw Halal Minced Beef during Display

Oleaster (wild olive tree) by-products represent a renewable and low-cost source of biopolyphenols. Leaf extracts (sylv.OLE) of Algerian oleaster, locally called a'hachad (Olea europaea subsp. europaea var. sylvestris), were applied at 1 and 5% (v/w) to raw Halal minced beef (HMB) in order to test its safety and shelf-life prolongation during retail/display. The total phenolic compound content in the extract was 198.7 ± 3.6 mg gallic acid equivalent. Ten compounds were identified in the sylv.OLE by High Performance Liquid Chromatography/Diode Array Detector (HPLC/DAD), of which oleuropein was the most abundant (43.25%). Samples treated with 5% sylv.OLE had significantly higher antimicrobial and antioxidant effects than those treated with 1% extract (p < 0.05). The addition of sylv.OLE reduced psychrotrophic counts as well as the level of pathogens (Salmonella enterica ser. Enteritidis and Shiga toxin-producing Escherichia coli O157:H7). A thiobarbituric acid reactive substance (TBARS) value of 2.42 ± 0.11 was reached throughout six days of retail/display in control samples, while the addition of 5% sylv.OLE reduced TBARS value by 58% (p < 0.05). The presence of sylv.OLE at the tested concentrations did not negatively influence the overall acceptability and bitterness of HMB.

Reducing Phenolics Related to Bitterness in Table Olives

Olives are one of the oldest food products in human civilization. Over the centuries, numerous methods have been developed to transform olives from a bitter drupe into an edible fruit. Methods of processing table olives rely on the acid, base, and/or enzymatic hydrolysis of bitter phenolic compounds naturally present in the fruit into nonbitter hydrolysis products. Today, there are three primary methods of commercial table olive processing: the Greek, Spanish, and Californian methods, in addition to several Artisanal methods. This review focuses on the technological, microbiological, chemical, and sensory aspects of table olive processing and the inherent benefits and drawbacks of each method. The table olive industry is facing challenges of environmental sustainability and increased consumer demand for healthier products. Herein, we examine current research on novel technologies that aim to address these issues.

Development and Validation of an Analytical Methodology Based on Liquid Chromatography-Electrospray Tandem Mass Spectrometry for the Simultaneous Determination of Phenolic Compounds in Olive Leaf Extract

A simple method was validated for the analysis of 31 phenolic compounds using liquid chromatography-electrospray tandem mass spectrometry. Proposed method was successfully applied to the determination of phenolic compounds in an olive leaf extract and 24 compounds were analyzed quantitatively. Olive biophenols were extracted from olive leaves by using microwave-assisted extraction with acceptable recovery values between 78.1 and 108.7%. Good linearities were obtained with correlation coefficients over 0.9916 from calibration curves of the phenolic compounds. The limits of quantifications were from 0.14 to 3.2 μg g-1. Intra-day and inter-day precision studies indicated that the proposed method was repeatable. As a result, it was confirmed that the proposed method was highly reliable for determination of the phenolic species in olive leaf extracts.

Safety assessment of ethanolic extract of Olea europaea L. leaves after acute and subacute administration to Wistar rats

Olea europaea L., popularly known as olive, is a plant widely used worldwide. Its leaves, fruit and oil are extensively consumed and present important pharmacological properties. However, studies regarding the toxicity of olive leaves are still limited in the literature. Therefore, the aim of the study was to investigate acute and subacute oral toxicities of the ethanolic extract of olive leaves (EEO) in Wistar rats through histopathology and biochemical and hematological parameters. Acute toxicity was assessed using a single dose of 2000 mg/kg of EEO administered by oral gavage to male and female rats. To assess subacute toxicity, EEO was administered during 28 days at different doses (100, 200 and 400 mg/kg) to male and female rats. At the end of the experiments, the liver and kidney were removed and examined microscopically, and blood was collected for hematological and biochemical parameters. A single dose of 2000 mg/kg did not induce mortality or any signs of toxicity among the animals treated. Animals exposed to EEO during 28 days did not present sign of abnormalities. Results demonstrated that EEO did not induce toxicity after exposure to single and repeated doses. However, more studies are needed to fully understand implications for human safety.

Use of phenolic compounds from olive mill wastewater as valuable ingredients for functional foods

Olive mill wastewater (OMW) is a pollutant by-product from the virgin olive oil production. Its high content in phenolic compounds makes them play an important role for their use in foods, for their high antioxidant significance. The present paper gives an overview on the techniques for OMW valuable ingredient separation, focusing on the most effective ones for their use in food products as functional ingredients. We report on effective methods to recover OMW phenolics, and give several examples on the use these extracts in foods. When added into vegetable oils, their effect on retarding lipid oxidation improves the oxidative status of the product, whilst several challenges need to be faced. OMW phenolic extracts were also used in food emulsions, milk products or other model systems, showing promising results and little or no negative impact on the sensory characteristics or other properties. Their possible use as antimicrobial agents is also another promising approach, as positive results were obtained when applied in meat products. Other examples of using natural phenolic extracts from other sources are suggested also for OMW extracts, to expand their use and thus to improve the nutritional and technological quality of foods.

Valorization of functional properties of extract and powder of olive leaves in raw and cooked minced beef meat

BACKGROUND

Olive leaves (OL), available in huge amounts from pruning, are known to be a useful source of biologically active compounds. This study investigated the potential application of OL as a supplement to minced beef meat in order to develop a functional product. The effect of OL extract or powder (100 and 150 µg phenols g^-1 meat) on the quality and stability of raw and cooked meat during refrigerated storage was examined.

RESULTS

Microwave drying at 600 W gave OL with the highest antioxidant quality (evaluated by TEAC/[phenols] (mg mg^-1 ) and DPPH/[phenols] (mg mg^-1 )) compared with other methods. OL showed an ability to inhibit (P < 0.05) lipid oxidation (TBARS values (mg MDA kg^-1 ) were reduced by 25-65%) and myoglobin oxidation (metmyoglobin production was 43-65% in control samples and 14-35% in treated samples). OL also improved the technological quality of the meat, decreasing (P < 0.05) storage loss (%) and defrosting loss (%) without affecting cooking loss (%) and Napole yield (%). Sensory properties were not modified by the added ingredient at the tested levels (P < 0.05).

CONCLUSION

OL (extract or powder) may have applications in the development of functional meat products of good technological quality that remain stable during storage. © 2016 Society of Chemical Industry.

Antimicrobial activity of Olea europaea Linné extracts and their applicability as natural food preservative agents

The antimicrobial activity of phenolic compounds from Olea (O.) europaea Linné (L.) is part of the scientific discussion regarding the use of natural plant extracts as alternative food preservative agents. Although, the basic knowledge on the antimicrobial potential of certain molecules such as oleuropein, hydroxytyrosol or elenolic acid derivatives is given, there is still little information regarding their applicability for food preservation. This might be primarily due to the lack of information regarding the full antimicrobial spectrum of the compounds, their synergisms in natural or artificial combinations and their interaction with food ingredients. The present review accumulates available literature from the past 40 years, investigating the antimicrobial activity of O. europaea L. derived extracts and compounds in vitro and in food matrices, in order to evaluate their food applicability. In summary, defined extracts from olive fruit or leaves, containing the strongest antimicrobial compounds hydroxytyrosol, oleacein or oleacanthal in considerable concentrations, appear to be suitable for food preservation. Nonetheless there is still need for consequent research on the compounds activity in food matrices, their effect on the natural microbiota of certain foods and their influence on the sensorial properties of the targeted products.

Olive leaves (Olea europaea L.) versus α-tocopheryl acetate as dietary supplements for enhancing the oxidative stability of eggs enriched with very-long-chain n-3 fatty acids

BACKGROUND

Ninety-six brown Lohmann laying hens were equally assigned into four groups with six replicates. Hens within the control group were given a corn/soybean-based diet supplemented with 30 g kg(-1) fish oil. Two other groups were given the same diet further supplemented with olive leaves at 5 (OL5) and 10 (OL10) g kg(-1) respectively, while the diet of the fourth group was supplemented with α-tocopheryl acetate (TOC) at 200 mg kg(-1). Eggs were analysed for lipid hydroperoxide and malondialdehyde (MDA) contents, fatty acid profile, α-tocopherol content and susceptibility to iron-induced lipid oxidation.

RESULTS

Neither OL nor TOC supplementation affected (P>0.05) the fatty acid composition. Dietary supplementation with OL10 or TOC reduced (P≤0.05) the lipid hydroperoxide content but exerted no (P>0.05) effect on the MDA content of fresh eggs compared with controls. Eggs submitted to iron-induced lipid oxidation from the OL5 group presented higher (P≤0.05) MDA levels than the control but lower (P≤0.05) than the OL10 group. Eggs from the TOC group presented lower (P≤0.05) MDA levels compared with all groups at all incubation time points.

CONCLUSION

The results of this study suggested that dietary supplementation with both OL10 and TOC could protect n-3 fatty acids in eggs from deterioration.

Effect of supplementation of the laying hen diet with olive leaves (Olea europea L.) on lipid oxidation and fatty acid profile of α-linolenic acid enriched eggs during storage

1. The aim of this study was to evaluate the effect of supplementation of the layer diet with olive leaves (Olea europea L.) on lipid oxidation and fatty acid profile of α-linolenic acid enriched eggs during refrigerated storage, and to compare this effect with α-tocopheryl acetate supplementation. 2. A total of 72 brown Lohmann laying hens, equally allocated to 3 groups, were fed on diets supplemented with 40 g/kg linseed oil, or linseed oil and olive leaves at 10 g/kg or linseed oil and α-tocopheryl acetate at 200 mg/kg. Collected eggs were analysed for fatty acid profile and lipid oxidation either fresh or following 60 d storage at 4°C. 3. Results showed that olive leaves or α-tocopheryl acetate supplementation reduced lipid hydroperoxide concentration in fresh eggs but had no effect on their fatty acid profile and malondialdehyde (MDA) content compared to controls. 4. Refrigerated storage for 60 d decreased the proportions of PUFAs but increased those of MUFAs in eggs from the control diet, whilst it had no effect on the fatty acid composition of eggs from the diets supplemented with olive leaves or α-tocopheryl acetate, which in turn showed decreased concentrations of lipid hydroperoxides and MDA.

Direct enrichment of olive oil in oleuropein by ultrasound-assisted maceration at laboratory and pilot plant scale

The possibility to improve the nutritional value of olive oil by enriching it in phenolic compounds from olive leaves (e.g., oleuropein) by ultrasonic maceration was studied. The experimental design used led to the following optimal extraction conditions: ultrasonic power of 60 W, temperature of 16°C and sonication duration of 45 min. The high total phenolic content (414.3 ± 3.2mg of oleuropein equivalent/kg of oil), oleuropein (111.0 ± 2.2mg/kg of oil) and α-tocopherol (55.0 ± 2.1g/kg of oil) concentrations obtained by optimized ultrasound-assisted extraction (UAE) proved the efficiency of this process when compared with the conventional solid-liquid extraction. Histochemical analyses showed that this efficiency is due to specific alteration of the phenol-containing leaf structures. Furthermore, the radical-scavenging activity of the processed oil (DPPH test) and its stability toward lipid autoxidation (heating test) confirmed its enrichment in antioxidants. Sensory evaluation of the enriched olive oil showed a slight increase in bitterness but an overall acceptability. Finally, the enriched olive oil was characterized by clear green color (L*, a*, b* parameters).

Olive leaves (Olea europea L.) and α-tocopheryl acetate as feed antioxidants for improving the oxidative stability of α-linolenic acid-enriched eggs

Ninety-six brown Lohmann laying hens were equally assigned into four groups with six replicates. Hens within the control group were fed a corn-soybean-based diet supplemented with 4% linseed oil. Two other groups were given the same diet further supplemented with 5 or 10 g ground olive leaves/kg feed, while the diet of the fourth group was further supplemented with 200 mg α-tocopheryl acetate/kg. Supplementing diets with olive leaves had no effect on egg production, feed intake and egg traits. Eggs collected 28 days after feeding the experimental diets were analysed for lipid hydroperoxides and malondialdehyde (MDA) content, fatty acid profile, α-tocopherol concentrations and susceptibility to iron-induced lipid oxidation. Olive leaves were also analysed for total and individual phenolics, and total flavonoids, whereas their antioxidant capacity was determined using both the DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2-azinobis3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity assays. Results showed that neither α-tocopheryl acetate nor olive leaves supplementation exerted (p>0.05) any effect on the fatty acid composition of n-3 eggs. Supplementing the diet with 5 g olive leaves/kg had no (p>0.05) effect on the hydroperoxide levels of n-3 eggs, while supplementing with 10 g olive leaves/kg or 200 mg α-tocopheryl acetate/kg, the lipid hydroperoxide levels were reduced (p≤0.05) compared to control. However, although hydroperoxides were reduced, MDA, a secondary lipid oxidation product, was not affected (p>0.05). Iron-induced lipid oxidation increased MDA values in eggs from all groups, the increase being higher (p≤0.05) in the control group and the group supplemented with 5 g olive leaves/kg. The group supplemented with 10 g olive leaves/kg presented MDA values lower (p≤0.05) than the control but higher (p≤0.05) than the α-tocopheryl acetate group, which presented MDA concentrations lower (p≤0.05) than all other experimental diets at all incubation time points.