Addition Of Olive Leaf Extract Research Articles

Physicochemical properties and sensory features of ripened, industrially prepared sausages, enriched with olive leaf extract to replace nitrite and nitrate

The use of nitrite and nitrate in meat products has been questioned due to the generation of N-nitroso compounds with carcinogenic effects. Thus, research has been focused on their replacement with several alternatives. This study is focused on evaluating the effects of a commercial olive leaf extract (OLE), marketed as dietary supplement, on protein and lipid oxidation, N-nitrosamine content and sensory properties of industrial sausages at the end of the ripening period. Five different formulations were prepared: F1 (OLE: 1000 mg/kg; NO2–NO3: 0 mg/kg), F2 (OLE: 1000 mg/kg; NO2–NO3: 75-75 mg/kg), F3 (OLE: 0 mg/kg; NO2–NO3: 0 mg/kg), F4 (OLE: 0 mg/kg; NO2–NO3: 75-75 mg/kg), F5 (OLE: 500 mg/kg; NO2–NO3: 35-35 mg/kg). The use of OLE in combination with a reduced dose of nitrite and nitrate (F5) significantly reduced the lipid and protein oxidation (p < 0.05) compared to the formulation with synthetic additives alone (F4). No differences were observed in terms of textural properties with the samples without the extract. The OLE did not affect the microbiological quality and enabled a significant reduction in the N-nitrosamines content. However, the addition of OLE decreased the intensity of red colour and determined the insurgence of a slight bitter taste in the sausages.

Improving Hydroxytyrosol Derivatives Content in Virgin Olive Oil using Ultrasound-assisted Maceration with Olive Leaf Extract

Background: Olive oil is rich in monounsaturated fatty acids and is an essential Mediterranean diet component. Many of its health benefits are associated with the presence of phenolic compounds. Several strategies for the enhancement of the phenolic content and, more specifically, the concentration of hydroxytyrosol derivatives in olive oils have been proposed, as extra virgin olive oil (EVOO) of high phenolic content is preferred by health-conscious consumers. Methods: The supplementation of EVOO with hydroxytyrosol derivatives from olive leaf extract was performed with the employment of ultrasound-assisted maceration at different concentration levels (2 g·L-1 oil and 4 g·L-1 oil), temperatures (20 and 40°C), and maceration times (20 and 40 min). The phenolic contents of enriched EVOOs were determined by spectrophotometric and HPLC methods. In addition, the effect of supplementation on the physicochemical parameters of EVOOs, namely acidity and extinction coefficients (K232 and K270), was also studied. Results: The addition of extract slightly increased the acidity values and extinction coefficients of the samples, and at the same time, it significantly improved their phenolic composition. The use of appropriate ultrasound-assisted maceration parameters (addition of olive leaf extract at a concentration level of 2 g L-1 at 20°C for 20 min) provided EVOO with acceptable values for total acidity (&lt;0.8%), K232 (&lt;2.5), and K270 (&lt;0.22), high contents of total phenolics and flavonoids, and improved hydroxytyrosol derivative contents. Conclusion: The enrichment of EVOO with leaf extract is a promising strategy to enhance its content in hydroxytyrosol derivatives, providing premium EVOOs with respect to their bioactive composition.

OLIVE LEAF EXTRACT INCORPORATED CHITOSAN FILMS FOR ACTIVE FOOD PACKAGING

Packaging materials serve as a barrier to protect the food from the environment and new approaches with improved properties, such as active packaging, is gaining more attention nowadays. In this study, chitosan films containing olive leaf extract (OLE) as an additive were prepared and characterized in terms of mechanical, structural and biological properties. The addition of OLE improved not only the tensile strength (32 MPa) and elongation (9.3%) of chitosan films but also their barrier properties such as water vapor transmission rate of 657.52 g/m2day and moisture retention capability of 90.41%. Furthermore, chitosan films gained antibacterial properties with the addition of OLE and possessed a dose and time-dependent antioxidant activity compared to their extract-free equivalents. As a consequence, the present study suggests that chitosan films incorporated with OLE are a promising alternative as an active food packaging with enhanced mechanical, barrier, antioxidant and antibacterial properties.

Bioavailability of Phenolic Compounds in Californian-Style Table Olives with Tunisian Aqueous Olive Leaf Extracts.

Recent advances in biotechnology have ensured that one of the main olive tree by-products is olive leaf extract (OLE), a rich source in bioactive compounds. The aim of this work was to study the phenolic composition in different OLEs of three Tunisian varieties, namely, 'Sayali', 'Tkobri', and 'Neb Jmel'. The in vitro biodigestibility effect after 'Sayali' OLE addition to Californian-style 'Hojiblanca' table olives was also studied. This OLE contained bioactive molecules such as hydroxytyrosol, tyrosol, oleropeine, Procianidine B1 (PB1), and p-cumaric acid. These compounds were also found in fresh olives after OLE was added. Furthermore, from fresh extract to oral digestion, the detected amount of bioavailable phenol was higher; however, its content decreased according to each phase of gastric and intestinal digestion. In the final digestion phase, the number of phenols found was lower than that of fresh olives. In addition, the phenolic content of Californian-style 'Hojiblanca' table olives decreased during the in vitro digestion process. The antioxidant activity of this variety decreased by 64% and 88% after gastrointestinal digestion, being the highest antioxidant capacity found in both simulated gastric and intestinal fluid, respectively. The results show us that the 'Sayali' variety is rich in phenolic compounds that are bioavailable after digestion, which could be used at an industrial level due to the related health benefits.

Effect of olive leaf (Olea europaea L.) extract addition to broiler diets on the growth performance, breast meat quality, antioxidant capacity and caecal bacterial populations

This study aims to evaluate the effect of olive leaf extract (OLE) on growth performance, breast meat quality, antioxidant capacity and caecal microbiota regulation. OLE containing 51.5% oleuropein, 25.6% polyphenols and 6.2% flavonoids, was designed to different supplement levels ranging from 0.1% OLE (OLE0.1) to 0.5% OLE (OLE0.5) into a basal diet, separately. The whole feeding period lasts for 35 days after 7-day hatching from the egg. 720 1-day-age healthy Arbour Acres male broilers were thus divided into five experimental groups and one control group, consist of 20 broilers per group for six parallel experiments in triplicate. The results showed that the levels of average daily feed intake (ADFI) and average daily weight gain (ADG) of the broilers were decreased (p < 0.05) after the addition of 0.3% OLE. Moreover, the breast meat shear force was decreased by 34.4% (p < 0.05). The glutathione (GSH) levels in the meat were increased by 76.64% (p < 0.05); the levels of total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) were increased by 50.4% and 120%, respectively. And the malondialdehyde (MDA) levels in the meat were reduced by 34.2% (p < 0.05). Additionally, a decreased intensity of Escherichia coli (p < 0.05) and an increased intensity of Lactobacillus and Bifidobacterium (p < 0.05) were observed. Overall, supplementing 0.3% OLE into daily diet enables enhancing breast meat antioxidation, amplifying the abundance of Lactobacillus and Bifidobacterium as well as diminishing the abundance of E. coli in the caecum. HIGHLIGHTS OLE contains 51.5% oleuropein, 25.6% of TP and 6.2% TF levels. OLE addition at 0.3% lowers shear force and raises the GSH’s level of the meat. OLE causes a decrease in E. coli and an increase in Lactobacillus and Bifidobacterium.

The Potential of Olive Leaf Extract as a Functional Ingredient in Yoghurt Production: The Effects on Fermentation, Rheology, Sensory, and Antioxidant Properties of Cow Milk Yoghurt.

Background: Yoghurt has been traditionally consumed for its high nutritional value and health-promoting benefits. The addition of plant extracts as a source of phenolic compounds and bio-flavonoids has attracted much attention recently since milk and dairy products are deficient in these health-protecting components. Accordingly, olive leaf extract (OLE) has been considered due to the presence of bioactive compounds, primarily polyphenols. Thus, the aim of this research was to investigate the possibility of adding OLE into cow milk yoghurt as a potential functional ingredient. Methods: Yoghurts enriched with OLE (1.5, 3, and 5% v/v) were produced and compared with yoghurt without OLE. In all samples acidity, viscosity, colour, syneresis, water holding capacity (WHC), microbiological parameters, sensory properties, total phenols, and antioxidant activity (DPPH and FRAP methods) were determined. Results: The addition of OLE resulted in shorter fermentation and lower pH, but it had no adverse effect on the viability of yoghurt starter bacteria. OLE-enriched yoghurts showed increased syneresis, higher total phenols content, and antioxidant activity, while WHC and viscosity decreased. Sensory properties were slightly poorer for yoghurts containing higher OLE concentrations. Considering all of the obtained results, the addition of 1.5% OLE appeared to be optimal.

Olive Leaf Extract (OLE) Addition as Tool to Reduce Nitrate and Nitrite in Ripened Sausages.

Olive leaf extract (OLE) is known to be a source of phenolic compounds with antioxidant and antimicrobial activities. This study investigated the effects of the OLE addition to reduce nitrate/nitrite (NO) content on the physico-chemical features of ripened pork sausages. Seven formulations of pork sausages were set up: CTRL (0 mg/kg OLE; 300 mg/kg NO), Tr1 (200 mg/kg OLE; 150 mg/kg NO), Tr2 (400 mg/kg OLE; 150 mg/kg NO), Tr3 (800 mg/kg OLE; 150 mg/kg NO), Tr4 (200 mg/kg OLE; 0 mg/kg NO), Tr5 (400 mg/kg OLE; 0 mg/kg NO), and Tr6 (800 mg/kg OLE; 0 mg/kg NO). At the end of the ripening period, all the samples were within hygienic limits and the substitution of the additives with OLE allowed the reduction of NO residual contents. Both OLE and NO influenced the colour parameters. At the highest dose of OLE, both alone and in combination with reduced dose of NO, no significant differences in terms of moisture, pH, and aw were found compared to CTRL. In absence of NO, a significant reduction of weight loss was observed. Moreover, in the samples without NO a reduction of the hardness was detected. Finally, the oxidative stability test showed that the increase of the OLE amount prolonged the induction time.

Polylactide Films with the Addition of Olive Leaf Extract-Physico-Chemical Characterization.

The aim of this work was to obtain and characterize polylactide films (PLA) with the addition of poly(ethylene glycol) (PEG) as a plasticizer and chloroformic olive leaf extract (OLE). The composition of OLE was characterized by LC-MS/MS techniques. The films with the potential for using in the food packaging industry were prepared using a solvent evaporation method. The total content of the phenolic compounds and DPPH radical scavenging assay of all the obtained materials have been tested. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (FTIR-ATR) allows for determining the molecular structure, while Scanning Electron Microscopy (SEM) indicated differences in the films’ surface morphology. Among other crucial properties, mechanical properties, thickness, degree of crystallinity, water vapor permeation rate (WVPR), and color change have also been evaluated. The results showed that OLE contains numerous active substances, including phenolic compounds, and PLA/PEG/OLE films are characterized by improved antioxidant properties. The OLE addition into PLA/PEG increases the material crystallinity, while the WVPR values remain almost unaffected. From these studies, significant insight was gained into the possibility of the application of chloroform as a solvent for both olive leaf extraction and for the preparation of OLE, PLA, and PEG-containing film-forming solutions. Finally, evaporation of the solvent from OLE can be omitted.

An evaluation of the quality characteristics of kefir fortified with olive (Olea europaea) leaf extract

PurposeThis study aims to produce a new type of healthy functional kefir by adding olive (Olea europaea) leaf extract and to determine its potential effect on the quality (physicochemical, sensory, phenolic contents and antioxidant properties) of kefir samples during storage at 4°C for 21 days.Design/methodology/approachFor this purpose, four kefir samples were produced by using olive leaf extract in different amounts (A: 0% (control), B: 0.1%, C: 0.15% and D: 0.35%). The physicochemical, sensory, phenolic contents and antioxidant properties of kefir samples were investigated during Days 1, 7, 14 and 21 of storage. The study was conducted to optimize the olive leaf extract addition level to obtain better-quality kefir functional food.FindingsFrom the results, it was determined that the addition of olive leaf extract affected the entire chemical components of the kefir samples (p < 0.05). It was found that the pH value decreased during storage. By contrast, it was observed that titration acidity values increased. The kefir sample with 0.35% olive leaf extract (D) had the highest total phenolic and antioxidant activity content (1,292.75 mg GAE/L and 10.20 mM TE, respectively) among the samples (p < 0.05). In the sensory analyses, the kefir sample with the highest score – in terms of sensory attributes – was the kefir sample containing 0.15% olive leaf extract (C).Originality/valueThus, it was concluded that kefir with added olive leaf extract could serve as a functional kefir of benefit to human health. When we looked at the enrichment studies on kefir as a functional product, no study has been found on the use of olive (Olea europaea) leaf extract, especially with kefir. In this sense, it is thought that the study will contribute to published literature.

Addition of Olive Leaf Extract to a Mixture of Algae and Extra Virgin Olive Oils Decreases Fatty Acid Oxidation and Synergically Attenuates Age-Induced Hypertension, Sarcopenia and Insulin Resistance in Rats.

Olive-derived products, such as virgin olive oil (EVOO) and/or olive leaf extracts (OLE), exert anti-inflammatory, insulin-sensitizing and antihypertensive properties and may be useful for stabilizing omega 3 fatty acids (n-3 PUFA) due to their high content in antioxidant compounds. In this study, the addition of OLE 4:0.15 (w/w) to a mixture of algae oil (AO) rich in n-3 PUFA and EVOO (25:75, w/w) prevents peroxides formation after 12 months of storage at 30 °C. Furthermore, the treatment with the oil mixture (2.5 mL/Kg) and OLE (100 mg/Kg) to 24 month old Wistar rats for 21 days improved the lipid profile, increased the HOMA-IR and decreased the serum levels of miRNAs 21 and 146a. Treatment with this new nutraceutical also prevented age-induced insulin resistance in the liver, gastrocnemius and visceral adipose tissue by decreasing the mRNA levels of inflammatory and oxidative stress markers. Oil mixture + OLE also attenuated the age-induced alterations in vascular function and prevented muscle loss by decreasing the expression of sarcopenia-related markers. In conclusion, treatment with a new nutraceutical based on a mixture of EVOO, AO and OLE is a useful strategy for improving the stability of n-3 PUFA in the final product and to attenuate the cardiometabolic and muscular disorders associated with aging.

Biophysical, Rheological, and Functional Properties of Complex of Sodium Caseinate and Olive Leaf Aqueous Polyphenolic Extract Obtained Using Ultrasound-Assisted Extraction

This study demonstrated the use of ultrasound-assisted extraction to render aqueous extract polyphenolic compounds from olive leaves. Sodium caseinate-olive leaf extract complexes were produced using different amounts of olive leaf extract (0, 0.5, 1, 1.5, and 2% w/v). Turbidity, solubility, antioxidant activity (DPPH and ABTS assays), foaming capacity and stability and surface hydrophobicity tests were done on each sample. To study the interaction mechanisms and structural changes, fluorescence, and Fourier-transform infrared were performed. Oil-in-water emulsions of the complexes were prepared and analyzed for their emulsifying properties (emulsifying activity index and emulsifying stability index), rheological properties and viscosity. Addition of olive leaf extract at higher amounts (1.5 and 2%) enhanced the turbidity, water solubility, antioxidant activity, and foam capacity/stability of protein-polyphenol complexes. Moreover, it was found that non-covalent interactions mainly hydrogen bonds were the main interaction mechanism of sodium caseinate/ olive leaf extract complexes. Surface hydrophobicity of complexes decreased with increasing amount of olive leaf extract. In terms of emulsion formation, the activity and stability increased with increasing the concentration of olive leaf extract. Addition of olive leaf extract also slightly increased the viscosity and viscoelastic parameters (storage and loss modulus).

Olive Leaf Extract Supplementation Combined with Calorie-Restricted Diet on Reducing Body Weight and Fat Mass in Obese Women: Result of a Randomized Control Trial.

The present trial aims to evaluate a supplementation of the olive leaf extract (OLE) in adjunct with a weight loss diet on anthropometric indices, glycemic indices, lipid profile, as well as the level of adipokines, and free fatty acid in obese women. We carried out an 8-week randomized, placebo-controlled, double-blind, parallel-group, clinical trial. The participants were randomly stratified according to age and they were assigned to one of the two study groups: Standard weight loss diet (estimated daily energy requirements minus 500 kcal) + OLE supplementation (n = 35) in intervention group or Standard weight loss diet (estimated daily energy requirements minus 500 kcal) + placebo (n = 35) in placebo group. The study groups were homogeneous regarding the baseline age, height, weight, body mass index (BMI), waist circumferences, married status, and physical activity levels (p > 0.05). The results of analysis of covariance presented significant decreases in BMI, fat mass, and body weight in the OLE group compared to those in the placebo group (p < 0.05). At the end of the study, the serum levels of fasting blood sugar, insulin, low-density lipoprotein cholesterol, total cholesterol, leptin, fatty free acid, and homeostasis model assessment–insulin resistance significantly decreased, and serum levels of high-density lipoprotein cholesterol and adiponectin elevated in the intervention group (p < 0.05). Based on results it seems that the addition of OLE to a hypocaloric diet for 8-week compared with a hypocaloric diet alone may be more effective in modifying obesity and metabolic risk factors.Trial RegistrationIranian Registry of Clinical Trials Identifier: IRCT20190129042552N2

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.

Bio-Based Active Packaging: Carrageenan Film with Olive Leaf Extract for Lamb Meat Preservation.

Carrageenan-based active packaging film was prepared by adding olive leaf extract (OLE) as a bioactive agent to the lamb meat packaging. The OLE was characterized in terms of its phenolic compounds (T.ph), antioxidant activity (AA), oleuropein, and minimum inhibitory concentration (MIC) against Escherichia coli. The film’s formulation consisted of carrageenan, glycerol as a plasticizer, water as a solvent, and OLE. The effects of the OLE on the thickness, water vapor permeability (WVP), tensile strength (TS), elongation at break (EB), elastic modulus (EM), color, solubility, and antimicrobial capacity of the carrageenan film were determined. The OLE had the following excellent characteristics: the T.ph value was 115.96 mgGAE∙g−1 (d.b), the AA was 89.52%, the oleuropein value was 11.59 mg∙g−1, and the MIC was 50 mg∙mL−1. The results showed that the addition of OLE increased the thickness, EB, and WVP, and decreased the TS and EM of the film. The solubility was not significantly affected by the OLE. The color difference with the addition of OLE was 64.72%, which had the benefit of being a barrier to oxidative processes related to light. The film with the OLE was shown to have an antimicrobial capacity during the storage of lamb meat, reducing the count of psychrophiles five-fold when compared to the samples packed by the control and commercial films; therefore, this novel film has the potential to increase the shelf life of lamb meat, and as such, is suitable for use as active packaging.

Acrylamide reduction after phenols addition to Californian-style black olives

A method for reducing the acrylamide formation in Californian-style black olive varieties by the addition of different phenol standards and olive leaf extract (OLE) during the sterilisation and baking process was described. A significant reduction in the acrylamide content (10–13%) of all three olive varieties studied was observed when hydroxytyrosol was added to olives before the sterilisation process. The addition of OLE (1:10 dilution) also reduced the acrylamide formation (35%). An acrylamide inhibition of around 54% occurred when individual phenol standards were added to OLE, mostly hydroxytyrosol. During the baking processes, the maximum acrylamide content was reached when extreme times and temperatures were applied. However, the addition of OLE in brine before thermal sterilisation mitigated the formation of acrylamide by more than twice that of the initial concentration, and the addition of phenols to the olives attenuated the acrylamide reduction by four-fold in both baking treatments. In addition, it was possible to reduce the acrylamide content even further when certain measures were applied in combination with the addition of phenols during the oxidised black olives elaboration process.

Addition of Olive Leaf Extract (OLE) for Producing Fortified Fresh Pasteurized Milk with An Extended Shelf Life.

An olive leaf extract (OLE) has been tested in vitro for its antibacterial activity and ability to inhibit α-glucosidase enzyme. OLE was also evaluated for its potential, when added to pasteurized milk, to preserve nutritional parameters and to limit microbial growth, thus prolonging shelf life. In vitro assays demonstrated a strong antibacterial efficacy of OLE mainly against Bacillus cereus and the capacity to inhibit α-glucosidase enzyme (IC50) when used at 0.2 mg oleuropein/mL. The milk fortification with OLE at 3.6 mg of oleuropein/mL of milk reduced total mesophilic bacteria at undetectable level after 6 d (expiration date) and by 1 log CFU/mL after 10 d. Moreover, OLE addition at 1.44 and 3.6 mg of oleuropein/mL of milk significantly reduced fat and lactose losses up to 10 d. The results motivate the use of the OLE to make a new functional milk with an extended shelf life.

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 1700mg/kg in olive flesh and 3500mg/L in brines olive flesh, whereas in the control fermentation the concentrations were around 900mg/kg and 2500mg/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.

Effects of olive leaf extract addition on fermentative and oxidative processes of table olives and their nutritional properties

An experimental investigation evaluated the possibility of increasing the nutritional value of fermented table olives by adding olive leaf extract (OLE). OLE was added to table olives fermented using indigenous bacteria and yeasts, and a commercial starter (Lactobacillus plantarum strain). Microbiological, physico-chemical, and sensory analyses showed that OLE addition resulted in fermented olives with higher levels of antioxidant, anti-inflammatory, and antimicrobial substances, but did not adversely affect their qualities. Moreover, OLE and the commercial starter functioned synergically against spoilage microorganisms. In addition, fermented olives had higher values of hardness, total phenols, antioxidant activity, hydroxytyrosol, and verbascoside. Nonanal and ethanol contents were lower in fermented olives when Lactobacillus plantarum and OLE were used, indicating lower degrees of oxidation and fermentation. Finally, olives fermented with OLE had a less bitter taste.

Use of olive leaf extract to reduce lipid oxidation of baked snacks

Olive leaves are a waste of the olive oil processing industry and represent a good source of phenolic compounds. The aim of this work was to assess the influence of olive leaf extract (OLE) on lipid oxidation of baked snacks, like breadsticks, made with wheat flour, extra virgin olive oil (EVO), white wine, and salt. Two EVOs having different peroxide value and antioxidant profile (total phenol content, tocopherols, carotenoids, and antioxidant activity) were considered. The snacks were subjected to oven test or stored in the usual conditions of retailer shelves. The obtained data highlighted that EVO plays a key role both for the quality and for the shelf-life of baked snacks and the use of OLE is recommended especially when baked snacks are produced with low quality EVO which therefore does not have a good content of natural antioxidants. The OLE addition significantly reduced the forced oxidative degradation during oven test, as evidenced by a decrease of 27% in oxidation-related volatile compounds and of 42% in triacylglycerol oligopolymers compared to control snacks (CTR) without OLE. Moreover, OLE effectively acted also in normal storage conditions, improving sensory data, induction times, antioxidant activity, and volatile compounds compared to CTR (i.e. hexanal 165.49 vs 38.31 μg g−1 in OLE-added). The amount of oxidation-related volatile compounds showed an opposite trend with the quality level of oil used.