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Article

Fortification of Olive Oil with Herbs and Waste By-Products towards Sustainable Development: Total Antioxidant Capacity, Phenolic Content, and In Vitro Predicted Bioavailability

by
Chrysoula Kaloteraki
1,
Panoraia Bousdouni
1,
Kalliopi Almpounioti
1,
Camille Ouzaid
2,
Olga Papagianni
1,
Fotini Sfikti
1,
Elina Dimitsa
1,
Dimitra Tsami
1,
Anastasia Grammatiki Sarivasilleiou
1,
Haralabos C. Karantonis
3,
Dimitrios Skalkos
4,
Aikaterini Kandyliari
1,5 and
Antonios E. Koutelidakis
1,*
1
Laboratory of Nutrition and Public Health, Unit of Human Nutrition, Department of Food Science and Nutrition, University of the Aegean, 81400 Myrina, Greece
2
Food Science Department, L’Institut Agro Dijon, 21000 Dijon, France
3
Laboratory of Food Chemistry–Technology and Quality of Food of Animal Origin, Department of Food Science and Nutrition, University of the Aegean, 81400 Myrina, Greece
4
Laboratory of Food Chemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece
5
Laboratory of Food Chemistry and Analysis, Department of Food Science and Human Nutrition, Agricultural University of Athens, 11855 Athens, Greece
*
Author to whom correspondence should be addressed.
Appl. Sci. 2023, 13(15), 8876; https://doi.org/10.3390/app13158876
Submission received: 17 July 2023 / Revised: 28 July 2023 / Accepted: 30 July 2023 / Published: 1 August 2023
(This article belongs to the Special Issue New Insights into Natural Antioxidants in Foods: 2nd Edition)
Versions Notes

Abstract

:
Nowadays, there is a high demand in many industrial countries for healthy foods and sustainable products and so to explore innovative food technologies, such as fortification with bioactive compounds such as antioxidants and polyphenols, that may be sourced from herbs or by-products. This study’s objective was to explore the fortification of refined olive oils with natural bioactive compounds such as the herbs rosemary (Rosmarinus officinallis, L.), basil (Ocimum basillicum, L.), sage (Salvia officinalis, L.), lemon balm (Melissa oficinallis, L.), St. John’s wort (Hypericum perforatum, L.), pink savory (Satureja thymbra, L.), dittany (Origanum dictamnus, L.), and by-products such as pomace from olives, olive leaves (Olea europaea, L.), orange peel (Citrus aurantium, L.), lemon peel (Citrus limon, L.), pomegranate peel (Punica granatum, L.), and mandarin peel (Citrus reticulata). The fortification of the refined olive oils was performed with the use of different methodologies such as conventional maceration (CM), incubation shaking maceration (ISM), and ultrasound-assisted maceration (UAM). Folin–Ciocalteau (FOLIN) and Ferric-Reducing Antioxidant Power (FRAP) assays were used to measure their total phenolic content and antioxidant capacity. All methods demonstrated that the temperature, sample concentration, and time of maceration are considered of high importance in the fortification of refined olive oil. In vitro digestion process showed the bioavailability of the antioxidant and phenolic compounds in the fortified olive oil that ranged from 4.84% to 53.11%. Furthermore, the refined olive oils fortified with pomace, basil, St. John’s wort, and pomegranate peel presented the highest antioxidant and phenolic predicted bioavailability indices during the in vitro process compared to the control refined olive oil. Finally, fortification with natural herbs or by-products can be considered an innovative method for the enhancement of the nutritional value of refined olive oils.

1. Introduction

The concept of ‘Mediterranean diet’ was first studied by A. Keys and F. Grande as the traditional dietary pattern found in olive-growing areas of Crete, Greece, and Southern Italy in the late 1950s and early 1960s [1]. General descriptions of Mediterranean diet (MedDiet) are similar amongst studies, emphasizing key components such as olive oil [2]. Olive oil (OO), a vegetable liquid fat obtained from olives (the fruit of Olea europaea), is MedDiet’s principal source of fat, while it is characterized by a high content of monounsaturated fatty acids [3]. In its unsaponifiable fraction, it contains a variety of bioactive compounds, such as antioxidants, associated with its organoleptic characteristics and several health benefits [4].
There are three market categories according to the European Regulations: extra virgin olive oil (EVOO), virgin olive oil (VOO), which both are obtained directly from olives, and refined olive oil (ROO) from oils that have been though a refining process [5].
Due to the different treatment methods of olive oils, quality characteristics vary between categories [6], while refined olive oil presents a decrease in important sensorial and nutritional factors such as aroma, taste, and natural antioxidants and phenolic compared to extra virgin and virgin olive oil [7].
Mediterranean countries yield the highest percentage of olive oil worldwide. However, more than 20% of the olive oil has to become refined to fulfill the regulations and to be appropriate for consumption [8]. The primary reason that extensive amounts of olive oil undergo the refining process is the low quality of the original olive fruit [9]. Nevertheless, the refining process eliminates antioxidant compounds that exist in higher-quality olive oils and, therefore, it limits the antioxidant effect of the end product [10]. Moreover, the lack of antioxidant components, such as phenolic compounds, has negative effects on the oxidative stability of the olive oil [11]. Therefore, a fortification of refined olive oil with antioxidants may present a research interest.
Food fortification has been used to enhance the nutritional value of food products and, consequently, a way to manage micronutrient deficiencies in the general population [12]. Food fortification leads to functional food products, while their consumption is related to the promotion of human health [13]. There are some research nutritional surveys that illustrate the beneficial role of functional foods towards human health due to the enhancement with antioxidants and polyphenols. However, there is a quite significant limitation of the foods that could be considered suitable to fortify because of high costs and/or minor quality of the texture and taste of the product. In addition, consumer acceptance of functional foods equals their knowledge towards healthy ingredients in fortified products (i.e., yogurt with pomegranate extract) and that leads to healthier food choices [13].
Furthermore, natural antioxidants can be considered the antioxidants that derive from herbs, fruits, and vegetables. Those have been preferred by consumers the most [14,15]. During food processing, there is a huge waste of fruits and vegetables that is thrown away, such as seeds, peels, etc. Many recent studies report that these by-products consist of high nutritional value due to natural bioactive compounds such as polyphenols, antioxidants, tannins, etc. [16,17]. Therefore, they have been used by the food industry to enrich conventional foods and develop innovative food products [18,19].
Other antioxidant sources can be considered the different parts of the plants such as roots, leaves, and stems, which are rich in polyphenols and flavonoids and have been used as food additives [20]. Other sources that have been used in food fortification are the herbal extracts, although with limited applications due to their strong sensorial characteristics [21]. Nevertheless, the food industry is steadily increasing their use, and finding better ways of isolating and incorporating bioactive compounds from herbal extracts is part of ongoing research [22].
The purpose of the present study was to investigate the different methods for the fortification of refined olive oils with herbs and by-products in order to increase their content in antioxidants and polyphenols. More specifically, rosemary, basil, sage, lemon balm, St. John’s wort, pink savory, dittany, pomace, olive leaves, orange peel, lemon peel, pomegranate peel, and mandarin peel were used to fortify the refined olive oil. The enhanced olive oil extracts were obtained by ultrasound-assisted maceration, incubator-assisted maceration, and conventional maceration and evaluated for their total antioxidant activity and total phenolic content. The predicted bioavailability of their bioactive compounds was also determined after performing in vitro digestion analysis.

2. Materials and Methods

2.1. Chemicals

Chemicals were attained from Sigma-Aldrich (St. Louis, MO, USA) and Merck Chemicals (Darmstadt, Germany).

2.2. Sample Collection and Preparation

Herbs and plant by-products were obtained from Lemnos Island, in the North Aegean, Greece, between November of 2021 and February of 2022. The samples included rosemary (Rosmarinus officinallis, L.), basil (Ocimum basillicum, L.), sage (Salvia officinalis, L.), lemon balm (Melissa oficinallis, L.), St. John’s wort (Hypericum perforatum, L.), pink savory (Satureja Thymbra, L.), dittany (Origanum dictamnus, L.), and by-products such as pomace from olives, olive leaves (Olea europaea, L.), orange peel (Citrus aurantium, L.), lemon peel (Citrus limon, L.), pomegranate peel (Punica granatum, L.), and mandarin peel (Citrus reticulata). All collected samples were dried in a heating oven (Binder GmbH, Tuttlingen, Germany) at 60 °C for 48 h and stored in airtight bags at dark conditions till further analysis [23].
As for the fortification procedure, refined olive oil was purchased from a local certified producer from Lemnos, Greece (Sousalis, Lemnos, Greece). Extra virgin and virgin olive oil that was used for the phenolic content analysis was purchased also from the same producer from Lesvos, Greece (AES Stypsis, Lesvos, Greece).
Three different methods, as described in Table 1, were applied for the fortification of the refined olive oil: conventional maceration (CM), incubator shaking maceration (ISM), and ultrasound-assisted maceration (UAM).

2.2.1. Conventional Maceration (CM)

Conventional maceration was achieved according to the method reported by Caporaso et al., with some minor adjustments regarding the quantity of the herbs and maceration time [24]. Samples were prepared in 250 mL Erlenmeyer flasks using either 2.5 g or 5 g of the dried sample in 30 g of refined olive oil. They were retained at 15 and 30 days of maceration in the dark at room temperature (37 ± 2 °C). Then, the samples were filtered and 2 g of enriched olive oil was analyzed the same day.

2.2.2. Incubator Shaking Maceration (ISM)

The incubator shaking maceration process was completed according to Karoui et al. methodology with some minor changes. This referred to the quantity of the herbs, the incubation time, and the temperature of the method [25]. Dried samples of 1 g, 2 g, or 3 g were applicable for the fortification of 30 g of refined olive oil in glass Duran bottles. Each bottle was then located in the incubator (SKI-4, China) and the temperature was set at 37 °C. Each bottle remained in the incubator for either 1 h, 2 h, or 3 h. Then, each of the above samples was filtered and analyzed in duplicate the same day.

2.2.3. Ultrasound-Assisted Maceration (UAM)

Samples were prepared in 250 mL glass bottles using either 1.5 g or 3 g of the dried samples per 30 g of refined olive oil. Each bottle was then allocated in an ultrasound water bath (Elmasonic P 70 H, Elma-Hans Schmidbauer GmbH & Co., Singen, Germany) for 30 or 60 min at 30 °C or 40 °C. Each extraction process was performed in duplicate. All of the above produced samples were then filtered and analyzed on the same day.

2.3. Sample Extract Analysis

2.3.1. Preparation of Sample for Antioxidant and Phenolic Analysis

The polar fraction of the sample extracts was modified according to Soares et al. [24], with some alterations. Briefly, 5 mL of methanol/water (40:10 v/v) was added to 2 g of oil sample and vortexed for 1 min. The mixtures were then placed in the ultrasound water bath (Elma Elmasonic P 70H Type Elma-Hans Schmidbauer GmbH & Co., Singen, Germany) for 15 min at room temperature. Then, the samples were centrifuged for 25 min at 4000× g (OHAUS model: FC5718R, Germany).

2.3.2. Total Phenolic Content by Folin–Ciocalteau Assay

Folin–Ciocalteau method determined the total phenolic content of the samples. This assay calculates the reductive capacity of the Folin–Ciocalteau reagent. A total of 100 μL of Folin–Ciocalteau reagent and 20 μL of the extracted oil were placed in 96-well plates and the absorbance was measured at 765 nm with a spectrophotometer (SPARK, TECAN, Switzerland) [25]. Tal phenolic content was described by a standard gallic acid (GAE) curve and the results were expressed in mg GAE per L of dried food sample and implemented in triplicate.

2.3.3. Total Antioxidant Activity by Ferric-Reducing Antioxidant Power Assay

Ferric-reducing antioxidant power (FRAP) assay was applied to evaluate the total antioxidant capacity. FRAP assay is based on the alteration of the TPTZ-Fe+3 to TPTZ-Fe2+. In total, 50 μL of Fe2+, 20 μL of TPTZ solution, and 20 μL of sample extract were placed in 96-well plates. The absorbance was measured at 595 nm with a spectrophotometer (SPARK, TECAN, Switzerland). The total antioxidant capacity was determined with the use of a standard FeSO4 curve and the results were deliberated in mmol of Fe2+ per L of sample extract in triplicate [26,27,28,29,30].

2.4. In Vitro Gastrointestinal Analysis

The in vitro assay was attained to stimulate the gastrointestinal digestion process and to estimate the predicted bioavailability of antioxidants and polyphenols. The methodology followed was as described by Kapsokefalou et al., with some modifications [31]. In more detail, 2 mL from each extract was allocated into 6-well plates along with 0.1 mL of human pepsin. The samples were placed in a shaking incubator (Shaking Incubator SKI-4, China) for 2 h at 37 °C. At the end of the incubation, a dialysis membrane was placed in each well and piperazine-N,N′-bis(2-ethanesulfonic acid) (PIPES) buffer reagent and the pH was adjusted to 6.3. Then, the samples were allocated in the shaking incubator (1 h, 37 °C) and a mixture of pancreatin and bile salts (0.5 mL) was added in each well and 2h of incubation was performed at 37 °C. The supernatant (fraction above the dialysis membrane) was centrifuged at 5000× g for 15 min at 4 °C. FRAP and Folin–Ciocalteau assays determined the total antioxidant capacity and phenolic content as described above.

2.5. Statistical Analysis

Statistical analysis was conducted using SPSS 21.0 software (SPSS Inc., Chicago, IL, USA). To test for normality in continuous variables, a Shapiro–Wilk test was implemented (p < 0.05). The total antioxidant capacity and total phenolic content of the fortified olive oil samples are expressed as mean ± standard deviation (SD). A three-way factorial ANOVA was conducted to investigate the differences between the maceration conditions in the phenolic and antioxidant content of the enriched refined olive oils for each method. A least significant difference (LSD) test was completed to detect significant differences between the samples (p < 0.05). To determine any correlations of antioxidant capacity and polyphenols before and after in vitro digestion process, a Pearson’s correlation test was used.

3. Results

3.1. Refined Olive Oil

Total phenolic content and antioxidant capacity of three selected olive oils (virgin, extra virgin, and refined) are presented in the following table (Table 2).
Extra virgin olive oil presented higher values of total antioxidant capacity and phenolic content, followed by virgin olive oil, while refined olive oil presented the lowest values (p < 0.05).

3.2. Conventional Maceration (CM)

Table 3 and Table 4 present the total phenolic content and antioxidant capacity values of the fortified refined olive oils using conventional maceration at 15 and 30 days between the two different quantities (2.5 g and 5 g).
The above fortified refined olive oils that resulted from the conventional maceration showed an increased phenolic content in comparison with the nonfortified refined olive oil, which was set as a control, with the average values ranging from 13.13 ± 3.84 mg GAE/L to 55.06 ± 8.99 mg GAE/L. The highest phenolic content in all conditions for the CM was demonstrated by the fortified refined olive oil with pink savory, with values ranging from 44.60 ± 11.39 mg GAE/L to 55.06 ± 8.99 mg GAE/L, with the highest value at 5 g concentration of herb for the 15 days. The lowest content was observed in pomace, ranging from 13.13 ± 3.84 mg GAE/L to 16.82 ± 5.85 mg GAE/L, with the lowest value at 2.5 g concentration for the 15 days. More specifically, lemon peel presented significant values of phenolic content at 15 days instead of 30 days at 2 g compared to 5 g. Other samples that showed significant differences in the phenolic content compared to either the 15 days and/or the 30 days are the following: rosemary, sage, lemon peel, dittany, and olive leaves (p < 0.05). Only pomegranate peel showed a decrease in the phenolic content when analyzed on the 30 days (16.96 ± 1.27, and 18.16 ± 1.81 mg GAE/L) instead of the 15 days (16.57 ± 1.03, and 15.49 ± 2.41 mg GAE/L).
Table 4 summarizes the total antioxidant capacity values that resulted from the CM extraction that ranged from 0.28 ± 0.01 mmol Fe2+/L to 1.63 ± 0.07 mmol Fe2+/L. The highest total antioxidant values are consistently displayed by the refined olive oil fortified with sage, with values ranging from 0.89 ± 0.30 mmol Fe2+/L to 1.63 ± 0.07 mmol Fe2+/L, with the highest antioxidant capacity at 5 g concentration at the 30 days extraction period. Other samples with relatively high antioxidant values and significant differences between the day period of extraction are the following: basil, sage, pomegranate peel, dittany, pink savory, and St. John’s wort (p < 0.05). Alternatively, those fortified with pomace and olive leaves have relatively low total antioxidant content, with values generally below 0.35 ± 0.01 mmol Fe2+/L. More specifically, lemon peel showed non-significant changes in the antioxidant capacity compared to different days of extraction in all quantities. Moreover, rosemary, orange peel, lemon peel, olive leaves, and pomace fortified refined olive oils showed non-significant changes (p > 0.05) between the different conditions, while those enriched with lemon balm, dittany, and sage demonstrate a stronger correlation (p < 0.01).

3.3. Incubation Shaking Maceration (ISM)

Different quantities (1, 2 and 3 g) of the seven herbs and six plant by-products were used to fortify refined olive oils using an incubator shaking method for three different time durations (60, 120, and 180 min) in a temperature of 37 °C. Table 5 demonstrates the total phenolic content of the enriched refined olive oil using the incubation method.
From the 13 samples, the highest phenolic content was detected in the refined olive oil enriched with St. John’s wort ranging from 26.49 ± 1.46 mg GAE/L to 42.66 ± 12.85 mg GAE/L, while the lowest was demonstrated by the pomegranate peel and lemon peel enriched olive oils with values ranging from 9.06 ± 1.14 mg GAE/L to 15.59 ± 2.48 mg GAE/L and 9.94 ± 1.41 mg GAE/L to 13.19 ± 1.8 mg GAE/L, respectively.
The sample concentration did not significantly affect the total phenolic content for the following fortified olive oils: rosemary, basil, orange peel, lemon peel, lemon balm, pomegranate peel, pink savory, and pomace (p > 0.05). The total phenolic content of the refined olive oil fortified with sage presented a significant difference at 3 g (p < 0.01). The refined olive oils fortified with St. John’s wort and mandarin peel presented high values of antioxidant capacity between 1 and 2 g of sample (p < 0.05), while the refined oil enriched with olive leaves displayed a significant difference at the concentration of 3 g (p < 0.05).
In Table 6, among the studied samples, the sage-enriched refined olive oil displayed the highest total antioxidant capacity, with significant differences at all time points and concentrations, with values ranging from 0.51 ± 0.06 mmol Fe2+/L to 1.28 ± 0.20 mmol Fe2+/L (p < 0.05). The lowest total antioxidant value was presented in the olive oil enriched with mandarin at the sample concentration of 1 g at the 60 min duration, with a mean value of 0.19 ± 0.02 mmol Fe2+/L.
In general, the refined olive oils enriched with mandarin peel, orange peel, and olive leaves showed the lowest total antioxidant values amongst the time durations and concentrations. The total antioxidant levels did not significantly differ compared to the g of the following samples: rosemary, basil, orange peel, lemon peel, pomegranate peel, dittany, and pink savory (p > 0.05). On the other hand, the g of the following food samples: sage, olive leaves, lemon balm, St. John’s Wort, and mandarin peel showed a significant difference in their antioxidant capacity (p < 0.05). Moreover, St. John’s Wort displayed the least statistical differences in its antioxidant capacity between all g of sample used (p < 0.05). It is noticeable that some samples increase total phenolic content and antioxidant capacity by increasing the mass, because some herbs and by-products are sensitive during extraction in longer times and high temperature conditions during extraction [32]. The longer a sample is extracted in the refined olive oil during incubation time, the more mass is required to release the natural bioactive compounds in the refined olive oil. For that reason, different masses and time periods have been chosen for the extraction of fortified olive oil.

3.4. Ultrasound-Assisted Maceration (UAM)

Different quantities (P2: 1.5 and 3 g) of seven herbs and six plant by-products were used to enrich refined olive oils using an ultrasound-assisted method for 30 and 60 min (P1) in temperatures of 30 °C and 40 °C (P3). The total phenolic contents and antioxidant capacity of the enriched refined olive oils with different time, quantity, and temperature are displayed in Table 7 and Table 8.
The refined olive oil fortified with basil displayed the highest total phenolic content when extracted at 30 min period in 30 °C, with a value of with a value of 58.15 ± 39.34 mg GAE/L (p < 0.01 and p < 0.05). Orange peel presented the most significant levels of phenolic content in the refined olive oil when extracted at all different conditions, with a p < 0.001. On the other hand, mandarin peel demonstrated the lowest total phenolic content, with a value of 0.11 ± 0.04 mg GAE/L at two different conditions: 30 min, 3 g, 40 °C, and 60 min, 3 g, 30 °C (non-significant). Furthermore, the refined olive oils enriched with sage and pink savory displayed significant levels when extracted in 1.5 g (p < 0.05, p < 0.01). Lemon peel and pomegranate peel, when extracted from refined olive oil at 40 °C for 30 min, presented significant phenolic values in the refined olive oil (p < 0.001, p < 0.01). Although, those fortified with dittany, pomace, olive leaves, and St. John’s wort presented non-significant values compared to the rest of the samples.
The fortified refined olive oil fortified with sage demonstrated the highest total antioxidant capacity and significant differences at all conditions and time intervals, with values ranging from 0.63 ± 0.10 mmol Fe2+/L to 1.69 ± 0.07 mmol Fe2+/L (p < 0.01, p < 0.05). The highest value was observed at the 1.5 g, 60 min duration and 40 °C (p < 0.001). The refined olive oils fortified with orange peel also showed relatively higher values regarding their antioxidant content and significant differences between all conditions (p < 0.05).
Some fortified refined olive oils that demonstrated higher phenolic content also showed high total antioxidant capacity, such as sage (from 0.63 ± 0.10 to 1.69 ± 0.07 mmol Fe2+/L) and pomegranate peel (from 0.43 ± 0.03 to 1.37 ± 0.15 mmol Fe2+/L (p < 0.05)).
It is important to mention that dittany extraction could not be performed in 3 g of the plant in the refined oil because the herb absorbed the larger quantity of the oil.

3.5. Evaluation of Total Antioxidant and Phenolic Content of Fortified Olive Oil Prior to and after In Vitro Digestion Process

In vitro digestion analysis was conducted for the fortified refined olive oil samples that presented among the highest amounts of total phenolic content and antioxidant capacity, as well as valuable sensory factors such as aroma, color, and texture during the extraction process.
The extraction process that was followed for each one of them was the following: orange peel, pomace, and St. John’s Wort were extracted by ultrasound-assisted maceration (40 °C, and 30 °C for 30 min). Pomegranate peel and basil were extracted by conventional maceration (30 days).
The different fortified olive oils with selected plant by-products and herbs, before and after in vitro digestion simulation, are presented in Table 9.
The average values of the total antioxidant capacity before digestion of the extracts varied from 0.32 ± 0.08 to 1.25 ± 0.09 mmol Fe2+/L. Olive oil that has been fortified with pomegranate peel showed the highest antioxidant capacity, followed by orange peel (1.24 ± 0.24 mmol Fe2+/L), with a non-significant difference (p > 0.05). The values for basil, St. John’s wort, and pomace are considered lower, with mean values of 0.42 ± 0.03 mmol Fe2+/L, 0.32 ± 0.08 mmol Fe2+/L, and 0.37 ± 0.05 mmol Fe2+/L, respectively. The total antioxidant capacity values range from 0.06 to 0.11 mmol Fe2+/L after digestion. Regarding the predicted bioavailability of total antioxidant capacity of the selected extracts, the refined olive oil enriched with pomace has the highest bioavailability (29.7%), followed by St. John’s wort (21.9%) and basil (21.4%), while those with the lowest bioavailability were orange peel and pomegranate peel, with 4.8% and 6.4%, respectively. The mean values of total phenolic content before digestion varied significantly (p < 0.05) from 17.38 to 64.35 mg GA/L. Orange peel has the highest phenolic content, followed by basil, with a non-significant difference. The values for pomegranate, pomace, and St. John’s wort were observed to be lower, with 42.31 ± 4.77, 20.27 ± 4.86 and 17.38 ± 8.59 mg GAE/L, respectively. After in vitro digestion process, the total phenolic content ranged from 9.23 ± 8.47 to 20.95 ± 13.93 mg GAE/L. St. John’s wort displayed the highest predicted bioavailability (53.1%), followed by pomegranate peel (49.5%) and pomace (48.6%), while orange peel (20.6%) and basil (19.4%) presented the lowest predicted bioavailability.
Regarding correlations between the samples before and after in vitro digestion experimental process, four samples (refined olive oils fortified with orange peel, pomegranate peel, pomace, and basil) suggest a significant correlation (p < 0.05), while Saint John’s wort illustrates significant correlation at the 0.001 level. As for the phenolic concentration, pomace displayed a significant correlation (p < 0.05), while pomegranate peel and basil presented a significant correlation at 0.01 level.

4. Discussion

The study of the antioxidant effects of bioactive compounds is supported by the current interest in natural products and the ongoing replacement of synthetic antioxidants with natural antioxidants from plant sources [33]. Numerous studies regarding food fortification with herbs and by-products, as well as the contribution of bioactive compounds to human health, have been conducted in recent years [25]. Refined olive oil is a food product that, due to the refining process, has much lower content of natural bioactive compounds such as polyphenols and antioxidants compared to other types of olive oils such as EVOO/VOO [34]. Although refined olive oil has a lower nutritional value, it is regularly consumed by a large part of the global population due to its low cost [30]. Hence, it can be used as a food matrix for food fortification. However, there is limited research in refined olive oil fortification compared to virgin/extra virgin enrichment [27].
In the food industry, the most used methods for fortifying olive oil are conventional maceration, followed by incubation shaking and ultrasound-assisted maceration with different extraction duration, as this can play an important role in oils’ fortification [35,36,37]. Therefore, our study aims to explore the most suitable extraction method amongst conventional, incubation-assisted maceration and ultrasound-assisted maceration for the fortification of refined olive oil with different herbs and by-products [37].
The present study showed that the conventional maceration, incubation-assisted, and ultrasound-assisted maceration water baths can be used for the fortification of refined olive oil with compounds rich in antioxidants and polyphenols. Nevertheless, it depends on the herb and/or plant by-product used in the fortification process to determine which method can be assumed as suitable for antioxidant and phenolic content enhancement. Our study results showed that refined olive oil fortified with pink savory, sage, basil, St. John’s wort, pomegranate, lemon, and orange peel extract presented the highest total antioxidant capacity and polyphenolic content among all three methods, comparable to the total antioxidant capacity and polyphenolic content of virgin and extra virgin olive oil studied. Yet, in each enrichment method used, there were observed differences in the antioxidant and phenolic content of the fortified refined olive oil as presented in detail below.
Conventional maceration has been mainly used in the food industry, as it is a technologically simple low-cost method [36]. Olive oil by-products have been examined as a protentional way of fortifying olive oil, using conventional maceration methods. Olive leaves have been used for the fortification of olive oil, using conventional maceration in different concentrations between 1 and 10% for 7 days, and the fortified final products presented a higher percentage of phenolic components compared to the unfortified samples [37]. A comparable study examined the fortification of refined olive oil with olive leaves, using conventional maceration for 5 days, and the phenolic content was significantly improved in the final fortified product [30]. Moreover, similar results were obtained in the study of Issaoui et al. [38], which utilized dry lemon in various concentrations to enrich olive oil (virgin (VOO) and refined olive oil (ROO)) by conventional maceration for a 2-month duration at room temperature. In contrast, Ayadi et al. [39] observed a decreased phenolic capacity when utilizing dry lemon zest instead of dried lemon at 5% concentration for 15 days duration at room temperature. This result of conventional maceration does not confirm our findings regarding lemon peel but this may be expected due to variations between different cultivars of the samples. Furthermore, similar results were presented by Khemakhem et al. [40], who performed a conventional maceration of 10 days’ duration to enrich olive oil with fresh instead of dried orange peel in the same concentration of 5%w/w.
In the case of the conventional maceration methods for oil fortification with bioactive compounds from herbs, there is a large field of research on extra virgin and virgin olive oil, while research on refined olive oil is limited [41]. Nevado et al., [42], Ayadi et al., [39], and Kasimoglu et al. [43] performed a conventional maceration on virgin olive oil by enriching it with a 5% dry sample for a duration of 10 and 15 days. The first observed an increase in the total antioxidant activity of the enriched olive oil, while the second observed a decrease in the phenolic capacity. Moreover, Ayadi et al. [39] used 5% and 15%w/w concentration of dry basil to enrich EVOO by conventional maceration at room temperature for 15 days with no phenolic increase in both concentrations. The results of the present study illustrated that refined olive oil fortification with 8% and 17% of dry basil resulted in an increased phenolic content in both the 15 and 30 day period during conventional maceration [39].
Regarding the incubator shaking maceration, there are not many studies that followed the same methodology for olive oil fortification with herbs or by-products. In the present study, it was presented that the phenolic content of most fortified refined oils with herbs and by-products was increased, while basil, sage, dittany, pomace, olive leaves, orange, and mandarin peel showed significant antioxidant capacity levels in all concentrations and times of extraction. According to literature data, Penalvo et al. [44] performed a similar shaking process to fortify virgin olive oil with oregano and the findings towards phenolic content agree with our findings when performing the incubator maceration method derived with our findings. Therefore, this method has promising results that may benefit from more research on fortifying olive oils using an incubator-assisted maceration.
In addition, the present study examined the ultrasound-assisted extraction maceration by using different times, temperatures, and concentrations of the herbs and by-products, presenting significant results towards antioxidant capacity and polyphenolic content to the refined olive oil. Different temperatures (30 °C/40 °C) and concentrations (5% w/w and 10% w/w) of the sample during the extraction process did not play an important role in enriching the antioxidant capacity of the refined oil. As for the phenolic content of fortified refined oil, there are some noticeable results. Lemon balm, St. John’s wort, and mandarin peel presented lower values during the ultrasound-assisted maceration process. This resulted because ultrasonic power plays an important role in phenolic degradation along with temperature conditions. The low observation of the total phenolic content of the above-mentioned samples is in line with the results of similar studies [45,46]. Additionally, refined olive oil with sage, lemon, and orange peel presented the highest content among others in 10% w/w concentration at all time periods and temperature conditions. Some differences observed comparing the above results with other studies: Japon-Lujan et al. [47] used an ultrasound-assisted maceration, with a 10% w/w concentration of dry olive leaves for 20 min at room temperature of ultrasound-assisted maceration, that eventually resulted in increased phenolic contents. This could compare with the study by Achat et al. [48], which also used olive leaves to fortify olive oil by ultrasound-assisted maceration for 45 min at 16 °C, presenting an increased final phenolic content. The above results also align with those outcomes since an increase in both phenolic content and antioxidant capacity was observed in refined olive oil with olive leaves using an ultrasound-assisted method in all conditions. However, for both measurements, all parameters presented non-significant differences, which may mean that either the sample used is not ideal for this extraction method, or that the method itself is not as effective for this specific purpose.
Following the in vitro gastrointestinal simulation, the values of total phenolic content and antioxidant capacity significantly decreased. The predicted bioavailability of polyphenols was found to vary among the selected samples, with refined olive oil enriched with pomace having the highest bioavailability, followed by St. John’s wort (53.11%), and basil the lowest (19.42%). Meanwhile, refined olive oil with orange peel (4.84%) and pomegranate peel (6.40%) presented the lowest predicted antioxidant bioavailability. These findings could be suggested as promising compared to other studies that have shown the importance of fortifying olive oils with polyphenols. More specifically, Alberdi-Cedeño J. et al. [49] presented that the enrichment of olive oil with phenolic bioactive compounds can increase the in vitro bioavailability and bioaccessibility of olive oil’s main components that could be absorbed from the intestinal wall.
Finally, the three extraction methods examined led to an increase in the total phenolic content and antioxidant capacity of the studied samples. Each herb and by-product showed different optimal extraction conditions. This leads to the conclusion that each proposed enrichment sample must be examined individually to identify the conditions under which it will achieve the optimum enrichment yield. In the present study, a wide range of samples were examined, which provides valuable information for the research community; however, further studies are needed to improve our knowledge of the behavior of the proposed enrichment samples as well as their phenolic and antioxidant profile. Moreover, further studies are needed to accurately identify whether the refined olive oil fortification with natural bioactive components can have beneficial aspects towards health, especially interventional human studies for the bioactivity and bioavailability of the bioactive compounds. Moreover, consumer preferences and organoleptic sensory tests of enriched refined olive oils are considered important to understand consumers’ acceptance over the proposed products.
The study has several limitations. One limitation of the study is the use of only one method for the measure of total antioxidant capacity (FRAP method). Extra methods, such as ORAC, DPPH, and ABTS, could be also used. Moreover, the determination of the profile of the phenolic compounds into the fortified olive oil, by using GC-MS or HPLC, would be important as further future analysis. One more limitation of the study is the temperature of 60 °C for the drying of plant material that possibly led to evaporation of an amount of the natural compounds.

5. Conclusions

Concluding, the fortification of refined olive oil with herbs and by-products using different enrichment methods could lead to the creation of novel, possibly functional products rich in antioxidants and polyphenols that may be a competitive addition to the agri-food sector, with parallel promotion of sustainable development. In the current study, different methodologies (conventional, incubation-assisted shaking maceration, and ultrasound-assisted maceration) were used to enhance refined olive oils that were then evaluated for their antioxidant capacity and phenolic content. All methods showed that different parameters such as time of maceration, temperature, and sample concentration play an important role during the extraction procedure of fortified olive oil with herbs and by-products. To be more specific, from the above results, it is noticeable that the refined olive oil fortified with pomace, pink savory, basil, St. John’s wort, pomegranate, mandarin, lemon, and orange peel presented the highest antioxidant and phenolic predicted bioavailability values during extraction in most of the methods used. For that reason, those samples are proposed for further research in the refined olive oil fortification sector. Although, there are some limitations of the study, since only two assays were used for measuring the total phenolic content and antioxidant capacity (Folin and FRAP), so it is recommended that more research with other assays should be conducted. To be more explicit, ORAC, DPPH, HPLC, and GC-MS are recommended to be performed to have a more accurate and reliable view of the above-mentioned fortified refined olive oils. Concluding, even if the data are promising, future research on different variations of the fortified olive oils should be examined to evaluate organoleptic characteristics and consumer preferences for these products, while nutritional interventional studies are needed for investigation of their possible effects on human health.

Author Contributions

Conceptualization, C.K., H.C.K., A.K. and A.E.K.; Data curation, P.B. and C.O.; Funding acquisition, D.S. and A.E.K.; Investigation, C.K., P.B., K.A., C.O., O.P., F.S. and A.G.S.; Methodology, C.K., K.A., C.O., O.P., F.S., E.D., D.T., A.G.S. and A.K.; Project administration, D.S. and A.E.K.; Resources, C.K., K.A., C.O., O.P., F.S., E.D., D.T., A.G.S. and D.S.; Software, C.K. and K.A.; Supervision, A.K. and A.E.K.; Validation, P.B., O.P., E.D., D.T., H.C.K., A.K. and A.E.K.; Visualization, H.C.K., A.K. and A.E.K.; Writing—original draft, C.K., P.B. and H.C.K.; Writing—review and editing, A.K. and A.E.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research received partial funding by the “BIOOLIVEPLUS” ERDF-North Aegean region funded program 2014–2020 (BAP2-0062094) of the OLIVE OIL COOPERATIVE STIPSIS LESVOS.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data is viable from the authors into the manuscript.

Acknowledgments

The authors would like to thank the OLIVE OIL COOPERATIVE SPIPSIS LESVOS for the supply of the olive oil used in the study.

Conflicts of Interest

There is no conflict of interest to declare.

References

  1. Keys, A.; Grande, F. Role of Dietary Fat in Human Nutrition. Am. J. Public Health 1957, 47, 1520–1530. [Google Scholar] [CrossRef]
  2. Davis, C.; Bryan, J.; Hodgson, J.; Murphy, K. Definition of the Mediterranean Diet; A Literature Review. Nutrients 2015, 7, 9139–9153. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  3. Wahrburg, U.; Kratz, M.; Cullen, P. Mediterranean Diet, Olive Oil and Health. Eur. J. Lipid Sci. Technol. 2002, 104, 698–705. [Google Scholar] [CrossRef]
  4. Servili, M.; Esposto, S.; Fabiani, R.; Urbani, S.; Taticchi, A.; Mariucci, F.; Selvaggini, R.; Montedoro, G.F. Phenolic Compounds in Olive Oil: Antioxidant, Health and Organoleptic Activities According to Their Chemical Structure. Inflammopharmacol 2009, 17, 76–84. [Google Scholar] [CrossRef]
  5. UK Government. Commission Implementing Regulation (EU) No 29/2012 of 13 January 2012 on Marketing Standards for Olive Oil (Codification). Volume 12. 2012. Available online: https://www.legislation.gov.uk/eur/2012/29/contents (accessed on 16 July 2023).
  6. Boskou, D.; Blekas, G.; Tsimidou, M. 4—Olive Oil Composition. In Olive Oil, 2nd ed.; Boskou, D., Ed.; Elsevier: Amsterdam, The Netherlands; AOCS Press: Champaign, IL, USA, 2006; pp. 41–72. ISBN 978-1-893997-88-2. [Google Scholar]
  7. Foscolou, A.; Critselis, E.; Panagiotakos, D. Olive Oil Consumption and Human Health: A Narrative Review. Maturitas 2018, 118, 60–66. [Google Scholar] [CrossRef] [PubMed]
  8. Lucci, P.; Bertoz, V.; Pacetti, D.; Moret, S.; Conte, L. Effect of the Refining Process on Total Hydroxytyrosol, Tyrosol, and Tocopherol Contents of Olive Oil. Foods 2020, 9, 292. [Google Scholar] [CrossRef] [Green Version]
  9. Kiritsakis, A.; Markakis, P. Olive Oil: A Review. In Advances in Food Research; Chichester, C.O., Mrak, E.M., Schweigert, B.S., Eds.; Academic Press: Cambridge, MA, USA, 1988; Volume 31, pp. 453–482. [Google Scholar]
  10. Papadopoulos, G.; Boskou, D. Antioxidant Effect of Natural Phenols on Olive Oil. J. Am. Oil Chem. Soc. 1991, 68, 669–671. [Google Scholar] [CrossRef]
  11. Bouaziz, M.; Feki, I.; Ayadi, M.; Jemai, H.; Sayadi, S. Stability of Refined Olive Oil and Olive-Pomace Oil Added by Phenolic Compounds from Olive Leaves. Eur. J. Lipid Sci. Technol. 2010, 112, 894–905. [Google Scholar] [CrossRef]
  12. Chadare, F.J.; Idohou, R.; Nago, E.; Affonfere, M.; Agossadou, J.; Fassinou, T.K.; Kénou, C.; Honfo, S.; Azokpota, P.; Linnemann, A.R.; et al. Conventional and Food-to-Food Fortification: An Appraisal of Past Practices and Lessons Learned. Food Sci. Nutr. 2019, 7, 2781–2795. [Google Scholar] [CrossRef] [Green Version]
  13. Siró, I.; Kápolna, E.; Kápolna, B.; Lugasi, A. Functional Food. Product Development, Marketing and Consumer Acceptance—A Review. Appetite 2008, 51, 456–467. [Google Scholar] [CrossRef]
  14. Dimitrios, B. Sources of Natural Phenolic Antioxidants. Trends Food Sci. Technol. 2006, 17, 505–512. [Google Scholar] [CrossRef]
  15. Pollard, J.; Greenwood, D.; Kirk, S.; Cade, J. Motivations for Fruit and Vegetable Consumption in the UK Women’s Cohort Study. Public Health Nutr. 2002, 5, 479–486. [Google Scholar] [CrossRef]
  16. Bhardwaj, K.; Najda, A.; Sharma, R.; Nurzyńska-Wierdak, R.; Dhanjal, D.S.; Sharma, R.; Manickam, S.; Kabra, A.; Kuča, K.; Bhardwaj, P. Fruit and Vegetable Peel-Enriched Functional Foods: Potential Avenues and Health Perspectives. Evid.-Based Complement. Altern. Med. 2022, 2022, 8543881. [Google Scholar] [CrossRef] [PubMed]
  17. Rifna, E.J.; Misra, N.N.; Dwivedi, M. Recent Advances in Extraction Technologies for Recovery of Bioactive Compounds Derived from Fruit and Vegetable Waste Peels: A Review. Crit. Rev. Food Sci. Nutr. 2023, 63, 719–752. [Google Scholar] [CrossRef]
  18. Sagar, N.A.; Pareek, S.; Sharma, S.; Yahia, E.M.; Lobo, M.G. Fruit and Vegetable Waste: Bioactive Compounds, Their Extraction, and Possible Utilization. Compr. Rev. Food Sci. Food Saf. 2018, 17, 512–531. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  19. Kumar, H.; Bhardwaj, K.; Sharma, R.; Nepovimova, E.; Kuča, K.; Dhanjal, D.S.; Verma, R.; Bhardwaj, P.; Sharma, S.; Kumar, D. Fruit and Vegetable Peels: Utilization of High Value Horticultural Waste in Novel Industrial Applications. Molecules 2020, 25, 2812. [Google Scholar] [CrossRef]
  20. Ortega-Ramirez, L.A.; Rodriguez-Garcia, I.; Leyva, J.M.; Cruz-Valenzuela, M.R.; Silva-Espinoza, B.A.; Gonzalez-Aguilar, G.A.; Siddiqui, M.W.; Ayala-Zavala, J.F. Potential of Medicinal Plants as Antimicrobial and Antioxidant Agents in Food Industry: A Hypothesis. J. Food Sci. 2014, 79, R129–R137. [Google Scholar] [CrossRef] [PubMed]
  21. Lourenço, S.C.; Moldão-Martins, M.; Alves, V.D. Antioxidants of Natural Plant Origins: From Sources to Food Industry Applications. Molecules 2019, 24, 4132. [Google Scholar] [CrossRef] [Green Version]
  22. Embuscado, M.E. Spices and Herbs: Natural Sources of Antioxidants—A Mini Review. J. Funct. Foods 2015, 18, 811–819. [Google Scholar] [CrossRef]
  23. Kandyliari, A.; Potsaki, P.; Bousdouni, P.; Kaloteraki, C.; Christofilea, M.; Almpounioti, K.; Moutsou, A.; Fasoulis, C.K.; Polychronis, L.V.; Gkalpinos, V.K.; et al. Development of Dairy Products Fortified with Plant Extracts: Antioxidant and Phenolic Content Characterization. Antioxidants 2023, 12, 500. [Google Scholar] [CrossRef]
  24. Soares, V.P.; Fagundes, M.B.; Guerra, D.R.; Leães, Y.S.V.; Speroni, C.S.; Robalo, S.S.; Emanuelli, T.; Cichoski, A.J.; Wagner, R.; Barin, J.S.; et al. Ultrasound Assisted Maceration for Improving the Aromatization of Extra-Virgin Olive Oil with Rosemary and Basil. Food Res. Int. 2020, 135, 109305. [Google Scholar] [CrossRef] [PubMed]
  25. Dimou, C.; Karantonis, H.C.; Skalkos, D.; Koutelidakis, A.E. Valorization of Fruits By-Products to Unconventional Sources of Additives, Oil, Biomolecules and Innovative Functional Foods. Curr. Pharm. Biotechnol. 2019, 20, 776–786. [Google Scholar] [CrossRef] [PubMed]
  26. Valenzuela, B.A.; Sanhueza, J.; Nieto, S. Natural Antioxidants in Functional Foods: From Food Safety to Health Benefits. Grasas Aceites 2003, 54, 295–303. [Google Scholar] [CrossRef] [Green Version]
  27. Britt, C.; Gomaa, E.A.; Gray, J.I.; Booren, A.M. Influence of Cherry Tissue on Lipid Oxidation and Heterocyclic Aromatic Amine Formation in Ground Beef Patties. J. Agric. Food Chem. 1998, 46, 4891–4897. [Google Scholar] [CrossRef]
  28. Clodoveo, M.L.; Dipalmo, T.; Crupi, P.; Durante, V.; Pesce, V.; Maiellaro, I.; Lovece, A.; Mercurio, A.; Laghezza, A.; Corbo, F.; et al. Comparison Between Different Flavored Olive Oil Production Techniques: Healthy Value and Process Efficiency. Plant Foods Hum. Nutr. 2016, 71, 81–87. [Google Scholar] [CrossRef] [PubMed]
  29. García, A.; Ruiz-Méndez, M.V.; Romero, C.; Brenes, M. Effect of Refining on the Phenolic Composition of Crude Olive Oils. J. Amer Oil Chem. Soc. 2006, 83, 159–164. [Google Scholar] [CrossRef]
  30. Paiva-Martins, F.; Correia, R.; Félix, S.; Ferreira, P.; Gordon, M.H. Effects of Enrichment of Refined Olive Oil with Phenolic Compounds from Olive Leaves. J. Agric. Food Chem. 2007, 55, 4139–4143. [Google Scholar] [CrossRef]
  31. Kapsokefalou, M.; Zhu, L.; Miller, D.D. Adding Iron to Green Tea May Decrease Its Antioxidant Capacity in Rats after an Oral Dose of the Mixture. Nutr. Res. 2006, 26, 480–485. [Google Scholar] [CrossRef]
  32. Reboredo-Rodríguez, P.; Figueiredo-González, M.; González-Barreiro, C.; Simal-Gándara, J.; Salvador, M.D.; Cancho-Grande, B.; Fregapane, G. State of the Art on Functional Virgin Olive Oils Enriched with Bioactive Compounds and Their Properties. Int. J. Mol. Sci. 2017, 18, 668. [Google Scholar] [CrossRef] [Green Version]
  33. Artajo, L.S.; Romero, M.P.; Morelló, J.R.; Motilva, M.J. Enrichment of Refined Olive Oil with Phenolic Compounds: Evaluation of Their Antioxidant Activity and Their Effect on the Bitter Index. J. Agric. Food Chem. 2006, 54, 6079–6088. [Google Scholar] [CrossRef]
  34. Paduano, A.; Caporaso, N.; Santini, A.; Sacchi, R. Microwave and Ultrasound-Assisted Extraction of Capsaicinoids From Chili Peppers (Capsicum annuum L.) in Flavored Olive Oil. J. Food Res. 2014, 3, 51–59. [Google Scholar] [CrossRef] [Green Version]
  35. Baccouri, B.; Rajhi, I.; Theresa, S.; Najjar, Y.; Mohamed, S.N.; Willenberg, I. The Potential of Wild Olive Leaves (Olea europaea L. Subsp. oleaster) Addition as a Functional Additive in Olive Oil Production: The Effects on Bioactive and Nutraceutical Compounds Using LC–ESI–QTOF/MS. Eur. Food Res. Technol. 2022, 248, 2809–2823. [Google Scholar] [CrossRef] [PubMed]
  36. Uddin, M.S.; Ferdosh, S.; Akanda, J.H.; Ghafoor, K.; Rukshana, A.H.; Ali, E.; Kamaruzzaman, B.Y.; Fauzi, M.B.; Hadijah, S.; Shaarani, S.; et al. Techniques for the Extraction of Phytosterols and Their Benefits in Human Health: A Review. Sep. Sci. Technol. 2018, 53, 2206–2223. [Google Scholar] [CrossRef]
  37. Rodrigues, N.; Silva, K.; Veloso, A.C.A.; Pereira, J.A.; Peres, A.M. The Use of Electronic Nose as Alternative Non-Destructive Technique to Discriminate Flavored and Unflavored Olive Oils. Foods 2021, 10, 2886. [Google Scholar] [CrossRef] [PubMed]
  38. Issaoui, M.; Flamini, G.; Hajaij, M.E.; Cioni, P.L.; Hammami, M. Oxidative Evolution of Virgin and Flavored Olive Oils under Thermo-Oxidation Processes. J. Am. Oil Chem. Soc. 2011, 88, 1339–1350. [Google Scholar] [CrossRef]
  39. Ayadi, M.A.; Grati-Kamoun, N.; Attia, H. Physico-Chemical Change and Heat Stability of Extra Virgin Olive Oils Flavoured by Selected Tunisian Aromatic Plants. Food Chem. Toxicol. 2009, 47, 2613–2619. [Google Scholar] [CrossRef]
  40. Khemakhem, I.; Yaiche, C.; Ayadi, M.A.; Bouaziz, M. Impact of Aromatization by Citrus Limetta and Citrus Sinensis Peels on Olive Oil Quality, Chemical Composition and Heat Stability. J. Am. Oil Chem. Soc. 2015, 92, 701–708. [Google Scholar] [CrossRef]
  41. Lamas, S.; Rodrigues, N.; Peres, A.M.; Pereira, J.A. Flavoured and Fortified Olive Oils—Pros and Cons. Trends Food Sci. Technol. 2022, 124, 108–127. [Google Scholar] [CrossRef]
  42. Nevado, J.J.B.; Robledo, V.R.; Callado, C.S.-C. Monitoring the Enrichment of Virgin Olive Oil with Natural Antioxidants by Using a New Capillary Electrophoresis Method. Food Chem. 2012, 133, 497–504. [Google Scholar] [CrossRef]
  43. Kasimoglu, Z.; Tontul, I.; Soylu, A.; Gulen, K.; Topuz, A. The Oxidative Stability of Flavoured Virgin Olive Oil: The Effect of the Water Activity of Rosemary. Food Meas. 2018, 12, 2080–2086. [Google Scholar] [CrossRef]
  44. Peñalvo, G.C.; Robledo, V.R.; Callado, C.S.-C.; Santander-Ortega, M.J.; Castro-Vázquez, L.; Victoria Lozano, M.; Arroyo-Jiménez, M.M. Improving Green Enrichment of Virgin Olive Oil by Oregano. Effects on Antioxidants. Food Chem. 2016, 197, 509–515. [Google Scholar] [CrossRef] [PubMed]
  45. Khan, M.; Vian, M.; Fabiano-Tixier, A.-S.; Dangles, O.; Chemat, F. Ultrasound-Assisted Extraction of Polyphenols (Flavanone Glycosides) from Orange (Citrus sinensis L.) Peel. Food Chem. 2010, 119, 851–858. [Google Scholar] [CrossRef]
  46. Nipornram, S.; Tochampa, W.; Rattanatraiwong, P.; Singanusong, R. Optimization of Low Power Ultrasound-Assisted Extraction of Phenolic Compounds from Mandarin (Citrus reticulata Blanco Cv. Sainampueng) Peel. Food Chem. 2018, 241, 338–345. [Google Scholar] [CrossRef]
  47. Japón-Luján, R.; Luque de Castro, M.D. Liquid-Liquid Extraction for the Enrichment of Edible Oils with Phenols from Olive Leaf Extracts. J. Agric. Food Chem. 2008, 56, 2505–2511. [Google Scholar] [CrossRef] [PubMed]
  48. Achat, S.; Tomao, V.; Madani, K.; Chibane, M.; Elmaataoui, M.; Dangles, O.; Chemat, F. Direct Enrichment of Olive Oil in Oleuropein by Ultrasound-Assisted Maceration at Laboratory and Pilot Plant Scale. Ultrason. Sonochem. 2012, 19, 777–786. [Google Scholar] [CrossRef]
  49. Alberdi-Cedeño, J.; Ibargoitia, M.L.; Guillén, M.D. Study of the In Vitro Digestion of Olive Oil Enriched or Not with Antioxidant Phenolic Compounds. Relationships between Bioaccessibility of Main Components of Different Oils and Their Composition. Antioxidants 2020, 9, 543. [Google Scholar] [CrossRef]
Table 1. Methodology used for the olive oil fortification.
Table 1. Methodology used for the olive oil fortification.
Methods for Oil AromatizationTemperature (°C)Duration (min/h/days)Food Mass of Herbs and By-Products (g)
Conventional maceration (CM)37 °C15 days/30 days2.5 g/5 g
Incubator shaking maceration (ISM)37 °C1 h/2 h/3 h1 g/2 g/3 g
Ultrasound assisted maceration (UAM)30/40 °C30 min/60 min1.5 g/3 g
Table 2. Total phenolic content and total antioxidant capacity of virgin, extra virgin, and refined olive oil.
Table 2. Total phenolic content and total antioxidant capacity of virgin, extra virgin, and refined olive oil.
Olive Oil TypeTotal Phenolic ContentTotal Antioxidant Capacity
Folin–Ciocalteau (mg GAE/L)Frap (mmol Fe2+/L)
Refined Olive Oil (ROO)10.83 ± 1.36 a0.20 ± 0.03 a
Virgin Olive Oil (VOO)15.34 ± 3.14 b0.47 ± 0.05 b
Extra Virgin Olive Oil (EVOO)20.47 ± 2.87 c0.50 ± 0.09 c
Data are presented as mean ± SD. Different letters in each column indicate statistically significant differences (p < 0.05).
Table 3. Total phenolic content of fortified refined olive oils using conventional maceration (CM).
Table 3. Total phenolic content of fortified refined olive oils using conventional maceration (CM).
Total Phenolic Content (mg GAE/L)
Food SampleCM (15 Days)CM (30 Days)P1P2
2.5 g5 g2.5 g5 g
Herbs
Rosemary38.55 ± 8.9135.91 ± 2.5221.37 ± 9.9829.84 ± 5.66*NS
Basil21.05 ± 6.5417.88 ± 1.8619.24 ± 3.9222.49 ± 11.97NSNS
Sage24.42 ± 6.7635.15 ± 2.8735.00 ± 9.0747.34 ± 6.14**
Lemon Balm15.55 ± 1.3919.80 ± 0.1518.67 ± 2.1922.92 ± 3.84NSNS
St. John’s Wort36.21 ± 3.3343.53 ± 4.1022.59 ± 7.8436.63 ± 5.72NS*
Pink Savory50.82 ± 2.9755.06 ± 8.9944.60 ± 11.3949.97 ± 6.10NSNS
Dittany22.96 ± 1.1727.64 ± 1.5234.52 ± 6.0037.83 ± 8.44*NS
By-products
Pomace13.13 ± 3.8416.82 ± 5.8514.14 ± 2.7414.84 ± 1.79NSNS
Olive Leaves36.57 ± 5.1834.81 ± 13.6421.82 ± 8.3326.15 ± 12.48**NS
Orange Peel27.36 ± 10.0840.07 ± 3.8626.15 ±11.4537.25 ± 25.93NS**
Lemon Peel44.40 ± 6.5535.39 ± 4.7828.72 ± 10.6616.50 ± 3.38***
Pomegranate Peel16.57 ± 1.0315.49 ± 2.4116.96 ± 1.2718.16 ± 1.81NSNS
Mandarin Peel34.77 ± 7.1336.28 ± 2.4617.97 ± 6.6031.42 ± 27.24NS*
Data are expressed as mean ± SD. P1: statistical differences between samples prepared with conventional maceration (CM) for 15 and 30 days. P2: statistical differences between samples of different mass (2.5 g and 5 g) macerated for the same day period. Significance level, ** p < 0.01, * p < 0.05, NS: non-significant (p > 0.05).
Table 4. Total antioxidant capacity of fortified refined olive oils using conventional maceration (CM).
Table 4. Total antioxidant capacity of fortified refined olive oils using conventional maceration (CM).
Total Antioxidant Capacity (mmol Fe2+/L)
Food SampleCM (15 Days)CM (30 Days)P1P2
2.5 g5 g2.5 g5 g
Herbs
Rosemary0.39 ± 0.050.40 ± 0.020.36 ± 0.010.38 ± 0.03NSNS
Basil0.31 ± 0.010.35 ± 0.010.38 ± 0.010.38 ± 0.01*NS
Sage0.89 ± 0.301.54 ± 0.071.05 ± 0.251.63 ± 0.07******
Lemon Balm0.33 ± 0.020.40 ± 0.020.41 ± 0.010.54 ± 0.02******
St. John’s Wort0.38 ± 0.020.39 ± 0.020.33 ± 0.050.34 ± 0.01*NS
Pink Savory0.56 ± 0.020.74 ± 0.030.52 ± 0.050.68 ± 0.07****
Dittany0.39 ± 0.020.44 ± 0.030.43 ± 0.010.51 ± 0.05****
By-Products
Pomace0.28 ± 0.030.28 ± 0.030.28 ± 0.050.31 ± 0.06NSNS
Olive Leaves0.31 ± 0.050.32 ± 0.050.32 ± 0.020.31 ± 0.04NSNS
Orange Peel0.35 ± 0.010.37 ± 0.020.34 ± 0.030.33 ± 0.01NSNS
Lemon Peel0.35 ± 0.030.35 ± 0.020.33 ± 0.010.32 ± 0.02NSNS
Pomegranate Peel0.28 ± 0.010.28 ± 0.010.33 ± 0.040.35 ± 0.01**NS
Mandarin Peel0.35 ± 0.020.34 ± 0.030.33 ± 0.240.29 ± 0.01*NS
Data are expressed as mean ±SD. P1: statistical differences between samples prepared with conventional maceration (CM) for 15 and 30 days. P2: statistical differences between samples of different mass (2.5 g and 5 g) macerated for the same day period. Significance level *** p < 0.001, ** p < 0.01, * p < 0.05, NS: non-significant (p > 0.05).
Table 5. Total phenolic content of fortified refined olive oils using incubation maceration.
Table 5. Total phenolic content of fortified refined olive oils using incubation maceration.
Total Phenolic Content (mg GAE/L)
Food SampleISM (60 min)ISM (120 min)ISM (180 min)P1P2P3
1 g2 g3 g1 g2 g3 g1 g2 g3 g
Herbs
Rosemary13.61 ± 0.7012.15 ± 1.0113.30 ± 2.0114.98 ± 1.3915.29 ± 2.9817.16 ± 2.1912.81 ± 1.4612.70 ± 0.6014.58 ± 1.19NSNSNS
Basil15.54 ±1.4812.83 ± 1.5913.26 ± 1.7415.64 ± 1.2312.29 ± 0.6316.36 ± 3.8411.31 ± 0.7813.13 ± 0.9613.09 ± 1.30NSNSNS
Sage17.85 ± 3.0721.81 ± 4.9933.22 ± 17.4117.25 ± 3.2728.61± 4.0032.51 ± 5.8317.77 ± 3.3225.22 ± 1.0336.07 ± 4.35NSNSNS
Lemon Balm28.95 ± 7.1027.59 ± 6.2333.13 ± 4.4427.65 ± 9.1625.11± 2.7927.70 ± 1.6526.54 ± 7.1028.98 ± 2.2123.32 ± 1.21NSNSNS
St. John’s Wort42.66 ± 12.8534.28 ± 7.5639.96 ± 3.7931.91 ± 1.8434.43± 1.5727.92 ± 3.1240.26 ± 12.8536.55 ± 3.2726.49 ± 1.46**NSNS
Pink Savory35.10 ± 25.0723.64 ± 2.5624.28 ± 2.9819.70 ± 10.4624.40± 1.9227.30 ± 1.5325.24 ± 18.7431.46 ± 15.2427.49 ± 2.03NSNSNS
Dittany26.75 ± 10.2614.68 ± 2.0123.71 ± 8.6721.99 ± 15.3423.08± 1.4912.81 ± 0.9839.49 ± 40.5514.00 ± 7.9013.08 ± 2.99NSNSNS
By-Products
Pomace13.43 ± 1.8311.67 ± 1.2322.07 ± 18.7918.01 ± 2.4617.18± 2.0816.54 ± 2.1618.60 ± 4.5316.94 ± 2.1616.30 ± 0.89NSNSNS
Olive Leaves29.03 ± 4.4614.71 ± 1.8112.04 ± 1.1417.37 ± 9.9112.51± 1.9613.31 ± 5.2113.99 ± 2.8520.12 ± 5.6913.73 ± 1.81NSNSNS
Orange Peel16.35 ± 9.8611.37 ± 1.0110.68 ± 3.9412.37 ± 1.0517.01± 4.8916.74 ± 5.4413.58 ± 0.8814.72 ± 1.4913.72 ± 2.32NSNSNS
Lemon Peel9.94 ± 1.4111.13 ± 0.4113.18 ± 1.3713.19 ± 1.8011.59 ± 2.3212.63 ± 0.7513.27 ± 1.8411.69 ± 1.0810.77 ± 1.04NSNSNS
Pomegranate Peel9.99 ± 0.629.06 ± 1.1413.20 ± 1.0910.85 ± 0.9510.84± 1.0911.53 ± 1.3313.09 ± 1.4012.77 ± 0.6415.59 ± 2.48NSNSNS
Mandarin Peel22.35 ± 10.6013.89 ± 2.4723.74 ± 1.5916.15 ± 1.0113.05± 1.4912.69 ± 1.3723.51 ± 6.7914.60 ± 3.0316.17 ± 3.71*NSNS
Data are expressed as mean ± SD. P1: statistical differences between samples prepared with 60 min versus 120 min of incubation maceration. P2: statistical differences between samples prepared with 120 min versus 180 min of incubation maceration. P3: statistical differences between samples prepared with 60 min versus 180 min of incubation maceration. Significance level, ** p < 0.01, * p < 0.05, NS: non-significant (p > 0.05).
Table 6. Total antioxidant capacity of fortified refined olive oils using incubation maceration.
Table 6. Total antioxidant capacity of fortified refined olive oils using incubation maceration.
Total Antioxidant Capacity (mmol Fe2+/L)
Food SampleISM (60 min)ISM (120 min)ISM (180 min)P1P2P3
1 g2 g3 g1 g2 g3 g1 g2 g3 g
Herbs
Rosemary0.30 ± 0.030.28 ± 0.020.36 ± 0.020.32 ± 0.040.34 ± 0.020.31 ± 0.030.30 ± 0.060.30 ± 0.030.31 ± 0.03NSNSNS
Basil0.34 ± 0.010.53 ± 0.180.32 ± 0.020.31 ± 0.020.34 ± 0.030.40 ± 0.080.23 ± 0.080.34 ± 0.040.33 ± 0.03*****
Sage0.55 ± 0.020.64 ± 0.041.02 ± 0.150.52 ± 0.070.92 ± 0.100.65 ± 0.080.51 ± 0.060.91 ± 0.121.28 ± 0.20NS******
Lemon Balm0.30 ± 0.020.31 ± 0.010.34 ± 0.030.33 ± 0.010.38 ± 0.020.36 ± 0.020.33 ± 0.010.35 ± 0.060.32 ± 0.03NSNSNS
St. John’s Wort0.29 ± 0.020.33 ± 0.030.40 ± 0.010.38 ± 0.010.42 ± 0.040.43 ± 0.040.35 ± 0.030.41 ± 0.040.36 ± 0.04*NSNS
Pink Savory0.41 ± 0.050.34 ± 0.050.63 ± 0.180.31 ± 0.020.49 ± 0.070.46 ± 0.110.45 ± 0.060.39 ± 0.080.58 ± 0.06NS*NS
Dittany0.26 ± 0.080.27 ± 0.050.31 ± 0.030.29 ± 0.080.41 ± 0.060.49 ± 0.140.31 ± 0.060.47 ± 0.060.24 ± 0.05*****
By-products
Pomace0.33 ± 0.050.30 ± 0.040.33 ± 0.010.35 ± 0.070.39 ± 0.010.43 ± 0.030.34 ± 0.030.32 ± 0.020.35 ± 0.02***NS
Olive Leaves0.28 ± 0.080.24 ± 0.020.30 ± 0.020.36 ± 0.010.25 ± 0.010.25 ± 0.010.31 ± 0.030.36 ± 0.060.34 ± 0.04NS***
Orange Peel0.23 ± 0.040.26 ± 0.030.31 ± 0.050.29 ± 0.010.29 ± 0.030.35 ± 0.020.28 ± 0.020.34 ± 0.050.30 ± 0.02*NSNS
Lemon Peel0.29 ± 0.010.27 ± 0.080.35 ± 0.060.34 ± 0.040.33 ± 0.030.33 ± 0.030.27 ± 0.030.28 ± 0.030.32 ± 0.04NSNSNS
Pomegranate Peel0.30 ± 0.020.28 ± 0.020.29 ± 0.020.33 ± 0.040.37 ± 0.070.34 ± 0.030.35 ± 0.040.31 ± 0.040.31 ± 0.02*NSNS
Mandarin Peel0.19 ± 0.020.26 ± 0.010.26 ± 0.020.30 ± 0.020.31 ± 0.030.35 ± 0.010.28 ± 0.020.25 ± 0.050.29 ± 0.02****NS
Data are expressed as mean ±SD. P1: significant differences between 60 min and 120 min of incubation maceration. P2: significant differences between 120 min and 180 min of incubation maceration. P3: significant differences between 60 min and 180 min of incubation maceration. Significance level *** p < 0.001, ** p < 0.01, * p < 0.05, NS: non-significant (p > 0.05).
Table 7. Total phenolic content of enriched fortified olive oils using ultrasound-assisted maceration.
Table 7. Total phenolic content of enriched fortified olive oils using ultrasound-assisted maceration.
Total Phenolic Content (mg GAE/L)
Food Sample30 °C40 °C30 °C40 °CP1P2P3
UAM (30 min)UAM (30 min)UAM (60 min)UAM (60 min)
1.5 g3 g1.5 g3 g1.5 g3 g1.5 g3 g
Herbs
Rosemary36.99 ± 35.5020.51 ± 7.4214.95 ± 4.2119.67 ± 0.8917.84 ± 1.1221.54 ± 5.6225.50 ± 4.8815.00 ± 1.74NSNSNS
Basil58.15 ± 39.3423.19 ± 9.8016.30 ± 2.9818.16 ± 0.3216.43 ± 1.3524.01 ± 3.2823.52 ± 3.1319.08 ± 2.85******
Sage43.41 ± 5.6930.36 ± 1.1127.64 ± 3.5847.90 ± 6.8638.91 ± 6.3451.16 ± 5.1229.95 ± 9.3535.75 ± 2.90NS*NS
Lemon Balm0.22 ± 0.0412.21 ± 1.570.23 ± 0.060.14 ± 0.020.33 ± 0.080.22 ± 0.010.28 ± 0.060.21 ± 0.02NSNSNS
St. John’s Wort0.37 ± 0.1712.57 ± 1.100.59 ± 0.500.16 ± 0.060.31 ± 0.090.17 ± 0.030.26 ± 0.040.14 ± 0.00NSNSNS
Pink Savory24.71 ± 3.1726.15 ± 3.9624.72 ± 6.2733.90 ± 4.5420.49 ± 3.1537.50 ± 3.5931.80 ± 6.1638.49 ± 10.28NS**NS
Dittany15.37 ± 1.38-12.01 ± 4.02-12.65 ± 2.08-12.32 ± 1.77-NS-NS
By-products
Pomace13.49 ± 1.3614.23 ± 0.7516.97 ± 1.4915.95 ± 3.4815.71 ± 3.7617.88 ± 2.3616.56 ± 1.9214.36 ± 1.39NSNSNS
Olive Leaves11.29 ± 4.0917.25 ± 5.2113.59 ± 2.2611.09 ± 1.1415.17 ± 1.2712.56 ± 1.5011.58 ± 1.8511.27 ± 1.45NSNSNS
Orange Peel38.71 ± 10.1736.28 ± 24.6036.62 ± 5.2464.35 ± 25.3119.95 ± 3.9521.64 ± 2.4421.64 ± 2.9342.67 ± 16.98*********
Lemon Peel27.03 ± 11.2232.52 ± 18.0347.21 ± 19.6541.46 ± 16.2429.34 ± 11.5128.47 ± 7.7317.37 ± 1.0820.63 ± 1.89***NSNS
Pomegranate Peel37.90 ± 13.2519.14 ± 5.0842.31 ± 4.7643.23 ± 5.8526.08 ± 4.0129.59 ± 4.9924.05 ± 3.3628.57 ± 12.42**NS*
Mandarin Peel0.21 ± 0.029.76 ± 1.240.23 ± 0.030.11 ± 0.040.24 ± 0.050.11 ± 0.030.22 ± 0.040.12 ± 0.02NSNSNS
Data are expressed as mean ± SD. P1: significant differences between ultrasound-assisted maceration time (30 min and 60 min). P2: significant differences between sample g per food sample (1.5 g and 3 g). P3: significant differences between ultrasound-assisted maceration temperatures (30 °C and 40 °C). Significance level *** p < 0.001, ** p < 0.01, * p < 0.05, NS: non-significant (p > 0.05).
Table 8. Total antioxidant capacity of fortified refined olive oils using ultrasound-assisted maceration.
Table 8. Total antioxidant capacity of fortified refined olive oils using ultrasound-assisted maceration.
Total Antioxidant Capacity (mmol Fe2+/L)
Food Sample30 °C40 °C30 °C40 °CP1P2P3
UAM (30 min)UAM (30 min)UAM (60 min)UAM (60 min)
1.5 g3 g1.5 g3 g1.5 g3 g1.5 g3 g
Herbs
Rosemary0.34 ± 0.050.31 ± 0.070.23 ± 0.080.53 ± 0.070.38 ± 0.050.32 ± 0.060.36 ± 0.020.42 ± 0.04NSNSNS
Basil0.42 ± 0.030.30 ± 0.040.27 ± 0.080.40 ± 0.070.39 ± 0.040.38 ± 0.070.36 ± 0.020.66 ± 0.17***NS
Sage0.63 ± 0.100.68 ± 0.131.05 ± 0.131.52 ± 0.561.32 ± 0.131.56 ± 0.101.69 ± 0.071.42 ± 0.15********
Lemon Balm0.27 ± 0.030.33 ± 0.070.32 ± 0.050.32 ± 0.050.33 ± 0.090.52 ± 0.080.35 ± 0.060.46 ± 0.04***NS
St. John’s Wort0.32 ± 0.080.35 ± 0.050.29 ± 0.030.39 ± 0.110.26 ± 0.050.33 ± 0.010.23 ± 0.020.28 ± 0.02NSNSNS
Pink Savory0.45 ± 0.020.52 ± 0.040.51 ± 0.070.41 ± 0.050.41 ± 0.030.50 ± 0.030.59 ± 0.060.60 ± 0.03NSNSNS
Dittany0.44 ± 0.03-0.41 ± 0.02-0.37 ± 0.06-0.40 ± 0.02-NS-NS
By-products
Pomace0.29 ± 0.010.32 ± 0.010.32 ± 0.020.32 ± 0.020.30 ± 0.070.31 ± 0.020.34 ± 0.040.32 ± 0.01NSNSNS
Olive Leaves0.33 ± 0.030.22 ± 0.030.32 ± 0.050.28 ± 0.050.31 ± 0.040.31 ± 0.030.27 ± 0.040.29 ± 0.03NSNSNS
Orange Peel0.37 ± 0.080.51 ± 0.150.97 ± 0.161.24 ± 0.240.36 ± 0.030.33 ± 0.050.58 ± 0.040.56 ± 0.05*******
Lemon Peel0.46 ± 0.080.56 ± 0.181.17 ± 0.071.03 ± 0.080.46 ± 0.020.61 ± 0.210.54 ± 0.030.44 ± 0.04***NS***
Pomegranate Peel0.50 ± 0.110.53 ± 0.241.25 ± 0.091.37 ± 0.150.59 ± 0.090.43 ± 0.030.53 ± 0.030.57 ± 0.14***NS***
Mandarin Peel0.26 ± 0.040.26 ± 0.070.30 ± 0.120.27 ± 0.030.22 ± 0.030.23 ± 0.050.23 ± 0.040.21 ± 0.04NSNSNS
Data are expressed as mean ± SD. P1: significant differences between ultrasound-assisted maceration time (30 min and 60 min). P2: significant differences between sample g per food sample (1.5 g and 3 g). P3: significant differences between ultrasound-assisted maceration temperatures (30 °C and 40 °C). Significance level *** p < 0.001, ** p < 0.01, * p < 0.05, NS: non-significant (p > 0.05).
Table 9. Total antioxidant capacity and total phenolic content of selected fortified olive oils before and after in vitro digestion and their predicted bioavailability indices.
Table 9. Total antioxidant capacity and total phenolic content of selected fortified olive oils before and after in vitro digestion and their predicted bioavailability indices.
Food SampleBefore DigestionAfter DigestionBioavailability of Total Antioxidant Capacity (BAvI %)Bioavailability of Total Phenolic Content (BAvI %)P1P2
Total Antioxidant Capacity
(mmol Fe2+/L)		Total Phenolic Content
(mg mgGAE/L)		Total Antioxidant Capacity
(mmol Fe2+/L)		Total Phenolic Content
(mg mgGAE/L)
Plant By-products
Orange peel1.24 ± 0.24 d64.35 ± 25.31 d0.06 ± 0.01 a13.28 ± 10.84 a4.8420.64****
Pomegranate peel1.25 ± 0.09 d42.31 ± 4.77 c0.08 ± 0.02 a20.95 ± 13.93 a6.4049.52***
Pomace0.37 ± 0.05 bc20.27 ± 4.86 b0.11 ± 0.10 a9.86 ± 8.39 a29.7348.64**
Herbs
Basil0.42 ± 0.03 c58.15 ± 39.34 d0.09 ± 0.03 a11.29 ± 7.29 a21.4319.42****
St. John’s Wort0.32 ± 0.08 b17.38 ± 8.59 b0.07 ± 0.01 a9.23 ± 8.47 a21.8853.11***NS
Data are expressed as mean ± SD. Different letters in the same group (antioxidant capacity or phenolic content) presented significant differences (p < 0.05) between samples. BAvI: Bioavailability Index. P1: Total antioxidant capacity: sample correlations between before and after in vitro digestion. P2: Total phenolic content: correlations between samples before and after in vitro digestion. Significance level *** p < 0.001, ** p < 0.01, * p < 0.05 NS: non-significant (p > 0.05).
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MDPI and ACS Style

Kaloteraki, C.; Bousdouni, P.; Almpounioti, K.; Ouzaid, C.; Papagianni, O.; Sfikti, F.; Dimitsa, E.; Tsami, D.; Sarivasilleiou, A.G.; Karantonis, H.C.; et al. Fortification of Olive Oil with Herbs and Waste By-Products towards Sustainable Development: Total Antioxidant Capacity, Phenolic Content, and In Vitro Predicted Bioavailability. Appl. Sci. 2023, 13, 8876. https://doi.org/10.3390/app13158876

AMA Style

Kaloteraki C, Bousdouni P, Almpounioti K, Ouzaid C, Papagianni O, Sfikti F, Dimitsa E, Tsami D, Sarivasilleiou AG, Karantonis HC, et al. Fortification of Olive Oil with Herbs and Waste By-Products towards Sustainable Development: Total Antioxidant Capacity, Phenolic Content, and In Vitro Predicted Bioavailability. Applied Sciences. 2023; 13(15):8876. https://doi.org/10.3390/app13158876

Chicago/Turabian Style

Kaloteraki, Chrysoula, Panoraia Bousdouni, Kalliopi Almpounioti, Camille Ouzaid, Olga Papagianni, Fotini Sfikti, Elina Dimitsa, Dimitra Tsami, Anastasia Grammatiki Sarivasilleiou, Haralabos C. Karantonis, and et al. 2023. "Fortification of Olive Oil with Herbs and Waste By-Products towards Sustainable Development: Total Antioxidant Capacity, Phenolic Content, and In Vitro Predicted Bioavailability" Applied Sciences 13, no. 15: 8876. https://doi.org/10.3390/app13158876

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