Novel Processes for the Extraction of Phenolic Compounds from Olive Pomace and Their Protection by Encapsulation

Abstract

Olive pomace, the solid by-product derived from olive oil production consists of a high concentration of bioactive compounds with antioxidant activity, such as phenolic compounds, and their recovery by applying innovative techniques is a great opportunity and challenge for the olive oil industry. This study aimed to point out a new approach for the integrated valorization of olive pomace by extracting the phenolic compounds and protecting them by encapsulation or incorporation in nanoemulsions. Innovative assisted extraction methods were evaluated such as microwave (MAE), homogenization (HAE), ultrasound (UAE), and high hydrostatic pressure (HHPAE) using various solvent systems including ethanol, methanol, and natural deep eutectic solvents (NADESs). The best extraction efficiency of phenolic compounds was achieved by using NADES as extraction solvent and in particular the mixture choline chloride-caffeic acid (CCA) and choline chloride-lactic acid (CLA); by HAE at 60 °C/12,000 rpm and UAE at 60 °C, the total phenolic content (TPC) of extracts was 34.08 mg gallic acid (GA)/g dw and 20.14 mg GA/g dw for CCA, and by MAE at 60 °C and HHPAE at 600 MPa/10 min, the TPC was 29.57 mg GA/g dw and 25.96 mg GA/g dw for CLA. HAE proved to be the best method for the extraction of phenolic compounds from olive pomace. Microencapsulation and nanoemulsion formulations were also reviewed for the protection of the phenolic compounds extracted from olive pomace. Both encapsulation techniques exhibited satisfactory results in terms of encapsulation stability. Thus, they can be proposed as an excellent technique to incorporate phenolic compounds into food products in order to enhance both their antioxidative stability and nutritional value.

Encapsulation of Olive Pomace Extract in Rocket Seed Gum and Chia Seed Gum Nanoparticles: Characterization, Antioxidant Activity and Oxidative Stability

“…Similar to our results, major compounds of olive pomace were reported by Skaltsounis [40][41][42]. Among the major phenolic compounds of OPE, hydroxytyrosol has gained attention due to having health properties such as antioxidant activity, and anti-inflammatory and antimicrobial properties [5,6]. In this study, prepared nanoparticles showed mean particle size in the range of 304.1-318 nm for blank and OPE-loaded RSGNPs and 425.2-490 nm for blank and OPE-loaded CSGNPs, respectively (Table 3).…”

“…Olive pomace contains many phenolic compounds with potential influence on human health, such as hydroxytyrosol, tyrosol, and luteolin [4]. The primary phenolic compounds of olive pomace are oleuropein (1.22-13.50 mg/g), hydroxytyrosol (0.61-8.70 mg/g), tyrosol (0.13-1.115 mg/g), luteolin (0.02-0.14 mg/g), vanillin (0.92-3.64 mg/g), and rutin (0.21-1.70 mg/g) [5,6]. However, phenolic compounds have poor stability, low solubility, low bioavailability and are easily decomposed when exposed to both environmental (light, oxygen, temperature, humidity) and gastrointestinal (pH, digestive enzymes) system conditions.…”

Olive byproducts and their bioactive compounds as a valuable source for food packaging applications

“…The incorporation of olive leaf extracts (Da Rosa et al., 2019; Zam, 2019) or pure compounds like hydroxytyrosol (HT) (Bermúdez‐Oria et al., 2018; Fortunati et al., 2017) in biodegradable films and coatings as antioxidant agents have been proposed as a sustainable alternative to chemical additives. However, the effectiveness of phenolic compounds may be comprised by their low water solubility and stability, rapid oxidation, and high susceptibility to environmental factors (e.g., temperature, humidity, pH, and light), which may deteriorate the functional properties of films and coatings and lead to the loss of their bioactivity (Chanioti et al., 2021). To resolve these issues, encapsulation techniques, including spray drying, freeze drying, and emulsification, were applied to entrap phenolic‐rich extracts from olive byproducts, improve their antioxidant capacity and stability during storage, and allow their controlled release.…”

“…To resolve these issues, encapsulation techniques, including spray drying, freeze drying, and emulsification, were applied to entrap phenolic-rich extracts from olive byproducts, improve their antioxidant capacity and stability during storage, and allow their controlled release. Due to the commercial availability of olive leaf extracts, more studies on the encapsulation of olive leaf extracts were performed when compared to those dealing with encapsulation of extracts from other olive byproducts F I G U R E 2 Diversified applications of olive byproducts from the olive oil industry (Chanioti et al, 2021;Paulo & Santos, 2020). Different wall materials, including chitosan, maltodextrin, and polylactic acid, were used for the encapsulation of phenolics obtained from olive byproducts (Chanioti et al, 2021).…”

A Sustainable Approach for Extracting Non-Extractable Phenolic Compounds from Mangosteen Peel Using Ultrasound-Assisted Extraction and Natural Deep Eutectic Solvents

“…That is why NaDES have been previously employed for the extraction of phenolic compounds from natural sources [17,19,21]. In addition, these solvents have enabled the extraction of phenolic compounds in combination with advanced extraction techniques such as ultrasound-assisted extraction (UAE), homogenate (HAE), high hydrostatic pressure (HHPAE), pressurized liquid extraction (PLE), and microwave-assisted extraction (MAE) [22][23][24][25]. The main advantages that these extraction techniques present over conventional ones are the reduction of operation time and adverse ecological effects, the decrease in the amount of solvent employed, economizing the operation cost, and maintaining the quality of the compounds of interest.…”