Recovery of Added-Value Compounds from Orange and Spinach Processing Residues: Green Extraction of Phenolic Compounds and Evaluation of Antioxidant Activity

Sequential Extraction and Characterization of Essential Oil, Flavonoids, and Pectin from Industrial Orange Waste

Orange is one of the primary fruits processed into juice and other products worldwide, leading to a vast amount of waste accumulation. Such waste has been considered as an attractive candidate for upcycling to obtain bioactive components remaining. The present study investigated the extraction of essential oil (EO), flavonoids, and pectin from industrial orange waste with a holistic approach. To maximize EO yield and d-limonene concentration, hydrodistillation (HD) conditions were selected to be 5.5 mL water/g solid for 180 min. Remaining solids were further used for flavonoid extraction where conventional solvent, sequential ultrasound + solvent, and ultrasound-assisted extraction (UE) were applied. UE applied for 50 min with 120 mL solvent/g solid yielded the highest total phenolic (TPCs) and total flavonoid contents (TFCs), antioxidant capacity, and hesperidin and neohesperidin concentrations. In terms of TPC, TFC, antioxidant capacity, and antibacterial activity, both EO and flavonoid fractions demonstrated moderate to high bioactivity. At the final step, ethanol precipitation was applied to obtain the pectin that was solubilized in hot water during HD and it was characterized by Fourier transform infrared, degree of esterification, and galacturonic acid content. Practical application: to ensure utilization in the food, pharmaceutical, and cosmetic industries, this study presents a combined method to obtain several value-added compounds from industrial orange waste. Bioactive EO and flavonoids obtained could have applications in functional food, supplements, or cosmetic formulations, whereas extracted pectin can be used in many formulated foods and drugs.

Hepatoprotective Mechanisms Induced by Spinach Methanolic Extract in Rats with Hyperglycemia-An Immunohistochemical Analysis

Spinach methanolic extract (SME) has a hepatoprotective effect due to its polyphenolic antioxidants; however, its action in parenchymal (PQ) and non-parenchymal (nPQ) cells remains unknown. This study investigates the hepatoprotective effect of SME on streptozotocin-induced hyperglycemic rats (STZ), focusing on immunohistochemical analyses. Methods: The extract was prepared, and the total polyphenols and antioxidant activity were quantified. Adult male Wistar rats were divided into four groups (n = 8): normoglycemic rats (NG), STZ-induced hyperglycemic (STZ), STZ treated with 400 mg/kg SME (STZ-SME), and NG treated with SME (SME) for 12 weeks. Serum liver transaminases and lipid peroxidation levels in tissue were determined. The distribution pattern and relative levels of markers related to oxidative stress [reactive oxygen species (ROS), superoxide dismutase-1, catalase, and glutathione peroxidase-1], of cytoprotective molecules [nuclear NRF2 and heme oxygenase-1 (HO-1)], of inflammatory mediators [nuclear NF-κB, TNF-α], proliferation (PCNA), and of fibrogenesis markers [TGF-β, Smad2/3, MMP-9, and TIMP1] were evaluated. Results: SME had antioxidant capacity, and it lowered serum transaminase levels in STZ-SME compared to STZ. It reduced NOX4 staining, and lipid peroxidation levels were related to low formation of ROS. In STZ-SME, the immunostaining for antioxidant enzymes increased in nPQ cells compared to STZ. However, enzymes were also localized in extra and intracellular vesicles in STZ. Nuclear NRF2 staining and HO-1 expression in PQ and nPQ were higher in STZ-SME than in STZ. Inflammatory factors were decreased in STZ-SME and were related to the percentage decrease in NF-κB nuclear staining in nPQ cells. Similarly, TGF-β (in the sinusoids) and MMP-9 (in nPQ) were increased in the STZ-SME group compared to the other groups; however, staining for CTGF, TIMP1, and Smad2/3 was lower. Conclusions: SME treatment in hyperglycemic rats induced by STZ may have hepatoprotective properties due to its scavenger capacity and the regulation of differential expression of antioxidant enzymes between the PQ and nPQ cells, reducing inflammatory and fibrogenic biomarkers in liver tissue.

In vivo antidiabetic effects of phenolic compounds of spinach, mustard, and cabbage leaves in mice

Leafy vegetables are considered to have health-promoting potentials, mainly attributed to bioactive phenolic compounds. The antidiabetic effects of spinach, mustard, and cabbage were studied by feeding their phenolic-rich aqueous extracts to alloxan-induced diabetic mice. The antioxidant, biochemical, histopathological, and hematological indices of the control, diabetic, and treated mice were studied. Phenolic compounds present in the extracts were identified and quantified using HPLC-DAD. Results showed ten, nineteen, and eleven phenolic compounds in spinach, mustard, and cabbage leave aqueous extracts, respectively. The body weight, tissue total glutathione (GSH) contents, fasting blood sugar, liver function tests, renal function tests, and lipid profile of the mice were affected by diabetes and were significantly improved by the extract treatments. Likewise, hematological indices and tissues histological studies also showed recovery from diabetic stress in treated mice. The study's findings highlight that the selected leafy vegetables potentially mitigate diabetic complications. Among the studied vegetables, cabbage extract was comparatively more active in ameliorating diabetic stress.

Valorization of cocoa, tea and coffee processing by-products-wastes

The growing threat of food insecurity together with some challenges in demography, health, malnutrition, and income instability around the globe has led researchers to take sustainable solutions to ensure secure production and distribution of food. The last decades have been remarkable in the agri-food supply chain for many food industries. However, vast quantities of food by-products and wastes are generated each year. These products are generally disposed in the environment, which could have remarkable adverse effects on the environment and biodiversity. However, they contain significant quantities of bioactive, nutritional, antioxidative, and aroma compounds. Their sustainable use could meet the increased demand for value-added pharmaceutical, nutraceutical, and food products. The amount of agri-food wastes and their disposal in the environment are predicted to double in the next decade. The valorization of these by-products could effectively contribute to the manufacture of cheaper functional food ingredients and supplements while improving regional economy and food security and mitigating environmental pollution. The main aim of this chapter is to present an understanding of the valorization of the wastes and by-products from cacao, coffee and tea processing with a focus on their bioactive, nutritional, and antioxidant capacity.

Concept for the valorization of cereal processing waste: Recovery of phenolic acids by using waste-derived tetrahydrofurfuryl alcohol and biochar

Valorization of agro-food waste by converting it into a renewable resource plays a crucial role in a bio-based circular economy. Therefore, this study was designed to evaluate the suitability of distillery stillage (DS), which comes from alcohol production from cereals, for producing value-added products that can be used synergistically. The main objective was to investigate the usefulness of two substances for the recovery of phenolic acids, which have antioxidant activity, from the liquid fraction of DS: namely, tetrahydrofurfuryl alcohol (THFA) as a solvent and biochar as an adsorbent, both produced from the solid fraction of cereal processing waste. The effect of THFA concentration (80 and 100%) on phenolic acid yield in ultrasound-assisted extraction was studied. The solubilization predictions of phenolic compounds by the Hansen solubility parameters were in accordance with the experimental results: the yield of phenolic acids in the extracts was highest (3.76 μg g^-1 dry mass) with 80% THFA. Among the extracted phenolic acids, hydroxycinnamic acids predominated over hydroxybenzoic acids, which may affect the bioactive properties of the extracts and their future applications for industrial purposes. Phenolic acids from the extracts were adsorbed on 17-170 g biochar L^-1 and desorbed into water at 40-60 °C. The phenolic acid recovery was highest (∼92%) when the biochar dose was 85 g L^-1 and when desorption was performed at 50 °C. After adsorption/desorption, ∼95% of the antioxidant activity of the phenolic acids in the extracts was maintained. As biochar has a smaller specific surface area than commercial powdered activated carbon (PAC), the biochar dose should be about 5 times higher than an equivalent PAC dose for adsorption efficiency above 90%.

Recovery of phenolic compounds from wine lees using green processing: Identifying target molecules and assessing membrane ultrafiltration performance

Winery wastes are rich in polyphenols with high added value to be used in cosmetics, pharmaceuticals, and food products. This work aims at recovering and purifying the polyphenolic fraction occurring in the malolactic fermentation lees generated during the production of Albariño wines. Phenolic acids, flavonoids, and related compounds were recovered from this oenological waste by green liquid extraction using water as the solvent. The resulting extract solution was microfiltered to remove microparticles and further treated by ultrafiltration (UF) using membranes of 30 kDa and 5 kDa molecular weight cut-offs (MWCOs). The feed sample and the filtrate and retentate solutions from each membrane system were analyzed by reversed-phase liquid chromatography (HPLC) with UV and mass spectrometric (MS) detection. The most abundant polyphenols in the extracts were identified and quantified, namely: caftaric acid with a concentration of 200 µg g^-1 and trans-coutaric acid, cis-coutaric acid, gallic acid, and astilbin with concentrations between 15 and 40 µg g^-1. Other minor phenolic acids and flavanols were also found. The UF process using the 30 kDa membrane did not modify the extract composition, but filtration through the 5 kDa poly-acrylonitrile membrane elicited a decrease in polyphenolic content. Hence, the 30 kDa membrane was recommended to further pre-process the extracts. The combined extraction and purification process presented here is environmentally friendly and demonstrates that malolactic fermentation lees of Albariño wines are a valuable source of phenolic compounds, especially phenolic acids.

Valorization of agri-food waste through the extraction of bioactive molecules. Prediction of their sunscreen action

The aim of this work was to identify the phenolic composition of 18 different vegetable residues and to determine the relationship between their phenolic compounds, antioxidant capacity and sun protection factor. For this purpose, samples of agri-food residues were analyzed to quantify their antioxidant capacity, total polyphenol and flavonoid content, sun protection factor and individual phenolic compounds through HPLC-DAD-FLD. Among the different phenolic compounds found in the extracts, the phenolic acids, especially caffeic acid, chlorogenic acid, p-coumaric acid and protocatechuic acid were the ones that have been most frequently identified, and, therefore, are present in a wide range of extracts. Black chai tea, lemon ginger tea and peanut extracts were the most antioxidant and photoprotective extracts. Phenolic compounds in the extracts have been found to contribute to their antioxidant activity and are closely correlated to their photoprotective capacity. A regression model that allows predicting the photoprotective capacity of any extract based on its total phenol content has been developed as a tool to determine the most suitable industrial application for each vegetable extract.

Valorization of distillery stillage by polyphenol recovery using microwave-assisted, ultrasound-assisted and conventional extractions

An increasing understanding of the negative environmental effects of waste discharges has made valorization of distillery by-products to recover added-value compounds a sound option for distillery stillage management. In this study, the recovery of bioactive compounds, i.e. polyphenols, from distillery stillage was performed by microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and conventional solid-liquid extraction (CSLE) to investigate the effects of extraction time, the concentration of ethyl acetate (EA) in a solvent mixture with ethanol and water, and solid-to-solvent ratio on the recovery yield and antioxidant activity of the extracts. The highest yields of total polyphenol content (TPC) (3.73 mg gallic acid equivalent/g) and phenolic acid content (2.51 μg/g) were obtained with 8-min MAE with 70% EA. MAE provided 1.2- and 1.4-times higher yield of phenolic acids and 1.2- and 1.6-times higher antioxidant activity than UAE and CSLE, respectively. Due to the approximately 3-times higher rate of extraction, the ratio between energy consumption and extraction yield was better in MAE than in UAE. Principal component analysis (PCA) showed that the antioxidant activity of the extracts was positively correlated with TPC and phenolic acid content. Six phenolic acids that were identified were present mainly in their free forms (up to 95% of the total), with a predominance of ferulic (up to 0.80 μg/g) and p-coumaric (up to 0.72 μg/g) acids.

Valorization of Waste Orange Peels: Aqueous Antioxidant Polyphenol Extraction as Affected by Organic Acid Addition

Waste orange peels (WOP) are a food processing residue rich in bioactive polyphenols. However, data on aqueous extraction processes for efficient polyphenol recovery are rather limited. The present study dealt with the optimization of WOP polyphenols, using a batch stirred-tank mode and water as solvent. After a preliminary single-factor examination, the implementation of response surface methodology revealed that optimum extraction time and temperature were 60 min and 55 °C, respectively. Under these conditions, the extraction afforded a total polyphenol yield of 26.13 ± 0.78 mg gallic acid equivalents per g dry mass. The use of aqueous solutions of citric, tartaric and lactic acid showed that total polyphenol yield may be significantly increased with 1% tartaric acid or equally with 2.5% citric acid. However, the effect on individual polyphenolic constituents was rather negligible, as determined by high-performance liquid chromatography. The discrepancies observed in the antioxidant properties of the extracts produced with water and acidified water were putatively attributed to some differences in the polyphenolic composition. The extraction methodology proposed is environmentally green and of low cost, and it could certainly be used as an effective means of recovering WOP polyphenols.

Upgrading the physiochemical and sensory quality of yogurt by incorporating polyphenol-enriched citrus pomaces with antioxidant, antimicrobial, and antitumor activities

Industrial pomaces are cheap sources of phenolic compounds and fibers but dumping them in landfills has negative environmental and health consequences. Therefore, valorizing these wastes in the food industry as additives significantly enhances the final product. In this study, the citrus pomaces, orange pomace (OP), mandarin pomace (MP), and lemon pomace (LP) were collected by a juice company and subjected to producing polyphenols and fiber-enriched fractions, which are included in functional yogurt; the pomace powder with different levels (1, 3, and 5%) was homogenized in cooled pasteurized milk with other ingredients (sugar and starter) before processing the yogurt fermentation. The HPLC phenolic profile showed higher phenolic content in OP extract, i.e., gallic acid (1,702.65), chlorogenic acid (1,256.22), naringenin (6,450.57), catechin (1,680.65), and propyl gallate (1,120.37) ppm with massive increases over MP (1.34–37 times) and LP (1.49–5 times). The OP extract successfully scavenged 87% of DPPH with a relative increase of about 16 and 32% over LP and MP, respectively. Additionally, it inhibits 77–90% of microbial growth at 5–8 μg/mL while killing them in the 9–14 μg/mL range. Furthermore, OP extract successfully reduced 77% of human breast carcinoma. Each of pomace powder sample (OP, MP, LP) was added to yogurt at three levels; 1, 3, and 5%, while the physiochemical, sensorial, and microbial changes were monitored during 21 days of cold storage. OP yogurt had the highest pH and lowest acidity, while LP yogurt recorded the reverse. High fat and total soluble solids (TSS) content are observed in OP yogurt because of the high fiber content in OP. The pH values of all yogurt samples decreased, while acidity, fat, and TSS increased at the end of the storage period. The OP yogurts 1 and 3% scored higher in color, flavor, and structure than other samples. By measuring the microbial load of yogurt samples, the OP (1 and 3%) contributes to the growth of probiotics (Lactobacillus spp) in yogurt samples and reduces harmful microbes. Using citrus pomace as a source of polyphenols and fiber in functional foods is recommended to enhance their physiochemical and sensory quality.

Response Surface Methodology Applied to the Optimization of the Preparation of Antioxidant and Antidiabetic Extracts from Phragmanthera capitata (Spreng.) Balle: Effect of Particle Size, Powder-to-Solvent Ratio, and Temperature

Phragmanthera capitata is a medicinal plant used in traditional medicine to treat several diseases, including diabetes. Its antioxidant properties and inhibitory effects on enzyme-carbohydrate digestion activities have been demonstrated. The present study aimed to provide data that can contribute to rationalizing the preparation of antioxidant and antidiabetic extracts from this plant. P. capitata (whole plant) growing on Persea americana was harvested at the fruiting stage. A response surface design-type central composite was applied to maximize the extraction yield, phenolic contents, and antioxidant and antidiabetic properties of the ethyl acetate extract of P. capitata. The influencing extraction factors were temperature, powder particle size, and solvent-to-powder ratio. The total phenolic content, total antioxidant capacity (TAC), DPPH scavenging ability, ferric reducing antioxidant power (FRAP), and antidiabetic (α-amylase and α-glucosidase inhibitory) effects of the extracts were determined using conventional methods. A temperature above 55°C contributed to the degradation of the extract, which was reflected in the GC-MS profile by a significant reduction in the number of compounds it contained. The optimal conditions were defined as 24.42°C for temperature, 250 µm powder particle size, and 8.30 (v:w) solvent-to-powder ratio. This extraction protocol resulted in more than twice the extraction yield (3.05%), TTC (62.30 mg TAE/g), TAC (41.41 mg AAE/g), FRAP (186.56 mg AAE/g), and α-amylase (IC₅₀ 15.05 µg/mL) and α-glucosidase (IC₅₀ 21.14 µg/mL) inhibitory activities compared to our previous results. Additionally, these optimal conditions led experimentally to the extraction of higher phenolic content and to the attainment of higher antioxidant and antidiabetic activity, which closely matched the predicted values. Using these conditions, it is possible to prepare an antidiabetic phytomedicine from P. capitatathat can prevent oxidative stress complications. However, further complementary studies should be carried out considering other factors that influence the composition and pharmacological properties of the extract.

Fruit and Vegetable Peel-Enriched Functional Foods: Potential Avenues and Health Perspectives

Fresh fruit and vegetables are highly utilized commodities by health-conscious consumers and represent a prominent segment in the functional and nutritional food sector. However, food processing is causing significant loss of nutritional components, and the generation of waste is creating serious economic and environmental problems. Fruit and vegetables encompass husk, peels, pods, pomace, seeds, and stems, which are usually discarded, despite being known to contain potentially beneficial compounds, such as carotenoids, dietary fibers, enzymes, and polyphenols. The emerging interest in the food industry in the nutritional and biofunctional constituents of polyphenols has prompted the utilization of fruit and vegetable waste for developing enriched and functional foods, with applications in the pharmaceutical industry. Moreover, the utilization of waste for developing diverse and crucial bioactive commodities is a fundamental step in sustainable development. Furthermore, it provides evidence regarding the applicability of fruit and vegetable waste in different food formulations especially bakery, jam, and meat based products.

Recovery of Natural Polyphenols from Spinach and Orange By-Products by Pressure-Driven Membrane Processes

Spinach and orange by-products are well recognized for their health benefits due to the presence of natural polyphenols with antioxidant activity. Therefore, the demand to produce functional products containing polyphenols recovered from vegetables and fruits has increased in the last decade. This work aims to use the integrated membrane process for the recovery of polyphenols from spinach and orange wastes, implemented on a laboratory scale. The clarification (microfiltration and ultrafiltration, i.e., MF and UF), pre-concentration (nanofiltration, NF), and concentration (reverse osmosis, RO) of the spinach and orange extracts were performed using membrane technology. Membrane experiments were carried out by collecting 1 mL of the permeate stream after increasing the flow rate in 1 mL/min steps. The separation and concentration factors were determined by HPLC-DAD in terms of total polyphenol content and by polyphenol families: hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids. The results show that the transmembrane flux depended on the feed flow rate for MF, UF, NF, and RO techniques. For the spinach and orange matrices, MF (0.22 µm) could be used to remove suspended solids; UF membranes (30 kDa) for clarification; NF membranes (TFCS) to pre-concentrate; and RO membranes (XLE for spinach and BW30 for orange) to concentrate. A treatment sequence is proposed for the two extracts using a selective membrane train (UF, NF, and RO) to obtain polyphenol-rich streams for food, pharmaceutical, and cosmetic applications, and also to recover clean water streams.

Recovery of polyphenols from distillery stillage by microwave-assisted, ultrasound-assisted and conventional solid-liquid extraction

Recovery of bioactive compounds from distillery waste could be an option for valorizing this waste. This study investigated how the extraction of polyphenols (which have antioxidant activity) from distillery stillage was affected by solvent type and concentration, extraction time, and method of extraction (conventional solid–liquid extraction, CSLE; ultrasound-assisted extraction, UAE; microwave-assisted extraction, MAE). Although recovery was similar with UAE and MAE, 3 min MAE with 80% ethanol and 80% methanol produced the highest yields of total phenolic content (TPC), total flavonoid content (TFC) and phenolic acids. With CSLE, TPC was 2.1–1.8-times lower than with MAE and 1.7–1.4-times lower than with UAE. Increasing the solvent concentration to 100% significantly decreased recovery. Six phenolic acids were recovered (ferulic and p-coumaric acid predominated), which were present mainly in the free form. There was a significant positive correlation between antioxidant activity, as measured with three methods (one based on the hydrogen atom transfer and two based on single electron transfer mechanisms), and phenolic acid content. With MAE and UAE, polyphenols were recovered more efficiently, with 2.1 times and 1.5 times higher antioxidant activity, and with 15 times and 9 times shorter extraction times, respectively, than with CSLE; thus, they can be considered "green" alternatives to CSLE.

Recovery of Polyphenols from Agri-Food By-Products: The Olive Oil and Winery Industries Cases

The production of olive oil and wine are two of the main agri-food economic activities in Southern Europe. They generate large amounts of solid and liquid wastes (e.g., olive pomace, olive mill wastewater, grape pomace, grape stems, wine lees, and wine processing wastewater) that represent a major environmental problem. Consequently, the management of these residues has become a big challenge for these industries, since they are harmful to the environment but rich in bioactive compounds, such as polyphenols. In recent years, the recovery of phenolic compounds has been proposed as a smart strategy for the valorization of these by-products, from a circular economy perspective. This review aims to provide a comprehensive description of the state of the art of techniques available for the analysis, extraction, and purification of polyphenols from the olive mill and winery residues. Thus, the integration and implementation of these techniques could provide a sustainable solution to the olive oil and winery sectors.