Antioxidant Activity and Determination of Phenolic Compounds from <Emphasis Type="Italic">Eugenia involucrata</Emphasis> DC. Fruits by UHPLC-MS/MS

Fruits have been the focus of several studies aimed at finding new antioxidant sources for protection against the damage caused by reactive species. In this study, the antioxidant activity and the presence of phenolic compounds in all parts (peel, pulp, and seeds) of Eugenia involucrata DC. fruits were evaluated. DPPH^·, ABTS^·+, and ORAC methods were used to determine the antioxidant activity, and an UHPLC-MS/MS method was developed for determining the phenolic compounds (gallic, chlorogenic, ferulic, p-coumaric and ellagic acids, quercetin, and myricetin). In the determination of both antioxidant activity and phenolic composition, the efficiency of solvents with different polarities—methanol/H₂O (80:20, v/v), ethanol/H₂O (80:20, v/v), methanol/acidified water with phosphoric acid pH 3.00 (80:20, v/v), and ethyl acetate—for the extraction of the phenolic compounds, was also evaluated. All parts of E. involucrata fruits showed antioxidant activity, in the range of 36.68 ± 1.44 to 873.87 ± 18.24 μmol TE g^?1, being the highest values found in the seeds and peel when more polar extraction solvents were used. Six, five, and three phenolic compounds were identified and quantified in the pulp, peel, and seeds, respectively, with the highest abundance as p-coumaric acid (14 ± 2 mg kg^?1) in the pulp, quercetin (47 ± 5 mg kg^?1) in the peel, and gallic acid (74 ± 4 mg kg^?1) in the seeds, also when more polar solvents were used. Although antioxidant activity methods suggested that the peel and seeds have more antioxidant potential, a wider variety of compounds were determined in the pulp.     

<Emphasis Type="Italic">Spirulina</Emphasis> sp. biomass dried/disrupted by different methods and their application in biofilms production

Arthrospira Spirulina biomass is a source of intracellular compounds with great commercial interest, such as phycocyanin and phenolic compounds. In this work, different cell disruption methods of the microalgae biomass dried in spouted bed and in conventional tray were performed, aiming lead to the better extraction yields of these compounds. The samples of both drying techniques with the most suitable cell disruption were used to biofilms production. FTIR, DSC, and SEM for all samples were performed. The samples dried in spouted bed with cell disruption by milling and by microwave showed the best results for the powder products, with phycocyanin contents of 75.0 and 85.4 mg g^?1, and total phenolic compounds of 41.6 and 41.9 mg g^?1, respectively. However, the tray drying/milling produced the biofilms with the best characteristics (tensile strength of 3.69 MPa and water vapor permeability of 1.67?×?10^?11 g m s^?1 m^?2 Pa^?1) and the highest thermal stability.     

Quantitative Profiling of Volatile and Phenolic Substances in the Wine Vernaccia di Serrapetrona by Development of an HS-SPME-GC-FID/MS Method and HPLC-MS

A headspace solid-phase microextraction coupled to gas chromatography with mass spectrometry and flame ionization detection (HS-SPME-GC-MS/FID) method has been developed for quantifying the main volatiles of the Italian sparkling red wine Vernaccia di Serrapetrona, leading to establish that the divinylbenzene/carboxen/polydimethylsiloxane-coated (gray) fiber, an equilibration time of 15 min, and an extraction time of 15 min at a temperature of 35 °C are the conditions representing the best compromise in terms of sensitivity and time expense, to carry out the analyses. Among the volatiles quantified, 2-phenylethanol, 3-methylbutyl acetate, and ethyl esters levels resulted to be above their odor thresholds, thus being probably responsible for the aroma of this wine with their positive attributes. Phenolic compounds, namely gallic acid, p-coumaric acid, caffeic acid, (+)-catechin, and (+)-epicatechin, were also quantified using high-performance liquid chromatography-MS, thus obtaining an overall characterization of molecules fundamental for both the sensory and the healthy characteristics of the wine. The total phenolic content was found to be in the range of 19.25–61.67 mg l^?1 with the most abundant compound being gallic acid (7.44–25.78 mg l^?1). Main differences in volatile and phenolic compounds between samples were discussed and analyzed by chemometric techniques as principal component analysis.     

Chemical Composition, Antioxidant Capacity, and Sensory Quality of Pomegranate (Punica granatum L.) Arils and Rind as Affected by Drying Method

The objective of this study was to evaluate the application of: (1) freeze drying, (2) convective drying (50, 60, or 70 °C), (3) vacuum–microwave drying (240, 360, or 480 W), and (4) a combined method of convective pre-drying and vacuum–microwave finish drying in the processing of pomegranate arils and rind. The quality parameters under study included sugars and organic acids, punicalagins and ellagic acid, total polyphenols, total antioxidant activity, and sensory quality. In general, drying led to a reduction in all studied parameters; however, the behavior of arils and rind was different. Vacuum–microwave drying at 240 or 360 W was the best drying treatment for arils, while rind required freeze drying or soft conditions of convective drying (50 °C). Further research is needed to obtain proper results with convective pre-drying and vacuum–microwave finish drying of arils and rind. With proper selection of the drying protocol, high-quality dried arils will be available for consumers; these arils will be characterized by high contents of fructose (25 g 100 g^?1), phytic acid (2.2 g 100 g^?1), punicalagins (0.57 mg g^?1), total polyphenols (1.6 mg eq gallic acid g^?1), high antioxidant capacity (0.6 mg eq Trolox g^?1), and high intensities of garnet color, sweetness, sourness, and fresh pomegranate aroma. Besides, dried rind with very high contents of active compounds (123 mg g^?1 of punicalagins and 108 mg eq gallic acid g^?1) and high antioxidant capacity (26 mg eq Trolox g^?1) will be also available as functional material.     

Optimization of Ultrasound-Assisted Extraction of Lycopene from Papaya Processing Waste by Response Surface Methodology

Lycopene possesses strong antioxidant ability, which may provide protection against cancer and other degenerative diseases. An ultrasound-assisted extraction method has been developed for the extraction of lycopene from papaya (Carica papaya L.) processing waste. Optimization conditions were firstly determined using single factor experiment, and then response surface methodology was used. Analysis showed that second-order polynomial models produced a satisfactory fitting of the experimental data with regard to lycopene (R ²?=?0.9147, P?<?0.001). The optimal conditions were 42.28 % ethanol in ethyl acetate as a solvent and extraction for 26.09 min at 50.12 °C. Under these conditions, the maximum yield of lycopene was 189.8?±?4.5 μg/g fresh weight (FW), which was higher than that obtained using the traditional extracting method (153.9?±?7.8 μg/g FW) and the Soxhlet extraction method (68.3?±?4.1 μg/g FW). The crude extract obtained could be used as either food additive or for further isolation and purification of lycopene. The results obtained are helpful for full utilization of papaya.     

Determination of Polyphenol Content by Formation of Unstable Compound Using a Mini-Pump Multicommutation System

This article describes a multicommuted flow procedure for photometric determination of the polyphenol content in wines and teas, exploiting the formation of unstable intermediate products, by the reaction of sodium hypochloride with gallic acid. Because the lifetime of the formed compound is very short, a special flow cell was designed in order to enable mixing of sample and reagent solution within the flow cell, thus allowing signal monitoring, while compound formation proceeded. The flow system manifold comprised three solenoid mini-pumps to propel sample, reagent solution, and carrier fluid. The photometer consisted of a photodiode and a light emitting diode (LED) with maximum emission at 490 nm. Under the selected operational conditions, useful features including a linear response ranging from 62 to 1000 mg L^?1 gallic acid solution (R?=?0.9987), a detection limit of 21 mg L^?1 gallic acid, a sampling rate of 120 determinations per hour, a relative standard deviation of 1.9 % (n?=?20) for a typical solution containing 400 mg L^?1 gallic acid, and a waste generation of 1.0 mL per determination were also achieved. Medium recovery values of 96.2?±?10.4 and 101.9?±?7.3 % for wines and teas, respectively, were achieved.     

Betalain and Phenolic Compositions,Antioxidant Activity of Tunisian Red Beet (Beta vulgaris L. conditiva) Roots and Stems Extracts

In the present study, betalains content, phenolic composition, and antioxidant activity of different parts of red beet (Beta vulgaris L. conditiva) (i.e., roots and stems) were compared. Crude extract of root showed the highest betalain content with a maximum of 53 ± 4 mg betanin eq and 46 ± 3 mg vulgaxantin I eq g^?1 of extract stems showed higher total phenolic concentration than roots, ranging between 2.0 ± 0.4 and 14.6 ± 0.5 mg gallic acid eq^?1 of extract. Chemical composition was analyzed using LC-MS. Betalains (vulgaxanthin I, betanin, and isobetanin) and phenolics (gallic acid, ferulic acid, chlorogenic acid, caffeic acid, vanillic acid, syringic acid, ellagic acid myricetin, quercetin, rutin, kampferol) were identified in roots and stems. Betalain extract obtained from roots showed higher antioxidant activity than extract obtained from stems.     

Characterization and transformation of the <Emphasis Type="Italic">Opuntia ficus indica</Emphasis> fruits

Opuntia ficus indica fruits have been associated with health effects, due to their protective actions against oxidation. Nevertheless, few studies about processing of Opuntia fruits are available’; therefore, we studied the pulp characteristics and processing of a local variety, for producing beverage nectars. The pulp had an average pH of 5.64, 13.47 °Brix, with total sugars (106 g L^?1), K (1180 mg L^?1), 503.3 µg L^?1 of β carotene, 120 mg L^?1 of total phenolic compounds, 4.9 mg and 46.9 mg L^?1 respectively for betacyanins and betaxanthins and 243.4 mg L^?1 of vitamin C. The formulated nectars with 35% of pulp (N35) and 45% of pulp (N45) had respectively 14 and 15 °Brix. Minor components represent 1109 and 1112 mg L^?1 of K for N35 and N45 respectively, β carotene (318.6 µg and 362.8 µg L^?1), and vitamin C 227 and 231 mg L^?1. We confirmed the stability and acceptability of these beverages after a month of storage, after stability and panel tests. Therefore, we suggest that the pulp processing can be used as a new form of agro industrial utilization of this underutilized fruit.     

Effect of drying kinetics on main bioactive compounds and antioxidant activity of acerola (Malpighia emarginata D.C.) residue

This study investigates the drying kinetics of residue of acerola, in a fixed‐bed dryer, analysing the effect of the process variables on the antioxidant properties of the residue. A complete factorial design 3² has been performed, where the independent variables studied were as follows: air velocity (0.5, 1.0 and 1.5 m s^?1) and air‐drying temperature (40, 50 and 60 °C). The bioactive compounds studied were L‐ascorbic acid, total phenolic, total flavonoids and antioxidant activity (expressed as IC₅₀) was determined using free radical DPPH^?. Both independent variables studied have shown to be statistically significant. The content of ascorbic acid was the highest at 60 °C and 1.0 m s^?1 (126.2 ± 0.004 mg 100 g^?1) while for the fresh residue 16.12 ± 0.003 mg 100 g^?1, whereas the total phenolic showed the highest content at 50 °C and 1.5 m s^?1 (46.2 ± 0.003 mg gallic acid.100 g^?1) while for the fresh residue 12.59 ± 0.001 mg gallic acid.100 g^?1. The drying conditions play an important role in determining the final quality of the product mainly in terms of antioxidant activity.     

Extraction of antioxidants and flavonoids from yuzu (<Emphasis Type="Italic">Citrus junos</Emphasis> Sieb ex Tanaka) peels: a response surface methodology study

In the present investigation, extraction of antioxidants and flavonoids from the peels of yuzu fruit using a single factor experiment and a response surface methodology (RSM) based on central composite design was studied. Four independent variables were evaluated at five levels with total 29 experimental runs, including ethanol concentration (EtOH), ratio of liquid to material (L/S), extraction temperature (T), and extraction time (t). The total phenolic content (TPC), total flavonoids content (TFC), two indicators of antioxidant capacity (FRAP and DPPH), and three individual major flavonoids in yuzu (hesperidin, naringin, and phloretin) served as the response functions. Quadratic polynomial equations were obtained by multiple regression analysis to predict the optimal extraction conditions. The regression analysis showed that >95?% of variations were explained by the models of different responses considered. The responses were significantly influenced by all studied factors. The Multiresponse optimized conditions targeted at maximizing all the responses were found to be EtOH?=?65.550?%; T?=?43.864?°C; t?=?119.673 min; and L/S?=?37.168 ml/g, with a desirability of 0.950. At the optimized conditions, the experimental values of FRAP (964.9?±?23.1 mgTE/g DW), DPPH (453.0?±?5.2 mgTE/g DW), TPC (1161.2?±?25.2 mgGAE/g DW), (TFC393.4?±?mgQE/g DW), hesperidin (337.2?±?4.0 mg/g DW), naringin (244.9?±?1.1 mg/g DW), and phloretin (43.9 mg/g DW) were in a reasonable agreement with the predicted values. The extraction method was applied successfully to extract antioxidants and flavonoids from yuzu peels. It also allows a fast and cost-saving process for extraction of the studied phytochemicals, in addition to improvement of the quantity of the targeted extract.     

Selection of the Solvent and Extraction Conditions for Maximum Recovery of Antioxidant Phenolic Compounds from Coffee Silverskin

The extraction of antioxidant phenolic compounds from coffee silverskin (CS) was studied. Firstly, the effect of different solvents (methanol, ethanol, acetone, and distilled water) on the production of antioxidant extracts was evaluated. All the extracts showed antioxidant activity (FRAP and DPPH assays), but those obtained with methanol and ethanol had significantly higher (p?<?0.05) DPPH inhibition than the remaining ones. Due to the lower toxicity, ethanol was selected as extraction solvent, and further experiments were performed in order to define the solvent concentration, solvent/solid ratio, and time to maximize the extraction results. The best condition to produce an extract with high content of phenolic compounds (13 mg gallic acid equivalents/g CS) and antioxidant activity [DPPH?=?18.24 μmol Trolox equivalents/g CS and FRAP?=?0.83 mmol Fe(II)/g CS] was achieved when using 60 % ethanol in a ratio of 35 ml/g CS, during 30 min at 60–65 °C.     

Effect of Subcritical Water on the Extraction of Bioactive Compounds from Carrot Leaves

Carrot leaves, which are generally considered as agricultural residue, are rich in bioactive compounds, such as polyphenols. This study investigates the extraction of polyphenols and luteolin (flavonoid) from freeze-dried and ground carrot leaves (d?<?100 μm) using subcritical water (SCW). Water at elevated temperatures and at high pressure (40 bar) could behave as low-polar solvent to enhance extraction of organic compounds. SCW was investigated at different temperatures (110–230 °C), time (0–114 min), and solid-liquid ratio (15 and 35 g/L). Accordingly, it was revealed that total phenolic content (TPC) from carrot leaves using SCW has an increasing trend with temperature and resulted in 42.83 ± 1.85 mg per g of dry weight in gallic acid equivalent at 210 °C/113.5 min. However, luteolin content using SCW extraction behaved differently, where increase of temperature adversely affected its content. Hot water extraction studies revealed the presence of optimum luteolin content (0.768 ± 0.009-mg/g dry weight) at 120 °C for 10 min. In conclusion, it was shown that carrot leaves are a promising feedstock to extract polyphenols that has high content of luteolin.     

Aqueous extraction kinetics of phenolic compounds from jamun (Syzygium cumini L.) seeds

In this study, aqueous extraction of phenolic compounds from jamun (Syzygium cumini L.) seed was undertaken. The effects of various parameters such as extraction temperature (34.8–85.2°C), extraction time (49.8–100.2 min), and liquid-to-solid ratio (9.8–60.2 mL/g) on the extraction yield, extract purity (i.e., total polyphenol content), and its antioxidant activities (1,1-diphenyl-2-picrlthydrazyl free radical scavenging assay and ferric reducing antioxidant power) were investigated. Response surface methodology was used to optimize the extraction conditions. The optimum extraction conditions (49.2°C, 89.4 min, and 51.6:1 mL/g) produced an extract with 17.3% extraction yield, high total polyphenol content (415 mg gallic acid equivalent/g dried extract) and significant antioxidant activity (IC₅₀: 35.4 ± 0.7 µg/mL). The high-performance liquid chromatography analysis of seed extract revealed the presence of gallic acid (90.8 mg/g dried extract), ellagic acid (36 mg/g dried extract), caffeic acid (26.07 mg/g dried extract), p-coumaric acid (0.26 mg/g dried extract), catechin (9.05 mg/g dried extract), epicatechin (0.42 mg/g dried extract), and quercetin (1.54 mg/g dried extract). Tannic acid (188.5 mg/g dried extract) was also identified as a major phenolic compound. The extraction kinetics was also studied and experimental data were fitted to four kinetic models such as first-order model, second-order model, Peleg’s model, and Minchev and Minkov model, to evaluate their applicability.     

Application of Ionic Liquid-Based Ultrasound-Assisted Extraction of Five Phenolic Compounds from Fig (<Emphasis Type="Italic">Ficus carica</Emphasis> L.) for HPLC-UV

Ionic liquid-based ultrasonic-assisted extraction (IL-UAE) was successfully developed to extract the known phenolics gallic acid, chlorogenic acid, rutin, psoralen, and bergapten present in the leaves, pulps, and peels of Ficus carica L. In this work, the proposed method was evaluated in comparison with regular ultrasonic-assisted extraction in which methanol was the extractant and exhibited higher efficiency. Moreover, ionic liquids with different cations were investigated and 1-butyl-3-methylimidazole hexafluorophosphate solution was selected as the optimal extractant at concentration of 1.0 mol L^?1. The corresponding extraction parameters including extraction solvent, the concentration of [BMIM][PF₆], solid–liquid ratio (g mL^?1), ultrasonic extraction time, and extraction temperature were optimized. The phenolics were then determined by high-performance liquid chromatography (HPLC). Under the optimized conditions, the content of gallic acid, chlorogenic acid, rutin, psoralen, and bergapten in leaves, pulps, and peels of F. carica L. was 12.67–37.16, 14.75–90.07, 107.91–222.37, 2.59–67.83, and 1.99–20.21 μg/0.1 g, respectively. This study suggests that IL-UAE is a rapid, simple, and green preparation technique.     

Process Intensification by Experimental Design Application to Microwave-Assisted Extraction of Phenolic Compounds from <Emphasis Type="Italic">Juglans regia</Emphasis> L.

Microwave-assisted extraction was applied to Juglans regia L. fresh male flowers and unripe walnut seeds to evaluate the total phenolic contents of the extracts as well as the percentage of water-soluble polyphenols. The research was planned using the Design of Experiments technique to investigate the role on the extraction efficiency of different parameters, such as temperature, time and number of microwave heating cycles, together with their possible interactions. Optimization was achieved by applying a Response Surface Methodology comprising a three-factor, two-level, full-factorial Face-Centred Central Composite Design. The two input variables with a significant effect on the recovery of phenols from fresh male flowers were the extraction temperature and the number of microwave cycles. In the case of unripe walnut seeds, a linear two-factor interaction model was selected, with significant interactions occurring between temperature and time, and time and number of microwave cycles. The best experimental conditions were as follows: 100 °C, 6 min, three microwave heating cycles and 22.7 ± 0.2 mg gallic acid equivalent (GAE)/g (total phenolic content, PC); energy consumption calculations suggested slightly different conditions: 60 °C, 30 min, three microwave heating cycles and 20.7 ± 0.3 mg GAE/g (TPC).     

Thermal transition and thermo-physical properties of potato (<Emphasis Type="Italic">Solanum tuberosum L</Emphasis>.) var. Russet brown

Potatoes are an important food in many regions of the world and are commonly used in a variety of food products. Thermal transition and thermo-physical properties of potatoes are important in order to design efficient food processes and select appropriate storage conditions. In this study, we determined the thermal transitions and thermophysical properties of raw and blanched/par-fried potato for a temperature range of ??32 to 21.1 °C. Using differential scanning calorimetry, we found an initial freezing point (T_f) at ??1.8?±?0.1 °C, an onset of melting (T_m^′) at ??9.9?±?0.2 °C and an unfreezable water content (X^′_w) for maximally freeze-concentrated raw potato at 0.21 kg water/kg potato. Corresponding values for blanched/par-fried potatoes were ??0.9?±?0.1 °C, ??11.0?±?0.2 °C and 0.18 kg water/kg potato. Results show that an increase in solids content decreased T_f of both raw and blanched potatoes. We modelled the relationship between them using the Chen model. The apparent specific heat (C_app) increased around T_f to 31.7?±?1.13 kJ/kg K for raw potato and 26.7?±?0.62 kJ/kg K for blanched/par-fried potato. For frozen raw potato at ??32 °C, thermal diffusivity (α) was 0.89?±?0.01?×?10?^?6 m²/s and thermal conductivity (k), 1.82?±?0.14 W/m K, respectively. These values were higher for frozen raw potato than for the unfrozen raw potato (0.15?±?0.01?×?10?^?6 m²/s and 0.56?±?0.08 W/m K, respectively at 21.1 °C). The apparent density (ρ) of frozen raw potato (992?±?4.00 kg/m³ at ??32 °C) was less than that for unfrozen raw potato (1053?±?4.00 kg/m³ at 21.1 °C), and a similar trend was obtained for blanched/par-fried potato (993?±?2.00 kg/m³ at ??32 °C and 1188?±?7.00 kg/m³ at 21.1 °C, respectively). This study established a correlation between thermo-physical properties and temperature. Findings may be used to inform the design and optimization of freezing processes and frozen storage for potato products.     

Ultraviolet Light-Assisted Photocatalytic Disinfection of <Emphasis Type="Italic">Escherichia coli</Emphasis> and Its Effects on the Quality Attributes of White Grape Juice

Ultraviolet (UV) light-assisted titanium dioxide (TiO₂) photocatalysis is an emerging technology in food safety that utilizes TiO₂ photocatalysts to accelerate the generation of reactive oxygen species during UV illumination. In this work, we studied the use of immobilized TiO₂-SiO₂ photocatalysts illuminated with UVA radiation (350 nm; 14.8 mW/cm²) for the inactivation of Escherichia coli ATCC 25922 in white grape juice, and compared the effectiveness of the photocatalytic disinfection with respect to the quality attributes of white grape juice against those of thermal and UVC (254 nm; 19.7 mW/cm²) treated samples. To obtain a 5-log reduction of the target microorganism, treatment durations of UVA in the absence and presence of the photocatalyst were 60 and 40 min, respectively. A 5-log reduction with UVC radiation led to the loss of health-related compounds such as vitamin C, total phenolic content, and total antioxidant capacity at 92.0?±?1.1%, 19.4?±?5.6%, and 54.3?±?10.0%, respectively. However, the same level of reduction with UVA led to a loss of 74.2?±?2.3%, 7.1?±?3.6%, and 39.7?±?2.5%, and with UVA-assisted photocatalytic method resulted in a loss of 75.8?±?6.1%, 13.6?±?5.8%, and 45.6?±?4.4% of vitamin C, total phenolic content, and total anti-oxidant capacity, respectively. Given its efficacy in deactivating E. coli while retaining a relatively higher level of health-related constituents in the fruit juice compared to other common pasteurization techniques, the photocatalyst developed in this study provides a promising technology for food disinfection.     

Effect of different solvents on volatile and non-volatile constituents of red bell pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.) and their in vitro antioxidant activity

The fresh fruit of Capsicum annuum L. (red bell pepper) was successively extracted using n-hexane, chloroform, ethyl acetate, ethanol and their percentage yield was calculated. The effectiveness of each extract on chemical composition and antioxidant activity was studied. The qualitative phytochemical evaluation of each extract of bell pepper was done by HPTLC and Gas chromatography–mass spectroscopy (GC-MS) analysis. The total content of phenols, flavonoids and carotenoids were estimated by standard chemical methods. Further, the antioxidant potential of each extract was measured via DPPH and reducing power assays. Gas chromatography–mass spectroscopy analysis showed that the majority of compounds were related to phenols and flavonoids. Further analysis of the extract by HPTLC verified the presence of different types of phenolic compounds in addition to flavonoids and carotenoids. Among the different solvent extracts analyzed, total phenolic content was higher in ethanol extract (7.136?±?0.03%, w/w) whereas ethyl acetate extract showed the presence of higher flavonoid content (4.0521?±?0.03%, w/w). The ethanol and ethyl acetate extracts of the fruit of C. annuum exhibited the highest radical scavenging activity with inhibition percentage of 53.66 and 49.55% at a concentration of 254 µg/ml. Based on the biochemical analysis and phytochemical screening, we conclude that C. annuum possess potent antioxidant potential and this ability of the extract is attributed to the presence of rich polyphenolic compounds.     

Supercritical fluid extraction of oils from apple seeds: Process optimization,chemical characterization and comparison with a conventional solvent extraction

Oils from apple seeds were extracted with the application of supercritical fluid (SFE) and Soxhlet techniques. The effect of SFE experimental variables such as pressure (10–30 MPa), temperature (40–60 °C) and carbon dioxide flow rate (1–8 L/h) on the yield, antioxidant activity and total phenolic content was investigated using a central composite design. The experimental data were fitted with a second-order polynomial equation using regression analysis. The maximum yield, obtained at the optimum processing conditions (24 MPa, 40 °C, 1 L/h of carbon dioxide flow rate, 140 min) was 20.5 ± 1.5% (w/w). For comparison, the yield from Soxhlet extraction was 22.5 ± 2.5% (w/w). Both techniques produced an oil with a fatty acids profile rich in linoleic acid. However, the extract from SFE was higher in linoleic acid (63.76 ± 4.96 g/100 g_oil) than that achieved by Soxhlet (49.03 ± 3.85 g/100 g_oil). Despite the higher unsaturated fatty acids content, SFE extracts reported a higher oxidative stability (21.4 ± 1.2 h) compared to that one extracted by Soxhlet (12.1 ± 1.1 h). This result was expport addressing the extraction of apple seed oil by supercritical fluid at pressures lower tha The most abundant phenolic compound found in the extract was phloridzin (2.96 ± 0.046 μg/gs_eed in SFE oil and 1.56 ± 0.026 μg/g_seed in Soxhlet). Instead, amygdalin, one of the antinutrients present in seeds, was not detected in the SFE oil.Industrial relevanceThe present study provided results addressing the extraction of apple seed oil by supercritical fluid at pressures lower than 30 MPa. The process allowed extracting an oil that was rich in unsaturated fatty acids, oxidative stable thanks to the high antioxidant activity, and free from anti-nutritional compounds.     

Optimization of Microwave-Assisted Extraction of Phenolic Antioxidants from Grape Seeds (Vitis vinifera)

Grape seeds (Vitis vinifera) are rich in phytochemicals that have antioxidant properties. The influence of independent variables such as microwave power (100, 150, and 200 W), extraction time (2, 4, and 6 min), and solvent concentration (30%, 45%, and 60% ethanol) and their interactions on total phenols and the antioxidant activity (1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric ion reducing antioxidant power (FRAP)) were determined; and the microwave-assisted extraction (MAE) process was optimized using a central composite design. The total phenols that were expressed as gallic acid equivalents (GAE), catechin equivalents (CAT), and tannic acid equivalents (TAE) were significantly influenced by the solvent concentration and the time of extraction. A numerical optimization was carried out to obtain the overall conditions for MAE of phenolic antioxidants from grape seed. The response variables were maximized for 6 min of MAE of grape seed (GS) with 32.6% ethanol at 121 W with a desirability function of 0.947. The predicted extraction yields were 13?±?0.89, 21.6?±?1.59, and 15.9?±?1.32 mg GAE, CAT, and TAE, respectively per gram of GS. The predicted antioxidant activity per gram of dry weight GS was 80.9% for the inhibition of DPPH and 135 μM ascorbic acid equivalents for FRAP test. The predicted response values were significantly correlated with the observed ones as follows: GAE r?=?0.995, CAT r?=?0.990, TAE r?=?0.996, DPPH r?=?0.996, and FRAP r?=?0.996.