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.     

Evaluation of antioxidant activities of Iranian sumac (R. coriaria L.) fruit and spice extracts with different solvents

The antioxidant capacity and phenolic content of three sumac (Rhus coriaria L.) samples, including brown sumac fruit, brown sumac powder and red sumac powder were investigated in the present study. Methanol, ethanol, distilled water, and a mixture of methanol and ethanol (1:1) were used as solvent systems. Antioxidant activities of extracts were screened using 1,1-diphenyl-2-picrylhydrazyl DPPH radical scavenging method. Phenolic content was determined through Folin–Ciocaltaeu procedure. The efficiency of the solvents used to extract phenols from the samples varied considerably. The phenolic content of brown sumac powder ranged from 2.906 to 2.997 gallic acid equivalents/100 g (GAE/100 g), while that of the brown sumac fruit was 2.438–2.529 GAE/100 g, and that of the red sumac powder was 2.172–2.263 GAE/100 g. Findings indicated that water extracts of sumac have effective antioxidant and radical scavenging activities as compared to other extracts.     

黄色洋葱皮不同溶剂多酚提取物的总酚、总黄酮含量及抗氧化活性

以黄色洋葱皮为原料,分别利用70%甲醇、70%乙醇和70%丙酮作为提取溶剂进行多酚类物质提取。测定提取物中的总酚含量、总黄酮含量并研究其抗氧化活性(DPPH自由基清除能力、ABTS自由基清除能力以及铁还原能力)。研究结果显示:利用甲醇作为提取剂所得的多酚类物质提取率最高(12.35%),并且提取物中总酚和总黄酮含量最高,分别为83.17、34.31 mg/g。同时,甲醇提取物对DPPH自由基和ABTS自由基的半抑制浓度IC₅₀分别为0.059和0.031 mg/mL,低于抗坏血酸而高于乙醇提取物和丙酮提取物。     

Composition and antioxidant activity of raisin extracts obtained from various solvents

Experiments were conducted to determine if the contents of phenolics and browning reaction products and antioxidant activity of raisin extracts were closely dependent on the extraction solvent. Enhanced extraction yields were obtained from solvent containing higher water concentrations. However, total phenolic content (TPC) was highest for extracts obtained from solvent to water ratios of 60:40 (v/v), whereby the extract obtained from ethanol:water (60:40, v/v) had the highest TPC of 375 mg gallic acid equivalents (GAE)/100 g extract. HMF content was highest in extracts obtained from 60% solvent, regardless of solvent type. The extract obtained from 60% methanol had the highest HMF content at 199 μg/g extract. Although the 60% solvents provided extract with high antioxidant components, the antioxidant activity of raisin extracts obtained from 80:20 (v/v) solvent/water was significantly higher than other raisin extracts obtained from different solvent concentrations. Phenolic acids, HMF, and low-molecular-weight flavonoids were responsible for the antioxidant activity, but not the high-molecular-weight flavonoids.     

Reutilization of mango byproducts: study of the effect of extraction solvent and temperature on their antioxidant properties

Mango biowastes, obtained after processing, contain large amounts of compounds with antioxidant activity that can be reused to reduce their environmental impact. The present study evaluates the effect of solvent (methanol, ethanol, acetone, water, methanol:water [1:1], ethanol:water [1:1], and acetone:water [1:1]), and temperature (25, 50, and 75 °C) on the efficiency of the extraction of antioxidants from mango peel and seed. Among the factors optimized, extraction solvent was the most important. The solvents that best obtained extracts with high antioxidant capacity were methanol, methanol:water, ethanol:water, and acetone:water (β-carotene test, antioxidant activity coefficient 173 to 926; thiobarbituric acid reactive substances test, inhibition ratio 15% to 89%; 2,2'-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid ABTS(·+); and 2,2-diphenyl-1-picrylhydrazyl DPPH· scavenging, 7 to 22 and 8 to 28 g trolox equivalent antioxidant capacity [TE] per 100 g mango biowaste on a dry matter basis [DW]). Similarly, the flavonoid (0.21 to 1.4 g (+)-catechin equivalents per 100 g DW), tannin (3.8 to 14 g tannic acid equivalents per 100 g DW), and proanthocyanidin (0.23 to 7.8 g leucoanthocyanidin equivalents per 100 g DW) content was highest in the peel extracts obtained with methanol, ethanol:water, or acetone:water and in the seed extracts obtained with methanol or acetone:water. From the perspective of food security, it is advisable to choose ethanol (which also has a notable antioxidant content), ethanol:water, or acetone:water, as they are all solvents that can be used in compliance with good manufacturing practice. In general, increasing temperature improves the capacity of the extracts obtained from mango peel and seed to inhibit lipid peroxidation; however, its effect on the extraction of phytochemical compounds or on the capacity of the extracts to scavenge free radicals was negligible in comparison to that of the solvent. PRACTICAL APPLICATION: There are many antioxidant compounds in mango peel and seed, and they could be used as a natural and very inexpensive alternative to synthetic food additives. However, the conditions in which the antioxidants are extracted must be optimized. This work proves that conditions such as extraction solvent or temperature have a crucial impact on obtaining extracts rich in antioxidants from mango biowastes.     

Enhancement of Bioactive Compounds and Antioxidant Activities of Olive (<Emphasis Type="Italic">Olea europaea</Emphasis> L.) Leaf Extract by Instant Controlled Pressure Drop

In this work, the effect of Détente Instantanée Contrôlée (DIC) (French for instant controlled pressure drop) on the total polyphenol, flavonoids, α-tocopherol contents, and antioxidant activities of olive leaves was studied. Olive leaf extracts were pre-treated at one cycle DIC under 0.1 MPa pressure for 11 s and followed by an extraction with 95% ethanol at 55 °C during 3 h. The phenolic compounds, flavonoïds, oleuropein, and α-tocopherol contents were determined, showing 66.63 mg gallic acid equivalent (GAE)/g db, 12 mg catechin equivalent (CE)/g db, 43.9 mg/g db, and 0.15 mg/g db for the untreated leaves against 239.37 mg GAE/g db, 28 mg CE/g db, 70.3 mg/g db, and 0.59 mg/g db for DIC-treated leaves, respectively. Therefore, DIC allows more availability of bioactive compounds contributing to a high antiradical activity (DPPH) compared to a synthetic antioxidant butylated hydroxytoluene (BHT). Both extracts showed a total antioxidant capacity (method of phosphomolybdenum) greater than that of the standard BHT. Likewise, both extracts have a reducing power (FRAP test) significant concentration-dependent. The DIC-treated leaves showed a higher antioxidant capacity compared to that of untreated leaves. Thus, DIC could be an effective treatment to promote the extraction of bioactive molecules of high antioxidant activities from olive leaves.     

Comparative analysis of antioxidant and antimelanogenesis properties of three local guava (Psidium guajava L.) varieties of Thailand, via different extraction solvents

The antioxidant and antimelanogenesis potentials of three local varieties of guava (Psidium guajava L.) from Thailand namely: Pansithong, Thai original and Kimju were studied. The extracts were made with water, 40 % ethanol and simulated gastrointestinal digestion (SGD). Antioxidant properties were determined by total polyphenolic compounds, DPPH assay, superoxide anion assay and hydroxyl radical assay. Antimelanogenesis properties were determined by anti-tyrosinase assay, total phenolic acid and total vitamin C contents. The results for antioxidant analysis revealed that Pansithong, when extracted by 40 % ethanol and SGD showed the presence of highest polyphenol compounds, and DPPH antioxidant activity respectively. Kimju exhibited the highest hydroxyl radical antioxidant activity among all extracts and highest superoxide anion antioxidant activity, when extracted by 40 % ethanol. The results for antimelanogenesis determination presented that Kimju showed highest tyrosinase inhibition, total phenolic acid and total vitamin C contents. It was concluded that Pansithong showed highest antioxidant potential while the highest antimelanogenesis potential was found in Kimju. Over all water has been found as the best solvent for antioxidant extraction followed by 40 % ethanol and SGD.     

Extraction of antioxidants from several berries pressing wastes using conventional and supercritical solvents

The solid waste generated in industrial berry juice production was considered as a low cost raw material for the extraction of natural antioxidants. Berries contain phenolic compounds with high antioxidant potential, including anthocyanins, proanthocyanidins, flavonols, catechins, benzoic and cinnamic acids. The solid residues generated from blueberry, cranberry and raspberry after pressing were extracted by conventional solvent extraction or by supercritical CO₂ (SC–CO₂) extraction. The effect of particle size and extraction time on the extraction yield, phenolic yield and phenolic content of the extracts produced by conventional solvents was assessed. Supercritical CO₂ extraction was performed during 2 h operating in the range 80–300 bar at 60 °C using 2.5 L CO₂/h. Maximum solubles yield of 5.20% were extracted from raspberry wastes at 200 bar, 3.89% from cranberry wastes at 250 bar and 1.4% from blueberry wastes at 200 bar. The highest phenolic content of the extracts was observed for blueberry pomace in the trap, with 9 grams of gallic acid equivalents per 100 g of extract. The ABTS (2, 2′-azino-bis-[3-ethylbenzotiazol-6-sulfonic acid]) and DPPH (α,α-diphenyl-β-picrylhydrazyl) radical scavenging capacity of the SC–CO₂ extracts was moderate in comparison with the activity of conventional solvent extracts.     

Screening of the phenolic profile and their antioxidative activities of methanol extracts of <Emphasis Type="Italic">Myrica rubra</Emphasis> fruits,leaves and bark

The phenolic composition in dried Myrica rubra fruits, leaves and bark were investigated for evaluation of its contribution to the antioxidant activity. The fruits, leaves and bark have the abundant phenolic compounds with the total phenolic content of 0.673, 0.276 and 0.136 mg/g (GA equivalents/FW), respectively. Ten phenolic compounds were isolated and identified in methanol extracts of Myrica rubra fruits by GC–MS analysis. Less phenolic compounds were found in leaves and bark than in fruits. However, the leaves and bark contain much higher concentrations of the trans-resveratrol over 100 μg/g than in fruits. The total antioxidant activities against the ·DPPH radical of those three samples were 0.438, 0.184 and 0.092 mg/g (Trolox equivalents/FW), respectively. The quantitative results indicated that a good correlation between the total antioxidant activity, total phenolic contents, and abundance of individual phenolic compound in Myrica rubra plants.     

Optimization of Antioxidant Compounds Extraction from Flesh of New Developed Apple Cultivar Using Response Surface Methodology

The response surface methodology (RSM) and the central composite rotatable design were used to optimize the antioxidant extraction from apple flesh of a new cultivar (Rural Issues and Agricultural Research Institute of Santa Catarina (EPAGRI) m-58/07). The extraction conditions were optimized by measured antioxidant capacities from the ferric-reducing power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays, and by the determination of total phenol content. The results showed that the most significant variable in the extraction procedure was solvent concentration. The optimal condition found was of 60 %, 5 mL/g, 30 °C, and 61 min for acetone aqueous solution, solvent to solid ratio, temperature, and time, respectively, resulting in optimal antioxidant capacities of 2,152.96 μmol TE/100 g DW by DPPH and 6,491.39 μmol Fe²⁺/100 g DW by FRAP essays, and total phenol amount of 485.62 mg GAE/100 g DW. The antioxidant capacity of EPAGRI m-58/07 was verified to be substantially higher than other cultivars commercially available.     

Radiation-induced enhancement of antioxidant activity in extracts of rosemary (Rosmarinus officinalis L.)

Dry rosemary leaf powder was subjected to 30 kGy of gamma ray irradiation, followed by solvent extraction with methanol, ethanol or water. The antioxidant activity of the extracts was assessed using the DPPH radical-scavenging method and the reducing power test. EC₅₀ values, using the radical-scavenging method, indicate a 22% increase in the antioxidant activity of ethanol and water extracts as a result of irradiation treatment. EC₅₀ values in the reducing power test show an increase of 45% and 28% for the ethanol and water extracts, respectively. The antioxidant activity of methanol extracts of irradiated rosemary remained the same as in the controls in both types of test. A high correlation was found between the EC₅₀ values obtained in the DPPH radical test and those from the reducing power test. Total phenolic content (Folin–Denis test) increased by 35% in the water extracts as a result of irradiation but remained the same in the methanol and ethanol extracts. The methanol extract showed the highest antioxidant activity and the highest amount of total phenolic compounds. Radiation reduced the good correlation between antioxidant activity and total phenolic content.     

Influence of pressurised liquid extraction and solid–liquid extraction methods on the phenolic content and antioxidant activities of Irish macroalgae

The efficiencies of pressurised liquid extraction (PLE) and a traditional solid–liquid extraction (SLE) at extracting antioxidant polyphenols from Irish macroalgae Ascophyllum nodosum, Pelvetia canaliculata, Fucus spiralis and Ulva intestinalis were compared. PLE was more effective for extracting polyphenols with acetone/water (80:20); however, when food‐friendly solvents of ethanol/water (80:20) and water were employed, SLE resulted in higher phenolic content in brown macroalgal extracts. For example, the Fucus spiralis SLE water and ethanol/water extracts displayed total phenolic contents (TPCs) of 130.58 ± 2.78 and 142.81 ± 1.77 μg phloroglucinol equivalents (PGE) mg^?1 sample, respectively, compared with TPCs of 90.79 ± 1.16 and 124 ± 6.54 μg PGE mg^?1 sample for the corresponding PLE extracts. All SLE aqueous ethanolic macroalgal extracts possessed higher DPPH radical scavenging abilities (RSA) and ferric reducing antioxidant power (FRAP) than their PLE equivalents . This study indicates that the application of high extraction temperatures (50–200 °C) and pressures (500–3000 psi) used in PLE does not enhance the antioxidant activities of macroalgal extracts relative to SLE extraction. The ability to produce antioxidant food‐friendly macroalgal extracts using SLE could represent significant cost reductions on an industrial scale further enhancing the potential of macroalgal polyphenols to be used in functional food preparations.     

Polyphenols contents and antioxidant capacity of 68 Chinese herbals suitable for medical or food uses

The present study estimated in vitro antioxidant activities of 68 common Chinese herbals both for medical and food uses, using Folin–Ciocalteu, ferric-reducing/antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assays. The results showed different extraction had various antioxidant properties. Six plant materials including Chinese White Olive, Clove, Pricklyash Peel, Villous Amomum Fruit, Chinese Star Anise and Pagodatree Flower appeared highest total phenolics (>45 mg gallic acid equivalents (GAE)/g) and flavonoids content (>45 mg rutin equivalents (RE)/g), which also showed highest antioxidant activity (FRAP value > 2.5 mmol/g, DPPH radical-scavenging capacity > 85%), indicating they have potentials for use as natural sources of antioxidant foods. The total phenolics content of these 68 plant extracts was significantly positively correlated (r² = 0.9467) with their antioxidant capacity. Therefore, the content of phenolic compounds could be used as an important indicator of its antioxidant capacity.     

大叶紫薇叶提取物抗氧化性能的研究

采用不同溶剂对大叶紫薇叶进行浸泡提取,计算提取率,并用FolinCiocalteu方法测定总酚含量;采用DPPH分析法和FRAP分析法评估了不同溶剂提取物的抗氧化活性,选出抗氧化活性最高的提取物添加到猪肉中,于4℃光照下贮存12d,通过测定贮存期间猪肉的TBARS值、pH值和亨特L、a、b值,评估了提取物抗脂质氧化、防腐保鲜和护色作用,并与BHT、VE、茶多酚比较。结果表明,不同溶剂提取物显示出不同的抗氧化活性,其中甲醇提取物抗氧化活性最高(高于BHT),其提取率和总酚含量也最高。大叶紫薇叶甲醇提取物在生猪肉中具有明显的抗脂质氧化和防腐保鲜的作用,且随着提取物含量的增大,抗氧化的效果增强,有明显的量效关系。     

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.     

Extraction of natural antioxidants from hazelnut (Corylus avellana L.) shell and skin wastes by long maceration at room temperature

The feasibility of obtaining antioxidant phenolic extracts from hazelnut by-products was investigated by long maceration at room temperature. The hard shells and defatted skins of both whole and chopped roasted hazelnut kernels were studied. Three solvent systems were employed and these included aqueous methanol, ethanol and acetone. Extraction yields as well as phenolic contents varied according to the by-product and the solvent used. Among the studied samples, the skin of whole roasted hazelnuts gave remarkably high extraction yields (about 30%) and extracts with the richest phenolic content (up to 502 mg/g, expressed as gallic acid equivalents).

Extracts were screened for antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidation of linoleic acid in vitro model systems. The extracts from the skin of whole roasted hazelnuts manifested the strongest antioxidant activity, similar or superior to butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) and -tocopherol, at equivalent concentrations. The presence of hazelnut fragments in the skin residue lowered the yield and the antioxidant activity of the extract. All the extracts were found to be very rich in tannins.     

黑小麦麸皮抗氧化活性成分提取及其抗氧化能力评价

黑小麦麸皮是黑小麦加工过程中的副产物,其富含多种生理活性物质,包括花青素、酚酸类物质、膳食纤维等。以黑小麦麸皮为原料,利用不同溶剂对其抗氧化活性成分进行提取并对其抗氧化能力评价研究。结果表明,75%乙醇提取物干物质得率最高,为10.72%;50%乙醇提取总酚含量最高,为2.9 mg/100 mL;50%乙醇提取物对1,1-二苯基-2-三硝基苯肼（DPPH）清除力最强,75%乙醇提取物对DPPH抗氧化物提取能力最强;75%丙酮提取物对2,2′-联氮-双-3-乙基苯并噻唑啉-6-磺酸（ABTS）清除力最强,75%甲醇提取物对ABTS抗氧化物提取能力最强。综合比较得出,50%乙醇更适于黑小麦麸皮抗氧化活性成分提取。     

Optimization of phenolic compound recovery and antioxidant activity of light and dark dried fig (Ficus carica L.) varieties

The optimum conditions for extraction of total phenolic contents (TPC) and for enhancing the antioxidant activity from light and dark dried figs were determined. The effects of the solvent nature (acetone, ethanol, methanol, or water), solvent concentration (20–80%), acetic acid concentration (0–2%), extraction temperature (25–70°C), extraction time (0.5–4 h), sample to solvent ratio (1/25–1/100), and number of extractions (1, 2, and 3) were determined. The TPC was used to identify antioxidant compounds. 2,2-diphenyl-1-picrylhydrazyl (DPPH) was used to evaluate antioxidant activity. All extraction parameters had significant effects (p<0.05) on the TPC and the antioxidant activities. The best conditions were obtained with double extraction using 60% acetone without acidification, at 40°C for 120 min, and with a 1/75 solid to solvent ratio. These conditions resulted in TPC concentrations of 469.46 (light variety) and 399.79 mg of gallic acid (GAE)/100 g (dark variety), and antioxidant activities of 96.47 and 102.28 mg of GAE/100 g, respectively.     

溶剂提取对青稞中不同形态多酚组成及抗氧化活性的影响

为研究不同极性溶剂对青稞全谷物中不同形态酚类化合物含量、组成及抗氧化性的影响,建立适宜于青稞全谷物中多酚提取的方法。以4?个不同品种青稞为原料,比较4?种不同溶剂及酸法、碱法分别对青稞中游离酚和结合酚含量、组成与抗氧化活性的影响。结果表明,所有提取试剂中80%丙酮溶液提取的游离态总酚含量（139.79～235.96?mg/100?g）及总黄酮含量（9.88～15.52?mg/100?g）最高,酸法提取的青稞结合态总酚含量是碱法的1.9～3.1?倍,结合态黄酮含量是碱法的1.3～2.9?倍;80%丙酮溶液提取物中检测到8～18?种青稞游离酚类化合物,且酚类化合物含量显著高于其他溶剂,绿原酸、苯甲酸、儿茶素、槲皮素、芦丁是其主要的游离酚类化合物。与碱法相比,酸法能释放出更多的结合酚类化合物类型及含量,没食子酸、p-香豆酸、丁香酸、苯甲酸、藜芦酸、橙皮苷是其主要的结合酚类化合物;参试青稞80%丙酮溶液提取物显示出最高的1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除能力（852.56～1?484.18?μmol/100?g）,2,2’-联氮-双-（3-乙基苯并噻唑啉-6-磺酸）二铵盐（2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate),ABTS）自由基清除能力（358.93～518.09?μmol/100?g）及铁离子还原能力（ferric ion reducing antioxidant power,FRAP）（1?250.55～2?041.16?μmol/100?g）。酸法水解参试青稞结合酚DPPH自由基清除能力、FRAP、ABTS＋?清除能力分别是碱法水解的7.6～10.3、1.2～1.8?倍和1.1～1.3?倍。因此,80%丙酮溶剂和酸法分别是青稞中游离酚与结合酚的适宜提取溶剂,且本研究表明青稞全谷物中富含丰富的酚类物质,是一种潜在的天然抗氧化剂来源。     

Optimization of microwave-assisted extraction of phenolics from potato and its downstream waste using orthogonal array design

While other extraction methods have been tempted, a microwave-assisted extraction (MAE) method coupled with the orthogonal array design was investigated for efficient extraction of the phenolic compounds in potato downstream wastes. Four parameters were examined for the MAE of the total phenolic content (TPC) and optimized at 60% ethanol, 80 °C, 2 min, solid-to-solvent ratio 1:40 (g/ml). The MAE was proven more efficient than the conventional solvent extraction by refluxing. The optimized model showed that the downstream wastes, both the supernatant and the residue contained high TPC, particularly the former (11.0 ± 0.26 mg GAE/g DW). The antioxidant activities (DPPH and FRAP) closely correlated with the TPC of the samples (r = 0.92–0.97). Chlorogenic acid and caffeic acid were found to be the predominant phenolic acids. The extracts of the downstream wastes from potato processing can be a promising candidate for functional foods and nutraceutical ingredients.