Comparison of thermal and non-thermal extraction methods on free and bound phenolics in pomegranate peel

Pomegranate peel is a valuable byproduct for phenolic extraction. However, comprehensive analysis on novel extraction methods is lacking. In this study, free and bound phenolics, extracted by thermal (heating) and non-thermal methods (conventional solvent, high pressure, and ultrasound), were systematically compared by UHPLC-QTOF-MS and UPLC-QQQ-MS. The total content of free phenolics, approximately 10 times to that of bound phenolics, showed no significant difference across different extraction methods. The highest yield of bound phenolics was obtained by heating and high-pressure methods and the composition was closely dependent on the degree of alkaline hydrolysis. Many of bound phenolics obtained by thermal extraction were small molecules. Meanwhile, a greater proportion of larger compounds were obtained by high-pressure extraction, indicating that high pressure was gentler than thermal extraction. Genistin, nicotiflorin and myricetin-3-galactoside were first reported in pomegranate peel. This study provides a solid foundation for purposeful extraction of phenolics from pomegranate peels for industry.     

Influence of origin source, different fruit tissue and juice extraction methods on anthocyanin, phenolic acid, hydrolysable tannin and isolariciresinol contents of pomegranate (Punica granatum L.) fruits and juices

To gain more comprehensive knowledge of pomegranate (Punica granatum L.) fruit composition and its impact on juice features, fruits and juices produced from fruits of eleven different provenances were investigated by HPLC–DAD-ESI/MSⁿ for their monomeric phenolic and lignan profiles. Total phenolics and antioxidant capacity were monitored by the Folin-Ciocalteu, ferric reducing antioxidative power and Trolox equivalent antioxidant capacity assays. Peels, mesocarp, seeds and juices obtained from isolated arils (PJAs) as well as from entire fruits were separately analyzed. Ellagitannins were found to be the predominant phenolics in all samples except in PJAs. However, due to the low lignan amounts, only isolariciresinol could be quantitated in peels and mesocarp. The peels and mesocarp revealed highest contents of hydrolyzable tannins (27–172 g/kg and 32–263 g/kg, respectively) and isolariciresinol (4.9–19.8 mg/kg and 5.0–13.6 mg/kg, respectively). To the best of our knowledge, a systematic investigation of monomeric phenolic compounds and isolariciresinol considering diverse pomegranate fruits has been performed for the first time. The study demonstrates that raw material and extraction process have significant impact on juice composition and thus must be carefully selected. Furthermore, pomegranate processors should select juice extraction processes according to the final designation of the product, that is, distinguish between dietary products being rich in phenolic compounds having an astringent taste, and juices for consumption having an appealing taste but lower amounts of phenolics, respectively. This study may further contribute to facilitate authenticity control of diverse pomegranate products and help predict sensory and biofunctional characteristics of pomegranate juices.     

Antioxidant capacities of phenolic compounds and tocopherols from Tunisian pomegranate (Punica granatum) fruits

This article aims to determine the phenolic, tocopherol contents, and antioxidant capacities from fruits (juices, peels, and seed oils) of 6 Tunisian pomegranate ecotypes. Total anthocyanins were determined by a differential pH method. Hydrolyzable tannins were determined with potassium iodate. The tocopherol (α-tocopherol, γ-tocopherol, and δ-tocopherol) contents were, respectively, 165.77, 107.38, and 27.29 mg/100 g from dry seed. Four phenolic compounds were identified and quantified in pomegranate peel and pulp using the high-performance liquid chromatography/ultraviolet method: 2 hydroxybenzoic acids (gallic and ellagic acids) and 2 hydroxycinnamic acids (caffeic and p-coumaric acids). Juice, peel, and seed oil antioxidants were confirmed by ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) methods. The highest values were recorded in peels with 25.63 mmol trolox equivalent/100 g and 22.08 mmol TE/100 g for FRAP and ORAC assay, respectively. Results showed that the antioxidant potency of pomegranate extracts was correlated with their phenolic compound content. In particular, the highest correlation was reported in peels. High correlations were also found between peel hydroxybenzoic acids and FRAP ORAC antioxidant capacities. Identified tocopherols seem to contribute in major part to the antioxidant activity of seed oil. The results implied that bioactive compounds from the peel might be potential resources for the development of antioxidant function dietary food.     

Bioactive compounds,pigments, antioxidant activity and antimicrobial activity of yellow prickly pear peels

The main goal of this research was to study the effects of pressure, extraction time and ethanol concentration on antioxidant activity, total phenolics, flavonoids, anthocyanins, carotenoids and betalains compounds extraction from yellow prickly pear peels. A Box–Behnken design and Response Surface Methodology were used to evaluate the effects and estimate the optimum extraction conditions. Antimicrobial activity was evaluated against Escherichia coli and Listeria innocua. Ethanol concentration was the variable that showed the highest effect on extraction yields but high-pressure increased extraction yields between 6% and 17%. Models showed good fitting and adequacy to the experimental data and the high correlation of models indicated that it can be employed to optimise extraction conditions. The experimental and predicted values differed <10% and the extracts inhibited the growth of both bacteria. High-pressure could be a promising extraction process to improve extraction of bioactives from prickly pear peels.     

Aroma,Sugar and Anthocyanin Profile of Fruit and Seed of Mahlab (Prunus mahaleb L.): Optimization of Bioactive Compounds Extraction by Simplex Lattice Mixture Design

In the present study, bioactive properties of black mahlab fruit and seed were investigated. Simplex lattice mixture design was used to determine the best solvent composition for the extraction of bioactive compounds of the samples. The content of total phenolics, total flavonoids, condensed tannins, total anthocyanins, and antiradical efficiency of mahlab fruit and seed extracts were investigated by spectrophotometric methods. Moreover, major sugar composition, individual anthocyanins, fatty acids, and aroma profile of the samples were determined by chromatographic methods. Effect of temperature on degradation of anthocyanins was also investigated, and degradation kinetic model parameters were calculated. Finally, the constructed simplex lattice mixture design model was optimized to estimate the optimum solvent mixtures that would yield maximum total phenolic content. The best solvent mixture was found to be 36 % of acetone and 64 % of water. It was concluded that the experimental and predicted values were in good agreement. Total phenolics and flavonoids of the fruit were 2,266 mg gallic acid equivalent/100 g of dry sample and 946.57 mg catechin equivalent/100 g of dry sample, respectively. Total anthocyanin content of the fruit was 505.7 mg/100 g of dry sample. Temperature showed a significant degradation effect on the anthocyanins.     

Bioactive compounds extracted by liquid and supercritical carbon dioxide from citrus peels

This work investigated the extraction of bioactive compounds from citrus peels, an agri-food waste. Carbon dioxide (CO₂), an eco-friendly solvent, was used under liquid and supercritical conditions to perform the extractions from orange, tangerine and lemon peels. The possibility of using ethanol as a cosolvent at small percentages up to 20% was also studied. The extraction yield, total polyphenolic content, individual polyphenolic profile, antiradical activity and volatile organic compounds of the extracts were evaluated. The highest yields were obtained when 20% ethanol was used as a cosolvent in both liquid (at 20 MPa and 20 °C) and supercritical (at 30 MPa and 60 °C) CO₂ extraction. In addition, the extracts obtained with liquid CO₂ + 20% ethanol showed the highest content of naringin (35.26, 44.05 and 19.86 mg g^-1 in orange, tangerine and lemon peel extracts, respectively) and terpenes, in particular limonene. This type of extract also showed the highest antiradical activity (31.78–59.51 µmolTE g^-1) as measured by both ABTS·+ and DPPH·. These findings show that the extraction with a liquid CO₂ and ethanol mixture could be a valid alternative to traditional solvent extraction using 80% less organic solvent and producing extracts with high antiradical capacity and rich in volatile organic compounds.     

Antioxidant activities of onion (Allium cepa L.) peel extracts produced by ethanol,hot water,and subcritical water extraction

Onion (Allium cepa L.) peels were extracted by ethanol, hot water and subcritical water (SW) extraction and their antioxidant activities were evaluated. Extraction yields of SW extraction were 4-fold higher than ethanol extraction. However, the ethanol extraction increased the total phenolics contents (327.5 mg GAE/g extract) and flavonoids contents (183.95 mg QE/g extract) in the onion peel extract. The onion peel extracts by ethanol extraction showed greater DPPH radical scavenging activities and greater antioxidant activities determined by ferric thiocyanate assay than those by hot water extraction and SW extraction at 165°C. Antioxidant activity of onion peel extract by SW extraction at 110°C was similar to that of ethanol extraction. HPLC profiles revealed that SW extraction at lower temperature (110°C) increased the concentration of quercetin. These results demonstrated that the onion peel extracts produced by SW extraction technique have great potential as a source for useful antioxidant.     

Evaluation of antioxidant properties of pomegranate peel extract in comparison with pomegranate pulp extract

Pomegranate is an important source of bioactive compounds and has been used for folk medicine for many centuries. Pomegranate juice has been demonstrated to be high in antioxidant activity and is effective in the prevention of atherosclerosis. In a previous study, we found that pomegranate peel had the highest antioxidant activity among the peel, pulp and seed fractions of 28 kinds of fruits commonly consumed in China as determined by FRAP (ferric reducing antioxidant power) assay. In this study, we extracted antioxidants from pomegranate peel, using a mixture of ethanol, methanol and acetone, and the antioxidant properties of the extract were further investigated as compared with the pulp extract. The contents of total phenolics, flavonoids, proathocyanidins and ascorbic acid were also measured. The results showed that pomegranate peel extract had markedly higher antioxidant capacity than the pulp extract in scavenging or preventive capacity against superoxide anion, hydroxyl and peroxyl radicals as well as inhibiting CuSO₄-induced LDL oxidation. The contents of total phenolics, flavonoids and proathocyanidins were also higher in peel extract than in pulp extract. The large amount of phenolics contained in peel extract may cause its strong antioxidant ability. We concluded that pomegranate peel extract appeared to have more potential as a health supplement rich in natural antioxidants than the pulp extract and merits further intensive study.     

Optimization of supercritical fluid extraction of bioactive compounds from grape (Vitis labrusca B.) peel by using response surface methodology

Supercritical fluid extraction (SFE) was applied for the extraction of valuable compounds from grape (Vitis labrusca B.) peel. Extraction was carried out according to an orthogonal array design (OAD) and independent variables selected were temperature, pressure and modifier concentration. SFE process was optimized by using response surface methodology (RSM) for the extract yield, total phenols, antioxidants and total anthocyanins from grape peel. Effects of extraction temperature and pressure were found to be significant on all responses. Optimal SFE conditions were identified as 45–46 °C temperature, 160–165 kg cm^? 2 pressure and 6–7% ethanol as modifier for maximum extract yield (12.31%), total phenols (2.156 mg GAE/100 mL), antioxidants (1.628 mg/mL) and total anthocyanins (1.176 mg/mL). Experimental values for response variables at these optimal conditions match well with the predicted values. Grape peel extracts obtained by SFE showed more than 93% DPPH radical scavenging activities.Industrial relevanceThis study describes the response surface optimization of supercritical fluid extraction (SFE) process for the enhanced recovery of total phenols, antioxidant and anthocyanins from grape peel. SFE uses CO₂ as supercritical fluid which is environment friendly solvent; allows extraction at lower temperature and the extracts obtained possess higher quality and safety. Industrially, it may be used as a promising technique for the extraction of bioactive compounds from plant materials.     

Characterisation and screening of the process stability of bioactive compounds in red fruit paste and red fruit juice

Epidemiological studies have related the consumption of fruits and vegetables to a lower risk of chronic diseases. Phytochemicals are held responsible for these desired effects; vitamin C and phenolic compounds being the most important ones in strawberries and raspberries. With respect to their role in health, it is valuable to study possible changes of these bioactive compounds during processing of fruits. In the present study, total phenolics, anthocyanins and vitamin C were firstly characterised in strawberries, raspberries and their juices. Thermal and high-pressure processes were screened for their effect on the bioactive compounds by treating strawberries and raspberries at different temperature–pressure combinations for one fixed treatment time (20 min). Thermal processing at atmospheric pressure (50–140 °C) had a degradative effect on anthocyanins and vitamin C. High-pressure processing (400, 600, 700 MPa combined with 20, 50, 80, 110 °C) showed no significant effect on the bioactive compounds in function of pressure. Breakdown of anthocyanins and vitamin C did occur at constant elevated pressure as temperature increased. No clear trends were perceptible for the amount of phenolic substances during processing.     

Pulsed electric field, ultrasound, and thermal pretreatments for better phenolic extraction during red fermentation

The moderate thermal (MT), ultrasound (US), and pulsed electric field (PEF) pretreatments are studied to enhance the phenolics extraction from Cabernet Franc (CF) grapes. The next pretreatment conditions are investigated: MT (50 °C, 15 min, 125 kJ/kg), US1 (24 kHz, 5 min, 121 kJ/kg), US2 (24 kHz, 10 min, 242 kJ/kg), US3 (24 kHz, 15 min, 363 kJ/kg), PEF1 (0.8 kV/cm, 100 ms, 42 kJ/kg), and PEF2 (5 kV/cm, 1 ms, 53 kJ/kg). The qualitative parameters of extracts (pH, °Brix, and color intensity), their total polyphenols content, anthocyanins, tannins, and free radical scavenging activity were determined during the whole period of alcoholic fermentation. The results show that all studied pretreatments improve phenolics extraction (anthocyanins and tannins content), color intensity, and scavenging activity of the samples during red fermentation. However, the moderate (0.8 kV/cm) and high (5 kV/cm) PEF were the most effective pretreatments and increased the phenolics extraction yield, respectively, on 51 and 62 %, while the MT and US3 pretreatments increased the phenolics extraction yield, respectively, on 20 and 7 %. The anthocyanin and tannins were also better extracted, and the color intensity was highest after the PEF pretreatments in comparison with the MT and US pretreatments.     

A process for turning pomegranate peels into a valuable food ingredient using ultrasound-assisted extraction and encapsulation

A new method for pomegranate peel application in food industries was developed based on the ultrasound-assisted extraction of phenolic compounds and their subsequent encapsulation by spray drying. The effects of various parameters on extraction yield, on encapsulation efficiency/yield, and on the main physical properties of the microcapsules (moisture content, bulk density, rehydration ability) were studied. Ultrasound was found to increase extraction yield, but mainly to shorten the treatment time by over 20 times. The maximum encapsulation efficiency was 99.80% and the optimum operating conditions were found to be: wall material, maltodextrin/whey protein isolate (50:50); inlet air temperature, 150 °C; drying air flow rate, 17.5 m³/h; ratio of wall to core material, 9/1; feed solid concentration, 30% (w/w). The encapsulated phenolic extract was found efficient in improving the shelf life of hazelnut paste, in spite of the limited solubility of the crude extract in such a high lipid content matrix.Industrial relevancePomegranate peels, a by-product of pomegranate juice and concentrate industries, present a wide range of pharmaceutical and nutraceutical properties. Therefore, the peels could have more beneficial applications in food industries instead of being used as animal feed or in commercial cosmetic products. In this work, a new method for pomegranate peel application was developed based on the ultrasound-assisted extraction of phenolics and their subsequent encapsulation by spray drying.     

果皮中酚类物质含量、抗氧化活性及在体外消化过程中成分的变化

从21 种果皮中筛选出总酚、总黄酮含量较高的果皮,并选择1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基、2,2’-联氨-双-3-乙基苯并噻唑啉-6-磺酸（2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid),ABTS）阳离子自由基清除力评价其抗氧化活性。对筛选出酚类物质含量高且抗氧化活性强的果皮进行体外模拟胃肠液消化,研究不同消化时间对总酚、总黄酮释放量的影响,并通过透析袋模拟肠道的吸收作用,考察其生物利用率,同时利用超高效液相色谱-二极管阵列检测器/电喷雾飞行时间质谱（ultra performance liquid chromatography-diode array detector/electrospray ionization-time of fight-mass spectrometry,UPLC-DAD/ESI-TOF-MS）研究模拟胃肠液消化前后酚类物质变化。结果表明：21 种果皮中石榴皮（总酚含量为（58.09±0.46）mg/g、总黄酮含量为（47.50±0.39）mg/g）和山竹皮（总酚含量为（52.09±1.52）mg/g、总黄酮含量为（36.07±0.46）mg/g）中酚类物质含量较高;石榴皮的抗氧化能力强于山竹皮;模拟胃液消化阶段,石榴皮中总酚和总黄酮释放量均增加,模拟肠液消化阶段总酚和总黄酮的释放量先增加后减少;与胃液消化阶段相比,肠液消化阶段总酚和总黄酮含量明显降低;生物利用率测定结果表明总酚的生物利用率在每个时间点均强于总黄酮;通过UPLC-DAD/ESI-TOF-MS从石榴皮提取物中共检测出的5 种酚类化合物（分别为α-安石榴苷、β-安石榴苷、鞣花酸己糖苷、鞣花酸脱氧己糖苷、鞣花酸）,其在胃液消化过程中损失率小于肠液消化,说明石榴皮中酚类物质在酸性环境中结构稳定。     

Microwave Maceration of Pinot Noir Grape Must: Sanitation and Extraction Effects and Wine Phenolics Outcomes

Pinot noir grapes have a unique phenolic profile which can impinge on the extraction and stabilisation of compounds such as anthocyanins and tannins which contribute to the colour and mouthfeel of red wine. This study examined the concentration of phenolic compounds in Pinot noir grape must and wine following application of a novel microwave maceration treatment for red grape must. Microwave maceration was shown to be highly effective for extraction of phenolics from grape solids into grape juice. When juices were fermented to wine, ultraviolet–visible spectrophotometry showed microwave maceration was associated with significantly higher concentrations of total phenolics, anthocyanin, tannin and pigmented tannin in wine at 18 months bottle age, compared with control wine. Mean tannin concentration in microwave treatment wine was 0.60 gm/L at 18 months, compared with 0.14 gm/L in control wine. The microwave treatment was also associated with a substantial and rapid decrease in the grape-associated yeast population, compared with control maceration, and a shorter lag phase at the outset of alcoholic fermentation. Based on this study, microwave maceration warrants further investigation as a potential industrial-scale application in red winemaking.     

Effects of UVB Light,Wounding Stress,and Storage Time on the Accumulation of Betalains,Phenolic Compounds,and Ascorbic Acid in Red Prickly Pear (<Emphasis Type="Italic">Opuntia ficus-indica</Emphasis> cv. Rojo Vigor)

Prickly pear (Opuntia ficus-indica cv. Rojo Vigor) fruit is an excellent source of secondary metabolites with health-promoting properties (i.e., betalains, flavonoids, and ascorbic acid), and thus, it is relevant to find postharvest treatments that increase their concentration. Postharvest abiotic stresses such as wounding and ultraviolet radiation can induce the accumulation of secondary metabolites in different horticultural crops. In the present study, the effect of ultraviolet B (UVB) radiation applied alone or combined with wounding stress on the accumulation of betalains, phenolics, and ascorbic acid in red prickly pear was evaluated. Whole and wounded fruit samples were treated with UVB radiation (6.4 W m^?2) for 0, 15, 90, and 180 min and stored for 24 h at 16 °C. The content of bioactive compounds was evaluated before and after storage. The application of UVB radiation for 15 min was the most adequate treatment to induce the accumulation of bioactive compounds. In this context, UVB radiation (15 min) of the wounded tissue resulted on an immediate accumulation of betalains (33–40%) and ascorbic acid (54–58%) in the pulp and peel of the fruit. Likewise, after storage, the pulp of irradiated whole fruits showed the highest accumulation of phenolics (125.8%) and betalains (49.8%) as compared with the control, whereas the stored wounded tissue treated with UVB presented accumulation of ascorbic acid in the pulp (67.2%) and peel (84.6%). The stressed tissue with enhanced concentration of nutraceuticals could be transformed into functional processed foods or used as raw material for the extraction of compounds with applications in health-related markets.     

Alternative Extraction Method of Bioactive Compounds from Mulberry (<Emphasis Type="Italic">Morus nigra</Emphasis> L.) Pulp Using Pressurized-Liquid Extraction

Black mulberry (Morus nigra L.) is one of the most important species of the genus Morus as its fruit contains substantial levels of anthocyanins and phenolic compounds which show a potentially positive effect on the human health. Nowadays, PLE is becoming a promising extraction technology. Therefore, the development of fast extraction methods of anthocyanins and phenolic compounds from mulberry pulp using pressurized-liquid extraction (PLE) has been studied in this paper. The operating conditions (solvent, temperature, pressure, purge time, pH, and flushing) were investigated by a Box–Behnken design. Analysis of the model clearly showed that the most influential factors were temperature and solvent composition. The optimum extraction conditions for anthocyanins were 47.2% methanol in water, a temperature of 75.5 °C, pressure of 200 atm, a purge time of 90 s, pH 3.01, and 50.2% for flushing. The best conditions for the extraction of phenolics were 74.6% methanol, 99.4 °C, 100 atm, 90 s purge, pH 7, and 100% flushing. The optimum extraction time was 10 min. The precision values of the methods were also evaluated and excellent results (RSD?<?5%) were obtained. The developed methods were successfully applied to several mulberry marmalade samples. The results using PLE were compared to those achieved by UAE methods. Similar extraction yields were obtained for anthocyanins by PLE and UAE under optimized conditions; however, PLE required less methanol consumption. Besides, PLE showed higher extraction efficiency for total phenolic compounds. From the results, it can be concluded that pressurized-liquid extraction can be considered as an efficient alternative and powerful tool for the extraction of bioactive compounds from mulberries.     

Optimization of extraction conditions of total phenolics, antioxidant activities, and anthocyanin of oregano, thyme, terebinth, and pomegranate

The purpose of this study was to evaluate the total phenolic extracts and antioxidant activity and anthocyanins of varieties of the investigated plants. These plants include oregano, thyme, terebinth, and pomegranate. The optimum extraction conditions including temperature and solvent of the extraction process itself were investigated. Total phenolic and anthocyanin extracts were examined according to Folin-Ciocalteu assay and Rabino and Mancinelli method, respectively. The effect of different extracting solvents and temperatures on extracts of phenolic compounds and anthocyanins were studied. Plant samples were evaluated for their antioxidant chemical activity by 2, 2-diphenyl-1-picrylhydrazl assay, to determine their potential as a source of natural antioxidant. Results showed that all tested plants exhibited appreciable amounts of phenolic compounds. The methanolic extract (60 °C) of sour pomegranate peel contained the highest phenolic extract (4952.4 mg/100 g of dry weight). Terebinth green seed had the lowest phenolic extract (599.4 mg/100 g of dry weight). Anthocyanins ranged between 3.5 (terebinth red seed) and 0.2 mg/100 g of dry material (thyme). Significant effect of different extracting solvents and temperatures on total phenolics and anthocyanin extracts were found. The methanol and 60 °C of extraction conditions found to be the best for extracting phenolic compounds. The distilled water and 60 °C extraction conditions found to be the best for extracting anthocyanin.     

石榴皮单宁的提取、纯化及抑菌作用的研究

石榴皮中含有丰富的单宁类物质,具有良好的抑菌活性。以丙酮为提取溶剂,采用超声波辅助法对石榴皮单宁进行提取,并用Amberlite XAD-16大孔吸附树脂纯化,经高效液相色谱对其组分进行分析后,采用琼脂稀释法做最小抑菌浓度实验,结果表明:石榴皮提取物的主要成分为安石榴苷,纯化后质量浓度由12.3%提高到64.2%;石榴皮粗提物对金黄色葡萄球菌、单核细胞增生李斯特氏菌、沙门氏菌和大肠杆菌的最小抑菌浓度分别为0.312、10、0.625mg/mL和大于10mg/mL,纯化物对四种菌的最小抑菌浓度分别为0.156、5、0.625、10mg/mL。      

Effect of Osmotic Dehydration Under High Hydrostatic Pressure on Microstructure, Functional Properties and Bioactive Compounds of Strawberry (Fragaria Vesca)

Sliced strawberries were subjected to combined osmotic dehydration (40 °Brix) and high hydrostatic pressure (HHP) at 100, 200, 300, 400 and 500 MPa for 10 min. This research was carried out to study the effects of pressure on firmness, polysaccharides, total dietary fibre and microstructure, functional properties (rehydration ratio and water holding capacity) and bioactive compounds (anthocyanins, flavonoid and total phenolic). HHP affected the texture of the fruits leading to soft fruits due to increasing pressure. Fruit microstructure evidenced influence of pressure presenting the pressurised samples irregular matrices compared to samples treated at 0.1 MPa (control samples). Polysaccharides increased with pressure. Total dietary fibre, anthocyanins, flavonoids and total phenolic content showed a decrease with pressure when compared to control samples. Based on results, minor alterations of the mentioned quality parameters were evidenced when working in the range of 300–500 MPa.     

Pressurised water extraction of polyphenols from pomegranate peels

Pomegranate peels are one of the most valuable by-products of the food industry in terms of polyphenols which are conventionally extracted from plant materials by organic solvents, especially with methanol. Pressurised water extraction was investigated for the extraction of polyphenols from pomegranate peels. The most important factors affecting the extraction results were found to be particle size, temperature, and static time. The results indicated that pressurised water extraction was as effective as conventional methanol extraction for the recovery of polyphenols from pomegranate peels. Total phenolic contents of pomegranate peels obtained by pressurised water extraction at optimised conditions and conventional solid–liquid methanol extraction were determined as 264.3 and 258.2 mg/g tannic acid equivalents, respectively. Hydrolyzable tannins were the predominant polyphenols of pomegranate peels corresponding to 262.7 mg/g tannic acid equivalents. Punicalagin content of pomegranate peels by pressurised water extraction was found to be 116.6 mg/g on dry matter basis.