Ultrasound-assisted heating extraction of pectin from grapefruit peel: optimization and comparison with the conventional method

Sugar beet pectin extracted by ultrasound or conventional heating: a comparison

The yield and quality of sugar beet pulp pectin obtained by ultrasound-assisted extraction (UAE) were compared to those obtained by conventional heating. Extraction temperature (70-90) °C, extraction time (2-4) h and pH (1-1.5) were considered as the variables for the conventional extraction while ultrasound frequency (20-60) kHz, time (10-30) min and amplitude (60-100%) were considered as the variables for UAE. The optimal conditions for maximum yield of pectin for conventionally and ultrasonically extracted pectin were determined by the central composite design and the Box Behnken design, respectively. The optimum conditions of conventional extraction were the temperature of 90 °C, time of 4 h and pH of 1. The optimum conditions of UAE were ultrasound frequency of 20 kHz, time of 10 min, and ultrasound amplitude of 96%. Extraction using the optimized conditions of conventional heating and UAE achieved the best yield of 20.75% and 20.85%, respectively. The degree of methyl esterification, ferulic acid content and molecular weight of UAE pectin were higher than conventionally extracted pectin but the content of galacturonic acid in UAE pectin was lower than that of conventionally extracted pectin. The infrared spectra of both pectins revealed the occurrence of polysaccharide component. The pectin achieved by UAE had higher lightness value than conventionally extracted pectin, confirming its application in different products partially in bright food products. The UAE pectin possessed higher viscosity than conventionally extracted pectin. The addition of UAE pectin increased all of the DSC gelatinization parameters. Overall, UAE could be a promising scalable and economical approach to obtain pectin with unique characteristics.

Citrus processing by-products: an overlooked repository of bioactive compounds

Citrus fruits contain plethora of bioactive compounds stored in edible as well as inedible part. Since, citrus fruits are processed mainly for juice, the residues are disposed in wastelands, hence, plenty of nutritional potential goes in vain. But if utilized wisely, the bioactive phytochemicals in citrus by-products have the ability to revolutionize the functional food industry. In the present review, the composition of citrus by-products in terms of bioactive components and their health benefits has been reviewed. Various extraction techniques used to extract these bioactives has been discussed and a brief overview of purification and utilization of the extracted compounds, in food and nutraceutical industry is also presented. Bioactives in citrus by-products are higher than the peeled fruit, which can be extracted, isolated and incorporated into food systems for development of health foods. From the studies reviewed, it was observed that research reported on utilization of citrus by-products is limited to mainly research labs; proper scale-up process and its adequate research commercialization is the need of hour to transform these bioactives into economical functional ingredients.

Hawthorn pectin: Extraction, function and utilization

Pectin has been widely used as emulsifiers, gelling agents, glazing agents, stabilizers, and thickeners in food products. Hawthorn pectin has a higher viscosity than other foods-derived pectin such as lemon and apple pectin. It is also reported as a multifunctional fruit substance, which reduces the risk of hyperlipidemia and dyslipidemia. Therefore, hawthorn pectin is a potential resource for the development of new drugs, functional foods, and health-care products. This review symmetrically summarized the extraction methods, physiological characteristics, functional properties, and processing technologies of hawthorn pectin. It laid a foundation for the further research of hawthorn pectin and promoted the diversified utilization of hawthorn.

New pectin derivatives with antimicrobial and emulsification properties via complexation with metal-terpyridines

Pectin is widely used in food and pharmaceutical industries. However, due to its polysaccharide nature it lacks antimicrobial activity. In the current work, new pectin derivatives with interesting optical and antimicrobial properties were prepared via supramolecular chemistry utilizing Fe- or Cu-terpyridine (Tpy-Fe and Tpy-Cu) motifs. To proof derivatization of pectin, ultraviolet-visible spectroscopy (UV-Vis) and Fourier Transform infrared (FTIR) were used. In addition, the prepared pectin derivatives retained the known emulsification activity of the non-modified sugar beet pectin as seen from the particle size analysis of oil-in-water emulsions. The prepared derivatives showed antibacterial activity toward selected Gram-positive and Gram-negative bacteria. In addition, cytotoxicity test showed that the Tpy-Fe-pectin derivative was non-toxic to cells of human hepatocarcinoma, breast adenocarcinoma MCF7, and colorectal carcinoma cells at concentrations up to 100 μg/ml, while Tpy-Cu-pectin had moderate toxicity toward the aforementioned cells at the same concentration levels. The prepared derivatives could have potential applications in emulsions with antibacterial activity.

A Structured Approach to Recover Valuable Compounds from Agri-food Side Streams

Food side streams contain useful compounds such as proteins, sugars, polyphenols, and amino acids that might get discarded during processing. The concentration of these components may be low (e.g., fruit side streams are mainly composed by water, around 90%, while polyphenol content in rapeseed meal is less than 3% dry weight) and therefore effective separation techniques should be evaluated. The aim of this review is to identify the different process steps (like pretreatment, volume reduction, phase change, solid removal, purification, and formulation) required to recover high-value products from agri-food residues. It reviews different plant-based byproducts as sources (cereal bran, fruit pomace, oilseed meals, fruit wastewater) of valuable compounds and discusses the relevant technologies required for processing (such as extraction, adsorption, crystallization, drying, among others). A structured approach to design recovery processes presented focused on high purity products. This work demonstrates that multiple high-value products can be recovered from a single agri-food side stream depending on the processing steps and the origin source (strong and soft structures and wastewater).

Continuous and pulsed ultrasound pectin extraction from navel orange peels

Pectin is a valuable product (up to 30 $kg^-1) that makes-up 20-30% of an orange's peel. The commercial extraction is lengthy (up to 6h) and energy intensive as it requires heating aqueous solutions (60-100 °C). Ultrasound speeds up the extraction process reducing processing time by macroscopic and microscopic mixing by acoustic cavitation. We adopted an ultrasonic horn to deliver a rated power of 500W at amplitudes of 20%, 40%, and 60% with and without pulsation to extract pectin from waste orange peels. These correspond to power densities of 0.08Wml^-1, 0.16Wml^-1 and 0.24Wml^-1, respectively. The extractions operated at a pH of either 2 or 3. The experimental data agree with the fitted values from the statistical model (R²=95.5%). The model confirms our predictions that yield increases with amplitude/power density and decreasing pH. The highest yield was (11%) at a pH of 2 and with continuous ultrasonic irradiation at a power density of 0.24Wml^-1. There is only a 1.3% difference between this datum and pulse ultrasound mode (1 s on/1 s off) at the same conditions - a Student's t test confirmed that there was no significant difference in yield between continuous and pulse mode. However, pulsing is more efficient in that it consumes less than half the energy of continuous operation (80kJ vs. 190kJ).

The Potential of Grape Pomace Varieties as a Dietary Source of Pectic Substances

Grape pomace is one of the most abundant solid by-products generated during winemaking. A lot of products, such as ethanol, tartrates, citric acid, grape seed oil, hydrocolloids, bioactive compounds and dietary fiber are recovered from grape pomace. Grape pomace represents a major interest in the field of fiber extraction, especially pectin, as an alternative source to conventional ones, such as apple pomace and citrus peels, from which pectin is obtained by acid extraction and precipitation using alcohols. Understanding the structural and functional components of grape pomace will significantly aid in developing efficient extraction of pectin from unconventional sources. In recent years, natural biodegradable polymers, like pectin has invoked a big interest due to versatile properties and diverse applications in food industry and other fields. Thus, pectin extraction from grape pomace could afford a new reason for the decrease of environmental pollution and waste generation. This paper briefly describes the structure and composition of grape pomace of different varieties for the utilization of grape pomace as a source of pectin in food industry.

Citrus pectin modified by microfluidization and ultrasonication: Improved emulsifying and encapsulation properties

In this study, modified citrus pectin treated with a combination of microfluidization and ultrasonication was compared to the original and ultrasonication treated pectin on hydrodynamic diameter, molecular weight, polydispersity, zeta potential, apparent viscosity, Fourier-transform infrared spectroscopy (FTIR), 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging capacity, scanning electron microscope (SEM), atomic force microscopy (AFM), their emulsifying properties and encapsulation properties. Modified pectin treated with a combination of microfluidization and moderate ultrasonication (MUB) was found to have lowest hydrodynamic diameter (418 nm), molecular weight (237.69 kDa) and polydispersity (0.12), and relatively low apparent viscosity among all pectin samples. Furthermore, it showed significantly higher DPPH radical scavenging capacity than the original pectin although only slightly higher than that of ultrasonication treated one (UB). MUB showed a thin fibrous morphology and decreased degree of branching from SEM and AFM. Emulsion stabilized by MUB had highest centrifugal and thermal stability compared to emulsions stabilized by UB and the original pectin. This could be attributed to higher interfacial loading of MUB (17.90 mg/m²) forming more compact interfacial layer observed by confocal laser scanning microscopy (CLSM). Moreover, both MUB and UB exhibited improved encapsulation functionality to protect cholecalciferol (vitamin D₃) from UV degradation compared to the original pectin.

Ultrasound assisted extraction (UAE) of bioactive compounds from fruit and vegetable processing by-products: A review

Growing fruit and vegetable processing industries generates a huge amount of by-products in the form of seed, skin, pomace, and rind containing a substantial quantity of bioactive compounds such as polysaccharides, polyphenols, carotenoids, and dietary fiber. These processing wastes are considered to be of negligible value compared to the processed fruit or vegetable due to lack of sustainable extraction technique. Conventional extraction has certain limitations in terms of time, energy, and solvent requirements. Ultrasound assisted extraction (UAE) can extract bioactive components in very less time, at low temperature, with lesser energy and solvent requirement. UAE as a non-thermal extraction technique is better equipped to retain the functionality of the bioactive compounds. However, the variables associated with UAE such as frequency, power, duty cycle, temperature, time, solvent type, liquid-solid ratio needs to be understood and optimized for each by-product. This article provides a review of mechanism, concept, factor affecting extraction of bioactive compounds with particular focus on fruit and vegetable by-products.

Outgoing and potential trends of composition, health benefits, juice production and waste management of the multi-faceted Grapefruit Citrus Χ paradisi: A comprehensive review for maximizing its value

Grapefruit (GF) Citrus Χ paradisi Macfad (F. Rutaceae) is one of the major citrus fruits that encompass a myriad of bioactive chemicals and most unique among citrus fruits. Nevertheless, no study has yet to assess comprehensively its multitudinous constituents, health benefits, and valuable waste products. Hereto, the present review provides an updated comprehensive review on the different aspects of GF, its juice production, waste valorization, enhancement of its byproducts quality, and compared to other citrus fruits. Grapefruit uniqueness among other citrus fruits stands from its unique taste, flavor, and underlying complex chemical composition. Despite limonene abundance in peel oil and grapefruit juice (GFJ) aroma, nootkatone and sulfur compounds are the key determinants of its flavor, whereas flavanones contribute to its bitter taste and in conjunction with limonoids. Different postharvest treatments and juice processing are reviewed and in context to its influence on final product quality and or biological effects. Flavanones, furanocoumarins, and limonoids appear as the most prominent in GF drug interactions affecting its metabolism and or excretion. Valorization of GF peel is overviewed for its utilization as biosrobent, its oil in aromatherapy, limonene as antimicrobial or in cosmetics, fruit pectin for bioethanol production, or as biosorbent, and peel phenolics biotransformation. The present review capitalizes on all of the aforementioned aspects in GF and further explore novel aspects of its juice quality presenting the full potential of this valued multi-faceted citrus fruit.

Ultrasound-assisted modification of functional properties and biological activity of biopolymers: A review

In this review, the recent applications of power ultrasound technology in improving the functional properties and biological activities of biopolymers are reviewed. The basic principles of ultrasonic technology are briefly introduced, and its main effects on gelling, structural, textural, emulsifying, rheological properties, solubility, thermal stability, foaming ability and foaming stability and biological activity are illustrated with examples reviewing the latest published research papers. Many positive effects of ultrasound treatment on these functional properties of biopolymers have been confirmed. However, the effectiveness of power ultrasound in improving biopolymers properties depends on a variety of factors, including frequency, intensity, duration, system temperature, and intrinsic properties of biopolymers such as macromolecular structure. In order to obtain the desired outcomes, it is best to apply optimized ultrasound processing parameters and use the best conditions in terms of frequency, amplitude, temperature, time, pH, concentration and ionic strength related to the inherent characteristics of each biopolymer. This will help employ the full potential of ultrasound technology for generating innovative biopolymers functionalities for various applications such as food, pharmaceuticals, and other industries.

High Biological Value Compounds Extraction from Citrus Waste with Non-Conventional Methods

Citrus fruits are extensively grown and much consumed around the world. Eighteen percent of total citrus cultivars are destined for industrial processes, and as a consequence, large amounts of waste are generated. Citrus waste is a potential source of high biological value compounds, which can be used in the food, pharmaceutical, and cosmetic industries but whose final disposal may pose a problem due to economic and environmental factors. At the same time, the emerging need to reduce the environmental impact of citrus waste and its responsible management has increased. For these reasons, the study of the use of non-conventional methods to extract high biological value compounds such as carotenoids, polyphenols, essential oils, and pectins from this type of waste has become more urgent in recent years. In this review, the effectiveness of technologies such as ultrasound assisted extraction, microwave assisted extraction, supercritical fluid extraction, pressurized water extraction, pulsed electric field, high-voltage electric discharges, and high hydrostatic pressures is described and assessed. A wide range of information concerning the principal non-conventional methods employed to obtain high-biological-value compounds from citrus waste as well as the most influencing factors about each technology are considered.

Optimization of acid-extraction of pectic fraction from grape (Vitis vinifera cv. Chardonnay) pomace, a Winery Waste

Chardonnay grape pomace was evaluated as a source of pectin. A central composite design was used in order to determine the effect of pH, extraction time (Et) and liquid: solid ratio (LS) on the yield and uronic acid (UA) content of the pectins extracted using boiling HNO₃ solution. The optimized extraction condition to reach the maximum yield and UA was pH = 2.08, Et = 135.23 min and LS = 35.11 ml/g, resulting in theoretical yield of 12.8% and UA of 64.4%. The experimental yield of the pectic fraction obtained under the optimized conditions (GPOP) was 11.1% and the UA was 56.8%. GPOP had ~25% glucose. It was treated with α-amylase and amyloglucosidase, resulting in the fraction α-GPOP. The starch-free pectic fraction was composed of 63.5% UA, 7.8% rhamnose, 6.0% arabinose, 13.6% galactose and minor amounts of other neutral monosaccharides. It contained a low-methoxyl pectin (degree of methyl-esterification 18.1%) and had an average molar mass of 154,100 g/mol. It consisted of 55.7% homogalacturonan and 35.2% rhamnogalacturonan I (RG-I). NMR analyses suggest that RG-I portion of α-GPOP is highly branched by short chains or single residues of arabinose and galactose.

Physicochemical properties and antioxidant activity of pectin from hawthorn wine pomace: A comparison of different extraction methods

In the paper, to enhance the value and utilization rate of hawthorn wine pomace waste, four kinds of pectin were gained from hawthorn wine pomace by hydrochloric acid method (HA-HP), citric acid method (CA-HP), cellulase method (E-HP) and microwave-assisted chelating agent method (MH-HP). The physical and chemical properties of extracted hawthorn pectin were analyzed, however, different extraction methods lead to different characteristics of extracted pectin samples. We found that the extracted hawthorn pectin was all low-methoxy pectin, and the highest extraction yield of 72.89% with high ash (9.20%) was obtained by the MH-HP method, while the galacturonic acid (Gal A) content was up to 72.24% after dealing with the CA-HP method which was the highest among the four samples, besides, the quality of gel formed by E-HP method was the best. What's more, the four extracted samples all reveled degrees of antioxidant activity with dose-dependent in vitro antioxidant, and it was CA-HP method had the best antioxidant activity, making this the first comprehensive research describing the extracting pectin from hawthorn wine pomace. This research also provides a base for industrial production of high-value products from low-cost raw materials.

Manothermosonication (MTS) treatment by a continuous-flow system: Effects on the degradation kinetics and microstructural characteristics of citrus pectin

Modified pectin (MP) was reported to have increased bioactivities compared with the original one. However, traditional modification methods such as using an acidic solvent with heating are not only costly but causing severe pollution as well. In this study, manothermosonication (MTS) with a continuous-flow system was utilized to modify citrus pectin. The citrus pectin (5 g/L) treated by MTS (3.23 W/mL, 400 kPa, 45 °C) exhibited lower molecular weight (Mw, 248.17 kDa) and PDI (2.76). The pectin treated by MTS (400 KPa, 45 °C, 5 min) exhibited a narrower Mw distribution and lowered more Mw (48.8%) than the ultrasound(US)-treated (23.8%). Pectin degradation data fitted well to kinetic model of 1/Mw_t -1/Mw₀ = kt (45-65 °C). A lower activation energy of 13.33 kJ/mol was observed in the MTS treatment compared with the US-treated (16.38 kJ/mol). The MTS-treated pectin lowered the degree of methoxylation (DM), mol% of rhamnose and galacturonic acid (GalA) while increased mol% of galactose (Gal), xylose (Xyl), and arabinose (Ara). The ¹H and ¹³C nuclear magnetic resonance showed that MTS could not alter the primary structures of citrus pectin. However, an elevated (Gal + Ara)/Rha and reduced GalA/(Rha + Ara + Gal + Xyl) molar ratios after MTS suggested that MTS resulted in more significant degradation on the main chains and less on the side chains of pectin, in agreement with the result of atomic force microscope. Moreover, the MTS-treated pectin exhibited a higher 1,1-diphenyl-2picryl hydrazyl radical scavenging capacity compared with original pectin.

Comparison of different ultrasound assisted extraction techniques for pectin from tomato processing waste

Concept of waste to wealth is a hot topic with research ongoing globally to reduce carbon footprint. In an effort to follow up this cause present study focused on tomato industry waste specifically the peel of tomatoes for extraction of pectin. Pectin extraction was performed using five different extraction techniques (Ultrasound assisted extraction (UAE); microwave assisted extraction (MAE); ohmic heating assisted extraction (O_HAE); ultrasound assisted microwave extraction (UAME) and ultrasound assisted ohmic heating extraction (UAO_HE) at different power levels to study its extraction and degradation kinetics and in turn to optimize the extraction process. The extracted pectin yield ranged from 9.30% for O_HAE to 25.42% for MAE. Also, there was very less difference in the yield of MAE and UAME extracted pectin, but at the cost of major difference in degree of esterification 59.76 ± 0.70 and 73.33 ± 1.76%, respectively. In addition, all the pectin extracted under optimized conditions was having acceptable purity, [Galacturonic acid (GalA) content ranged from 675.8 ± 11.31 to 913.3 ± 20.50 g/kg of pectin]. FTIR analysis confirmed the presence of functional groups in the finger print region of identification for polysaccharide in all the extracted pectin. According to obtained results, UAME can be considered as better green extraction technology in terms of extraction yield as well as in quality of pectin compared to the other treatments used. Therefore, results suggest that UAME can be used as an efficient pectin extraction method from tomato processing waste.

Ultrasonic modification of pectin for enhanced 2-furfurylthiol encapsulation: process optimization and mechanisms

BACKGROUND

Pectin is an intriguing polymer, which is usually regarded as a byproduct from agricultural and biological processes. In previous studies, ultrasound treatment has been explored to improve the functionality of pectin but most of that work focused on aspects of molecular structure and the chemical properties of pectin. In this study, we utilized ultrasound treatment to modify the physiochemical properties of pectin. Using ultrasound treatment, we evaluated the emulsifying capability of pectin as a function of ultrasonic time and power density, using a response surface approach. A very potent yet unstable coffee-like aroma compound, 2-furfurylthiol, was also used for comparing the encapsulation feasibility of emulsion made with original pectin and ultrasound-treated pectin.

RESULTS

Our results showed that the particle size of pectin was highly correlated with power density and ultrasound time. Approximately 370 nm of pectin particle size could be reached at a power density of 1.06 W mL^-1 for 40 min. Ultrasound treatment increased emulsion droplet size but significantly improved emulsifying capacities, such as centrifugal stability and surface loading, although it was highly dependent upon the ultrasound treatment condition. When used as the encapsulation wall material, the ultrasound-modified pectin had significantly enhanced performance compared with the original, in terms of flavor retention over time at 45 °C and 65 °C.

CONCLUSION

Ultrasound treatment was able to modify the physiochemical properties of pectin, which thus improved emulsification stability and encapsulation feasibility by forming a thicker layer at the oil / water interface to protect the core materials. © 2019 Society of Chemical Industry.

Effects of acoustic power and pH on pectin-enriched extracts obtained from citrus by-products. Modelling of the extraction process

BACKGROUND

The ultrasound-assisted extraction of pectic polysaccharides from orange by-products was investigated. Kinetics of mechanical agitation (0.2 × g) and acoustic (US1: 542 W L^-1 and US2: 794 W L^-1 ) extractions, were obtained and modelled at different pH values (1.5 and 2.0). All extractions were carried out at 25 °C, using citric acid as the extraction solvent.

RESULTS

Higher pectic polysaccharides extraction yields were obtained with ultrasonic assistance, in comparison with the results obtained using mechanical agitation. Moreover, yield increases were significantly higher using the more acidic pH. Thus, at pH 1.5, pectin yield increased from ∼19%, obtained with agitation, to ∼47%, applying ultrasound; whereas, at pH 2.0, this increase was from ∼10%, with agitation, to ∼18%, applying ultrasound. A considerable decrease of the galacturonic acid proportion was observed on the extracts when ultrasound were applied for 60 min under pH 2.0. High methoxyl pectins were extracted at pH 1.5 whereas at pH 2.0, pectins exhibited a low methylation degree. Curves of acoustic and mechanical agitation extractions were properly represented by a second-order rate model (average mean relative error ≤ 7.4%). The extraction rate constant, initial extraction rate and maximum yield were determined for all experimental conditions.

CONCLUSION

Overall, the results clearly indicated that the effect of ultrasound was highly dependent on the pH. Therefore, adequate acidic conditions must be applied in order to improve the efficiency of ultrasound on the pectin extraction process. © 2019 Society of Chemical Industry.

Microwave-assisted hydrothermal extraction of non-structural carbohydrates and hemicelluloses from tobacco biomass

Microwave-assisted hydrothermal extraction of non-structural carbohydrates and hemicelluloses from tobacco biomass was investigated. Non-structural carbohydrates extraction was optimized by an Optimal design. The maximum yields for the leaf and stem were 118.57 mg/g and 120.33 mg/g biomass, respectively. The extracted stem residue was further treated for hemicelluloses extraction. A temperature of 200 °C without holding was proved to be the most efficient condition to produce a hemicelluloses yield of 105.15 mg/g. GPC results showed that the Mw values of precipitated hemicelluloses decreased from 143.5 kDa to 13.25 kDa with increasing temperature and holding time, while the un-precipitated fraction were ranging from 11.83 to 4.88 kDa. Monosaccharide analysis revealed that hemicelluloses extracted at lower temperature are heterogeneous compositional type, including xylan, glucuronoxylan and xylanglucan, while the ratio of xylose increased significantly (up to 72.64%) with increasing temperature. The developed microwave-assisted hydrothermal extraction process opens new avenues for a sustainable tobacco-based biorefinery.

Pectic polysaccharides from purple passion fruit peel: A comprehensive study in macromolecular and conformational characterizations

A polysaccharide (PFPP) from purple passion fruit peel was optimally extracted, with the highest yield (10.05%, w/w) obtained under 35 °C extraction temperature, 240 W ultrasonic power, 65:1 mL/g liquid-to-solid ratio, 0.6% (w/v) ammonium oxalate, 30 min extraction time and pH 2.0. According to composition analyses, pectic PFPP and its fractions (PFPP-10, -15 and -20) were revealed as linear homogalacturonans interrupted by rhamnogalacturonan I in different lengths and extensities, where low esterification degrees (35.35-39.66%) were indicated via FT-IR. Furthermore, based on macromolecular models, comprehensive analyses on macromolecular and conformational characterizations of PFPP fractions were conducted quantitatively through, e.g., shape factor (1.42-1.79), Mark-Houwink-Sakurada exponent (0.55-0.74), conformational power-law exponent (0.52-0.58), fractal dimension (1.72-1.94) and persistence length (6.73-13.47 nm). Therefore, different semi-flexible coil conformations were proposed schematically, where lower molecular-weight PFPP fractions were less flexible. This could provide a molecular basis for precise re-utilizations of PFPP in food and pharmaceutical industries.

Eco-friendly extraction and physicochemical properties of pectin from jackfruit peel waste with subcritical water

BACKGROUND

Water is generally considered to be a safe and green solvent suitable for use in natural product extraction. In this study, an eco-friendly subcritical water method was used to extract pectin from waste jackfruit peel (JFP-S), which was compared with pectin obtained by the traditional citric acid method (JFP-C).

RESULTS

The extraction process was optimized using response surface methodology (RSM), and the optimum process parameters were as follows: extraction temperature 138 °C, extraction time 9.15 min, liquid / solid (L/S) ratio 17.03 mL g^-1 . Under these conditions, the pectin yield was 149.6 g kg^-1 (dry basis). Pectin obtained from the two extraction methods displayed a high degree of esterification and the monosaccharide composition was consistent. The galacturonic acid content of JFP-S and JFP-C was 52.27% and 56.99%, respectively. JFP-S had more hairy regions and side chains than JFP-C. The molecular weight of JFP-S was 113.3 kDa, which was significantly lower than that of JFP-C (174.3 kDa). Fourier-transform infrared spectroscopy (FTIR) indicated that two samples had similar pectin typical absorption peaks. According to differential scanning calorimetry (DSC), both JFP-S and JFP-C had relatively good thermal stability. JFP-S demonstrated lower apparent viscosity and elasticity than JFP-C. Meanwhile, the G' and G'' moduli of JFP-S were lower, which found expression in the gel textural characterization of the samples.

CONCLUSION

This work showed that the subcritical water method is an efficient, time-saving, and eco-friendly technology for the extraction of pectin from jackfruit peel compared with the traditional citric acid method. The physicochemical properties of pectin could be changed during subcritical water extraction. © 2019 Society of Chemical Industry.

Optimization of an Ultrasound-Assisted Extraction for Simultaneous Determination of Antioxidants in Sesame with Response Surface Methodology

Sesame is a nutritional agricultural product with medicinal properties. Accurate determination of micronutrients is important for the improvement of sesame quality and nutrition assessments. Our previous study showed that 10 antioxidants—d-homoproline, vitamin B₂, coniferyl aldehyde, hesperidin, phloretin, N-acetyl-l-leucine, l-hyoscyamine, ferulic acid, 5-methoxypsoralen, and 8-methoxypsoralen—in sesame were potential characteristic nutrients in sesame. Herein, simultaneous detection of 10 different types of antioxidants was developed by using ultrasound-assisted extraction coupled with liquid chromatography-tandem mass spectrometry (UAE-LC-MS/MS) with the help of response surface methodology. The significant variables and levels were screened and optimized by combining the single factor experiment, Plackett–Burman test, and Box–Behnken design. The optimal conditions for extraction of target antioxidants in sesame were methanol solution of 75.0%, liquid-to-material ratio of 20:1 (mL/g), extraction temperature of 50 °C, extraction power of 410.0 W, extraction time of 65 min. The total yield of targets was 21.74 μg/g under the optimized conditions. The mobile phase used was 0.1% formic acid in acetonitrile and 0.1% formic acid in water, and the column was a Thermo Syncronis C18 reverse phase column (100 mm × 2.1 mm, 3 μm). All targets required only one injection and could be quickly separated and assayed within 7 min. The limits of detection and limits of quantification for these 10 nutritional compounds ranged from 0.01 to 0.11 µg/kg and from 0.04 to 0.34 µg/kg, respectively. The validation results indicated that the method had reasonable linearity (R² ≥ 0.9990), good recoveries (71.1%–118.3%), satisfactory intra-day precision (≤9.6%) and inter-day precision (≤12.9%), and negligible matrix effects (≤13.8%). This simultaneous quantification method was accurate, fast, and robust for the assessment of sesame nutrition.

Ultrasound-Assisted Extraction of Pectin from Malus domestica ‘Fălticeni’ Apple Pomace

The use of an ultrasonic treatment for the extraction of pectin from Malus domestica ‘Fălticeni’ apple pomace, its effects on extraction yield and galacturonic acid content, and degree of esterification of the extracted pectin were investigated. The optimization of the extraction process showed that the highest yield of 9.183% pectin, with a 98.127 g/100 g galacturonic acid content and 83.202% degree of esterification, was obtained at 100% amplitude, pH of 1.8, SLR of 1:10 g/mL, and 30 min. The pectin obtained in optimal extraction conditions was compared to commercial citrus and apple pectin in terms of chemical composition (determined by FT-IR), thermal behaviour (analyzed by differential scanning calorimetry), rheological properties, and morphological structure (analyzed by scanning electron microscopy). By comparison to commercial citrus and apple pectin samples, the FT-IR analysis of pectin extracted by ultrasound treatment confirmed the high degree of esterification and showed similarity to that of apple pectin (88.526%). It was found that the thermal behaviour of the pectin obtained by ultrasound-assisted extraction was influenced by the narrower distribution of molecular weights and the orderly molecular arrangement, while the rheological properties (high viscosity, G0, and G1) of this sample were influenced by the morphological structure and the galacturonic acid content. The correlation coefficient showed a strong positive relationship between viscosity and galacturonic acid content (r = 0.992**).