Modification of citrus and apple pectin by power ultrasound: Effects of acid and enzymatic treatment

Properties of lime peel pectin as mainly influenced by ethanol and protein-based purification methods

BACKGROUND

Lime peel, obtained from juice factory waste, is considered as a source of pectin. Lime peel pectin samples, extracted by three extraction procedures of 90 °C heating for 120 min, 90 °C heating for 90 min and then 32 min of ultrasound, and 80 °C heating for 60 min and then 22 min of ultrasound, and purified by two methods using ethanol and sodium caseinate (SC), were prepared and characterized.

RESULTS

The results showed that the purification method significantly affected the lime pectin samples properties. Pectin samples purified with SC had a transparent and film-like appearance, whereas the ethanol-purified pectin samples showed an amorphous and opaque appearance. Pectin samples purified with ethanol showed higher extraction recovery (approximately 20%), whereas the lowest pectin yield was observed for the purification with SC (approximately 10%). Although SC purification did not enhance the pectin yield, it diminished the level of 'non-pectin' components and resulted in purer pectin. The bands at 1045-1076 cm-1 , relating to neutral sugars, had higher intensities in ethanol-purified pectin samples, indicating their higher sugar contents. Also the samples purified with SC exhibited more thermal stability, probably as a result of the presence of protein in their structure.

CONCLUSION

In the present study, under the same or varying extraction conditions, the most important element distinguishing pectins in terms of appearance, physicochemical, thermal and Fourier transform infrared characteristics was the type of purification method. Purification with SC may result in pectins with more non-esterified galacturonic acids from the homogalacturonan fraction. © 2023 Society of Chemical Industry.

Effects of ultrasonic intensity and time on rheological properties of different concentrations of xanthan gum solution

This work aimed to examine the impacts of ultrasonic treatments (40 kHz) at different intensities (0, 75, and 150 W) and time (0, 5, 10, 15, and 20 min) on the rheological properties of different concentrations (at 3 levels of 0.10, 0.15, and 0.20 %, w/v) of xanthan gum solution (XGS). The results confirmed that the apparent viscosity of XGS decreased from 68.75 to 30.38 mPa.s with increasing ultrasonic power from 0 to 150 W (shear rate = 61 s-1, 0.2 %, 20 min). In addition, the apparent viscosity of XGS decreased by enhancing the sonication time. Various rheological equations (power-law, Bingham, Herschel-Bulkley, Casson, and Vocadlo) were employed to fit the empirical values, and the results confirmed that the power-law equation was the best fit to describe the flow behaviour of XGSs. The consistency coefficient (CC) of XGS significantly decreased from 1222.7 to 635.1 mPa.sn (p < 0.05) while ultrasonic power enhanced from 0 to 150 W (0.2 %, 10 min). Furthermore, the CC of XGS decreased significantly (p < 0.05) while the duration of ultrasound treatment enhanced. The flow behaviour index (FBI) of various concentrations of XGS enhanced while the intensity and duration of ultrasound treatment enhanced.

Structural, chemical and technofunctional properties pectin modification by green and novel intermediate frequency ultrasound procedure

The impact of intermediate frequency ultrasound (IFUS, 582, 864 and 1144 kHz), mode of operation (continue and pulsed) and ascorbic acid (Aa) addition on the structural, chemical and technofunctional properties of commercial citrus high methoxyl-grade pectin (HMP) was investigated. The chemical dosimetry of IFUS, monitored by the triiodide formation rate (I3-), demonstrated that the pulsed ratio (1900 ms on/100 ms off) at the three frequencies was similar to that of continue mode but IFUS1144 kHz produced more acoustic streaming demonstrated by the height liquid measured using image analysis. In presence of Aa, HMP presented higher fragmentation than in its absence. IFUS did not give rise any changes in the main functional groups of the HMP. In general, a reduction in molecular weight was observed, being the presence of Aa the most influencing factor. Regarding monosaccharides, IFUS modified the structure of homogalacturonan and rhamnogalacturonan-I and increased of GalA contents of the HMP in presence of Aa at the above three frequencies. A reducing of the consistency index (k) and increasing of the flow index (n) of HMP were showed by IFUS frequency and Aa addition. The emulsifying activity and stability index were increased for HMP treated by IFUS in continue mode at all frequencies and in presence of Aa. The results presented in this research shown the effectiveness of IFUS as tool to modify pectin into different structures with different functionalities.

Rheological properties and color indexes of ultrasonic treated aqueous solutions of basil, Lallemantia, and wild sage gums

This research aimed to analyze the impacts of sonication on the rheological properties and color indexes of aqueous solutions of Basil seed gum (BSG), Lallemantia seed gum (LSG), and Wild sage seed gum (WSG). The apparent viscosity (AV) of aqueous solutions of gums decreased with increasing shear rate (SR) from 12.2 s-1 to 134.5 s-1. Also, the AV (at SR = 61 s-1) of BSG, LSG, and WSG solutions reduced from 0.015 to 0.006 Pa.s, 0.023 to 0.010 Pa.s, and 0.009 to 0.004 Pa.s with enhancing the sonication time from 0 to 20 min, respectively. Various rheological equations were employed to fit the empirical values, and the findings confirmed that the Power law (PL) model was the best fit to explain the flow behaviour of these gums solutions. The consistency coefficient (k-index) of BSG, LSG, and WSG solutions significantly (p < 0.05) reduced from 0.108 to 0.017 Pa.sn, 0.143 to 0.033 Pa.sn, and 0.034 to 0.014 Pa.sn with increasing sonication time from 0 to 20 min, respectively. The flow behaviour index (n-index) of the gums solutions increased with increasing sonication time. By applying ultrasound, the lightness (L⁎) and blueness/yellowness (b⁎) indexes of the solutions were increased, and the greenness/redness (a⁎) index was reduced.

Effects of sunflower pectin on thermal stability of purple sweet potato anthocyanins at different pH

The present study aimed to examine the impact of sunflower pectin (SFP) on the thermal stability and antioxidant activity of purple sweet potato anthocyanins (PSPA) at varying pH levels. It was observed that the pH value significantly influenced the ability of pectin to protect anthocyanins from thermal degradation, which was found to be associated with the rate of binding between PSPA and SFP. The binding rate of PSPA-SFP was observed to be highest at pH 4.0, primarily due to the influence of electrostatic interaction and hydrogen bonding. Monoacylated anthocyanins exhibited a binding rate approximately 2-4 % higher than that of diacylated anthocyanins. The PSPA-SFP demonstrated its highest thermal stability at pH 4.0, with a corresponding half-life of 14.80 h at 100 °C. Molecular dynamics simulations indicated that pectin had a greater affinity for the flavylium cation and hemiketal form of anthocyanins. The antioxidant activity of anthocyanins in PSPA and PSPA-SFP increased with increasing pH, suggesting that anthocyanins at high pH had higher antioxidant activity than anthocyanins at low pH.

Rheological properties of carboxymethyl cellulose (CMC) solution: Impact of high intensity ultrasound

Today sonication process is used as a new green tool with unique impacts on foods preservation and processing. Ultrasonic modification is an appropriate strategy to obtain good gums with useful physicochemical characteristics and molecular structure. This research aimed to analyze the impacts of sonication at different intensities (0, 75, and 150 W) and time (0, 5, 10, 15, and 20 min) on the viscosity and rheological characteristics of carboxymethyl cellulose (CMC) solution. The results confirmed that the apparent viscosity of CMC solution reduced from 0.030 to 0.021 Pa.s with increasing shear-rate from 12.2 s-1 to 134.5 s-1 (75 W for 10 min). Also, the apparent viscosity of CMC solution reduced from 0.028 to 0.019 Pa.s with enhancing the sonication time from 0 to 20 min (shear-rate = 61 s-1, 150 W). Various rheological equations were employed to fit the empirical values, and the results confirmed that the Power law model was the best fit to explain the flow behaviour of CMC solution. The consistency coefficient of CMC solution significantly reduced from 0.065 Pa.sn to 0.032 Pa.sn (p < 0.05) with enhancing sonication time from 0 to 20 min (75 W). Furthermore, the consistency coefficient of CMC solution decreased significantly (p < 0.05) while the ultrasonic power enhanced. Flow behaviour index of CMC solution enhanced significantly (p < 0.05) while the intensity and time of sonication enhanced.

Gelling properties of lysine-amidated citrus pectins: The key role of pH in both amidation and gelation

The amidation of pectin by amino acids has been widely applied due to its safety and excellent gelling properties. This study systematically examined the effects of pH on the gelling properties of lysine-amidated pectin during amidation and gelation. Pectin was amidated over the range of pH 4-10, and the amidated pectin obtained at pH 10 showed the highest degree of amidation (DA, 27.0 %) due to the de-esterification, electrostatic attraction, and the stretching state of pectin. Moreover, it also exhibited the best gelling properties due to its greater numbers of calcium-binding regions (carboxyl groups) and hydrogen bond donors (amide groups). During gelation, the gel strength of CP (Lys 10) at pH 3-10 first increased and then decreased, with the highest gel strength at pH 8, which was due to the deprotonation of carboxyl groups, protonation of amino groups, and β-elimination. These results show that pH plays a key role in both amidation and gelation, with distinct mechanisms, and would provide a basis for the preparation of amidated pectins with excellent gelling properties. This will facilitate their application in the food industry.

Ultrasound- and Microwave-Assisted Extraction of Pectin from Apple Pomace and Its Effect on the Quality of Fruit Bars

The article investigates the process of pectin extraction using ultrasonic and microwave techniques from apple pomace generated during juice production in the context of circular bioeconomy. The extraction yield, equivalent mass, content of methoxyl groups, content of anhydrogalacturonic acid, and degree of esterification of pectin were investigated. These indicators varied depending on the parameters and extraction method. The resulting pectin displayed a co-extracted total polyphenol content (TPC) ranging from 2.16 to 13.05 mg GAE/g DW and a DPPH radical inhibition capacity of 4.32-18.86 μmol TE/g. It was found that the antioxidant activity of raw pectin is correlated with TPC and with the content of terminal groups released during the polysaccharide degradation process. The extracted pectin was used as a binding and coating agent for dried fruit bars. Evaluation of water activity (a_w), TPC and total flavonoid content (TFC), together with sensory and microbiological analyses of the fruit bars over a period of 360 days, revealed a protective effect of pectin: reducing moisture loss, minimizing the degradation of bioactive compounds during storage, and maintaining the potential antioxidant activity of the product.

Physicochemical properties and Pb2+ adsorption capacity of freeze-dried hawthorn pectin fractions by gradient ethanol precipitation

Three fractions of FHP20, FHP40 and FHP60 were obtained from freeze-dried hawthorn pectin by gradient ethanol precipitation (20-60 %), and their physicochemical properties and adsorption performance on Pb²⁺ were investigated. It was found that the content of galacturonic acid (GalA) and esterification of FHP fractions gradually reduced with the increase of ethanol concentration. FHP60 had the lowest molecular weight (60.69 × 10³ Da), and the composition and proportion of monosaccharides were significantly different. The experimental results of Pb²⁺ adsorption showed that the adsorption process fitted well with the Langmuir monolayer adsorption and the pseudo-second-order models. Our findings suggested that pectin fractions with good homogeneity of molecular weight and chemical construction can be obtained by gradient ethanol precipitation, and hawthorn pectin could be developed as a potential adsorbent for Pb²⁺ removal.

Interaction between ultrasound-modified pectin and icaritin

Pectin can improve the bioaccessibility of icaritin as a nanocarrier, and ultrasound can modify the pectin structure. However, the interaction between ultrasound-modified pectin (UMP) and icaritin remains unclearly. In this work, the effects of UMP on the physiochemical properties of icaritin/pectin micelles (IPMs) were investigated. The IPMs prepared with UMP (UMP-IPMs) showed lower encapsulation efficiencies and loading capacities, comparing with native IPMs. UMP-IPMs had smaller particle sizes (325-399 nm) than native IPMs (551 nm). The Mw, viscosity, G' and G" of pectin were determined. NMR spectra indicated that the repeating unit in pectins remained consistently before and after ultrasound treatment, and 7-OH of icaritin was involved in hydrogen bond formation with pectin. The larger chemical shift movement of 6-H and 7-OH for U3-IPMs than P0-IPMs suggested that stronger hydrogen bond interaction between icaritin and pectin. UMP-IPMs exhibited stronger anti-proliferation activities against HepG2 cells than native IPMs.

Understanding the impact of pectin on browning of polyphenol oxidation system in thermal and storage processing

Browning of some processed fruit products was affected not only by polyphenol oxidation but also by cell wall polysaccharides (pectin). The study was performed to understand the mechanism of browning in the pectin system. The catechin/chlorogenic acid oxidation system in three pectins significantly enhanced their browning during thermal storage with pectin structure- and concentration-dependent. Particularly, the structural and physicochemical properties of pectin were examined to determine its effects on the kinetics of polyphenol oxidation and the stability of free polyphenols. Moreover, pectin impacted the fluorescence characteristics of polyphenols by cross-linking with the aromatic ring of polyphenols. In turn, the interaction between polyphenols and pectin impacted the chemical bond vibration of pectin, thereby affecting its optical features and browning. The correlation analysis revealed that the monosaccharide composition, Ratio 1, Ratio 2, Ratio 3, methyl esterification, ζ-potential, and polydispersity index of pectin were significantly correlated with the browning of the pectin-polyphenol oxidation system.

Food and fruit waste valorisation for pectin recovery: Recent process technologies and future prospects

Pectin possesses a dual property of resistance and flexibility and thus has diverse commercial value which has generated research interest on this versatile biopolymer. Formulated products using pectin could be useful in food, pharma, foam, plasticiser and paper substitute industries. Pectin is structurally tailor-made for greater bioactivity and diverse applications. Sustainable biorefinery leaves greener footprints while producing high-value bioproducts like pectin. The essential oils and polyphenols obtained as byproducts from a pectin-based biorefinery are useful in cosmetics, toiletries and fragrance industries. Pectin can be extracted from organic sources following eco-friendly strategies, and the extraction techniques, structural alterations and the applications are continually being upgraded and standardized. Pectin has great applications in diverse areas, and its green synthesis is a welcome development. In future, growing industrial application of pectin is anticipated as research orients on biopolymers, biotechnologies and renewable source-based processes. As the world is gradually adopting greener strategies in sync with the global sustainable development goal, active involvement of policy makers and public participation are prime. Governance and policy framing are essential in the transition of the world economy towards circularity since green circular bioeconomy is ill-understood among the public in general and within the administrative circles in particular. Concerted efforts by researchers, investors, innovators, and policy and decision makers to integrate biorefinery technologies as loops within loop of biological structures and bioprocesses is suggested. The review focusses on generation of the different nature of food wastes including fruits and vegetables with cauterization of their components. It discusses the innovative extraction and biotransformation approaches for these waste conversions into value-added products at cost-effective and eco-friendly way. This article compiles numerous effective and efficient and green way pectin extraction techniques with their advantages with varying success in an integrated manner.

The Preparation and Potential Bioactivities of Modified Pectins: A Review

Pectins are complex polysaccharides that are widely found in plant cells and have a variety of bioactivities. However, the high molecular weights (M_w) and complex structures of natural pectins mean that they are difficult for organisms to absorb and utilize, limiting their beneficial effects. The modification of pectins is considered to be an effective method for improving the structural characteristics and promoting the bioactivities of pectins, and even adding new bioactivities to natural pectins. This article reviews the modification methods, including chemical, physical, and enzymatic methods, for natural pectins from the perspective of their basic information, influencing factors, and product identification. Furthermore, the changes caused by modifications to the bioactivities of pectins are elucidated, including their anti-coagulant, anti-oxidant, anti-tumor, immunomodulatory, anti-inflammatory, hypoglycemic, and anti-bacterial activities and the ability to regulate the intestinal environment. Finally, suggestions and perspectives regarding the development of pectin modification are provided.

Effect of ultrasound pretreated hydrocolloid batters on quality attributes of fried chicken nuggets during post-fry holding

In this study, batters formulated with different hydrocolloids (i.e., pectin, locust bean gum, xanthan gum, guar gum, hydroxypropyl methylcellulose and methylcellulose) were treated with ultrasound as edible coatings for fried chicken nuggets. Quality characteristics (i.e., batter pickup, flow behaviours, thermal properties, moisture loss, color and textural properties) in chicken nuggets coated with ultrasound treated batters were evaluated before and after post frying exposure to heat lamp. Ultrasonication significantly reduced batter pickup, flow behavior and gelatinization enthalpy, revealing its tendency to alter functional properties of batter systems. Rheological evaluation of all batter samples revealed a pseudoplastic (shear thinning) flow characteristic when fitted to power law model, with ultrasonicated (US) samples exhibiting a significantreduction in viscosity over non-ultrasonicated (NUS) samples. Compared to the control NUS, fat content of chicken nuggets coated with US-treated batters decreased by 39.0, 60.9, 62.87, 64.1, 65.7, and 65.0 % for pectin, locust bean gum, xanthan gum, guar gum, hydroxypropyl methylcellulose and methylcellulose, respectively. Finally, chicken nuggets coated with US and NUS treated batters exhibited greater cutting force values immediately after frying but declined within the first 10 min of heat lamp exposure and increased subsequently with extended heat lamp holding time. Furthermore, NUS-treated guar gum resulted in chicken nuggets with the most minimal variability in cutting force during post-frying holding, indicating that crispiness was maintained. Overall, application of ultrasound as a batter pretreatment technique can be exploited by the frying food industry as an alternative approach to producing low fat chicken nuggets with appreciable quality attributes.

Ultrasonic effects on molecular weight degradation, physicochemical and rheological properties of pectin extracted from Premna microphylla Turcz

The high molecular weight and poor solubility of pectin extracted from Premna microphylla Turcz (PEP) limits its application. Therefore, in this paper, the degradation effects of PEP under ultrasound irradiation and the influences of ultrasonic on the PEP processing characteristics were investigated. The results indicated that the M_w of PEP decreased significantly with a narrow distribution after ultrasonic treatment. The degradation kinetics of PEP at different ultrasound intensities were sufficiently described by the 2nd-order kinetics eq. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis suggested that ultrasonic treatment destroyed the ordered structure inside the PEP, resulting in a looser microscopic morphology. Compared with the control, the thermal stability of PEP was significantly boosted after ultrasonic treatment. Rheological analysis illustrated that the sonicated PEP presented lower apparent viscosities than the original PEP. While the elasticity and thermal reversibility of the degraded products was enhanced. Ultrasonic treatment prominently weakened its shear thinning fluid behavior and thixotropy, thus improved its processing quality. Therefore, desirable PEP can be prepared by ultrasonic irradiation. The results can provide a reference for the development and application of PEP.

The effect of sonication-synergistic natural deep eutectic solvents on extraction yield, structural and physicochemical properties of pectins extracted from mango peels

In this study, eco-friendly deep eutectic solvents (DESs) were used as extracting agents for the first time in the extraction of pectins from mango peel. Two novel green solvents including betaine-citric acid (Bet-CA) and choline chloride-malic acid (ChCl-MaA) were screened, and the extraction conditions were further optimized by full factor design experimental along with RSM. In addition, ultrasound treatment also had an influence on extraction yield, structural and physicochemical properties of extracted pectins. Two DES-extracted pectins had significantly higher yield, larger molecular weight and particles size than HCl-extracted pectin. High intensity ultrasound power enhanced the yield of low-ester pectins, but decreased the molecular weight and particles size of the pectins extracted. Monosaccharide compositions analysis showed that higher content of galacturonic acid (GalA) and larger HG region were observed in two DESs-extracted pectins. Fourier transform infrared spectra (FT-IR) of all pectins extracted were similar, with slight differences. Two DESs-extracted pectins exhibited higher DE values than HCl-extracted pectin. Thermal analysis and zeta potential results showed that HCl-extracted pectin had better stability than ChCl-MaA-extracted pectin. Additionally, HCl-extracted pectin had higher viscosity properties than two DESs-extracted pectins or commercial pectin (CP). Moreover, it was found that HCl-extracted pectin was in a colloid state, while two DESs-extracted pectins or CP were in a flow state. Ultrasound treatment significantly improved the yields of pectin/low-ester pectin. Additionally, ultrasound treatment remarkably decreased the viscosity and viscoelastic properties of the pectins extracted. The results were conducive to our understanding of the relationship between extraction conditions and physicochemical properties of the pectins extracted, which provides theoretical basis for the functional application of mango peel pectins in the food and pharmaceutical industry.

Trends in "green" and novel methods of pectin modification - A review

Modification of hydrocolloids to alter their functional properties using chemical methods is well documented in the literature. There has been a recent trend of adopting eco-friendly and "green" methods for modification. Pectin, being a very important hydrocolloid finds its use in various food applications due to its gelling, emulsifying, and stabilizing properties. The adoption of various "green" methods can alter the properties of pectin and make it more suitable for incorporation in food products. The novel approaches such as microwave and pulsed electric field can also be utilized for solvent-free modification, making it desirable from the perspective of sustainability, as it reduces the consumption of organic chemicals. Pectic oligosaccharides (POSs) produced via novel approaches are being explored for their biological properties and incorporation in various functional foods. The review can help to set the perspective of potential scale-up and adoption by the food industry for modification of pectin.

Recent Advances in the Application of Enzyme Processing Assisted by Ultrasound in Agri-Foods: A Review

The intensification of processes is essential for the sustainability of the biorefinery concept. Enzyme catalysis assisted by ultrasound (US) may offer interesting opportunities in the agri-food sector because the cavitation effect provided by this technology has been shown to improve the efficiency of the biocatalysts. This review presents the recent advances in this field, focused on three main applications: ultrasound-assisted enzymatic extractions (UAEE), US hydrolysis reactions, and synthesis reactions assisted by US for the manufacturing of agri-food produce and ingredients, enabling the upgrading of agro-industrial waste. Some theoretical and experimental aspects of US that must be considered are also reviewed. Ultrasonic intensity (UI) is the main parameter affecting the catalytic activity of enzymes, but a lack of standardization for its quantification makes it unsuitable to properly compare results. Applications of enzyme catalysis assisted by US in agri-foods have been mostly concentrated in UAEE of bioactive compounds. In second place, US hydrolysis reactions have been applied for juice and beverage manufacturing, with some interesting applications for producing bioactive peptides. In last place, a few efforts have been performed regarding synthesis reactions, mainly through trans and esterification to produce structured lipids and sugar esters, while incipient applications for the synthesis of oligosaccharides show promising results. In most cases, US has improved the reaction yield, but much information is lacking on how different sonication conditions affect kinetic parameters. Future research should be performed under a multidisciplinary approach for better comprehension of a very complex phenomenon that occurs in very short time periods.

Structure and Applications of Pectin in Food, Biomedical, and Pharmaceutical Industry: A Review

Pectin is a biocompatible polysaccharide with intrinsic biological activity, which may exhibit different structures depending on its source or extraction method. The extraction of pectin from various industrial by-products presents itself as a green option for the valorization of agro-industrial residues by producing a high commercial value product. Pectin is susceptible to physical, chemical, and/or enzymatic changes. The numerous functional groups present in its structure can stimulate different functionalities, and certain modifications can enable pectin for countless applications in food, agriculture, drugs, and biomedicine. It is currently a trend to use pectin to produce edible coating to protect foodstuff, antimicrobial bio-based films, nanoparticles, healing agents, and cancer treatment. Advances in methodology, use of different sources of extraction, and knowledge about structural modification have significantly expanded the properties, yields, and applications of this polysaccharide. Recently, structurally modified pectin has shown better functional properties and bioactivities than the native one. In addition, pectin can be used in conjunction with a wide variety of biopolymers with differentiated properties and specific functionalities. In this context, this review presents the structural characteristics and properties of pectin and information on the modification of this polysaccharide, its respective applications, perspectives, and future challenges.

Recent advances in extraction technologies for recovery of bioactive compounds derived from fruit and vegetable waste peels: A review

Fruits and vegetables are the most important commodities of trade value among horticultural produce. They are utilized as raw or processed, owing to the presence of health-promoting components. Significant quantities of waste are produced during fruits and vegetables processing that are majorly accounted by waste peels (∼90-92%). These wastes, however, are usually exceptionally abundant in bioactive molecules. Retrieving these valuable compounds is a core objective for the valorization of waste peel, besides making them a prevailing source of beneficial additives in food and pharmaceutical industry. The current review is focused on extraction of bioactive compounds derived from fruit and vegetable waste peels and highlights the supreme attractive conventional and non-conventional extraction techniques, such as microwave-assisted, ultrasound assisted, pulsed electric fields, pulsed ohmic heating, pressurized liquid extraction, supercritical fluid extraction, pressurized hot water, high hydrostatic pressure, dielectric barrier discharge plasma extraction, enzyme-assisted extraction and the application of "green" solvents say as well as their synergistic effects that have been applied to recover bioactive from waste peels. Superior yields achieved with non-conventional technologies were identified to be of chief interest, considering direct positive economic consequences. This review also emphasizes leveraging efficient, modern extraction technologies for valorizing abundantly available low-cost waste peel, to achieve economical substitutes, whilst safeguarding the environment and building a circular economy. It is supposed that the findings discussed though this review might be a valuable tool for fruit and vegetable processing industry to imply an economical and effectual sustainable extraction methods, converting waste peel by-product to a high added value functional product.

Delineating the inherent functional descriptors and biofunctionalities of pectic polysaccharides

Pectin is a plant-based heteropolysaccharide macromolecule predominantly found in the cell wall of plants. Pectin is commercially extracted from apple pomace, citrus peels and sugar beet pulp and is widely used in the food industry as a stabilizer, emulsifier, encapsulant, and gelling agent. This review highlights various parameters considered important for describing the inherent properties and biofunctionalities of pectins in food systems. These inherent descriptors include monosaccharide composition, galacturonic acid content, degree of esterification, molecular weight, structural morphology, functional group analysis, and functional properties, such as water and oil holding capacity, emulsification, foaming capacity, foam stability, and viscosity. In this study, we also delineate their potential as a nutraceutical, prebiotic, and carrier for bioactive compounds. The biofunctionalities of pectin as an anticancer, antioxidant, lipid-lowering, and antidiabetic agent are also conceptually elaborated in the current review. The multidimensional characteristics of pectin make it a potential candidate for use in food and biomedical science.

Effects of ultrasound on the enzymatic degradation of pectin

Ultrasound-assisted enzymatic maceration (UAEM) has gained considerable interest in the fruit juice industry, owing to its potential to increase juice yield and content of polyphenols while simultaneously saving time and energy. In this study, the effects of UAEM (ultrasonic probe, 20 kHz, 21 W*cm^-2 and 33 W*cm^-2) on pectin degradation in a continuous circulation system were investigated over 60 and 90 min. Main pectinolytic enzymes activities of (polygalacturonase, pectin lyase and pectin methylesterase) of a commercial enzyme preparation were examined for individual synergistic effects with US. Pectin hydrolysis by UAEM differed significantly compared to treatment with ultrasound or enzymes alone regarding the profile of degradation products compared to treatment with ultrasound or enzymes alone. Ultrasound fragmented pectin to less branched oligomers of medium molecular weight (Mp approx. 150 kDa), which were further degraded by pectinolytic activities. The low molecular weight fraction (<30 kDa), which is known to be beneficial for juice-quality by adding nutritional value and stabilizing polyphenols, was enriched in small oligomers of homogalacturonan-derived, rhamnogalacturonan I-derived, and rhamnogalacturonan II-derived residues. Synergistic effects of ultrasound application enhanced the effective activities of polygalacturonase and pectin lyase and even prolonged their performance over 90 min, whereas the effective activity of pectin methylesterase was not affected. Final marker concentrations determined by each enzyme assay revealed a considerable higher total process output after UAEM treatment at reduced temperature (30 °C) comparable to the output after conventional batch maceration at 50 °C. The obtained results demonstrate the high potential of UAEM to produce high-quality juice by controlling pectin degradation while reducing process temperature and equally highlight the matrix and enzyme specific effects of a simultaneous US treatment.

Behaviour of citrus pectin and modified citrus pectin in an azoxymethane/dextran sodium sulfate (AOM/DSS)-induced rat colorectal carcinogenesis model

Large intestine cancer is one of the most relevant chronic diseases taking place at present. Despite therapies have evolved very positively, this pathology is still under deep investigation. One of the recent approaches is the prevention by natural compounds such as pectin. In this paper, we have assessed the impact of citrus pectin and modified citrus pectin on colorectal cancer in rats (Rattus norvegicus F344) to which azoxymethane and DSS were supplied. The lowest intake of food and body weight were detected in animals fed with citrus pectin, together with an increase in the caecum weight, probably due to the viscosity, water retention capacity and bulking properties of pectin. The most striking feature was that, neither citrus pectin nor modified citrus pectin gave rise to a tumorigenesis prevention. Moreover, in both, more than 50% of rats with cancer died, probably ascribed to a severe dysbiosis state in the gut, as shown by the metabolism and metagenomics studies carried out. This was related to a decrease of pH in caecum lumen and increase in acetate and lactic acid levels together with the absence of propionic and butyric acids. A relevant increase in Proteobacteria (Enterobacteriaceae) were thought to be one of the reasons for enteric infection that could have provoked the death of rats and the lack of cancer prevention. However, a reduction of blood glucose and triacylglycerides level and an increase of Bifidobacterium and Lactobacillaceae were found in animals that intake pectin, as compared to universal and modified citrus pectin feeding.

The effect of high-power ultrasound on the rheological properties of strawberry pulp

This study investigated the effects of high-power ultrasound (HPU, 0-45 °C, 242-968 W/cm², 2-16 min) on the rheological properties of strawberry pulp. Following the HPU treatment, the strawberry pulp exhibited an increase in apparent viscosity, storage modulus (G'), and loss modulus (G″). The water-soluble pectin (WSP), pectin methylesterase (PME) activity, and free calcium ions (Ca²⁺) of the strawberry pulp after HPU treatment were investigated to determine a possible reason for this phenomenon. HPU caused a significant decrease in the degree of esterification (DE), molecular weight (Mw), and particle size of strawberry WSP, but no significant changes were evident in the galacturonic acid (GalA) content and the zeta (ζ)-potential (P > 0.05), resulting in decrease in the apparent viscosity. Moreover, the largest reduction of PME activity was 22.6% after HPU treatment at 605 W/cm² and 45 °C for 16 min, indicating that the PME was resistant to the HPU treatments. The free Ca²⁺ content in the strawberry pulp was significantly decreased after exposure to HPU (P < 0.05). The maximal reduction of 52.01% in the free Ca²⁺ was achieved at 605 W/cm² and 45 °C for 16 min. The overall results indicated that the high residual activity (RA) of PME after HPU might induce the low esterification of WSP, while HPU promoted the interaction of free Ca²⁺ and low-methylated pectin, to form the network structure of Ca²⁺-low-methylated pectin, resulting in an increase in viscosity in the complex strawberry system.

Ultrasonic treatment at different pH values affects the macromolecular, structural, and rheological characteristics of citrus pectin

Ultrasonic degradation has become a promising strategy for producing modified pectin (MP). In this study, the impact of ultrasonic treatment at various pH values (4.0, 7.0, and 10.0) on the macromolecular, structural and rheological characteristics of citrus pectin was investigated. Results demonstrated that ultrasonic irradiation at the higher pH led to larger reductions in the intrinsic viscosity and weight-average molecular weight of pectin. The degradation kinetics of pectin at different pH values under ultrasound well fitted to a second-order reaction kinetics model. Acoustic cavitation, β-elimination, and demethylation led to the breakage of glycosidic linkages of side chains and methoxyl groups of pectin, but did not have noticeable influences on the main chain of pectin. The ultrasonic treatment at a high pH led to an apparent change in the rheological characteristics of pectin. Therefore, ultrasonic treatment at various pH values can be developed as a viable means to prepare desirable MP.

Impacts of thermal and non-thermal processing on structure and functionality of pectin in fruit- and vegetable- based products: A review

Pectin, a major polysaccharide found in the cell walls of higher plants, plays major roles in determining the physical and nutritional properties of fruit- and vegetable-based products. An in-depth understanding of the effects of processing operations on pectin structure and functionality is critical for designing better products. This review, therefore, focuses on the progress made in understanding the effects of processing on pectin structure, further on pectin functionality, consequently on product properties. The effects of processing on pectin structure are highly dependent on the processing conditions. Targeted control of pectin structure by applying various processing operations could enhance textural, rheological, nutritional properties and cloud stability of products. While it seems that optimizing product quality in terms of physical properties is counteracted by optimizing the nutritional properties. Therefore, understanding plant component biosynthesis mechanisms and processing mechanisms could be a major challenge to balance among the quality indicators of processed products.

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.

Treatment with Subcritical Water-Hydrolyzed Citrus Pectin Ameliorated Cyclophosphamide-Induced Immunosuppression and Modulated Gut Microbiota Composition in ICR Mice

Subcritical water can effectively hydrolyze pectin into smaller molecules while still maintaining its functional regions. Pectic heteropolysaccharide can mediate immune regulation; however, the possible effects of subcritical water-hydrolyzed citrus pectin (SCP) on the immune response remain unclear. Therefore, the effects of SCP on immunomodulatory functions and intestinal microbial dysbiosis were investigated using a cyclophosphamide-induced immunosuppressed mouse model. In this research, immunosuppressed ICR mice were administrated with SCP at dosages of 300/600/1200 mg/kg.bw by oral gavage, and body weight, immune organ indexes, cytokines, and gut microbiota were determined. The results showed that subcritical water treatment decreased the molecular mass and increased the content of galacturonic acid in citrus pectin hydrolysates. Meanwhile, the treatment with SCP improved immunoregulatory functional properties and bioactivities over the original citrus pectin. For example, SCP protected immune organs (accelerated recovery of immune organ indexes) and significantly enhanced the expression of immune-related cytokines (IL-2, IL-6, IFN-γ, and TNF-α). The results of the 16S rDNA sequencing analysis on an IlluminaMiSeq platform showed that SCP normalized Cy-induced gut dysbiosis. SCP ameliorated Cy-dependent changes in the relative abundance of several taxa, shifting the balance back to normal status (e.g., SCP increased beneficial Muribaculaceae, Ruminococcaceae, Bacteroidaceae, and Prevotellaceae while decreasing pathogenic Brevundimonas and Streptococcus). The results of this study suggest an innovative application of citrus pectin as an immunomodulator.

Ultrasonic-assisted citrus pectin modification in the bicarbonate-activated hydrogen peroxide system: Chemical and microstructural analysis

The modified pectin (MP) showed the improved functional properties than the native one. The aim of present study was to develop the ultrasonic accelerated bicarbonate-hydrogen peroxide system for pectin modification to generate short fragments with advanced bioactive properties. The depolymerization effects of this system on the physicochemical properties, structural features, and bioactivity of the degraded fragments were studied systematically. The results indicated that the molecular weight of pectin was reduced drastically from 1088 kDa to 33 kDa within 50 min under an optimized condition (M_H2O2-M_NaHCO3 = 1:2.5, 50 °C, and ultrasound intensity = 11.4 W/cm³). The resulting fragments also showed lower degree of methoxylation and rheological viscosity. The investigation on the sample structures and active oxygen species demonstrated that the highly active O₂^- species generated from HCO₄^- of NaHCO₃-H₂O₂ acted preferentially on the GalA backbone in the HG region, while the RG-I region was maintained; and ultrasound enhanced the degradation efficiency via both chemical effects (increasing the transformation of free radicals) and mechanical effects (disaggregating polysaccharide clusters). The atomic force microscope (AFM) imaging directly verified the branched-chain morphology of pectin and the small-strand degradation fragments. Moreover, ultrasound and NaHCO₃-H₂O₂ treatment induced high galactose content in the degraded products, contributing to an improved inhibitory activity against A549 lung cancer cells, as shown by MTT assay.

Interactions of Anthocyanins with Pectin and Pectin Fragments in Model Solutions

Anthocyanins determine the color and potential health-promoting properties of red fruit juices, but the juices contain remarkably less anthocyanins than the fruits, which is partly caused by the interactions of anthocyanins with the residues of cell wall polysaccharides like pectin. In this study, pectin was modified by ultrasound and enzyme treatments to residues of polysaccharides and oligosaccharides widely differing in their molecular weight. Modifications decreased viscosity and degrees of acetylation and methylation and released smooth and hairy region fragments. Native and modified pectin induced different effects on the concentrations of individual anthocyanins after short-term and long-term incubation caused by both hydrophobic and hydrophilic interactions. Results indicate that both pectin and anthocyanin structure influence these interactions. Linear polymers generated by ultrasound formed insoluble anthocyanin complexes, whereas oligosaccharides produced by enzymes formed soluble complexes with protective properties. The structure of the anthocyanin aglycone apparently influenced interactions more than the sugar moiety.

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**).

Enzymatic Production and Characterization of Pectic Oligosaccharides Derived from Citrus and Apple Pectins: A GC-MS Study Using Random Forests and Association Rule Learning

Pectic oligosaccharides (POS) from citrus and apple pectin hydrolysis using ViscozymeL and Glucanex200G have been obtained. According to the results, maximum POS formation was achieved from citrus pectin after 30 min of hydrolysis with ViscozymeL, with a yield of 652 mg g^-1 and average molecular mass ( M_w) of 0.8-2.5 kDa, while with Glucanex200G, the yield was 518 mg g^-1 and M_w was 0.8-7.1 kDa. Digalacturonic and trigalacturonic acids were identified among other low M_w compounds as di- and tri-POS. In addition, differences in GC-MS spectra of all oligosaccharides found in the hydrolysates were studied by employing random forests and other algorithms to identify structural differences between the obtained POS, and high prediction rates were shown for new samples. Chemical structures were proposed for some influential m/ z ions, and 12 association rules that explain differences according to pectin and enzyme origin were built. This information could be used to establish structure-function relationships of POS.