The potential of subcritical water as a “green” method for the extraction and modification of pectin: A critical review

Passion fruit peel-derived low-methoxyl pectin: De-esterification methods and application as a fat substitute in set yogurt

Passion fruit pectin, originally high methoxyl pectin, undergoes substantial conversion into low methoxyl pectin (LMP) through de-esterification. This de-esterification is significance for reducing the application of sugar in food, as calcium ions can replace excessive sugar during gel formation. In this study, LMPs derived from passion fruit pectin were prepared using four methods: low-temperature alkali, room temperature alkali, enzymatic, and dielectric barrier discharge plasma (DBD)-assisted enzyme (DBDE). The de-esterification conditions were optimized, leading to the selection of LMPs with a degree of esterification for the analysis of molecular weight, monosaccharide composition, and gel properties. The results revealed significant differences in the structure and properties of LMPs depending on the de-esterification method applied. The galacturonic acid content of LMPs significantly increased, with LMP from DBDE (LMP-DBDE) exhibiting the highest increase at 47.81 %. Additionally, the molecular weights of LMPs significantly decreased, with LMP-DBDE showing the smallest decrease. LMP-DBDE demonstrated higher apparent viscosity, thermal stability, and gel properties, facilitating the formation of gels. After 21 days of storage, 0.40 % LMP-DBDE yogurt showed no whey separation, significantly extending its shelf life. Therefore, LMP-DBDE exhibits potential as a fat substitute, combining the advantages of LMP with enhanced water-holding capacity, and presenting promising applications in low-fat dairy products.

Shellfish polysaccharides: A comprehensive review of extraction, purification, structural characterization, and beneficial health effects

Global food systems are currently facing great challenges, such as food sources, food safety, and environmental crises. Alternative nutritional resources have been proposed as part of the solution to meeting future global food demand. In the natural resources, shellfish are the major component of global aquatic animals. Although most studies focus on the allergy, toxin, and contamination of shellfish, it is also a delicious food to the human diet rich in proteins, polysaccharides, minerals, and omega-3. Among the functional ingredients, shellfish polysaccharides possess nutritional and medicinal values that arouse the great interest of researchers. The selection of the extraction approach and the experimental condition are the key factors that influence the extraction efficiency of shellfish polysaccharides. Importantly, the purification of crude polysaccharides comprises the enrichment of shellfish polysaccharides and isolation of fractions, also resulting in various structural characteristics and physicochemical properties. Chemical modification is also an efficient method to further improve the biological activities of shellfish polysaccharides. This review summarizes the extraction, purification, structural characterization, and chemical modification methods for shellfish polysaccharides. Additionally, the beneficial health effects of shellfish polysaccharides are highlighted, with an emphasis on their potential mechanism. Finally, current challenges and perspectives on shellfish polysaccharides are also spotlighted.

Upcycling olive pomace into pectic elicitors for plant immunity and disease protection

Olive oil production generates substantial quantities of pomace, which are often disposed of in soil, leading to adverse effects on agriculture and the environment. Furthermore, climate change exacerbates plant diseases and promotes the use of toxic phytochemicals in agriculture. However, olive mill wastes can have high potential as reusable and valuable bioresources. Using diluted ethanol, an environmentally friendly solvent, we extracted a fraction containing short and long oligogalacturonides, short arabino-oligosaccharides and polysaccharides. The obtained extract elicited key features of plant innate immunity in Arabidopsis seedlings, including the phosphorylation of mitogen-activated protein kinases MPK3 and MPK6 and the upregulation of defence genes such as CYP81F2, WRKY33, WRKY53, and FRK1. Notably, pretreatment of adult Arabidopsis and tomato plants with the olive pomace extract primed defence responses and enhanced their resistance to the phytopathogens Botrytis cinerea and Pseudomonas syringae. Our results highlight the opportunity to upcycle the two-phase olive pomace collected at the late stage of olive oil campaign, in low-cost and sustainable glycan elicitors, contributing to reducing the use of chemically synthesized pesticides.

A critical review of persimmon-derived pectin: Innovations in extraction, structural characterization, biological potentials, and health-promoting effects

Persimmon-derived pectin (PP) is a versatile dietary polysaccharide with considerable industrial and biological significance, demonstrating a range of functionalities and health-promoting benefits. This review explores the changes in PP during postharvest and processing, detailing structural alterations and extraction techniques for optimal characteristics. Key functional attributes of PP-such as emulsification, rheology, antioxidant capacity, immunomodulation, and gut microbiota regulation-highlight its potential applications in food, healthcare, pharmaceuticals, and cosmetics. The review also explores methods to enhance the functional properties of PP through synergistic interactions with polyphenols. A strategic roadmap for advancing PP research is proposed, connecting extraction methods, structural characteristics, and functional properties to tailor PP for specific applications in food science and technology. Overall, persimmon-derived pectin is positioned as a valuable food-derived bioactive ingredient with diverse capabilities, poised to drive innovation and advance nutritional science across multiple sectors.

Pectin extracted from red dragon fruit (Hylocereus polyrhizus) peel and its usage in edible film

Pectin was extracted from red dragon fruit (Hylocereus polyrhizus) peel using two different extraction methods: subcritical water extraction (SCWE) and conventional acid extraction (AE), from two different types of peels, fresh peel puree and dried peel powder. SCWE method on fresh peel puree showed an ∼18.88 % increase in pectin yield compared to AE. Extracted pectin is classified as low methoxyl pectin (DE: 8.51-50.64 %), with an average molecular weight ranging from 115.23 kDa to 577.84 kDa and a Gal-A content of 44.09 % - 53.90 %. The potential of pectin from fresh peel puree to be applied as a biodegradable film was further explored. Different pectin concentrations (3-5 % w/v) were used to prepare the films. Regarding the film performance, PF-S5, which was produced from SCWE with 5 % of pectin concentration, exhibits better thermal stability (Tdmax 250 °C, residue of 28.69 %) and higher moisture barrier (WVP 5.59 × 10-11 g.cm-1.s-1.Pa-1). In comparison, PF-A showed lower water solubility (45.14-69.15 %), higher water contact angle (33.01° - 44.35°), and better mechanical properties (TS: 2.12-4.11 MPa, EB: 48.72-61.39 %). Higher molecular weight accompanied by higher DE and Gal-A content contributes to better pectin film properties.

Recent progress in the extraction of terpenoids from essential oils and separation of the enantiomers by GC-MS

Terpenoids possess significant physiological activities and are rich in essential oils. Some terpenoids have chiral centers and could form enantiomers with distinct physiological activities. Therefore, the extraction and separation of terpenoids enantiomers are very important and have attracted extensive attention in recent years. Meanwhile, the specific distribution and enantiomer excess results (the excess of one enantiomer over the other in a mixture of enantiomers) could be used as quality markers for illegitimate adulteration, origin identification, and exploring component variations and functional interrelations across different plant tissues. In this study, an overview of the progress in the extraction of terpenoids from essential oils and the separation of their enantiomers over the past two decades has been made. Extraction methods were retrieved by the resultant network visualization findings. The results showed that the predominant methods are hydrodistillation, solvent-free microwave extraction, headspace solid-phase microextraction and supercritical fluid extraction methods. GC-MS combined with chiral chromatography columns is commonly used for the separation of enantiomers, while 2D GC is found to have stronger resolution ability. Finally, some prospects for future research directions in the extraction and separation identification of essential oils are proposed.

Exploring the potential of waste biomass-derived pectin and its functionalized derivatives for water treatment

Environmental pollution remains a constant challenge due to the indiscriminate use of fossil fuels, mining activities, chemicals, drugs, aromatic compounds, pesticides, etc. Many emerging pollutants with no fixed standards for monitoring and control are being reported. These have adverse impacts on human life and the environment around us. This alarms the wastewater management towards developing materials that can be used for bulk water treatment and are easily available, low cost, non-toxic and biodegradable. Waste biomass like pectin is extracted from fruit peels which are a discarded material. It is used in pharmaceutical and nutraceutical applications but its application as a material for water treatment is very limited in literature. The scientific gap in literature review reports are evident with discussion only on pectin based hydrogels or specific pectin derivatives for some applications. This review focuses on the chemistry, extraction, functionalization and production of pectin derivatives and their applications in water treatment processes. Pectin functionalized derivatives can be used as a flocculant, adsorbent, nano biopolymer, biochar, hybrid material, metal-organic frameworks, and scaffold for the removal of heavy metals, ions, toxic dyes, and other contaminants. The huge quantum of pectin biomass may be explored further to strengthen environmental sustainability and circular economy practices.

Response Surface Optimization for Water-Assisted Extraction of Two Saponins from Paris polyphylla var. yunnanensis Leaves

The process of extracting polyphyllin II and polyphyllin VII by water-assisted extraction was established and optimized in this study. Response surface methodology was used to establish a prediction model to optimize the extraction conditions. Based on the one-way test, the Box-Behnken design with three factors and three levels was used for the experimental program, and the composition analysis was carried out by high-performance liquid chromatography (HPLC). The optimal extraction conditions for polyphyllin II and polyphyllin VII were as follows: extraction time of 57 and 21 min, extraction temperature of 36 and 32 °C, solid-to-liquid ratio of 1:10 and 1:5 g/mL, respectively, and the yields of polyphyllin II and polyphyllin VII were 1.895 and 5.010%, which was similar to the predicted value of 1.835 and 4.979%. The results of the ANOVA showed that the model fit was good, and the Box-Behnken response surface method could optimize the water-assisted extraction of saponins from the leaves of Paris polyphylla var. yunnanensis. This study provides a theoretical basis for the application of polyphyllin II and polyphyllin VII in pharmaceutical production.

Green Extraction of Pectin from Sugar Beet Flakes and Its Application in Hydrogels and Cryogels

Sugar beet flakes, a by-product of the sugar industry, were used as a source for pectin extraction that was performed using conventional citric acid extraction (CE) and two non-conventional extraction techniques-microwave-assisted extraction (MAE) and pulsed ultrasound-assisted extraction (PUAE). The influence of extraction conditions was studied for each technique based on pectin yield and galacturonic acid content, and spectroscopic, chromatographic and colorimetric methods were used for pectin characterization. Better results for pectin yield were achieved through CE (20.80%), while higher galacturonic acid content was measured in pectin extracted using PUAE (88.53 g/100 g). Pectin extracted using PUAE also presented a higher degree of methylation and acetylation. A significant increase in the molecular weight of pectin was observed for the PUAE process (7.40 × 105 g/mol) by comparison with conventional extraction (1.18 × 105 g/mol). Hydrogels and cryogels prepared with pectin from sugar beet flakes also showed differences in physicochemical parameters determined by the method of pectin extraction. Hydrogels had higher bulk density values irrespective of the pectin extraction method, and overall lower values of the textural parameters. Cryogels prepared with pectin from CE showed higher values of the textural parameters of hardness, adhesiveness, cohesiveness, gumminess and chewiness, while gels obtained with pectin from MAE and PUAE had higher thermal stability. The results of this study prove that sugar beet flakes can be considered a potential source for pectin production, and the extracted pectin is suitable for obtaining hydrogels and cryogels with physicochemical parameters comparable to the commercial citrus and apple pectin available on the market.

Effect of subcritical water temperature on the structure, antioxidant activity and immune activity of polysaccharides from Glycyrrhiza inflata Batalin

In this study, the polysaccharide from Glycyrrhiza inflata Batalin extracted by hot water (HW-GP) was further physically modified with subcritical water to obtain novel polysaccharides (SW-GP). Comparative analysis was conducted to examine the disparities in conformation and bioactivity between HW-GP and SW-GP, aiming to precisely regulate the structure of the polysaccharides and enhance their bioactivity by controlling subcritical water temperature. The results showed that, compared with HW-GP, subcritical water modification (100-160 °C) not only significantly reduced the molecular weight of polysaccharides (from 5.586 × 105 g/mol to 1.484 × 105 g/mol), but also modulated the intermolecular interaction forces, which maintain the conformation of the polysaccharides, including electrostatic and hydrophobic interactions, thereby dynamically transforming the polysaccharide chain conformation from triple helix to random coil, and the strength of the chain conformation shifted from rigid to flexible. In addition, the modification of the SW-GP structure by subcritical water also enhanced its biological activity. SW-GP (140 °C) with low molecular weight and semi-rigid triple helix conformation showed the best scavenging effect on the DPPH, ABTS, and hydroxyl radicals, and exhibited excellent antioxidant activity. SW-GP (130 °C) with medium molecular weight and semi-rigid triple helix conformation significantly promoted the proliferation and phagocytosis of RAW264.7 cells, as well as increased the release levels of NO, TNF-α, IL-6, and IL-1β, and the immunomodulatory activity was much higher than that of other polysaccharides. These findings confirmed the feasibility of using subcritical water temperature as a regulatory feature for the structure and bioactivity of glycyrrhiza polysaccharides, which may have reference significance for the modification of polysaccharides with heightened bioactivity.

Effect of H2O2-assisted ultrasonic bath on the degradation and physicochemical properties of pectin

The effects of H2O2-assisted ultrasonic bath degradation technology on pectin were investigated. The degradation efficiency with different pectin concentrations, H2O2 concentrations, ultrasonic power, and ultrasonic time was analyzed. The results showed that pectin concentration was negatively correlated with the degradation efficiency of pectin, while, H2O2 concentration, ultrasonic power, and ultrasonic time were positive correlated with the degradation efficiency. Besides, the apparent viscosity and viscoelasticity of the degraded pectin decreased significantly. The antioxidant activity increased after the H2O2-assisted ultrasonic bath treatment. The results of FTIR, NMR, laser particle size, SEM, XRD, and AFM analysis indicated that the degradation treatment did not destroy the main structure of pectin. The average particle size and crystallinity of pectin decreased. The degree of aggregation and the height of the molecular chain decreased significantly. In conclusion, the H2O2-assisted ultrasonic bath degradation technique could effectively degrade pectin. This study provided a comprehensive analysis of the degradation of pectin under H2O2-assisted ultrasonic bath, which will be beneficial to further develop H2O2-assisted ultrasonic bath techniques for pectin degradation.

Unlocking the Bioactive Potential of Pomegranate Peels: A Green Extraction Approach

Pomegranate (Punica granatum L.) is well known for its high content of bioactives, including polyphenols, flavonoids, and tannins, which have been shown to exhibit a wide range of biological activities, such as antioxidant, antimicrobial, and anticancer effects. It is worth noting that the majority of these molecules are found in the peels, which are usually disposed of after processing, causing a significant amount of waste, amounting to more than 3.6 million t/y. This work investigates microwave-assisted extraction (MAE) in water for the recovery of antioxidants from pomegranate peels (PP), including the optimisation of temperature and extraction times. The total phenolic, anthocyanin, flavonoid, and tannin contents of the recovered extracts were determined, as well as their antioxidant activities, which were found to be 356.35 mgGAE/gExtr, 303.97 µgCy3G/gExtr, 37.28 mgQE/gExtr, 56.48 mgGAE/gExtr, and 5.72 mmolTE/gExtr, respectively (according to the adopted reference). All results were compared with those obtained using a conventional protocol. In addition, the potential for water recycling by means of downstream nanofiltration in optimised MAE was investigated, leading to overall water reuse of approx. 75%. Power consumption (20.92 W/mgGAE) and common green metrics, Reaction Mass Efficiency (RME), E-Factor, and the Process Mass Intensiti/efficiency (PMI, PME), were considered in evaluating the proposed PP valorisation strategy. Finally, the biological activities of the main products were assessed. The antimicrobial properties of the PP extracts against three Gram-positive and three Gram-negative bacteria and their antiproliferative activity towards human cancer cells were tested. S. aureus bacteria was the most susceptible to the PP extracts. All tested products displayed antiproliferative activity against HeLa cells when higher concentrations were tested, with D-PP/NF (obtained from dried PP and sequential nanofiltration) being the most effective. This result was also confirmed via clonogenic analysis, which generally indicated the possible anti-cancer activity of pomegranate peel extracts obtained using this green approach.

Perspectives on Thermochemical Recycling of End-of-Life Plastic Wastes to Alternative Fuels

Due to its resistance to natural degradation and decomposition, plastic debris perseveres in the environment for centuries. As a lucrative material for packing industries and consumer products, plastics have become one of the major components of municipal solid waste today. The recycling of plastics is becoming difficult due to a lack of resource recovery facilities and a lack of efficient technologies to separate plastics from mixed solid waste streams. This has made oceans the hotspot for the dispersion and accumulation of plastic residues beyond landfills. This article reviews the sources, geographical occurrence, characteristics and recyclability of different types of plastic waste. This article presents a comprehensive summary of promising thermochemical technologies, such as pyrolysis, liquefaction and gasification, for the conversion of single-use plastic wastes to clean fuels. The operating principles, drivers and barriers for plastic-to-fuel technologies via pyrolysis (non-catalytic, catalytic, microwave and plasma), as well as liquefaction and gasification, are thoroughly discussed. Thermochemical co-processing of plastics with other organic waste biomass to produce high-quality fuel and energy products is also elaborated upon. Through this state-of-the-art review, it is suggested that, by investing in the research and development of thermochemical recycling technologies, one of the most pragmatic issues today, i.e., plastics waste management, can be sustainably addressed with a greater worldwide impact.

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 (Mw) 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.

Health-Promoting Activities and Associated Mechanisms of Polygonati Rhizoma Polysaccharides

Polygonati Rhizoma, a typical homology of medicine and food, possesses remarkable anti-fatigue, anti-aging, metabolic regulatory, immunomodulatory, anti-inflammatory, neuroprotective, anti-diabetes, and anti-cancer effects. Among bioactive phytochemicals in Polygonati Rhizoma, polysaccharides play important roles in the health-promoting activities through the mechanisms mentioned above and potential synergistic effects with other bioactives. In this review, we briefly introduce the updated biosynthesis of polysaccharides, the purification method, the structure characterization, and food applications, and discuss in detail the biological activities of Polygonati Rhizoma polysaccharides and associated mechanisms, aiming at broadening the usage of Polygonati Rhizoma as functional food and medicine.

Advances in Polygonatum sibiricum polysaccharides: Extraction, purification, structure, biosynthesis, and bioactivity

Polygonatum sibiricum has been used as food and medicine for thousands of years, and P. sibiricum polysaccharides (PSPs) have become the hot research spot due to their various health-promoting functions. Numerous studies have shown that PSPs possess huge potential in the application of functional food and medicine fields. However, the research status and features of the preparation process, molecular structure, and bioactivities of PSPs are unclear. Therefore, this review makes a comprehensive summary and proposes new insights and guidelines for the extraction, purification, structural features, biosynthesis, and multiple bioactivities of PSPs. Notably, it is concluded that PSPs mainly contain several types of polysaccharides, including fructan, pectin, galactomannan, glucomannans, arabinogalactan, and galactan, and multiple bioactivates, including osteogenic activity, anti-obesity, anti-diabetes, anti-depression, antioxidant, antiglycation, and protective effect against neurotoxicity and gut microbiota regulating activity. This review contributes to the structure-function study and resource utilization of P. sibiricum and its polysaccharides in food fields.

Extraction optimization and characterization of persimmon peel pectin extracted by subcritical water

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Persimmon peel pectin (PPP) was extracted by subcritical water.

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PPP had low M_w of 21.79 kDa and its degree of esterification was 40.61 %.

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PPP attributed to a degradation temperature of 228.05 ℃.

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The IC₅₀ of PPP to ABTS•+ was 9.8-times that of commercial citrus pectin in vitro.

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PPP altered microbial intestinal communities in mice.

Persimmon peel pectin (PPP) was extracted by subcritical water via the response surface methodology. The optimal crude PPP extraction yield of 7.62 ± 0.7 % was found at 138 °C, 2.84 min, and liquid–solid ratio of 1:10.02. After treatment of deproteinization and decolorization with papain and hydrogen peroxide, 83.19 % of protein and 78.56 % of the colour in crude PPP were removed, respectively. PPP owned the M_w of 21.79 kDa and its uronic acids content was 64.03 %. PPP was further affirmed by fourier transform infrared, X-ray diffractometer and ¹H NMR analysis. Moreover, the degradation temperature (228.05 ℃) of PPP was verified via differential scanning calorimetry. Then, the IC₅₀ of PPP to ABTS•+ was 9.8 times that of commercial citrus pectin. Moreover, PPP could change microbial communities and selectively enrich Bacteroides, Cetobacterium, Erysipelatoclostridium, Parabacteroides and Phocaeicola sartorii. This study demonstrated that subcritical water was practicable for extraction of persimmon peel pectin.