Pectin Fractions Research Articles

Effect of the ripening stage on the pulsed vacuum drying behavior of goji berry (Lycium barbarum L.): Ultrastructure, drying characteristics, and browning mechanism

In current work, the effect of ripening stages (I, II, and III) on pulsed vacuum drying (PVD) behavior of goji berry was explored. The shortest drying time of goji berry was observed at stage I (6.99 h) which was 13.95 %, and 28.85 % shorter than those at stages II, and III, respectively. This phenomenon was closely associated with the ripening stage, as contributed by the initial physiochemical differences, ultrastructure alterations, and moisture distribution. In addition, lower maturity suffered more severe browning, primarily due to the enzymatic and non-enzymatic reactions of phenolics, followed by pigment degradation and the Maillard reaction. Additionally, the PVD process promoted the rupture and transformation of the pectin fractions, also causing browning either directly or indirectly through participation in other chemical reactions. These findings suggest that the appropriate ripening stage of goji berry should be considered as having a significant impact on drying behaviors and quality attributes.

Suppressing the rhamnogalacturonan lyase gene FaRGLyase1 preserves RGI pectin degradation and enhances strawberry fruit firmness

Plant rhamnogalacturonan lyases (RGLyases) cleave the backbone of rhamnogalacturonan I (RGI), the “hairy” pectin and polymer of the disaccharide rhamnose (Rha)-galacturonic acid (GalA) with arabinan, galactan or arabinogalactan side chains. It has been suggested that RGLyases could participate in remodeling cell walls during fruit softening, but clear evidence has not been reported. To investigate the role of RGLyases in strawberry softening, a genome-wide analysis of RGLyase genes in the genus Fragaria was performed. Seventeen genes encoding RGLyases with functional domains were identified in Fragaria × ananassa. FaRGLyase1 was the most expressed in the ripe receptacle of cv. Chandler. Transgenic strawberry plants expressing an RNAi sequence of FaRGLyase1 were obtained. Three transgenic lines yielded ripe fruits firmer than controls without other fruit quality parameters being significantly affected. The highest increase in firmness achieved was close to 32%. Cell walls were isolated from ripe fruits of two selected lines. The amount of water-soluble and chelated pectins was higher in transgenic lines than in the control. A carbohydrate microarray study showed a higher abundance of RGI epitopes in pectin fractions and in the cellulose-enriched fraction obtained from transgenic lines. Sixty-seven genes were differentially expressed in transgenic ripe fruits when compared with controls. These genes were involved in various physiological processes, including cell wall remodeling, ion homeostasis, lipid metabolism, protein degradation, stress response, and defense. The transcriptomic changes observed in FaRGLyase1 plants suggest that senescence was delayed in transgenic fruits.

Emulsifying properties of biopolymer extracts from Opuntia ficus indica cladodes

The use of natural extracts in the field of cosmetics and pharmaceuticals is increasing due to the growing demand for sustainable and safe products, together with their potential therapeutic benefits. Bioextracts from the parenchyma of Opuntia ficus indica cladodes were characterized and evaluated as emulsifying agents. They contain pectin together with variable amounts of arabinogalactan-protein complex (AGP), as in many polysaccharides of natural origin. Their protein content varies according to the purification steps: 11.4 wt% for the raw mucilage (Mofi), 4.7 wt% for the pectin fraction (Pofi) and less than 0.5 wt% for the filtrated pectin fraction (FPofi). Part of the AGP contained in the Mofi and Pofi extracts precipitates as particles with a ∼5 µm diameter. Mofi at 1.5 wt% concentration is an efficient emulsifier of oil-in-water emulsions of medium-chain triglycerides or sunflower oil with stability against coalescence for more than three months. Pofi is less efficient and FPofi does not allow the stabilization of emulsions. The performance of emulsifiers is directly related to the protein content of the extracts and the role of the insoluble particles is essential. The insoluble particles of AGP are responsible for the stabilization through a Pickering effect. The emulsions have the characteristic properties of Pickering emulsions.

Fractionation and physicochemical characterization of dietary fiber of kenaf (Hibiscus cannabinus L.) seed.

Kenaf seeds are underutilized kenaf plant by-products, containing essential nutrients including dietary fiber (DF), which can be potentially utilized as food ingredients. The present study aimed to evaluate the physicochemical characteristics of kenaf seed fiber fractions extracted from kenaf seed. Defatted kenaf seed powder yielded four DF fractions: alkali-soluble hemicellulose (146.4 g kg-1 ), calcium-bound pectin (10.3 g kg-1 ) and acid-soluble pectin (25.4 g kg-1 ) made up the soluble fibre fraction, whereas cellulose (202.2 g kg-1 ) comprised the insoluble fraction. All fractions were evaluated for their physicochemical properties. The DF fractions contained glucose, mannose, xylose and arabinose, and a small amount of uronic acid (1.2-2.7 g kg-1 ). The isolated pectin fractions had a low degree of esterification (14-30%). All the isolated DF fractions had high average molecular weights ranging from 0.3 to 4.3 × 106 g mol-1 . X-ray diffractogram analysis revealed that the fractions consisted mainly of an amorphous structure with a relative crystallinity ranging from 31.6% to 44.1%. The Fourier-transform infrared spectroscopy spectrum of kenaf seed and its DF fractions showed typical absorption of polysaccharides, with the presence of hydroxyl, carboxyl, acetyl and methyl groups. Scanning electron microscopy analysis demonstrated that the raw material with the rigid structure resulted in soluble and insoluble DF fractions with more fragile and fibrous appearances, respectively. The soluble DF demonstrated greater flowability and compressibility than the insoluble fractions. These findings provide novel information on the DF fractions of kenaf seeds, which could be used as a potential new DF for the food industry. © 2023 Society of Chemical Industry.

Cell wall modifications during storage: Changes in the texture behavior of the canned yellow peach

Textural changes in canned yellow peach (CYP) soaked in a concentrated sucrose syrup that led to softening during storage were always accompanied by the depolymerization of the cell wall, as the result of the cell wall-modifying enzymes. In this study, we evaluated the changes in texture, pectin fractions (namely, WEP, CEP and AEP) and pectinase activities (namely, PME and PG) during storage. Results showed that the undoubted decrease in Gal contents of all pectin fractions (∼44.16%, ∼36.98% and ∼ 66.59% declines in WEP, CPE and AEP, respectively) were observed as well as the reduced texture properties. Specially, the hardness, chewiness and resilience of CYP dramatically decreased at the first 40 days-storage. Upon the storage, PG activities were significantly facilitated, while PME activities were markedly inhibited. Together with the results of molar mass and monosaccharide composition, sucrose syrup could promote the conversion and depolymerization in HG region of AEP fraction. Moreover, sugar ratio analysis and 13C NMR spectroscopy also illustrated the changes in pectin structures, contributing to the texture softening of CYP, which was confirmed by the gradual depolymerization and solubilization in HG regions of all the pectin fractions.

A clean label O/W pickering emulsion stabilized by pectin-containing lignocellulosic nanofibrils isolated from apple pomace

With the increasing demand for clean-label food, LCNF is considered a promising candidate to replace artificial surfactants in O/W emulsion. However, the isolation of LCNF usually requires the use of costly and toxic oxidants or grafting reagents to introduce charged groups for higher fibrillation degree and better emulsifying properties. In this study, a new pectin-containing apple nanofibril (A-NF) with native dissociated carboxyl groups (-COO-) was successfully produced from apple pomace by alkaline demethylation followed by high-pressure homogenization. These “native” charged A-NFs are 10–30 nm in diameter and ∼1 μm in length, and can be well dispersed in water for several months due to the release of up to 1.30 mmol/g nanofibrils of -COO- from the insoluble pectin (ISP) fraction by alkaline demethylation. Among A-NFs, A–NF–24h showed the best emulsifying properties (70.85 m2/g of EAI and 94.71% of ESI) and highest emulsion stability (∼1.00 μm of the oil droplet size during 14-day storage). Emulsion microstructure showed that LCNF not only irreversibly adsorbed at the oil-water interface, providing electrostatic stability, but also offered depletion stability by fabricating an entangled network with the unabsorbed portion. Moreover, molecular dynamics simulations further explained that the A-NF system displayed lower absorption energy of −1659.43 kJ/mol and diffusion cofactor of oil molecules of 16.67 μm2/s than that of CNF system at the interface, thus enhancing the emulsion stability. Altogether, these native A-NFs exhibit good colloidal stability, comparable emulsifying properties and emulsion stability, and have promising applications in clean-label O/W emulsions.

Peeling mechanism of tomato induced by HHAIB: Microscopic, ultrastructure, chemical, physical and mechanical properties perspectives

In order to better manage the peeling degree and avoid unnecessary losses, the current work aimed to explore the peeling mechanism of a novel peeling technology, high-humidity hot air impingement blanching (HHAIB). The relationships between HHAIB peeling performance and the changes in skin temperature, skin structure, water state, pectin fractions content, and skin mechanical properties of tomatoes were analyzed. Results showed, after HHAIB treatment, the epicuticular wax was disrupted, the skin exhibited more and longer random cracks, the degradation of inner skin tissue was observed by transmission electron microscopy, the free water percentage increased resulting in water loss in the whole tomato, the water-soluble pectin contents decreased in tomato fleshes, while the contents of chelate-soluble pectin and sodium-carbonate-soluble pectin increased. HHAIB heating reduced the elongation at break, and increased Young's Modulus of tomato peel. This study revealed the HHAIB peeling mechanism and provided new insights for developing HHAIB peeling technology.

Chemical and microstructural characterization of easy- and hard-to-cook Jack bean (Canavalia ensiformis (L.) DC.) collections

Differences in the microstructure and the chemical composition of pectic polymers were investigated from three Jack bean collections with different hard-to-cook (HTC) levels, as confirmed by the optimal cooking time analysis. These collections showed different cell and starch granule sizes, where the hardest-to-cook bean (Jombang collection) had the smallest maximum cell perimeter (285 μm), the smallest starch granule perimeter (98 μm), and the highest frequency of small intercellular space indicating more linkage in the middle lamella. No significant difference was observed in the frequency of small intercellular spaces between Malang and Cilacap despite having different optimal cooking times. Jack bean cotyledon cell walls were mainly composed of insoluble polysaccharide rich in arabinose and galactose. The beans contained high covalently bound pectin fractions (NEF) ranging from 78% to 83%. Higher bound phenolics (ferulic acid) were found with the increase in the optimal cooking times of the collections. Overall, the findings suggest the occurrence of cell wall linkage and highlight the importance of ferulic acid pectin crosslink in HTC Jack bean. This study could help develop strategies to reduce cooking time to promote the utilization of Jack bean.

Verifying the Optimal Extraction Method and Content of Red Okra Extracts and Crude Pectin Using Response Surface Methodology (RSM)

Recently, many studies have reported the properties and functionality of okra pectin. However, these studies are about green okra pods, and pectin in red okra pods, stems, and roots has not been reported. Therefore, this study aimed to optimize the red okra extraction method using response surface methodology (RSM) analysis and evaluate the effects of extraction time, temperature, solvent ratio, and pH on the extract yield and crude pectin content. Based on RSM analysis, 4.35 h, 98.04 °C, 23.34 solvent ratio, and pH 3.36 are the optimal parameters for extracting crude pectin from red okra, and the crude pectin content was predicted to be 40.83%. When red okra was extracted under these extraction conditions (4 h, 100 °C, 23 solvent ratio, and pH 3), the extraction yield was 45.26%, and the crude pectin content was 38.42%, which was similar to the yield obtained under the conditions derived from the RSM analysis. In addition, the pH control using hydrochloric acid was replaced with citric acid, and the changes in extract yield and crude pectin content were compared. When citric acid was used, the extract yield was 49.15% (8.6% increase), and the crude pectin content was 42.76 ± 2.56% (11.3% increase); compared to when hydrochloric acid was used, the yield increased. Finally, the standardization of red okra raw materials was determined by analyzing the extraction yield and crude pectin content by part, harvest time, and size of red okra using the established extraction method using citric acid. As a result, it was confirmed that the extraction yield obtained from the established extraction method was reached from the extraction of red okra fruits up to 12 cm in size that were harvested between July and November. Additionally, compared to the non-pectin fraction, the crude pectin fraction isolated from red okra pod extract showed significantly higher total phenolic content (TPC) and total flavonoid content (TFC). These findings, reported for the first time, may contribute to the development of processes to purify red okra pectin, functional evaluation studies of pectin, and potential applications of red okra extract in various industries and research.

Effect of pasteurization processing and storage conditions on softening of acidified chili pepper: Pectin and it related enzymes

The softening of acidified chili peppers induced by processing and storage has become a major challenge for the food industry. This study aims to explore the impact of pasteurization techniques, thermal processing (TP), high-pressure processing (HPP), addition of sodium metabisulfite (SMS), and storage conditions (25 °C, 37 °C, and 42 °C for 30 days) on the texture-related properties of acidified chili pepper. The results showed that the textural properties of samples were destructed by TP (the hardness of samples decreased by 19.43 %) but were less affected by HPP and SMS. Compared with processing, storage temperature had a more dominant impact on texture and pectin characteristics. With increased storage temperature, water-solubilized pectin fraction content increased (increased by 160.99 %, 136.74 %, and 13.01 % in TP, HPP, and SMS-stored groups, respectively), but sodium carbonate-solubilized pectin fraction content decreased (decreased by 29.84 %, 26.81 %, and 8.60 % in TP-, HPP-, and SMS-stored groups, respectively), especially in TP-stored groups. Multivariate data analysis showed that softening was more closely related to pectin conversion induced by acid hydrolysis and pectinase depolymerization. This finding offers new perspectives for the production of acidified chili pepper.

Modulating temperature and pH during subcritical water extraction tunes the molecular properties of apple pomace pectin as food gels and emulsifiers

This study explores the cascade extraction of polyphenols and pectins from apple pomace and their potential application as food emulsifiers. The extraction of polyphenols was achieved by a simple method using ethanol and resulted in remarkable antioxidant activity. Pectic polysaccharides were sequentially extracted (5, 10 and 15 min) using subcritical water at two different temperatures (120 °C and 140 °C) and three different pH conditions (pH 3.0, 5.0 and 7.0). Acidic pH resulted in higher pectin yields when combined with higher temperature, whereas neutral conditions were less selective towards pectin. Pectin with different branching patterns could be isolated by tuning the process conditions. Linear homogalacturonan (HG) was preferentially isolated at milder conditions, whereas more branched rhamnogalacturonan (RG-I) populations required longer extraction times. Subcritical water enabled the extraction of pectins with different degrees of methoxylation (DM) depending on the extraction pH, which enabled the production of pectin acid gels with varying rheological properties. Low DM pectin was directly recovered from apple pomace at lower pH, eliminating the need for its conventional derivatization from high DM pectin. The emulsifying properties of two apple pomace pectin fractions with high and low methoxyl content were compared; the pectin with higher methoxyl content showed higher emulsifying capacity and stability. This study demonstrates that the relative abundance of the different pectic domains and the methoxylation of pectin can be controlled by subcritical water extraction, which has important implications for the valorization of pectic-rich agricultural wastes into valuable food ingredients.

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.

A wide diversity exists in pectin structure from thirteen apple cultivars

To emphasize that differences in pectin structure among cultivars play a crucial role in the texture and quality of fruits and vegetables, the sugar content and methyl-esterification of pectin fractions from 13 apple cultivars was studied. Cell wall polysaccharides were isolated as alcohol-insoluble solids (AIS) and subsequently extracted to yield water-soluble solids (WSS) and chelating-soluble solids (ChSS). All fractions contained significant amounts of galacturonic acid, while sugar compositions varied between cultivars. AIS and WSS pectins showed a degree of methyl-esterification (DM) > 50 %, while ChSS pectins had either a medium (∼50 %) or low (<30 %) DM. Homogalacturonan as major structure was studied using enzymatic fingerprinting. Methyl-ester distribution of pectin was described by degrees of blockiness and -hydrolysis. Novel descriptive parameters were obtained by measuring the levels of methyl-esterified oligomers released by endo-PG (DBPGme) and PL (DBPLme). Pectin fractions differed in relative amounts of non-, moderately-, and highly methyl-esterified segments. WSS pectins were mostly lacking non-esterified GalA sequences, while ChSS pectins had medium DM and many non-methyl-esterified blocks or a low DM with many intermediate methyl-esterified GalA blocks. These findings will be of help to better understand physicochemical properties of apple and its products.

Structural characterization of water-soluble polysaccharides isolated from leaves of Hedera nepalensis

BackgroundHedera nepalensis is a traditional medicinal plants, and the dried leaves of it are generally used for the cure and treatment of many diseases, also widely known as Chang-Chun-Teng in Chinese. Until now, structural characterization of water-soluble polysaccharides isolated from leaves of Hedera nepalensis have been scarcely studied, even though the chemical compounds derived from it and their biological activities have been widely studied.MethodsWater-soluble polysaccharides (WHNP) were isolated from the dried leaves of Hedera nepalensis, and their structural features were investigated. One neutral polysaccharide fraction (WHNP-N) and three major pectin fractions (WHNP-A2b, WHNP-A2c and WHNP-A3b) were obtained from WHNP, respectively. There was no analysis of the neutral fraction (WHNP-N), while the structural characterization of three major pectin fractions (WHNP-A2b, WHNP-A2c and WHNP-A3b) were further studied by monosaccharide composition, HPGPC, NMR and methylation analyses.ResultsThe results indicated that two fractions WHNP-A2b (Mw = 45.8 kDa) and WHNP-A3b (Mw = 58.6 kDa) were mainly composed of rhamnogalacturonan I (RG-I). In WHNP-A2b, RG-I domains primarily substituted with α-L-1,5/1,3,5-arabinan, type II arabinogalactan (AG-II), β-D-1,4-galactan and/or type I arabinogalactan (AG-I) as side chains, while RG-I-type pectin of WHNP-A3b mainly branched with α-L-1,5/1,3,5-arabinan, β-D-1,4-galactan and AG-II side chains. WHNP-A2c (Mw = 12.4 kDa) was primarily comprised of galacturonic acid (GalA, 60.8%), and enzymatic analysis indicated that this fraction mainly consisted of rhamnogalacturonan I (RG-I), rhamnogalacturonan II (RG-II) and homogalacturonan (HG) domains with mass ratios of 1.8:1.0:0.6. On the other hand, WHNP-A2c was found to be rich in RG-I domains, which contained α-L-1,5/1,3,5-arabinan, AG-II, β-D-1,4-galactan and/or AG-I as side chains. The HG domains of WHNP-A2c was released in the form of un-esterified and partly methyl-esterified and/or acetyl-esterified oligogalacturonides with a 1 to 7 degree of polymerization after endo-polygalacturonase degradation.ConclusionOur results reveal the structural characteristics of these polysaccharide fractions, which will contribute to elucidating their structure–activity relationships.Graphical

Effects of thermal treatments on the extraction and in vitro fermentation patterns of pectins from pomelo (Citrus grandis)

Pomelo peel, a by-product of fruit processing, is an excellent source of pectin. We aimed to study the effects of thermal treatments on the extraction and in vitro fermentation patterns of pectins from pomelo peel. We used subcritical water extraction and hot water extraction, with or without chelator (citric acid or EDTA-2Na) assistance to obtain the pectins. The pectin fractions were characterized by their constituent monosaccharide composition and molecular weight (Mw) distribution. The degree of methyl esterification of pomelo pectins was determined using FT-IR spectroscopy. We also compared the fermentation patterns of the pectin using an in vitro simulated human gut fermentation model, monitored Mw changes during fermentation by high performance size exclusion chromatography (HPSEC), and analyzed short-chain fatty acid (SCFA) using gas chromatograph. Our results showed that both chelator assistance and subcritical water treatment increased the pectin yield. Chelator-assisted extraction increased the pectin Mw and decreased the degree of methyl esterification (DM) whereas, subcritical water treatment had the opposite effect. Pectin with low rhamnogalacturonan-I (RG-I) and high homogalacturonan (HG) domain can be obtained from the used pomelo peels by citric acid-assisted extraction. Although gut microbiota intensively utilized uronic acid (UA) of pomelo during early fermentation stages, constituent neutral monosaccharides were consumed even faster than UA. Pomelo pectins enhanced the relative abundance of Bacteroides and Prevotella 9, and stimulated the production of SCFA, particularly acetic acid. Generally, pomelo pectin could be considered a new source for modulating gut microbiota towards a healthy pattern in functional foods.

Characterization of hawthorn pectin gained via different ethanol concentrations.

Pectin is identified as an effective delivery material due to its excellent gel-forming ability, low immunogenic properties, biocompatibility, and biodegradability. These excellent properties depend on the preparation method of pectin. In the study, four pectin fractions (named: CAHP30, CAHP40, CAHP50, and CAHP60, respectively) were obtained by different ethanol precipitations (30%, 40%, 50%, and 60%). Physicochemical properties, antioxidant activity, and emulsifying ability of HP were investigated and analyzed. Results showed that the surface structure of pectin was changed by ethanol fractional precipitation, and four fractions were low methoxy pectin. They had different monosaccharide compositions, but all rich in GalA. The Mw/Mn of CAHP30, CAHP40, CAHP50, and CAHP60 were 3.29, 2.57, 2.66, and 2.77, respectively. CAHP30 and CAHP60 had excellent emulsifying ability; moreover, CAHP60 was endowed with additional lipid antioxidant capacity and had the best thermal stability. E-CAHP40 exhibited a property between the entangled network structure. Overall, pectin with specific properties could be obtained by different ethanol concentrations.

Вплив овочевих пюре різних способів оброблення на органолептичні та фізико-хімічні показники морозива молочного

The purpose of the research is the scientific substantiation of the effect of vegetables with an increased content of soluble pectin on the quality indicators of low-calorie milk ice cream technology. The object of the research is low-calorie milk ice cream technology. The technological and functional properties of pectin-containing purées from vegetables (carrots, beets, tomatoes, zucchini and broccoli) as part of ice cream with their varied content in the range from 10 to 35% were studied. Sensory indicators, mass fraction of soluble pectin, water activity, active acidity, overrun and resistance to melting were chosen as the quality criteria of the obtained ice cream samples with vegetables. A higher yield of soluble pectin was found in fermented vegetable purées compared to purées subjected to thermal-acid treatment. It was found that fermentation and thermal-acid treatment of purée reduce the water activity in vegetables due to the increased content of soluble pectin. It was proved that the solids of vegetables increase the resistance to melting of ice cream. Based on the set of quality indicators of ice cream samples with vegetables, it was determined that vegetable purées from carrots, beets and zucchini have the highest technological activity, broccoli purée is a bit lower, and tomato purée is the lowest. Based on the comparative analysis of the research results, recommendations were developed for the preparation of basic recipes of ice cream with vegetables in the ranges of their content for the enzymatic processing method: carrots — 20—25%, beets — 15—20%, zucchini — 20—30%, broccoli — 15—20% and tomatoes — 25—30%; for thermo-acid processing: carrots — 15—20%, beets — 10—15%, zucchini — 15—20%, broccoli — 10—15% and tomatoes —20—25%. The introduction of vegetable purees in a lower amount than the recommended values gives the ice cream samples unexpressed sensory indicators, while exceeding the norms leads to uncharacteristic taste, aroma and consistency of ice cream. Carrot, beetroot and zucchini purée of various pretreatment methods can be used as separate vegetable multifunctional fillers, and broccoli and tomato purée is recommended to be used in combination with other vegetables

A Novel Strategy to Improve Cloud Stability of Orange-Based Juice: Combination of Natural Pectin Methylesterase Inhibitor and High-Pressure Processing.

This study investigated the prospect of producing cloud-stable orange-based juice by combining high-pressure processing (HPP) with a natural kiwifruit pectin methylesterase inhibitor (PMEI) during chilled storage. Kiwifruit is rich in a PMEI, which greatly improves the cloud loss caused by the pectin methylesterase (PME) demethylation of pectin. The results show that the cloud loss of orange juice occurred after 3 days, while the orange-kiwifruit mixed juice and kiwifruit puree were cloud stable during 28 days' storage. Although, the kiwifruit puree contained larger particles compared to the orange juice, its higher viscosity and solid-like behavior were dominant, improving the cloud stability of the juice systems. In addition, the particle size distribution and rheological properties were highly related to PME activity, PMEI activity, and pectin characterization. The kiwifruit PMEI showed higher resistance to HPP and storage time than PME. More water-solubilized pectin fractions with a high molecular mass were found in the kiwifruit puree, leading to its high viscosity and large particle size, but a more chelator-solubilized pectin fraction with a low esterification degree was observed in the orange juice, resulting in its cloud loss. In general, the outcome of this work provides a novel strategy to improve the cloud stability of orange-based juices using natural PMEIs and nonthermal processing technologies.

Pectins, hemicellulose and lignocellulose profiles vary in leaves among different aromatic Vanilla species (Orchidaceae)

The alcohol-insoluble residue in Vanilla dressleri, V. odorata, V. planifolia and V. pompona mature leaves was fractionated into water-, oxalate-, HCl- and NaOH-soluble pectins, hemicellulose and lignocellulose. Neutral sugars and uronic acids of each fraction were determined by high-performance anion exchange chromatography-pulsed amperometric detection. V. dressleri differentiated from the other three species based on the higher amounts of the HCl-soluble pectin fraction and the amount of glucose exceeding 5–7 times the values found in the NaOH-soluble pectin fraction in the other species, as well as a cellulose/hemicellulose ratio of ca. 2/3. Analogously, V. planifolia could also be distinguished by its higher cellulose/hemicellulose ratio of ca. 7. In addition to taxonomical implications, these results might be instrumental for defining adequate conditions for cell wall digestion aiming at protoplast isolation and appropriate media composition for cell wall regeneration during protoplast culture, which has been elusive in the Orchidaceae.

Effect of chromium stress on metal accumulation and cell wall fractions in Cosmos bipinnatus

As one of the major pollutants in the environment, chromium (Cr), a heavy metal, poses a serious threat to urban green spaces and human life and health. Cosmos bipinnatus is considered a potential accumulator of Cr, and the differences in cellular Cr distribution and compartmentalization may uncover the mechanisms involved in its tolerance to Cr. To elucidate the effects of Cr stress on C. bipinnatus and determine the mechanism of Cr tolerance in C. bipinnatus, we investigated the physiological indicators, subcellular distribution and chemical forms, cell wall fractions and their Cr contents, uronic acid content in the cell wall fractions, and Fourier transform infrared spectroscopy (FTIR) of the cell wall. The results showed that the antioxidant enzyme activities in C. bipinnatus under Cr stress and most of the Cr were fixed in the cell wall. Notably, changes in the content of pectin fractions in the cell wall affected the accumulation of Cr in the cell wall of C. bipinnatus and the stability of negatively charged groups. In addition, the carboxyl and hydroxyl groups played a role in fixing metal in various parts of the C. bipinnatus cell wall.