Sodium bicarbonate reduces the cooked hardness of lotus rhizome via side chain rearrangement and pectin degradation

H2O2-mediated cell wall remodeling and pectin demethylesterification are involved in maintaining postharvest texture of table grape by sulfur dioxide

Berry texture affects consumer acceptance and postharvest shelf life of table grapes. This study elucidates how sulfur dioxide (SO2) treatment maintains grape texture quality, focusing on the role of hydrogen peroxide (H2O2)-mediated cell wall modifications. SO2 treatment exhibited effects similar to those of H2O2 treatment, resulting in firmer berries with more intact cell wall structures, higher contents of chelate-soluble pectin, sodium carbonate-soluble pectin, hemicellulose, and cellulose, with lower levels of water-soluble pectin compared to untreated fruit. Moreover, it delays pectin nanostructure disassembly and reduces degree of pectin methylesterification, which facilitates the formation of calcium bridges between demethylesterified pectin and increased calcium ions, thereby strengthening the cell wall and weakening enzymatic pectin degradation. Conversely, combining ROS generation inhibitors with SO2 mitigated these effects. Overall, these findings highlight the role of H2O2-mediated cell wall modification in maintaining grape postharvest texture through SO2 treatment, providing new insights for managing grape postharvest softening.

Physicochemical and antioxidant properties of pectin from Actinidia arguta Sieb.et Zucc (A. arguta) extracted by ultrasonic

Pectin was extracted from Actinidia arguta Sieb. et Zucc (A.arguta) using the ultrasound-assisted acid method and the single acid method. The physicochemical properties, structure, and antioxidant properties of two different pectins were investigated. The results showed that the extraction yield of the ultrasound-assisted acid method is higher than that of the single acid method. The molecular structure of A. arguta pectin extracted by the ultrasound-assisted acid method belongs to a mixed structure of RG-I and HG-type domains. Through structural feature analysis, the ultrasound-assisted extraction pectin (UAP) has a more branched structure than the single acid-extracted pectin (SAP). The SAP has a higher degree of esterification than the UAP. The physical property results show that the viscosity, solubility, and water-holding capacity of the UAP are better than those of the SAP. The antioxidant test results show that the hydroxyl radical scavenging and reducing powers of the UAP are superior to those of the SAP. This study shows the composition, physicochemical properties, and antioxidant activity of A. arguta pectin extracted by the ultrasonic-assisted extraction method to provide a theoretical basis for its application as an antioxidant and other food additives in the food industry.

Ripening induced degradation of pectin and cellulose affects the medium-and short-wave infrared drying characteristics of mulberry

Mulberries were categorized into five stages of ripening (D1-D5, 0.905-1.055 g/cm3) based on their density, and their physicochemical properties, tissue structure, cell wall polysaccharide properties, and drying characteristics were investigated. As mulberry ripening progressed, the TSS and water-soluble pectin content rapidly increased, while the contents of TA, hardness, chelate-, sodium carbonate-soluble pectin, hemicellulose, and cellulose decreased gradually. Pectin nanostructure and monosaccharide composition indicated that both the main and side chains of pectin undergo depolymerization. Medium- and short-wave infrared drying time initially decreased and then increased during mulberry ripening, with D4 fruits exhibiting the shortest drying time. Compared with D4 fruits, the collapse of cell structure in D5 fruits prolongs their drying time. The results demonstrate that ripeness significantly affects mulberry drying characteristics, which is related to changes in cell structure and pectin properties. Utilizing mulberry density to determine ripeness and grading is an effective approach to achieving optimal drying.

Effect of pulp cell wall polysaccharides on citrus fruit with different mastication traits

Mastication trait is a primary quality attribute of citrus fruit, influencing consumer demands and industrial processing conditions. However, the underlying causes of differences in mastication traits of citrus remain unclear. In this study, microscopy, spectroscopy and diffraction techniques were applied to investigate the physicochemical properties of Hongmeiren (HMR), Satsuma (WM) and Nanfeng tangerine (NF) with superior, moderate and inferior mastication traits, respectively. Ultrastructure indicated that NF had more neatly arranged and regularly shaped cells than HMR and WM. The monosaccharide composition of NF revealed that multi-branched Na2CO3-soluble pectin (NSF) enhanced intercellular adhesion. Additionally, FT-IR analysis revealed more intense vibrations of O2-H····O6 intramolecular hydrogen bonds within NF cellulose, which resulted in a higher crystallinity of cellulose (73.75%) than HMR (32.53%) and WM (43.76%). Overall, the high content and crystallinity of cellulose, the multi-branched NSF and the high content of hemicellulose contributed to the inferior mastication trait of citrus fruit.

Potential role of cell wall pectin polysaccharides, water state, and cellular structure on twice "increase-decrease" texture changes during kohlrabi pickling process

Pickled kohlrabi is a traditional and favored vegetable product in China. During pickling, the hardness, springiness, and chewiness of kohlrabi all experienced a typical change with twice "increase-decrease" trend. However, little is known about its mechanism. In this study, in situ analysis including immunofluorescence, low field nuclear magnetic, and transmission electron microscopy were used to explore the effects of cell wall pectin, water state, and cellular structure on kohlrabi texture changes during pickling. Results revealed that at the early stage, due to the rapid loss of water after three times salting, the cells shrank and the interstitial space reduced, resulting in the first increase on kohlrabi texture. Subsequently, the dehydration-rehydration caused by the first brine processing resulted in the first decrease on kohlrabi texture. Then under the action of PME enzyme, more low-esterified pectin was produced, and chelate-soluble pectin with more branched structure was further formed, leading to another elevation of the sample texture. As the pickling continued, under the combined action of PG and PME, the molecular weight of pectin was decreased and the rigidity of the cell tissue was destroyed, caused kohlrabi texture continued to decline. These researches could provide important information and guidance for better maintaining the texture of pickled vegetables during processing.

Analysis of pectin-cellulose interaction in cell wall of lotus rhizome with assistance of ball-milling and galactosidase

The current study sought to depict the structural feature of polysaccharides extracted from Na2CO3 unextractable fraction (LUN) of lotus rhizome using galactosidase with assistance of ball milling. The extracted polysaccharides were a complex of cellulose microfibrils and the RG-I structural domain of pectin, and the top three monosaccharides were glucose, galactose and galactose uronic acid, which allowed to tune the properties of the enzyme-hydrolyzed polysaccharide from LUN after 15 and 45 min of ball milling. The data of XRD revealed that pectin has a masking effect on the diffraction peaks of cellulose components. The removing of the polysaccharides could increase the degree of crystallinity and the pectin-cellulose interaction mainly occured through the galactan side chain was speculated. Textural characterization by SEM exhibited a cross-linked rod-like structure, which is similar to the structure of cellulose microfibrils. The morphological analysis of AFM revealed that L15-P (enzyme-hydrolyzed polysaccharide from LUN after 15 min of ball milling) contained relatively ordered and uniform network structures. Overall, the present study provides an important insight into cell wall of lotus rhizome matrix polysaccharide.

Comparative Analysis of the Physicochemical Properties and Metabolites of Farinose and Crisp Lotus Roots (Nelumbo nucifera Gaertn.) with Different Geographical Origins

Lotus roots are widely consumed vegetables because of their great taste and abundant nutrients, but their quality varies with the environments and cultivar. This study systematically compared farinose (Elian No. 5) and crisp (Elian No. 6) lotus root cultivars from three geographical origins. Pasting and texture characteristics verified that Elian No. 5 possessed lower hardness and lower ability to withstand shear stress and heating during cooking compared with Elian No. 6. Untargeted metabolite profiling was first performed using ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) combined with a Zeno trap. In total, 188 metabolites were identified based on the matching chemistry database. Multivariate analysis demonstrated that lotus roots from different cultivars and origins could be adequately distinguished. Sixty-one differential metabolites were identified among three Elian No. 5 samples, and 28 were identified among three Elian No. 6 samples. Isoscopoletin, scopoletin, and paprazine were the most differential metabolites between Elian No. 5 and Elian No. 6. These results can inform future research on the discrimination and utilization of lotus roots.

Acetic Acid Immersion Alleviates the Softening of Cooked Sagittaria sagittifolia L. Slices by Affecting Cell Wall Polysaccharides

This study investigated the mechanism for acetic acid pretreatment to improve cell wall integrity and thereby enhance the hardness of cooked Sagittaria sagittifolia L. slices by affecting polysaccharides in the cell wall. Distilled water immersion and 0.6% acetic acid immersion (the solid/liquid ratio is 1:10) for 15 h at room temperature could result in the conversion of pectin through different reactions during thermal processing. Combined in situ and in vitro analysis demonstrated that acetic acid pretreatment could promote the interaction of cellulose microfiber or hemicellulose with RG-Ⅰ side chains during thermal processing of S. sagittifolia L. slices, promote the entanglement between linear pectin molecules and make hemicellulose show a lower molecular weight under cooking, making it easy to firmly bind to pectin, which resulted in texture changes. The findings may help improve the texture of thermally processed vegetables and fruits and deep processing of starchy vegetables.

Rheological and gelling properties of Nicandra physalodes (Linn.) Gaertn. pectin in acidic media

Nicandra physalodes (Linn.) Gaertn. polysaccharide (NPGP) was previously recognized as a pectic polysaccharide, with a high galacturonic acid content (87.8%) and a low methoxylation degree (28%). In the present study, it was found that NPGP can form self-supporting gels when cooling its heated solutions (2.0%, w/v) acidified by citric acid. It was demonstrated that the decrease in pH led to the suppression in electrostatic repulsions between the pectin chains, thereby promoting pectin chain-chain association mainly through hydrogen bonding. As the pH decreased from 3.2 to 2.4, the gel strength and gel thermal stability were continuously increased. Moreover, it was shown that sucrose addition slightly promoted the gelation and gel thermal stability of NPGP, but the effect of monovalent ions (Na⁺) and divalent ions (Ca²⁺) was not significant. Conclusively, our results indicate that NPGP is a new gelling polysaccharide that shows great potential in formulation of acidic gel foods.