This study compared the differences in structural, rheological, and gelling properties between pectin extracted from fresh (SF) and dried (GF) lemon peel. The results indicated that drying treatment significantly altered the molecular structure of pectin. SF pectin exhibited higher galacturonic acid content (308.94 mg/g), weight average molecular mass (343.67 kDa), and esterification degree (64.88%), with a structure predominantly composed of linear homogalacturonan (HG). In contrast, GF pectin showed a higher proportion of neutral sugars, greater branching (R₃ = 0.127), lower weight average molecular mass (212.62 kDa), and a reduced degree of esterification (56.57%). Small-angle X-ray scattering analysis revealed that SF pectin possessed a larger radius of gyration (R_g = 22.31 nm) and a smaller cross-sectional radius (R_c = 8.18 nm), indicating an extended, slender, and more rigid rod-like conformation. Conversely, GF pectin exhibited a smaller R_g (22.23 nm) and a larger R_c (8.66 nm), suggesting a more compact molecular conformation with a thicker cross-section. Rheological analysis demonstrated that both types of pectin exhibited shear-thinning behavior and their flow curves were fitted by the power-law model. Due to its more extended molecular conformation, SF pectin exhibited higher viscosity and viscosity coefficient (k). Dynamic oscillatory tests further indicated that SF pectin had higher storage modulus (G') and loss modulus (G”), exhibiting superior gel strength, thermal stability, and mechanical properties (such as hardness) compared with GF pectin. As temperature increased, the viscosity of the system decreased, and the fluid behavior approached that of a Newtonian fluid. SF pectin demonstrated higher flow activation energy, indicating greater temperature sensitivity. This study, from the perspective of molecular conformation, elucidated the mechanism by which drying treatment affected pectin functionality by causing its degradation and structural reorganization, providing a theoretical basis for selecting processing methods for raw materials in lemon pectin extraction.

In order to systematically understand the osmotic dehydration behavior of strawberries with different small-molecule sugars, especially oligosaccharides and sugar alcohols, as well as their effect on the quality of freeze-dried strawberries, the osmotic dehydration kinetics of strawberries with 10 common small-molecule sugars (at a concentration of 40 °Brix) was fitted using two mathematical models and the physicochemical properties of freeze-dried strawberries obtained after osmotic dehydration were characterized. The results showed that the Weibull model was more suitable for describing the solid gain (SG) of osmotically dehydrated strawberries, while the Peleg model could better describe the water loss (WL). The SG of strawberries differed depending on the sugars used. More specifically, the SG of strawberries was 6.84 g/100 g after osmotic dehydration with sorbitol, which was 6.16 times higher than that with isomalt oligosaccharides. In addition, after osmotic dehydration, the hardness of strawberries was enhanced by 94.58% to 223.23%; the crispness of strawberries dehydrated with glucose, fructose and sorbitol was decreased by 16.70%, 20.74% and 41.45%, respectively. The texture characteristics of strawberries dehydrated with fructooligosaccharide were the closest to those with sucrose. Overall, considering the osmotic efficiency, sensory and nutritional quality and production cost, fructooligosaccharide seems to be a superior solute for osmotic dehydration of fruits and vegetables compared to sucrose.

Composite gel network systems were prepared by mixing sodium alginate (ALG) with low methoxyl pectin (LMP) with the addition of Ca²⁺. The effect of different LMP/ALG ratios and Ca²⁺ concentrations on gel properties including gel strength, moisture state and gel network structure was investigated. At an LMP/ALG ratio of 3:7, the largest gel strength of 0.545 N. The gel strength increased with the increase in Ca²⁺ concentration, and the gel network showed a dense microstructure with small pores. The rheological properties of the composite gels were analyzed based on three strain models, revealing that the two polysaccharides formed an interpenetrating network in the composite gel system. This study provides a scientific reference and theoretical basis for improving the gel properties of ALG and LMP and for expanding their applications in foods.

Recently, pectin has been used as an alternative for commercial prebiotic products to modulate gut microbiota. In this study, the standard diet (Chow group) and high fat diet containing 0% (HF group), 1%, 3%, 5%, 8% or 12% (m/m) apple pectin (HF-P group) were offered ad libitum for 8 weeks to 4-week C57BL/6J mice (n=10/group). Results showed that body weight gain (R²=–0.990), subcutaneous adipose accumulation (R²=–0.930), serum triglyceride elevation (R²=–0.879), acetate (R²=0.955) and propionate concentration reduction (R²=0.985) were suppressed by pectin from 1% to 12%, indicating dose response to pectin consumption. Moreover, abundance of obesity-related bacteria Coriobacteriaceae, and pectin-degradating bacteria, Faecalibaculum, Ruminococcus were significantly increased with pectin dosage increased, and the R² were 0.936, 0.963 and 0.937, respectively. Besides, attenuations for colonic injury and liver steatosis were observed after adding 5% and 8% pectin, respectively. This study confirmed the dose-sensitive manner of pectin to alleviate HF-induced obesity by modulating gut microbiota and enhancing short-chain fatty acids production.