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The carboxymethylated (1 → 6)-α-dextran (CM-dex) was synthesized by introducing carboxymethyl groups at different degrees of substitution (DS). The resulting dex1-1, dex2-1, dex3-1, and dex4-1 products had degrees of substitution of 0.57, 0.78, 1.13, and 1.25, respectively. The dex3-1 showed the highest glass transition temperature (T g) of 215.96 °C, whereas T g of pure dextran was 149.83 °C. TGA results indicated that the residual loss was reduced along with the increase of DS in the high-temperature region (450–600 °C). Besides, the CM-dex had stronger scavenging capacity against OH radicals but lower scavenging capacity for DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals compared to that of pure dextran. The carboxymethylation of (1 → 6)-α-dextran will extend the applications for modified dextran. • The (1 → 6)-α-dextran is carboxymethylated with chloroacetic acid. • Carboxymethylation improved the thermal stability of dextran. • Dex3–1 had the highest T g of 215.96 °C. • The OH radical scavenging ability of dextran increased with degree of substitution. [ABSTRACT FROM AUTHOR]

Dextran is widely used as a model polysaccharide to study the interactions between polysaccharides and small molecule sugars. This study examined water sorption isotherms and glass transition temperatures (T g) of mixtures of dextran with trehalose, lactose and sucrose for understanding how different disaccharides affect dextran's processing adaptation and storage performance relevant to water sorption. At the same chemical composition, monolayer water (m 0) was dextran & sucrose (dex&suc) > dextran & trehalose (dex&tre) > dextran & lactose (dex&lac). The higher ratios of dextran, the higher was the Guggenheim constant (C) value of the mixtures. The compatibility of dextran and disaccharides was dex&tre > dex&lac > dex&suc. Gordon–Taylor model showed dex&tre (2:1) best inhibited water plasticization. Furthermore, trehalose and lactose were more effective in preventing morphological changes of hydrous matrices in the mixtures. The crystallinities of samples at 43% relative humidity (RH) were slightly lower than that at 11% RH. [Display omitted] [ABSTRACT FROM AUTHOR]

Microcapsules can provide better protection for probiotics during freeze-drying and gastrointestinal digestion. This study aims to investigate the effect of microencapsulation using the product of the Maillard reaction of whey protein and carboxymethylated dextran (CM. dex) on the viability of Lactobacillus plantarum LP90 (L p) as related to freeze-drying, gastrointestinal tolerability and storage stability. The results demonstrate that the glycosylation product was successfully obtained by the dry heating method, and the product was verified by SDS–PAGE, infrared spectroscopy (FTIR), and intrinsic fluorescence spectroscopy. The grafting degree of whey protein and CM. dex, as measured by the OPA method, was 53.87%, 57.60%, and 61.21% at 1, 3, and 5 days of the Maillard reaction, respectively. With increasing Maillard reaction time, the glass transition temperature (T g) of conjugates increased, and WP–CD 5d had the highest T g , which was 156.31 °C. At the same time, WP–CD 5d had the best protection effect under freeze-drying, and the survival rate was 87.37%. Microencapsulated L p had better tolerance over 5 h of simulated gastrointestinal juice treatment fluid. L p had the best storage stability protected by WP-CD 5d , for which k was 0.102. [Display omitted] • Carboxymethylated dextran was applied on microencapsulation of probiotics. • WP-CD 5d had the highest glass transition temperature (T g), which was 156.31 °C. • Microencapsulated LP90 decreased slightly in gastrointestinal simulant. • L p had the best storage stability protected by WP-CD 5d , which k was 0.102. [ABSTRACT FROM AUTHOR]