Vacuum-driven partially hydrolyzed guar gum structural modulation: A strategy to enhance butyrate production in gut...

Partially hydrolyzed guar gum (PHGG) exhibits numerous physiological benefits, including hypoglycemic effects and gut microbiota modulation, making it widely applicable in the food industry. In this study, the effects of spray drying (SD), freeze drying (FD), and vacuum drying (VD) on the structural characteristics and bioactivities of PHGG were systematically compared. Specifically, SDPHGG most effectively preserved sugar components (total sugar content: 0.87 g/g dry weight; reducing sugar content: 0.05 g/g dry weight), whereas FDPHGG exhibited the highest weight-average molecular weight (22.47 kDa). Meanwhile, VDPHGG showed the smallest particle size (D₅₀: 34.76 μm; mean volume: 35.16 μm), the lowest water holding capacity (6.75 g/g) and oil holding capacity (1.17 g/g), the highest swelling capacity (28.27 mL/g), the lowest Turbiscan Stability Index, and the fastest sedimentation rate. Furthermore, VDPHGG exhibited a rod-like nanostructure accompanied by degradation of CH and CO bonds. In vitro fecal fermentation results indicated that VDPHGG produced the highest butyrate concentration (1.63 μg/mL at 24 h), which was 2.74- and 2.24-fold higher than that of SDPHGG and FDPHGG, respectively. Additionally, VDPHGG promoted the proliferation of genera including Phascolarctobacterium, Bacteroides, Parabacteroides and Parasutterella. These findings indicate that VD optimizes the particle size and structure of PHGG, thereby enhancing butyrate production and advancing the development of functional nutraceuticals.