Abstract:Sophorɑ jɑponicɑ pods treated with and without ultra-high pressure were used as raw materials for the extraction of locust bean gum （LBG） via an ultrasound-assisted composite enzymatic hydrolysis method.Single-factor experiments were conducted to investigate the effects of extraction temperature， enzyme activity，enzymatic hydrolysis time， and solid-liquid ratio on the extraction yield of LBG. On the basis of the results of single-factor experiments， response surface methodology （RSM） was employed to optimize the extraction conditions. The optimized conditions were employed to separate and purify LBG. The composition， structure， and physicochemical properties of LBG were analyzed by high-performance liquid chromatography， differential scanning calorimetry （DSC）， and Congo red staining. The experimental results demonstrated that the optimal extraction conditions were determined as follows： extraction temperature of 90 ℃， mixed enzyme addition level 0.4%， enzymatic hydrolysis time of 1.5 h， and solid-liquid ratio of 1∶20 （g/mL）. The extraction yield of LBG from ultra-high pressure-treated raw materials reached （19.30±0.12）%， which was 6.17% higher than that from non-ultra-high pressure-treated raw materials. Compositional and structural studies revealed that the relative molecular weight of LBG ranged from 7.60×104 to 2.45×106 Da. The monosaccharides of the four alcohol-precipitated components included galactose （Gal）， mannose （Man）， glucose （Glc）， arabinose， xylose，and rhamnose， with Man， Glc， and Gal being the main monosaccharides. LBG extracted from ultra-high pressure-treated raw materials exhibited superior water-holding capacity， oil-holding capacity， and swelling capacity. DSC results indicated that LBG possessed good thermal stability. The Congo red staining results showed that none of the four LBG components exhibited the characteristic triple-helix structure.