| Sugar beet is mainly used in sugar industry, according to the FAO statistics, total production of sugar beet ranked eighth in the world, up to 10 million tons in 2013 in China. Sugar beet pulp is a by-product of sugar beet sugar, containing about 28% pectin in the dry base, so the beet pulp can be used as the raw material for extracting pectin. In this paper, we study on sugar beet pulp as raw material, using ultrasonic/microwave-assisted acid method(UMAAM) to extract sugar beet pectin, and studies the structure and function characteristics; use high hydrostatic pressure(HHP) to treat solution of sugar beet pectin, study the effect of HHP treatment on its structure and physicochemical properties, aiming at effective utilization of beet pulp, provide theoretical basis for new way of processing.With sugar beet pulp as raw material, we used UMAAM to extract sugar beet pectin. Based on the result of single factor experiment, response surface methodology was used to predict the response of the interaction of the independent variables: heating temperature, heating time, and solid-to-liquid ratio. From the results the selected optimal conditions were heating temperature 92 °C, heating time 37 min, and solid-to-liquid ratio 1:30. Under these conditions, the yield and galacturonic acid content of the pectin was 26.16 % and 75.38 %, respectively.Traditional acid method is the most commonly used in extraction of pectin; UMAAM was compared with traditional acid method on sugar beet pectin yield, structure and physicochemical properties. Molecular weight of sugar beet pectin preparade by UMAAM(6.36×105 Da) was significantly higher than traditionalacid method(2.96×105 Da). The composition of pectin monosaccharide of the two methods was similar, and the galacturonic acid was the major, 75.38 % and 72.84 % respectively. The viscosity of two pectin at p H 3 and 5 was significantly higher than p H 7 and 8, the viscosity SBP1 prepared by UMAAM were higher than SBP2(preparaed by traditional acid method) under the condition of p H 3, 5, 7 and 8; emulsion particles of SBP1 was significantly less than SBP2; and emulsifying activity and emulsifying stability of SBP1 were higher than SBP2. These results suggested that UMAAM is an efficient method in extracting pectin and has the potential to be used in the sugar beet industry.SBP1 was treated under different pressure conditions at p H 3, 5, 7 and 8, the Mw of SBP1 was reduced with the increase of the pressure; at p H 3 and 7, the degree of esterification(DE) and acetylation(DA) showed little changes, but DE and DA were reduced significantly in p H 8. FT-IR images spectra in 1560-1540 cm-1 was exposed after the HHP treatment at p H 3 and 7. The EAI and ESI of SBP were significantly improved after HHP treatment at p H3, p H7 and p H 8, the EAI was better at p H 3 and p H 7, and the ESI was the best at p H 3. SBP1 was treated at 450 MPa with different times; the emulsifying properties of pectin had little changes along with the HHP treatment time.After treated under 450 MPa for 30 min, the σ0, G’ and G‖ of SBP1 was increased significantly when adding 2 mmol/L calcium ions, and the molecular weight was increased from 2.25 × 105 Da to 6.07 × 105 Da. Along with the increasing of calcium ions concentration, the structure and rheological properties of SBP1 change little, but the the molecular weight was decreased; After adding 0.1 mol/L sodium ions, The σ0 of SBP1 was increased significantly, and pectin chains formed reticular by crosslinking with molecular weight significantly increased to 11.95 × 105 Da. However, when the concentration of sodium ion was increased to 0.6 mol/L, the G’ and G‖ of SBP1 was increased obviously, of which the molecular weight was decreased to 5.53×105 Da with virgate structure. |
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