超高压处理对甜菜果胶结构及乳化特性的影响

Effects of High Hydrostatic Pressure on the Structural and Emulsifying Properties of Sugar Beet Pectin

【目的】明确超高压处理对甜菜果胶结构和乳化特性的影响,为甜菜果胶在食品工业中的应用提供理论依据。【方法】配制1%(w/v)甜菜果胶溶液,比较不同压力(0.1、250、350、450和550 MPa)、p H 7条件下处理30 min,450 MPa、p H 7条件下处理不同时间(10、20、30和50 min),以及450 MPa、不同p H(p H 3、p H 7和p H 8)条件下处理30 min对甜菜果胶结构及乳化特性的影响。【结果】在不同压力条件下对p H 7的甜菜果胶溶液进行处理,随着压力升高,甜菜果胶分子量由5.58×105 Da(0.1 MPa)降至1.56×105 Da(550 MPa);酯化度和乙酰化度分别由61.29%和18.17%(0.1 MPa)增至68.24%和21.72%(550 MPa);红外图谱显示甜菜果胶在1 760—1 730 cm-1和1 630—1 600 cm-1处的峰均比未加压处理的更为明显,在1 560—1 540 cm-1也出现一个明显的吸收峰;在250 MPa处理30 min后,甜菜果胶的乳化活性由209 m2·g-1增至230 m2·g-1,乳化稳定性由79 min增至97 min,乳化液粒径D4,3降低,比表面积Sv升高。继续增加压力,果胶的乳化特性变化不显著。在450 MPa下对p H 7的甜菜果胶做不同时间处理,发现随加压时间延长,甜菜果胶分子量、酯化度、乙酰化度、乳化活性及稳定性均未发生显著变化。在450 MPa加压处理30 min后,p H 3、7和8条件下果胶分子量分别由原来的5.88、5.58和5.44×105 Da降至2.38、2.25和2.49×105 Da;p H 3和p H 7的甜菜果胶酯化度变化不明显,乙酰化度显著升高,分别由19.35%和18.17%增至24.84%和21.70%;而p H 8的甜菜果胶酯化度和乙酰化度显著降低,分别由70.13%和19.53%降至50.24%和16.41%;p H 3、p H 7和p H 8的甜菜果胶在加压处理后乳化活性和乳化稳定性均显著提高,超高压处理后p H 3和p H 7的甜菜果胶乳化活性较高,p H 3甜菜果胶乳化稳定性最好。【结论】超高压处理降低了甜菜果胶的分子量,使果胶中的蛋白暴露,改善了甜菜果胶的乳化特性。

[Objective] This study aimed to clear the effect of high hydrostatic pressure （HHP） on the structural and emulsifying properties of sugar beet pectin, and provide a theoretical basis for the applications of sugar beet pectin in food industry.[Method] 1% （w/v） of sugar beet pectin solution was prepared, and treated under different pressures （0.1, 250, 350, 450 and 550 MPa） and pH 7 for 30 min; 450 MPa and pH 7 for different times （10, 20, 30 and 50 min）; 450 MPa and different pH values （pH 3, pH 7 and pH 8） for 30 min. After that, the structural and emulsifying properties were compared with the untreated samples. [Result]When the sugar beet pectin solution was treated under different pressure conditions at pH 7, with the increase of pressure, the Mw of sugar beet pectin was reduced from 5.58×10^5 Da （0.1 MPa） to 1.56×10^5 Da （550 MPa）, and the degree of esterification （DE） and acetylation （DA） were increased from 61.29% and 18.17% （0.1 MPa） to 68.24% and 21.72% （550 MPa）, respectively. FT-IR spectra in 1 760-1 730 cm^-1 and 1 630-1 600 cm^-1 regions of SBP showed more clearly than untreated SBP, and FT-IR images spectra in 1 560-1 540 cm^-1 was appeared after the HHP treatment. After 250 MPa treated for 30 min, the emulsifying activity （EA） and the emulsifying stability （ES） of SBP were increased from 209 m2·g^-1 and 79 min to 230 m2·g^-1 and 97 min, the volume mean diameter （D4,3） was decreased and the specific surface （Sv） was increased. However, the emulsifying properties of pectin were not significantly changed after continued to increase pressure. There were no significant differences in Mw, DA, DE and emulsifying properties between different processing times under 450 MPa. Mw of SBP under pH 3, pH 7 and pH 8 conditions were reduced from 5.88, 5.58 and 5.44×10^5 Da to 2.38, 2.25 and 2.49×10^5 Da after 450 MPa treated for 30 min; the DE of SBP did not change significantly under pH 3 and pH 7 conditions, the DA was increased from 19.35% and 18.17% to 21.70% and 24.84%, respectively;but the DA and DE were reduced from 70.13% and 19.53% down to 50.24% and 16.41% under pH 8 condition; the EA and ES of SBP were significantly improved after high pressure treatment at pH 3, pH 7 and pH 8, the EA was better at pH 3 and pH 7 conditions, and the ES was the best at pH 3. [Conclusion] These results suggest that HHP treatment reduced the molecular weight of sugar beet pectin, induced the protein exposure, and also improved the emulsifying properties of sugar beet pectin.