铁皮石斛多糖的凝胶特性表征

Characterization of the Gel Properties of Dendrobium officinale Polysaccharides

为探究不同因素对铁皮石斛多糖凝胶特性的影响,研究多糖浓度、成胶温度、碱和离子对铁皮石斛多糖凝胶特性、持水性、乙酰基含量等的影响,通过差示扫描量热仪(DSC)、傅里叶红外光谱仪(FTIR)、X射线衍射仪(XRD)对多糖的性质进行表征。结果表明,多糖质量浓度从5 mg/mL增加到25 mg/mL时,其凝胶强度从70.87 g增加到206.39 g,持水性从78.52%增加到94.25%;在温度达到40℃时,凝胶强度达到最大为129.29 g,对应的持水性也最大为90.58%;随着不同碱(NaOH、Na_(2)CO_(3)、KOH、K_(2)CO_(3))质量浓度的升高,凝胶强度均先持续增加后降低,凝胶的持水性均逐渐降低,在同等碱添加量条件下,形成的凝胶强度大小顺序为Na_(2)CO_(3)>K_(2)CO_(3)>NaOH>KOH;电解质方面,钠离子可以提高凝胶的强度和持水性,而尿素会显著降低凝胶的强度和持水性。FTIR图谱表明:乙酰基的吸收峰强度随Na_(2)CO_(3)添加量的升高而降低。多糖的脱乙酰程度与碱含量有关。XRD结果表明:其衍射峰强度与碱的添加量有关,表现为碱添加量越高,衍射峰越强。DSC结果表明:随着碱量的增多,水吸收峰的峰值温度升高,峰的热焓值增大。凝胶形成机理可能与乙酰基的水解促进多糖分子间的相互作用有关。

In order to explore the effects of different factors on the characteristics of Dendrobium officinale polysaccharide gel,the effects of polysaccharide concentration,gelation temperature,alkali and ion on the characteristics,water reten tion,acetyl group content of Dendrobium officinale polysaccharide gel were studied.The properties of polysaccharide were characterized by differential scanning calorimetry(DSC),Fourier infrared spectroscopy(FTIR)and diffractometer(XRD).The results showed that when the mass concentration of polysaccharide increased from 5 mg/mL to 25 mg/mL,its gel strength increased from 70.87 g to 206.39 g,and its water holding capacity increased from 78.52%to 94.25%.When the temperature reached 40℃,the maximum strength of gel was 129.29 g,and the corresponding water holding capacity was 90.58%.With the increase of the mass concentration of different alkalis(NaOH,Na_(2)CO_(3),KOH,K_(2)CO_(3)),the strength of gel continuously increased at first and then decreased,and the water holding capacity of gel gradually decreased.Under the condition of the same amount of alkali addition,the strength of gel formed was in the order of Na_(2)CO_(3)>K_(2)CO_(3)>NaOH>KOH.In terms of electrolyte,sodium ion could improve the strength and water retention of gel,while urea could significantly reduce the strength and water retention of gel.FTIR spectra showed that the absorption peak intensity of acetyl group group decreased with the increase of Na2CO3 addition.The degree of deacetylation of polysaccharides was related to their alkali content.The XRD results indicated that the diffraction peak intensity was related to the amount of alkali added,and the higher the amount of alkali added,the stronger the diffraction peak.The DSC results indicated that as the amount of alkali increases,the peak temperature of the water absorption peak increases,and the enthalpy value of the peak increases.The mechanism of gel formation may be related to the hydrolysis of acetyl group group promoting the interaction between polysaccharide molecules.