疏水改性壳聚糖的合成与乳化性能研究

Synthesis and emulsification properties of hydrophobically modified chitosan

壳聚糖(CS)不同的分子量和脱乙酰度赋予了其多样性,但强亲水性限制了其在食品、化妆品等领域的应用。因此,若通过疏水改性降低壳聚糖的强亲水性可扩展其作为乳化剂的应用。本文通过美拉德反应以酪蛋白疏水多肽(CHP)对不同分子量和脱乙酰度的壳聚糖进行疏水改性。以60℃,相对湿度75%,反应时间3天以及CHP和CS质量比1∶3为美拉德反应的较优条件。获得接枝度为3.10%~15.08%的系列接枝物,并通过红外和荧光光谱对接枝物进行结构分析。经酪蛋白疏水多肽改性得到的接枝物可以用于稳定乳状液的制备。对乳状液稳定性进行考察,以质量分数为1%的接枝物稳定50%橄榄油的O/W乳状液。壳聚糖稳定的乳状液在7天破乳,而接枝物可以为乳液液滴提供较大的静电排斥力,为乳状液提供了良好的长期储存稳定性,保持28天不破乳。

As a natural polysaccharide,chitosan(CS)has excellent biocompatibility,biodegradability and renewability.Chitosan has different molecular weight and deacetylation degree.However,its strong hydrophilicity limits its application in food,cosmetics and other fields.Therefore,hydrophobic modification of chitosan can decrease the strong hydrophilicity and expand its application as emulsifier.That is,hydrophobic groups are introduced into its hydrophilic skeleton.However,the safety of chemical modifications needs to be considered.Maillard reaction does not use any chemical cross-linking agent,and the reaction process is simple and the products are biocompatible.As one of the main hydrophobic proteins,casein can be used to improve the amphiphilicity of polysaccharides.After enzymatic hydrolysis,casein hydrophobic peptides(CHP)can provide peptides with more hydrophobic groups.In this study,Maillard reaction was used to modify chitosan with CHP.The optimized conditions of Maillard reaction were temperature of 60℃,relative humidity of 75%,reaction time of three days,and the mass ratio of CHP to CS of 1∶3.The grafting degree was calculated through the content of free amino groups.The grafting degree for this series obtained was from 3.10%to 15.08%.In addition,the browning index increased as Maillard reaction was going on.Infrared spectroscopy and fluorescence spectroscopy were used for structural analysis.The vibration absorption peak of protein side chain changed after the reaction.The typical Schiff base was synthesized after Maillard reaction.Amadori product was formed after cyclization and rearrangement.The CHP-modified chitosan can stabilize emulsion.An O/W emulsion(50%olive oil in water)stabilized with 1%CHP-modified chitosan was prepared.The emulsion stabilized with CS breaks at the 7th day.In contrast,the emulsion stabilized with CHP-modified chitosan has large Zeta potential which provides large electrostatic repulsion between droplets,inhibiting demulsification,flocculation or coalescence of the emulsion.The particle size and particle size distribution of the emulsion have little change during the storage period.The emulsion has excellent long-term storage stability in 28 days.