合成了支链淀粉(PU)的羧甲基化衍生物,并评估了其作为蓝莓采后保存的涂层。通过醚化反应获得羧甲基普鲁兰,CMP1,CMP2和CMP3的取代度分别为0.52,0.34和0.26。红外光谱和核磁共振结果显示属于羧甲基的羰基的特征信号。热分析表明,CMP1、CMP2和CMP3衍生物的热稳定性值为209.91℃,214.73C,225.52°C,分别,并且相对于Td为238.84°C的PU较低。此外,确定了由于羧甲基化导致的玻璃化转变温度的增加。化学改性降低了相对于PU(71.34°)的接触角,CMP1,CMP2和CMP3的值为39.89°,53.72°和60.61°,分别。羧甲基化还增加了膜的水蒸气渗透性和机械性能。此外,发现CMP分子影响光学性质。与天然支链淀粉相比,基于CMP的涂料的应用降低了蓝莓的质量损失和成熟速率,因此,CMP分子的包装可以用作能够延迟成熟和延长水果保质期的涂层。
Carboxymethylated derivatives of pullulan (PU) were synthesized and evaluated as coating for the postharvest preservation of blueberries. Carboxymethylpullulan was obtained by etherification reaction with the substitution degrees of 0.52, 0.34, and 0.26 for CMP1, CMP2, and CMP3 respectively. Infrared spectroscopy and nuclear magnetic resonance results showed characteristic signals of the carbonyl group belonging to the carboxymethyl group. Thermal analysis showed that CMP1, CMP2, and CMP3 derivatives presented thermal stability values of 209.91 C, 214.73 C, and 225.52 °C, respectively, and were lower with respect to PU with Td of 238.84 °C. Furthermore, an increase in the glass transition temperature due to
carboxymethylation was determined. The chemical modification decreased the contact angle with respect to PU (71.34°) with values for CMP1, CMP2, and CMP3 of 39.89°, 53.72° and 60.61°, respectively. The
carboxymethylation also increased the water vapor permeability and mechanical properties of the films. In addition, it was found that the CMP molecules affected the optical properties. The application of CMP-based coatings reduced the mass loss and ripening rate of blueberries compared to native pullulan, therefore, packaging from CMP molecules could be used as a coating capable of delaying ripening and extending the shelf life of fruits.