Abstract：
BACKGROUND: Walnut proteins display poor solubility and dispersity under acidic pH conditions, which limits their application in acidic beverages and foods. This study aimed to fabricate stable nanocomplexes between phosphorylated walnut protein (PWPI) and chitosan (CS) in an acidic pH and to investigate the encapsulation capacity of the complexes.
RESULTS: The PWPI/CS nanocomplexes prepared at a mass ratio of 2:1 showed small Z-average sizes (approximately 285 nm at pH 5.5 and 222 nm at pH 3.5) with a narrow particle distribution (polydispersity index <0.3). Caffeic acid phenethyl ester (CAPE) can be effectively encapsulated into PWPI/CS with improved solubility. Circular dichroism analysis indicated that PWPI/CS and CAPE-loaded PWPI/CS (PWPI/CS-CAPE) had reduced α-helical content and increased β-sheet content. Fourier transform infrared spectroscopy analysis further identified the different driving forces for the complexation of PWPI and CS at pH 3.5 and 5.5 and confirmed the successful encapsulation of CAPE. The rheological results revealed that the PWPI/CS and PWPI/CS-CAPE formed at pH 3.5 (PWPI/CS-CAPE-3.5) had a higher apparent viscosity and better viscoelasticity than the complexes formed at pH 5.5. The PWPI/CS-CAPE-3.5 also showed good stability under heat treatment, salt treatment, and long-term storage. The PWPI/CS-CAPE complexes showed controlled release of CAPE.
CONCLUSIONS: Walnut protein and chitosan nanocomplexes prepared at acidic pH levels were stable and promising carriers for CAPE, which could expand the application of walnut proteins in the food industry. © 2023 Society of Chemical Industry.
RESULTS: The PWPI/CS nanocomplexes prepared at a mass ratio of 2:1 showed small Z-average sizes (approximately 285 nm at pH 5.5 and 222 nm at pH 3.5) with a narrow particle distribution (polydispersity index <0.3). Caffeic acid phenethyl ester (CAPE) can be effectively encapsulated into PWPI/CS with improved solubility. Circular dichroism analysis indicated that PWPI/CS and CAPE-loaded PWPI/CS (PWPI/CS-CAPE) had reduced α-helical content and increased β-sheet content. Fourier transform infrared spectroscopy analysis further identified the different driving forces for the complexation of PWPI and CS at pH 3.5 and 5.5 and confirmed the successful encapsulation of CAPE. The rheological results revealed that the PWPI/CS and PWPI/CS-CAPE formed at pH 3.5 (PWPI/CS-CAPE-3.5) had a higher apparent viscosity and better viscoelasticity than the complexes formed at pH 5.5. The PWPI/CS-CAPE-3.5 also showed good stability under heat treatment, salt treatment, and long-term storage. The PWPI/CS-CAPE complexes showed controlled release of CAPE.
CONCLUSIONS: Walnut protein and chitosan nanocomplexes prepared at acidic pH levels were stable and promising carriers for CAPE, which could expand the application of walnut proteins in the food industry. © 2023 Society of Chemical Industry.
摘要：
背景：核桃蛋白在酸性pH条件下的溶解性和分散性差，这限制了它们在酸性饮料和食品中的应用。本研究旨在在酸性pH下制备磷酸化核桃蛋白（PWPI）和壳聚糖（CS）之间的稳定纳米复合物，并研究复合物的包封能力。
结果:以2:1的质量比制备的PWPI/CS纳米复合物显示小的Z平均尺寸(在pH5.5下约285nm,在pH3.5下约222nm),具有窄的颗粒分布(多分散指数<0.3)。咖啡酸苯乙酯（CAPE）可以有效地包封到PWPI/CS中，并具有改善的溶解度。圆二色性分析表明，PWPI/CS和CAPE负载的PWPI/CS（PWPI/CS-CAPE）的α螺旋含量降低，β折叠含量增加。傅里叶变换红外光谱分析进一步确定了在pH3.5和5.5下PWPI和CS络合的不同驱动力，并证实了CAPE的成功包封。流变结果表明，在pH3.5下形成的PWPI/CS和PWPI/CS-CAPE（PWPI/CS-CAPE-3.5）比在pH5.5下形成的复合物具有更高的表观粘度和更好的粘弹性。PWPI/CS-CAPE-3.5在热处理下也表现出良好的稳定性，盐处理,和长期储存。此外，PWPI/CS-CAPE复合物显示CAPE的受控释放。
结论：在酸性pH下制备的PWPI/CS纳米复合物是CAPE的稳定和有前途的载体，这将扩大核桃蛋白在食品工业中的应用。本文受版权保护。保留所有权利。
结果:以2:1的质量比制备的PWPI/CS纳米复合物显示小的Z平均尺寸(在pH5.5下约285nm,在pH3.5下约222nm),具有窄的颗粒分布(多分散指数<0.3)。咖啡酸苯乙酯（CAPE）可以有效地包封到PWPI/CS中，并具有改善的溶解度。圆二色性分析表明，PWPI/CS和CAPE负载的PWPI/CS（PWPI/CS-CAPE）的α螺旋含量降低，β折叠含量增加。傅里叶变换红外光谱分析进一步确定了在pH3.5和5.5下PWPI和CS络合的不同驱动力，并证实了CAPE的成功包封。流变结果表明，在pH3.5下形成的PWPI/CS和PWPI/CS-CAPE（PWPI/CS-CAPE-3.5）比在pH5.5下形成的复合物具有更高的表观粘度和更好的粘弹性。PWPI/CS-CAPE-3.5在热处理下也表现出良好的稳定性，盐处理,和长期储存。此外，PWPI/CS-CAPE复合物显示CAPE的受控释放。
结论：在酸性pH下制备的PWPI/CS纳米复合物是CAPE的稳定和有前途的载体，这将扩大核桃蛋白在食品工业中的应用。本文受版权保护。保留所有权利。
