Effects of synergistic action of courgette polysaccharide and coumalic acid on pasting, rheological, and thermal properties of potato starch

The effects of courgette polysaccharides (CP) and coumalic acid (COA) on gelatinization, rheology, thermodynamics, microstructure, freeze–thaw stability, and in vitro digestibility of potato starch (PS) were studied. The synergistic effect of CP and COA on PS was further analyzed. The results showed that peak viscosity (PV) decreased from 6649.00 to 3462.50 mPa s and 3825.00 mPa s, respectively, after CP and COA were added. Under the combined effect of the two, it will be as low as 3225.50 mPa s. Besides, trough viscosity (TV), breakdown viscosity (BV), and final viscosity (FV) had the same trend. The presence of CP and COA can significantly delay the short-term retrogradation of PS, especially in the case of high dose of CP and low dose of COA. Rheological tests showed that all sample gels belonged to the weak gel system (tan δ < 1) and pseudoplastic fluids. Meanwhile, the results of thermodynamic, Fourier transform infrared, and Raman spectroscopy exhibited that the presence of CP and COA significantly retarded the retrogradation of PS, especially at higher levels. In addition, the presence of CP and COA significantly reduced the formation of PS gel structures, especially when acting together. Furthermore, CP and COA reduced the content of rapidly digestible starch in PS and increased the content of resistant starch. Differently, CP can increase the slowly digestible starch content, whereas COA did the opposite. In the ternary composite system, CP and COA will also interact and restrict each other. Hence, the characteristics of PS can be better improved by adjusting the ratio of CP and COA. Meanwhile, the results of the study can provide potential possibilities for the application of CP and COA in food and improve the quality of PS-related products.