Enhancing the Functional and Prebiotic Properties of Chinese Quince Pectin by Modifying Its Structure Through Acidic and Alkaline Extraction at Elevated Temperatures

Chinese quince (Chaenomeles sinensis (Thouin) Koehne) represents an underutilized resource abundant in pectin. In this work, pectin was extracted using either an acidic extraction solution (ACP, pH = 2) or an alkaline method (ALP, pH = 12) at elevated temperatures of 100°C, 120°C, 140°C, and 160°C, yielding samples designated as ACP-1, −2, −3, −4 and ALP-1, −2, −3, −4. The structural characteristics of these pectins (e.g., molecular weight, degree of esterification, and monosaccharide composition) were examined, followed by evaluation of their antioxidant activity, rheological properties, and in vitro fermentation profiles. The results showed that alkaline-extracted pectins (ALPs) exhibited smooth surface morphologies and variable yields (4.28%–16.19%), whereas acid-extracted pectins (ACPs) displayed wrinkled surfaces with stable yields (11.17%–12.79%). ACPs exhibited better thermal stability and a higher degree of esterification (61.41%–64.18%) compared to ALPs (44.96%–49.56%). The molecular weight of both ALPs and ACPs decreased with increasing extraction temperature. Furthermore, the structural differences between the pectins influenced their functional properties. ALP-4 and ACP-4 demonstrated enhanced antioxidant activity, whereas ALP-2 and ACP-2 displayed better apparent viscosities. Notably, ALP-4 promoted more efficient colonic fermentation, yielding elevated levels of short-chain fatty acids (SCFAs). These findings provide valuable guidance for the extraction and application of Chinese quince pectin.