From Byproduct to Functional Carbohydrate: Advances in Extraction and Physicochemical and Nutrition-Related Properties of Passion Fruit Peel Pectin

The increasing global demand for sustainable hydrocolloids has positioned passion fruit peel as a strategic alternative to traditional citrus and apple sources, owing to the associated unique molecular composition, which is rich in rhamnogalacturonan-I (RG-I). However, important gaps remain in understanding how extraction-induced structural modifications influence specific nutritional outcomes. This review critically assesses the effects of novel green extraction methods, including ultrasonic, microwave, and enzyme-assisted techniques, on the extraction efficiency, molecular integrity, and degree of branching of passion fruit peel pectin (PFPP). In contrast to prior primarily descriptive compilations, this review analyzes available data to elucidate relationships between the fine structure of PFPP (e.g., degree of esterification) and the associated metabolic pathways in the intestine. Specifically, this review explores the effects of PFPP on the gut microbiota composition and short-chain fatty acid production, and proposes future research directions based on these findings. Additionally, we highlight challenges associated with industrial-scale PFPP production, including technical limitations and equipment costs, and offer recommendations for improvement. This review provides a new perspective for developing targeted prebiotic carbohydrates, transcending mere waste utilization toward precise nutritional interventions.