Raspberry Pomace as a Bioactive-Rich Food Ingredient: Composition, Extractability, Functionality, and Applications

Raspberry pomace, the by-product of juice and puree production, is a structurally complex material composed of seeds, skin-derived fiber, and residual pulp, and is enriched in hydrolysable tannins, together with dietary fiber and minor lipophilic constituents. Despite this compositional richness, current knowledge remains dispersed across compositional, technological, and biological studies, limiting coherent interpretation of its functional potential. This review integrates current evidence on raspberry pomace composition, pre-processing, extraction, bioaccessibility, bioactivity, and food applications, with particular emphasis on the structural association of phenolics with cell wall components and its implications for extractability. Reported total phenolic contents in whole raspberry pomace generally range from 15 to 40 mg GAE/g dry mass, with ellagitannins representing the dominant subclass, while anthocyanins are present at lower levels due in part to processing losses. Extraction strategies, including ultrasound-assisted, enzyme-assisted, and natural deep eutectic solvent-based systems, indicate that phenolic recovery is strongly influenced by matrix accessibility in addition to solvent selection. Biological evidence supports antioxidant, anti-inflammatory, and antiproliferative effects, with additional gut-mediated responses reported in animal models; however, human clinical evidence remains scarce. Food applications demonstrate technological feasibility across multiple matrices, although practical inclusion levels are constrained by structural and sensory factors.