Carbohydrate-Protein Hydrogels as Fat Replacers: Design Criteria and Benchmarking Against Full-Fat Systems

Reducing saturated fat while preserving the sensory quality of full-fat foods remains a major formulation challenge because fat contributes simultaneously to body, lubrication, flavor delivery, and thermal transitions. Carbohydrate-protein (CP) hydrogels are increasingly explored as oil-free fat replacers, but many systems are developed and evaluated in isolation, with limited benchmarking against the full-fat references they are intended to replace. This review considers the literature from two benchmarking prospectives: (i) bulk-fat analog benchmarking, in which self-standing gels are compared with bulk fats; and, (ii) product-level benchmarking, in which CP hydrogels are assessed within specific food matrices against full-fat controls. Across both paradigms, the evidence indicates that successful fat replacement cannot be predicted by a single instrumental match. Instead, performance depends on convergence across rheology, tribology, microstructure, water distribution, breakdown behavior, and thermal response. In practical terms, the most transferable design criteria are rheological compatibility within the relevant processing and consumption ranges, lubrication behavior that supports creaminess and mouthcoating, microstructural length scales that avoid graininess or chalkiness, and category-specific thermal and breakdown behavior that reproduces full-fat transitions such as meltability, softening, or juiciness. Viewing the literature through these two benchmarking logics helps distinguish when bulk similarity is informative, when in-product benchmarking is essential, and why apparently promising CP hydrogels often fail in real food application.