Development of high-protein snack bars using walnut and almond press cakes in the context of circular economy

Abstract

In the context of sustainable food innovation and circular economy principles, this study explores the potential of nut press cakes—specifically from walnuts (Juglans regia L.) and almonds (Prunus amygdalus)—as protein-rich ingredients for the formulation of functional snack bars. These oilseed by-products, typically underutilized or discarded, are not only valuable sources of plant-based protein but also contain beneficial lipids, particularly unsaturated fatty acids. The research focused on developing formulations that align with consumer demand for healthy, protein-enriched, and energy-balanced snacks. Two main directions guided product development: (1) achieving a high protein content—above 20% of total energy, in accordance with Regulation (EC) No. 1924/2006 on nutrition claims; and (2) formulating sugar-free variants by replacing conventional sweeteners with natural alternatives. Four formulations were tested based on varying ratios of walnut to almond press cake: 100% walnut, 75:25, 50:50, and 25:75. All formulations met the criteria for “high in protein” claims and demonstrated favorable nutritional profiles, including reduced caloric values compared to commercial counterparts. Sensory evaluation, revealed a high level of consumer acceptance across all samples, with the majority of ratings clustering around “like it” and “like it very much” (according to the 9-point hedonic scale,) particularly for formulations based on balanced walnut–almond ratios (50:50 and 75:25). This study demonstrates the feasibility of upcycling oilseed press cakes into value-added functional snacks, contributing to waste reduction and offering nutritionally dense, clean-label alternatives in the growing market of protein-enriched convenience foods.