Silkworm pupae protein isolate as a sustainable functional ingredient: Extraction optimization and application in sponge cake

Abstract

Abstract The increasing global population necessitates sustainable and nutritious alternative protein sources, positioning edible insects as a promising solution. Silkworm ( Bombyx mori ) pupae (SP), a by-product of silk production abundant in Thailand, are a rich source of high-quality protein. This study investigated the impact of different extraction solvents (water, saline, and alkaline) on the amino acid profiles, antioxidative capacities, and functional properties (emulsifying and foaming capacities) of SP protein isolates. Alkaline extraction yielded protein isolates (ASP) with a balanced amino acid composition, elevated antioxidant activities, and superior emulsifying activity index and foaming stability, compared to bovine serum albumin. Consequently, ASP was selected to enrich sponge cake, a low-ratio foam-type cake that relies on air bubble stability. Sponge cakes with 0, 5, 10 and 15% wheat flour substitution by ASP were prepared and evaluated for their quality and sensory properties. While water activity remained unaffected, the specific volume of SP sponge cakes significantly increased with higher ASP substitution levels. Texture analysis revealed a softening effect at lower substitution rates (up to 10%), followed by increased hardness at 15%. Sensory evaluation indicated no significant difference in liking scores in appearance, colour, and texture across all formulations, but liking scores in odour and taste declined with increasing ASP concentration. Overall, the study demonstrates the potential of alkaline-extracted SP protein isolates as a functional ingredient in sponge cake up to a 5% substitution level, improving specific volume without compromising sensory acceptability. Further research is needed to address off-flavours and explore broader applications in bakery products.