Valorisation of raspberry seed processing waste via sustainable extraction technologies for clean-label antimicrobial and antioxidant ingredients

Raspberry seeds, a by-product of fruit processing, represent a sustainable source of bioactive compounds with potential applications in the food and pharmaceutical industries. This study aimed to characterize the volatile and non-volatile chemical profiles of raspberry seed extracts and assess their antimicrobial and antibiofilm activities. Three extraction techniques were employed: supercritical fluid extraction (SFE), simultaneous hydrodistillation–extraction (SHDE), and ultrasound-assisted hydrodistillation (UAHD). SFE enabled the efficient, solvent-free recovery of phenolic compounds, with vanillin identified as the most abundant constituent (up to 398.3 μg/g), alongside trans -cinnamic acid as a phenylpropanoid compound. A total of 22 phenolic compounds were quantified. Extracts obtained via SHDE and UAHD yielded essential oil (EO) fractions rich in carbonyl compounds, including hexanal, (E,E)-2,4-decadienal, and 2,4-heptadienal, many of which were formed as thermal degradation artefacts of fatty acids. Antimicrobial testing revealed that the SHDE extract exhibited broad-spectrum activity, whereas SFE extracts showed no inhibitory effect. Therefore, subsequent antimicrobial evaluation focused on volatile fractions. The UAHD-derived EO (E1) demonstrated selective activity, with MIC values as low as 128 μg/mL in liquid phase assays. The E1 also inhibited Staphylococcus aureus biofilm formation in a concentration-dependent manner, with significant suppression observed at 1024 μg/mL. This is the first report detailing EO extraction from raspberry seeds using UAHD. These findings highlight the potential of raspberry seed waste as a source of functional antimicrobial ingredients and support the integration of complementary extraction techniques to valorize it.