Antibacterial and antibiofilm activities of hazelnut by-product extract

Aims This work aims (i) to evaluate in vitro the antibacterial and antibiofilm activities of an extract collected from a hazelnut by-product (skins) against spoilage bacteria and foodborne pathogens and (ii) to assess its effects on the microbiological quality and sensory/technological characteristics of beef burgers. Methods and results The antibacterial properties of hazelnut skin extract (HSE) at concentrations ranging from 2.5 to 20 mg mL−1 were evaluated using a modified protocol based on the method described by the Clinical and Laboratory Standards Institute. In parallel, the biofilm-eradicating potential was assessed according to the Innovotech guidelines, which describe a standardized method for biofilm disruption studies. In vivo experiments were also conducted on beef burgers containing 2% and 4% HSE, along with untreated controls. Each sample underwent microbiological and physicochemical analyses at 0, 3, and 6 days of refrigerated storage. During in vitro assays, HSE exhibited greater antibacterial activity against Gram-positive bacteria, with growth inhibition occurring at lower concentrations. Conversely, in vivo tests revealed no statistically significant differences in microbiological parameters between control and HSE-treated burgers. Furthermore, adding different concentrations of HSE to the treated samples did not significantly affect the pH, although it altered the acidification dynamics, which occurred earlier on day 3 in burgers containing 4% HSE. Finally, both concentrations of HSE resulted in significant differences in weight loss and color. Conclusions In light of these findings, further studies are required to enhance HSE bioavailability in food matrices and to minimize its impact on their sensory/technological properties.