Beyond brewing: ß-acid rich hop extract in the development of a multifunctional polylactic acid-based food packaging.

Hops' (Humulus lupulus L.) phytochemicals are well known for their bioactivity. In the present study, the functional properties of hop extract rich in ß-acids, as potassium-salts structures (KBA), were investigated to develop a sustainable active food packaging. Polylactic acid (PLA)-based sheets were incorporated with increasing concentrations of hop extract (0.1-5 % w/w in terms of KBA) and characterized through performance and bioactive properties. KBA-added sheets presented decreased crystallinity and affected mechanical and thermal properties, especially with higher KBA amounts. The sheets' surface hydrophobicity gradually decreased by KBA-extract addition, while the water vapor permeability was not affected. A Fickian diffuse behavior and a better fit to application in fatty foods were observed during release tests. UV-blocking and antioxidant properties were improved by KBA incorporation. Furthermore, results from antibacterial assays revealed great susceptibility of Staphylococcus aureus and Listeria monocytogenes towards sheets added with 5 % of KBA. Moreover, the atomic force microscopy (AFM) observations revealed that KBA led to strong effects on the cell membranes of both bacteria, including disruption of membrane integrity and cell death. Therefore, this study is a sign of great prospects of hop ß-acids use, as KBA compound, in the production of sustainable active packaging for safe food shelf-life extension.

Exposure to cellulose acetate films incorporated with garlic essential oil does not lead to homologous resistance in Listeria innocua ATCC 33090.

Essential oils (EOs) have been considered potential green additives for active food packaging. However, sub-lethal concentrations of EOs may lead to bacterial resistance, which is a concern. In this sense, the effects of 1% (GEO1) and 10% (GEO10) of garlic EO in cellulose acetate-based films regarding homologous resistance in Listeria innocua were investigated after incubation at 37 °C/24 h and 7 °C/10 d. The films were also characterized and tested on sliced mozzarella cheese as interfold packaging for 8-days storage at 7 °C. The EO did not alter the mechanical properties of the films nor their thermal degradation profile. However, GEO10 was less permeable to water vapor than GEO1. When tested against L. innocua, the incubation at 7 °C enhanced the films' antimicrobial effect: log reductions of 4.3 and 5.7 were obtained for GEO1 and GEO10, respectively. Moreover, 86.3% of L. innocua cells were injured at sub-lethal level when exposed to GEO10. Despite this, no occurrence of homologous resistance was found. When the active films were tested on cheese against the natural microbiota, they resulted in slices of mozzarella with fewer contaminants, however the reduction was not significant. Nevertheless, we considered this an important finding to the food industry since this work suggested that GEO is a safe active compound from the point of view of homologous resistance to be used against Listeria.

Concentração inibitória mínima de óleo essencial de gengibre frente a microrganismos patogênicos / Minimum inhibitory concentration of ginger oil essential against pathogenic microorganism

Óleos essenciais extraídos de condimentos representam uma alternativa para conservação de alimentos processados, em especial pela atividade antimicrobiana. No presente trabalho foi determinada a Concentração Mínima Inibitória (CMI) frente a B. cereus, E. coli, P. aeruginosa, S. Typhimurium e S. aureus, por microdiluição em caldo in vitro em microplacas de 96 poços. O maior potencial antimicrobiano do óleo foi evidenciado frente a S. aureus(CMI de 3,13%), seguido por E. coli (6,25%) e S. Typhimurium (12,5%). A comprovação da atividade antimicrobiana do óleo demonstra seu potencial de aplicação como ingrediente natural, evidenciado pelo seu efeito na inibição de microrganismos patogênicos frequentemente associados a doenças de origem alimentar.

Semisynthetic Phenol Derivatives Obtained from Natural Phenols: Antimicrobial Activity and Molecular Properties.

Semisynthetic phenol derivatives were obtained from the natural phenols: thymol, carvacrol, eugenol, and guaiacol through catalytic oxychlorination, Williamson synthesis, and aromatic Claisen rearrangement. The compounds characterization was carried out by 1H NMR, 13C NMR, and mass spectrometry. The natural phenols and their semisynthetic derivatives were tested for their antimicrobial activity against the bacteria: Staphylococcus aureus, Escherichia coli, Listeria innocua, Pseudomonas aeruginosa, Salmonella enterica Typhimurium, Salmonella enterica ssp. enterica, and Bacillus cereus. Minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values were determined using concentrations from 220 to 3.44 µg mL-1. Most of the tested compounds presented MIC values ≤220 µg mL-1 for all the bacteria used in the assays. The molecular properties of the compounds were computed with the PM6 method. Through principle components analysis, the natural phenols and their semisynthetic derivatives with higher antimicrobial potential were grouped.