This study aims to assess the occurrence of Staphylococcus aureus in chicken fillets and to
control its growth using various lyophilized seaweed extracts (i.e., Halimeda opuntia (HO), Actinotrichia
fragilis, and Turbinaria turbinata) by an agar disk diffusion assay in vitro. Results showed that
prevalence of S. aureus in breast and thigh samples reached of 92% and 84%, respectively. Lyophilized
HO extract was the only seaweed that showed the antibacterial activity against S aureus with a
significant difference at p < 0.05. The minimum inhibitory concentration (MIC) of HO extract was
1.5%, with an inhibition zone of 8.16 ± 0.73 mm. Regarding 1,1-diphenyl-2-picrylhydrazyl (DPPH)
scavenging activity, IC50 was recorded at 55.36 µg/mL, whereas cytotoxic IC50 of the lyophilized
HO extract on peripheral blood mononuclear cells (PBMCs) was 33.7 µg/mL; a higher IC50 of
HO extracts permits their use as a safe food additive in meat products. Moreover, total phenolic
compounds and total flavonoids compounds recorded 20.36 ± 0.092 and 16.59 ± 0.029 mg/mL,
respectively. HPLC analyses of phenolic compounds profiles exhibited many bioactive substances
and the higher ratio was daidzein with 10.84 ± 0.005 µg/mL and followed by gallic acid with a
value of 4.06 ± 0.006 µg/mL. In a challenge study, chicken fillet (CHF) experimentally inoculated
with S. aureus (ST) and treated with the lyophilized HO algal extract at 4% and 6% (CHF/ST/HO)
showed a complete reduction of S. aureus count on the 6th and 4th days in chicken fillet stored at 4 ◦C,
respectively. Moreover, CHF/ST/HO at 4% and 6% of HO extract enhanced the sensory attributes of
grilled un-inoculated chicken fillet. Thus, lyophilized HO extracts are promising antibacterial and
antioxidant candidates in the chicken meat industry.