Detection of Clostridium botulinum in Some Egyptian Fish Products, Its Control In Vitro Using Citrus Leaves Extracts, and Applicability of Citrus limon Leaf Extract in Tuna

This study aims to detect Clostridium botulinum and its control using natural leaf extracts of Citrus limon, Citrus sinensis, and Citrus unshiu in Egyptian fish products, e.g., canned tuna, canned sardine, canned mackerel, fesikh, moloha, and renga, as well the application of C. limon in tuna. Moreover, the antibacterial activity of the C. limon leaf extract was also estimated. In the water extract, ascorbic acid, total flavonoid content (TFC), and total phenolic content (TPC) were determined by volumetric, aluminum chloride, and Folin-Ciocalteu approaches, respectively. The antioxidant ability of the extract was analyzed in vitro via free radical scavenging (DPPH) and Ferric reducing assays. The results showed variability in the distribution of the total number of positive C. botulinum in fish samples from three different governorates under study, which were (24) Alexandria, (16) Beheira, and (17) Gharbia, out of the 120 tested samples in each governorate. Additionally, the findings revealed that all three Citrus extracts contain an appropriate number of secondary metabolites, with a sustainable presence of saponin and tannins in the C. limon extract. Furthermore, all Citrus extracts inhibited bacterial growth by increasing the inhibition zone, with C. limon being the best extract (25 mm) compared to C. sinensis and C. unshiu. The overall results showed the high antioxidant and anti-Clostridium powers (p < 0.05) of C. limon leaf extract, indicating its preservative activity in fishery products during storage. Finally, C. limon leaf extract can fight off C. botulinum and is considered a promising natural preservation candidate in ensuring safe and fresh fishery products.

Evaluation of the Prevalence of Staphylococcus aureus in Chicken Fillets and Its Bio-Control Using Different Seaweed Extracts

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.