Evaluation Of Combined Anti-Bacterial Effects of Turmeric (Curcuma longa) And Black Pepper (Piper guineense) on The Shelf Life of Smoked Oreochromis Oreochromis niloticus (Linnaeus, 1758)

Abstract

This study evaluated the antibacterial effects of combined turmeric (Curcuma longa) and black pepper (Piper guineense) powder on the shelf life of smoked Oreochromis niloticus. Fresh turmeric rhizomes and dried black pepper fruits were ground into fine powders and mixed in a 1:1 ratio to produce turmeric–black pepper powder (TBP). Four treatments (0%, 10%, 20%, and 30%) were prepared. Fish samples were assigned to the treatments in triplicate, soaked in the respective formulations for one hour, smoked at 85 ± 5°C for 16 hours, and stored under ambient conditions for eight weeks. pH and microbial loads were determined at two-week intervals. The pH of the control decreased from 6.037 ± 0.015 to 5.183 ± 0.215 after eight weeks, whereas the 30% TBP treatment showed only a slight decrease from 6.190 ± 0.010 to 6.127 ± 0.006. All treated samples maintained acceptable pH values, while the control fell below the recommended range. Significant differences (P < 0.05) were observed between treated samples and the control. At week 8, the control recorded the highest total plate count (6.9 × 10⁶ CFU/g), lactic acid bacterial count (1.4 × 10⁷ CFU/g), and fungal count (7.9 × 10⁶ CFU/g), whereas the 30% TBP treatment had the lowest corresponding counts of 5.4 × 10³, 3.0 × 10², and 7.6 × 10³ CFU/g, respectively. These reductions were significant (P < 0.05). The findings demonstrate that combined turmeric and black pepper powder effectively maintained pH stability and suppressed microbial growth in smoked O. niloticus. The 30% TBP treatment is therefore recommended as a natural preservative to enhance quality and extend the shelf life of smoked O. niloticus.