PENGARUH KONSENTRASI NANOPARTIKEL PERAK IONIK TERHADAP DAYA HAMBAT BAKTERI Lactobacillus casei DAN pH SUSU

The Effect of Ionic Silver Nanoparticles Concentrations on the Inhibition of Lactobacillus casei and pH of MilkABSTRACTTechnological developments support the creation of various nanoparticles that can be utilized, one of which is silver nanoparticles. This study aims to determine the effect of ionic silver nanoparticle concentration on Lactobacillus casei growth inhibition, pH change and curdling of UHT milk. Variation in the concentration of ionic silver nanoparticles of 5, 10, 15, and 20 ppm was tested for their characteristics through UV-VIS spectrophotometry, showing the wave peaks at 413–430 nm, and through the PSA test resulting in the Z-average of 87.2 nm. Ionic silver nanoparticles were tested against L. casei using the Kirby-Bauer diffusion method for 72 hours. The test results showed a change in the clear zone that tended to increase for the concentration of silver nanoparticles 5, 10, 15 and 20 ppm with the gradient values of 0,0032; 0,0280; 0,0395; dan 0,0317, respectively. Tests for pH and UHT milk curdling were carried out for 78 hours and showed that ionic silver nanoparticles tended to be more able to maintain milk pH ±30 hours and curdling ±24 hours longer than milk that was not treated with ionic silver nanoparticles.Keywords: electrolysis; Lactobacillus casei; milk; nanoparticles; silver ABSTRAKPerkembangan teknologi mendukung terciptanya berbagai nanopartikel yang dapat dimanfaatkan, salah satunya nanopartikel perak. Penelitian ini bertujuan untuk mengetahui pengaruh konsentrasi nanopartikel perak ionik terhadap daya hambat Lactobacillus casei, kadar pH, dan penggumpalan pada susu UHT. Variasi konsentrasi nanopartikel perak ionik 5, 10, 15, dan 20 ppm diuji karakteristiknya melalui spektrofotometri UV-VIS dengan hasil puncak gelombang serapan berada pada kisaran 413–430 nm dan uji PSA dengan hasil Z-average berada pada 87,2 nm. Sampel larutan nanopartikel perak ionik diujikan terhadap bakteri L. casei menggunakan metode difusi Kirby-Bauer