Electronic Theses and Dissertation

Susu kambing merupakan bahan pangan bergizi yang dapat diolah menjadi produk pangan fungsional melalui fermentasi menggunakan bakteri asam laktat. Untuk meningkatkan aktivitas antibakterinya, dapat ditambahkan bahan alami yang mengandung senyawa bioaktif. Daun jambu biji putih (Psidium guajava L.) mengandung flavonoid, tanin, saponin, alkaloid, quercetin, kaempferol, dan senyawa fenolik yang berpotensi sebagai antibakteri. Penambahan ekstrak daun jambu biji putih pada susu kambing fermentasi dilakukan untuk mengetahui kemampuannya menghambat pertumbuhan Propionibacterium acnes, salah satu bakteri penyebab jerawat. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) dengan empat perlakuan konsentrasi ekstrak daun jambu biji putih, yaitu P0 tanpa penambahan ekstrak, P1 dengan penambahan ekstrak 2%, P2 dengan penambahan ekstrak 4%, dan P3 dengan penambahan ekstrak 6%. Susu kambing difermentasi menggunakan kultur Streptococcus thermophilus dan Lactobacillus plantarum. Parameter yang diamati meliputi aktivitas antibakteri terhadap Propionibacterium acnes, Total Plate Count (TPC) bakteri asam laktat, dan nilai pH susu kambing fermentasi. Data hasil penelitian dianalisis menggunakan analisis sidik ragam (ANOVA) dan dilanjutkan dengan uji Duncan untuk mengetahui perbedaan
antarperlakuan. Berdasarkan hasil penelitian, penambahan ekstrak daun jambu biji putih memberikan pengaruh sangat nyata terhadap aktivitas antibakteri, Total Plate Count (TPC) bakteri asam laktat, dan nilai pH susu kambing fermentasi. Rataan luas zona hambat pada perlakuan P0,
P1, P2, dan P3 berturut-turut sebesar 0,0; 0,0; 0,8; dan 8,3 mm², dengan aktivitas antibakteri tertinggi diperoleh pada perlakuan P3. Nilai TPC bakteri asam laktat pada P0, P1, P2, dan P3 berturut-turut sebesar 9,4; 9,3; 9,3; dan 8,9 log CFU/mL. Hasil tersebut menunjukkan
adanya penurunan jumlah bakteri asam laktat seiring dengan peningkatan konsentrasi ekstrak, tetapi jumlah bakteri asam laktat masih berada pada kisaran yang tinggi. Rataan nilai pH pada P0, P1, P2, dan P3 berturut-turut sebesar 3,8; 3,8; 3,8; dan 4,5. Peningkatan nilai pH pada P3 diduga berkaitan dengan menurunnya jumlah bakteri asam laktat selama proses fermentasi. Berdasarkan hasil penelitian dapat disimpulkan bahwa penambahan ekstrak daun jambu biji putih pada susu kambing fermentasi meningkatkan aktivitas antibakteri terhadap Propionibacterium acnes, namun menyebabkan penurunan jumlah bakteri asam laktat dan peningkatan nilai pH. Perlakuan dengan penambahan ekstrak daun jambu biji putih 6% merupakan perlakuan terbaik karena menghasilkan aktivitas antibakteri tertinggi, dengan jumlah bakteri asam laktat yang masih tinggi dan nilai pH yang masih sesuai dengan karakteristik susu fermentasi.

Goat milk is a nutritious food that can be processed into a functional food product through fermentation using lactic acid bacteria. To enhance its antibacterial activity, natural ingredients containing bioactive compounds can be added. White guava leaves (Psidium guajava L.) contain flavonoids, tannins, saponins, alkaloids, quercetin, kaempferol, and phenolic compounds that have potential antibacterial properties. The addition of white guava leaf extract to fermented goat milk was conducted to determine its ability to inhibit the growth of Propionibacterium acnes, one of the bacteria associated with acne. This study used a Completely Randomized Design (CRD) with four treatments involving different concentrations of white guava leaf extract: P0 without extract, P1 with 2% extract, P2 with 4% extract, and P3 with 6% extract. Goat milk was fermented using cultures of Streptococcus thermophilus and Lactobacillus plantarum. The observed parameters included antibacterial activity against Propionibacterium acnes, Total Plate Count (TPC) of lactic acid bacteria, and pH value of fermented goat milk. The data were analyzed using Analysis of Variance (ANOVA), followed by Duncan’s Multiple Range Test to determine differences among treatments. The results showed that the addition of white guava leaf extract had a highly significant effect on antibacterial activity, Total Plate Count (TPC) of lactic acid bacteria, and pH value of fermented goat milk. The mean inhibition zone areas for P0, P1, P2, and P3 were 0.0, 0.0, 0.8, and 8.3 mm², respectively, with the highest antibacterial activity observed in P3. The TPC values of lactic acid bacteria for P0, P1, P2, and P3 were 9.4, 9.3, 9.3, and 8.9 log CFU/mL, respectively. These results indicate a decrease in the number of lactic acid bacteria with increasing extract concentration; however, the bacterial counts remained relatively high. The mean pH values for P0, P1, P2, and P3 were 3.8, 3.8, 3.8, and 4.5, respectively. The increase in pH in P3 was presumably associated with the decrease in the number of lactic acid bacteria during fermentation. Based on the results, it can be concluded that the addition of white guava leaf extract to fermented goat milk increased its antibacterial activity against Propionibacterium acnes, but resulted in a decrease in the number of lactic acid bacteria and an increase in pH. The treatment with 6% white guava leaf extract (P3) was considered the best treatment because it produced the highest antibacterial activity, while maintaining a relatively high number of lactic acid bacteria and a pH value that remained within the characteristics of fermented milk.