Electronic Theses and Dissertation

Susu merupakan bahan pangan hewani yang kaya akan protein, lemak, vitamin, mineral, dan laktosa, namun mudah mengalami kerusakan akibat pertumbuhan mikroorganisme. Salah satu upaya untuk meningkatkan mutu, keamanan, dan masa simpan susu adalah melalui fermentasi menggunakan bakteri asam laktat, seperti Streptococcus thermophilus dan Lactobacillus bulgaricus. Proses fermentasi tidak hanya memperpanjang daya simpan susu, tetapi juga menghasilkan produk pangan fungsional yang memiliki nilai gizi lebih baik serta mengandung senyawa bioaktif yang bermanfaat bagi kesehatan. Pengembangan susu fermentasi dapat dilakukan dengan penambahan bahan alami yang kaya senyawa bioaktif, salah satunya adalah puree kuini (Mangifera odorata Griff.). Buah kuini mengandung vitamin C, flavonoid, β-karoten, dan senyawa fenolik yang berpotensi sebagai antioksidan alami, serta mengandung gula sederhana yang dapat dimanfaatkan oleh bakteri asam laktat selama proses fermentasi. Penambahan puree kuini diharapkan mampu meningkatkan kandungan asam laktat dan aktivitas antioksidan susu fermentasi, sekaligus meningkatkan pemanfaatan buah kuini yang mudah rusak dan memiliki nilai ekonomi relatif rendah pada saat panen. Oleh karena itu, penelitian ini dilakukan untuk mengkaji pengaruh penambahan puree kuini terhadap kandungan asam laktat dan aktivitas antioksidan susu fermentasi.
Penelitian ini bertujuan untuk mengetahui pengaruh penambahan puree kuini terhadap kandungan asam laktat dan aktivitas antioksidan susu kambing fermentasi serta mengkaji hubungan antara kedua parameter tersebut. Penelitian dilaksanakan pada April 2026 di Laboratorium Teknologi Pengolahan Susu dan Laboratorium Analisis Pangan dan Hasil Pertanian, Universitas Syiah Kuala. Penelitian menggunakan Rancangan Acak Lengkap (RAL) dengan empat perlakuan, yaitu P0 (0%), P1 (10%), P2 (20%), dan P3 (30%) penambahan puree kuini, masing-masing dengan empat ulangan sehingga diperoleh 16 satuan percobaan. Susu kambing difermentasi menggunakan starter Streptococcus thermophilus dan Lactobacillus bulgaricus sebanyak 5% dan diinkubasi pada suhu 37°C selama 18 jam.
Hasil penelitian menunjukkan bahwa kandungan asam laktat susu fermentasi berkisar antara 1,08–1,20%, dengan nilai tertinggi pada perlakuan P3 (30%) sebesar 1,20%. Namun, penambahan puree kuini tidak berpengaruh nyata (P>0,05) terhadap kandungan asam laktat. Aktivitas antioksidan seluruh perlakuan termasuk kategori sangat kuat dengan nilai IC₅₀ berkisar antara 7,11–22,74 µg/mL. Aktivitas antioksidan terbaik diperoleh pada perlakuan P3 (30%) dengan nilai IC₅₀ sebesar 7,11 µg/mL, yang menunjukkan kemampuan menangkal radikal bebas paling tinggi dibandingkan perlakuan lainnya. Dengan demikian, puree kuini berpotensi dimanfaatkan sebagai bahan tambahan alami dalam pengembangan susu fermentasi fungsional yang memiliki aktivitas antioksidan tinggi.

Milk is an animal-derived food that is rich in protein, fat, vitamins, minerals, and lactose. However, it is highly perishable due to the growth of microorganisms. One approach to improving the quality, safety, and shelf life of milk is fermentation using lactic acid bacteria, such as *Streptococcus thermophilus* and *Lactobacillus bulgaricus*. Fermentation not only extends the shelf life of milk but also produces functional foods with enhanced nutritional value and bioactive compounds that are beneficial to human health. The development of fermented milk can be enhanced through the addition of natural ingredients rich in bioactive compounds, one of which is kuini (*Mangifera odorata* Griff.) puree. Kuini fruit contains vitamin C, flavonoids, β-carotene, and phenolic compounds that have potential as natural antioxidants. In addition, it contains simple sugars that can be utilized by lactic acid bacteria during the fermentation process. The addition of kuini puree is expected to increase the lactic acid content and antioxidant activity of fermented milk while also promoting the utilization of kuini fruit, which is highly perishable and has relatively low economic value during the harvest season. Therefore, this study was conducted to evaluate the effect of kuini puree addition on the lactic acid content and antioxidant activity of fermented milk. This study aimed to determine the effect of kuini puree addition on the lactic acid content and antioxidant activity of fermented goat milk and to examine the relationship between these two parameters. The research was conducted in April 2026 at the Dairy Processing Technology Laboratory and the Food and Agricultural Product Analysis Laboratory, Universitas Syiah Kuala. A Completely Randomized Design (CRD) was employed with four treatments: P0 (0%), P1 (10%), P2 (20%), and P3 (30%) kuini puree addition. Each treatment was replicated four times, resulting in a total of 16 experimental units. Goat milk was fermented using a 5% starter culture consisting of *Streptococcus thermophilus* and *Lactobacillus bulgaricus* and incubated at 37°C for 18 hours. The results showed that the lactic acid content of the fermented milk ranged from 1.08% to 1.20%, with the highest value observed in treatment P3 (30%) at 1.20%. However, the addition of kuini puree had no significant effect (P>0.05) on the lactic acid content. The antioxidant activity of all treatments was classified as very strong, with IC₅₀ values ranging from 7.11 to 22.74 µg/mL. The highest antioxidant activity was obtained in treatment P3 (30%), which exhibited the lowest IC₅₀ value of 7.11 µg/mL, indicating the greatest free radical scavenging capacity among all treatments. In conclusion, kuini puree has considerable potential as a natural additive in the development of functional fermented milk with high antioxidant activity.