<![CDATA[ ABSTRACT This study was aimed to determine the effect of red dragon fruit juice and soursop juice and length of incubation on the quality of yoghurt. This study used a completely randomized design with two factors: the ratio of red dragon juice with soursop juice (S) : (90% : 10%, 70% : 30%, 50% : 50%, 30% : 70%, 10% : 90%), and length of incubation (T) : (4 hours), (7 hours), and (10 hours). The results showed that the ratio of red dragon fruit juice with soursop juice gave highly significant effect on total acid, color hedonic test, color score test, and yoghurt viscosity score test. The duration of incubation gave highly significant effect on total acid, pH, total lactic acid bacteria and yoghurt viscosity score test. The interaction of the two factors gave no significant effect on all parameters except on total yoghurt acid. Ratio of red dragon juice with soursop juice of 10% : 90% and 10 hours of incubation time produced the best quality of yoghurt. The best product was analyzed antioxidant activity that was equal to 73,7697 μg/ml. Keywords: Incubation Time, Red Dragon Fruit Juice, Soursop Juice, Yoghurt. ABSTRAK Penelitian ini untuk menentukan pengaruh perbandingan sari buah naga merah dengan sari buah sirsak dan lama inkubasi terhadap mutu yoghurt. Penelitian ini menggunakan metode rancangan acak lengkap dengan dua faktor yaitu perbandingan sari buah naga merah dengan sari buah sirsak (S) : (90% : 10%, 70% : 30%, 50% : 50%, 30% : 70%, 10% : 90%), dan lama inkubasi (T) : (4 jam), (7 jam), dan (10 jam). Hasil penelitian menunjukkan bahwa perbandingan sari buah naga merah dengan sari buah sirsak memberikan pengaruh berbeda sangat nyata terhadap total asam, uji hedonik warna, uji skor warna, dan uji skor kekentalan yoghurt. Lama inkubasi memberikan pengaruh berbeda sangat nyata terhadap total asam, pH, jumlah bakteri asam laktat dan nilai skor kekentalan yoghurt. Interaksi kedua faktor memberikan pengaruh berbeda tidak nyata terhadap semua parameter kecuali terhadap total asam yoghurt. Perbandingan sari buah naga merah dengan sari buah sirsak 10% : 90% dan lama inkubasi 10 jam menghasilkan yoghurt dengan mutu terbaik. Produk terbaik dilakukan analisa aktivitas antioksidan yaitu sebesar 73,7697 μg/ml. Kata kunci: Lama inkubasi, Sari Buah Naga Merah, Sari Buah Sirsak, Yoghurt.]]>
