Study of Synbiotic Yoghurt Fortification with Red Dragon Fruit Peel Extract (Hylocereus polyrhizus) and Stevia Against Emulsion Properties and Color

ABSTRACT. The research aimed to study the emulsion properties of the fortified synbiotic yoghurt fortification red dragon fruit peel extract (Hylocereus polyrhizus) and stevia as sweeteners. The research material is probiotic yoghurt, synbiotic fortified with red dragon fruit skin extract (Hylocereus polyrhizus) 20% made from 10% skim milk and yoghurt starter containing Lactobacillus bulgaricus and Streptococcus thermophilus (1:1), and the addition of 0.5% stevia to synbiotic. The research method was an experimental completely randomized design with treatment T1 = probiotic yoghurt, T2 = synbiotic yoghurt fortified red dragon fruit (Hylocereus polyrhizus) peel extract 20% and T3 = T2 + 0.5% stevia, with 3 replications (v/v). . The variables observed were emulsion activity, emulsion stability, turbidity, whiteness index (WI) and yellowness index (YI). The results showed that fortification of evaporated red dragon fruit peel extract (Hylocereus polyrhizus) and stevia sweetener gave a significant difference (P0.05) to the average emulsion activity, a very significant difference to the average of whiteness index and yellowish index (P0.01) and did not give a significant difference (P0.05) on the average of emulsion stability and turbidity of synbiotic yoghurt. It was concluded that 20% fortification of red dragon fruit skin (Hylocereus polyrhizus) and 0.5% stevia sweetener could improve the emulsion properties of synbiotic yoghurt.  (Kajian yoghurt sinbiotik fortifikasi ekstrak kulit buah naga merah (Hylocereus polyrhizus) dan stevia terhadap sifat emulsi dan warna) ABSTRAK. Tujuan penelitian adalah mempelajari profil emulsi dan warna yoghurt sinbiotik fortifikasi ekstrak kulit buah naga merah (Hylocereus polyrhizus) dan bahan pemanis stevia. Materi penelitian adalah yoghurt probiotik, sinbiotik yang difortifikasi dengan ekstrak kulit buah naga merah (Hylocereus polyrhizus) 20 % yang dibuat dari susu skim 10% dan starter yoghurt yang mengandung Lactobacillus bulgaricus dan Streptococcus thermophilus (1:1), serta penambahan stevia 0,5% pada yoghurt sinbiotik. Metode penelitian adalah percobaan dengan Rancangan Acak Lengkap dengan perlakuan T1= yoghurt probiotik, T2= yoghurt sinbiotik fortifikasi ekstrak kulit buah naga merah (Hylocereus polyrhizus) 20% dan T3 = T2 + 0,5% stevia, dengan 3 ulangan (v/v). Variabel yang diamati diantaranya aktivitas emulsi, stabilitas emulsi, turbiditas, serta warna ditinjau dari indeks keputihan (WI) dan indeks kekuningan (YI). Hasil penelitian menunjukkan bahwa fortifikasi ekstrak kulit buah naga merah (Hylocereus polyrhizus) evaporasi dan bahan pemanis stevia memberikan perbedaan yang nyata (P0,05) terhadap rata-rata aktivitas emulsi, perbedaan yang sangat nyata terhadap rata-rata indeks keputihan dan indeks kekuningan (P0,01) dan tidak memberikan perbedaan nyata (P0,05) terhadap rata-rata stabilitas emulsi dan turbiditas yoghurt sinbiotik. Disimpulkan bahwa fortifikasi kulit buah naga merah (Hylocereus polyrhizus) 20% dan bahan pemanis stevia 0,5% dapat memperbaiki sifat emulsi yoghurt sinbiotik.