<![CDATA[Inferior red dragon fruit has the potential as a source of natural dye. This research aimed to examined the quality of natural dye powder as a referenced for optimization. To optimized the formula for natural dye powder based on rejected dragon fruit, and to examined the physical and chemical quality of natural dye powder at the optimum formula. The varied ingredients in this research were ascorbic acid and tween 80. The upper and lower limits of use of both ingredients were 3% and 1% for ascorbic acid, as well as 1% and 0.5% for tween 80. The method used laboratory experimental method and quantitative analysis data. The experimental design used in this research was an experiment with the application of the simplex lattice design (SLD) method, so that several formulas were obtained based on the variation of two factors. Results of the observation data were inputted into the Design-Expert version 13 application so that a regression equation is obtained to determine the optimum formula. All data were presented in tables and graphs and analyzed descriptively. The results showed that F5 (ascorbic acid 3%: tween 80 0.5%) was the optimum formula because it had the highest desirability of 0.998 with a water content of 2.15%; total dissolved solids 9.66%; pH 3.766; L 53.71, a 14.20; b 7.39; dissolved time 61.33 seconds; Chroma 16,00; Hue 27.33? (red), and anthocyanin content 3,37 mg/mL. On exposure to the sun, outdoor and indoor experienced the highest degradation, namely 30.48% and 0.93%, respectively. Keywords: Ascorbic Acid, Red Dragon Fruit, Foam Mat Drying, Natural Dye, Tween 80 Buah naga merah inferior berpotensi sebagai sumber pewarna alami. Penelitian ini bertujuan untuk mengkaji kualitas serbuk pewarna alam sebagai acuan optimasi. Mengoptimalkan formula bubuk pewarna alami berbahan dasar buah naga afkir, dan menguji kualitas fisik dan kimia bubuk pewarna alami pada formula optimum. Variasi bahan dalam penelitian ini adalah asam askorbat dan tween 80. Batas atas dan bawah penggunaan kedua bahan tersebut adalah 3% dan 1% untuk asam askorbat, serta 1% dan 0,5% untuk tween 80. Metode yang digunakan adalah metode eksperimen laboratorium dan data analisis kuantitatif. Rancangan percobaan yang digunakan dalam penelitian ini adalah percobaan dengan penerapan metode simplex lattice design (SLD), sehingga diperoleh beberapa rumus berdasarkan variasi dua faktor. Data hasil observasi dimasukkan ke dalam aplikasi Design-Expert versi 13 sehingga diperoleh persamaan regresi untuk menentukan formula optimum. Seluruh data disajikan dalam bentuk tabel dan grafik serta dianalisis secara deskriptif. Hasil penelitian menunjukkan bahwa F5 (asam askorbat 3%: tween 80 0,5%) merupakan formula optimum karena memiliki desirabilitas tertinggi 0,998 dengan kadar air 2,15%; total padatan terlarut 9,66%; pH 3,766; L 53,71, a 14,20; b 7,39; waktu terlarut 61,33 detik; Kroma 16,00; Hue 27,33? (merah), dan kandungan antosianin 3,37 mg/mL. Pada paparan sinar matahari, outdoor dan indoor mengalami degradasi tertinggi yaitu masing-masing 30,48% dan 0,93%. Kata kunci : Asam Askorbat, Buah Naga Merah, Foam Mat Drying, Pewarna Alami, Tween 80]]>
