ABSTRAK Donat umumnya berbahan baku terigu, namun adakalanya ditambahkan kentang kukus lumat yang biasa disebut donat kentang. Suhu air yang digunakan dalam pembuatan donat kentang oleh masyarakat sangat bervariasi, mulai dari air es sampai air hangat. Penelitian ini bertujuan untuk mengetahui pengaruh suhu air terhadap kualitas donat kentang dan mendapatkan suhu air untuk menghasilkan donat kentang dengan volume pengembangan optimum. Penelitian dilakukan menggunakan Rancangan Acak Kelompok (RAK) satu faktor yaitu suhu air (5, 13,75, 22,5, 31,25 dan 40oC) diulang 3 kali. Donat kentang dibuat dengan menambahkan kentang lumat sebanyak 40% (b/b terigu) dalam formula, dicampur hingga terbentuk adonan, diistirahatkan, dibulatkan per 30g, difermentasi, dan digoreng. Kualitas donat berupa volume spesifik, daya serap minyak, jumlah dan luasan pori serta profil tekstur dianalisis. Data diolah menggunakan ANOVA dan bila menujukkan beda nyata (α=5%) dilanjutkan uji BNT (Beda Nyata Terkecil)α=5%. Suhu air optimum ditentukan dengan menggunakan Response Surface Methodology (RSM) One Factor model kuadratik dengan variabel bebas suhu air (X1) dan variabel respon volume pengembangan (Y1). Hasil penelitian menunjukkan bahwa suhu air berpengaruh nyata terhadap volume spesifik, daya serap minyak dan jumlah pori; namun tidak mempengaruhi tekstur dan luasan pori. Hasil verifikasi RSM menunjukkan bahwa suhu air yang ditambahkan sebesar 24,7oC pada pembuatan donat kentang memberikan respon volume pengembangan yang maksimum sebesar 155,94%. Donat tersebut memiliki  kadar air 28,35%; abu 0,69%; protein 8,30%; lemak 17,68%; karbohidrat 44,97%; total gula 14,67%; serat kasar 5,57%; volume spesifik 4,39 cm3/g; densitas kamba 0,23 g/cm3; daya serap minyak 10,66%; hardness 131,45 N; cohesiveness 0,81; springiness 4,40 mm. Kata Kunci: Donat; Kentang; Optimasi; Suhu Air  ABSTRACT Donut is generally made from wheat flour, however it can be added other materials such as mashed potatoes to create potatoes donut. People use various ingredients formulation to make it, including variations in temperature of added water, from cold to warm water. This research aims to discover how the temperature of the added water affects the donut quality as well as the optimum temperature resulting to the maximum volume of the donut. The experiment uses Randomized Complete Design using one factor, temperature of added water (5; 13.75; 22.5; 31.25; and 40oC), with three time replications. Potatoes donut is made by adding 40% mashed potatoes (w/w of wheat flour) to the formula, mixed to form dough, rested, rounded per 30g, proofed and fried. The quality parameters of donut such as specific volume, oil absoption, pores number and texture profile are analyzed. Afterwards, the data acquired will be processed by using ANOVA and LSD (Least Significant Difference) at α = 5%. Optimum temperature will be determined using One Factor RSM (Response Surface Methodology) where X1 interprets independent variable, temperature of added water and Y1 interprets response variable, rising volume. The results indicate that added water temperature significantly affects the donut’s specific volume, oil absorption capacity, and  total pores. Insignificant effect, however, is experienced by texture profile and pores area. RSM verification result suggests that added water at 24,7oC results to 155.94% of increasing volume which is the optimum response. In addition, the donut has 28.35% of water content, 0.69% of ash content, 8.3% of protein, 17.68% of fat, 44.97% of carbohydrate, 14.67% of total sugar, 5.57% of crude fiber, specific volume of  4.39 cm3/g, bulk density of 0.23 g/cm3, oil absorption capacity of 10.66%, hardness of 131.45 M, cohesiveness of 0.81, springiness of 4.4 mm.  Keywords: Donut, Potato; Optimazion; Water Temperature