Teknologi modifikasi pada tepung non konvensional memungkinkan menaikkan kemampuan subtitusi terhadap terigu pada produk roti dan manfaat fungsional. Tujuan penelitian ini adalah mempelajari perubahan sifat fisik dan profil gelatinisasi tepung uwi ungu yang dimodifikasi secara fisik. Metode modifikasi yang digunakan adalah hidrotermal annealing. Faktor penelitian adalah suhu (40, 45, 50, 55, 60°C) dan waktu (1, 6, 12, 18, dan 24 jam). Rancangan penelitian disusun menurut rancangan Central Composite Design pada Response Surface Methodology (RSM). Nilai WSI mengalami peningkatan hingga 64% pada kisaran suhu 45-50°C dan waktu 12-18 jam. Perlakuan suhu dan waktu di atas atau dibawah rentang perlakuan tersebut menghasilkan nilai yang WSI rendah hingga 58%. Sementara itu, nilai WAI paling rendah (8,75 g/g) diketahui terjadi pada kombinasi kisaran suhu 60°C dan waktu 1 jam. Kondisi tersebut juga terjadi pada kombinasi suhu 40°C dan waktu 24 jam. Perlakuan annealing tidak mengubah bentuk granula. Sementara itu, annealing menurunkan nilai peak viscosity, final viscosity secara berturut hingga 151 cP, 355 cP, dan menaikkan peak time hingga 13 menit. Peningkatan nilai peak time menunjukkan peningkatan stabilitas pati akibat pengaruh hidrotermal annealing. Kata kunci: annealing, sifat fisik, profil gelatinisasi

Starch modification technology has a potential to increase the ability of non conventional flour to subtitute wheat flour on bakery products, while also gives more functional benefits. The purpose of this research was to study changes in physical properties, and gelatinization profile of modified purple yam flour. The modification method used was hydrothermal annealing. Temperature (40, 45, 50, 55, 60°C) and time (1, 6, 12, 18, and 24 h) were two factors studied. Design experiment was prepared by using Central Composite Design in Response Surface Methodology (RSM). Water Solubility Index (WSI) increased to reach 64% at 45-50°C and 12-18 h. The lowest WSI was 58% which happened at treatment outside the highest range. Meanwhile, the lowest WAI value (8.75 g/g) was resulted from annealing at 60°C and in 1h. Similar WAI value was also shown by annealed flour at 40°C and 24 h. Annealing didn’t alter the form of granules as seen by microscope. Meanwhile, annealing decreased the value of peak viscosity, final viscosity to 151 cP, 355 cP, respectively, and increased the peak time to 13 min. Increase in peak time indicated the rising stability of starch under the influence of annealing. Keywords: hydrothermal annealing, physical properties, gelatinization profile

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