ABSTRACTThis study aimed to determine the effect of immersion time on the physicochemical characteristics and proximate values of gadung tuber flour. This study was conducted using a completely randomized design (CRD) with three treatments, which were 12 hours of immersion (P1), 24 hours of immersion (P2), and 36 hours of immersion (P3). The results show that the selected treatment was P2, which was immersed for 24 hours at a temperature of 60 ºC and a heating time of 15 hours. The results of the physicochemical test show that the P2 product had a very significant increase in viscosity, swelling power, and solubility, which reached 1.64%, 7.09%, and 1.92%, respectively. Meanwhile, the P2 product contained 11.08% water, 3.24% ash, 10.11% protein, 75.24% carbohydrates, 8.02% fat, and 19.25 ppm of HCN. The results show that gadung tuber flour has a water content that met the national standard.Keywords: gadung flour, sea water, proximate, physicochemicalABSTRAKPenelitian ini bertujuan untuk menentukan pengaruh lama perendaman terhadap karakteristik fisikokimia dan nilai proksimat tepung umbi gadung. Penelitian ini dilakukan menggunakan rancangan acak lengkap (RAL), perlakuan berjumlah 3, perendaman 12 jam ( P1) , perendaman 24 jam ( P2) , dan perendaman 36 jam 9 (P3). Hasil penelitian yang diperoleh perlakuan terpilih P2 diperoleh dari hasil perendaman 24 jam pada suhu 60ºc dan lama pemanasan 15 jam. Hasil uji fisikokimia menunjukan bahwa tepung gadung dengan perendaman 24 jam (P2) memiliki pengaruh sangat nyata terhadap peningkatan viskositas yang memiliki nillai 1.64%, nilai swelling power sebesar 7,09% dan nilai kelarutan sebesar 1,92% . Sedangkan nilai kandungan kimia produk tepung gadung terpilih hasil perendaman 24 jam (P2) pada suhu 60oc dengan lama pemanasan 15 jam meliputi kadar air 11,08% , kadar abu 3,24%, kadar protein 10,11% karbohidrat 75,24% , kadar lemak 8,02% dan kadar HCN 19,25 ppm. Berdasarkan hasil penelitian tepung umbi gadung memiliki kadar air yang telah memenuhi standar SNI.kata kunci : tepung gadung, air laut, proksimat, fisikokimia.