ABSTRAKSemi Refined Carrageenan merupakan salah satu produk carrageenan dengan tingkat kemurnian lebih rendah dibandingkan dengan refined carrageenan. Semi Refined Carrageenan merupakan tepung hasil ekstraksi rumput laut jenis Kappaphycus alvarezii berwarna putih kekuningan, dapat membentuk gel sehingga sangat berperan dalam industri makanan dan obat-obatan. Tujuan penelitian untuk mendapatkan konsentrasi pelarut KOH dan NaOH yang tepat dalam proses ekstraksi tepung Semi Refined Carrageenan rumput laut Kappaphycus alvarezii. Metode yang digunakan dalam penelitian ini adalah metode eksperimental, yaitu mengekstraksi Kappaphycus alvarezii menggunakan larutan alkali KOH dan NaOH yang direndam selama 4 menit. Hasil yang diperoleh menunjukkan bahwa rendemen tertinggi terdapat pada larutan KOH 5% (56,10%) dan larutan NaOH 3% (42,29%), kadar air pada larutan KOH 5% (15,45%) dan larutan NaOH 1% (16,50%), kadar abu larutan KOHÂ 4% (4,85%) dan larutan NaOH 2% (3,50%), nilai pH terbaik terdapat larutan KOH 3% (8,14) dan larutan NaOH 3% (8,01) dan viskositas laju alir pada larutan KOH 3% (36,50 mL/detik) dan larutan NaOH 3% (38,10 mL/detik). Dari hasil penelitian dapat disimpulkan bahwa rendemen tertinggi terdapat pada larutan KOH 5% dan larutan NaOH 3%.Kata Kunci: alkali, carrageenan, KOH, Kappaphycus alvarezii, NaOHABSTRACTSemi Refined Carrageenan is a carrageenan product with a lower level of purity compared to refined carrageenan. Semi Refined Carrageenan is flour extracted from Kappaphycus alvarezii type of seaweed, yellowish white in color, can form a gel so that it plays a very important role in the food and medicine industry. The aim of the study was to obtain the correct concentration of KOH and NaOH solvents in the extraction process of Kappaphycus alvarezii seaweed Semi Refined Carrageenan flour. The method used in this study is an experimental method, namely extracting Kappaphycus alvarezii using an alkaline solution of KOH and NaOH soaked for 4 minutes. The results obtained showed that the highest yield was found in 5% KOH solution (56.10%) and 3% NaOH solution (42.29%), water content in 5% KOH solution (15.45%) and 1% NaOH solution ( 16.50%), ash content of 4% KOH solution (4.85%) and 2% NaOH solution (3.50%), the best pH values were 3% KOH solution (8.14) and 3% NaOH solution (8 0.01) and the viscosity of the flow rate in 3% KOH solution (36.50 mL/second) and 3% NaOH solution (38.10 mL/second). From the results of the study, it can be concluded that the highest yield is found in 5% KOH solution and 3% NaOH solution.Keywords : alkali, carrageenan, KOH, Kappaphycus alvarezii, NaOH