ABSTRAKBuah belimbing (Averrhoa carambola L.) adalah buah tropis yang mengandung senyawa antioksidan tinggi. Buah belimbing biasa dikonsumsi langsung ataupun dijadikan berbagai olahan agar dapat disimpan lebih lama. Tujuan dari penelitian ini adalah membuat formulasi serbuk minuman instan ekstrak belimbing manis dengan penambahan asam sitrat pada tiga konsentrasi berbeda serta mengukur kandungan flavonoid, vitamin C dan kapasitas antioksidan dari minuman serbuk minuman instan tersebut. Konsentrasi asam sitrat yang digunakan adalah 0,5% (formula 1), 0,75% (formula 2) dan 1% (formula 3). Hasil penelitian menunjukan bahwa formula 2 menghasilkan serbuk instant dengan rasa paling disukai panelis berdasarkan pengukuran parameter warna, aroma, dan rasa. Hasil uji kandungan kimia dan aktifitas biologis menunjukan bahwa produk serbuk minuman instan ekstrak kering belimbing manis formula 2 memiliki kadar flavonoid 4,50%, vitamin C 0,12% dan kapasitas antioksidan136,875 mg SAG/g serbuk. Data ini menunjukan bahwa serbuk minuman instant buah belimbing manis berpotensi dikembangkan sebagai minuman kesehatan berkadar antioksidan tinggi.Kata kunci : Antioksidan, belimbing manis, serbuk minuman instan DETERMINATION OF FLAVONOID CONTENT AND ANTIOXIDANT ACTIVITY FORMULA INSTANT DRINK POWDER IN SWEET SPINAL EXTRACT (Averrhoa carambola L.) ABSTRACTSweet star (Averrhoa carambola L.) is a tropical fruit which contains high level ofantioxidant compounds. Besides consumed directly, this fruit usually is processed to preserve and extend the storage period. This study was aimed to formulate the instant powder drink from the extract of sweet star fruit and to determine its flavonoid content and antioxidant activity. The instant powder drink was formulated with the addition citric acid at three different concentration of citric acid that are formula 1 (citric acid0,5%), formula 2 (0,75%) and formula 3 (1%). The result of hedonic test shows thatformula 2 obtained most preferred colour, taste and flavour based on hedonic test according to determine flavonoid content, vitamin C and antioxidant capacity. Determination of biochemical content show that the instant powder contains 4,5 % flavonoid, 0,12% of vitamin C and 136,875 mg ascorbic acid equivalent antioxidant capacity (AEAC/g). It can be concluded that the formula 2 instant powder drink formulated from extract sweet star fruit has a potent to be developed as high vitamin C anti-oxidant instant healthy drink.Keywords : Antioxidant, sweet starfruit, instan drink powder