Judul: Yellowfin Tuna (Thunnus albacares) Skin Collagen as Active Ingredients Candidate in Anti-aging Cream
Abstrak: Penambahan bubuk kolagen kulit ikan tuna sirip kuning (Thunnus albacares) sebagai kandidat bahan aktif dalam pembuatan krim anti-aging dapat berperan sebagai pelembab bagi kulit. Penelitian ini bertujuan menentukan karakteristik krim anti-aging serta konsentrasi kolagen kulit ikan tuna sirip kuning (T. albacares) terbaik sebagai kandidat bahan aktif pada sediaan krim anti-aging. Tahapan penelitian ini yaitu pembuatan sediaan krim anti-aging dan penentuan formula terbaik. Krim anti-aging diformulasikan dengan penambahan kolagen sebanyak 0%, 0,5%, dan 1% (b/b). Formulasi sediaan krim anti-aging terbaik didapati pada krim dengan penambahan kolagen larut pepsin kulit tuna sirip kuning dengan konsentrasi 0,5% (KA). Sediaan krim anti-aging terpilih telah sesuai dengan acuan yang ada. Sediaan krim KA (0,5% kolagen kulit tuna sirip kuning), memiliki rata-rata nilai sensori 7,06, nilai pH sebesar 7,53, daya sebar 7,05 cm, daya lekat 21,81 detik, viskositas 9650 ± 268,51 cP, dan kemampuan melembabkan kulit sebanyak 26,19%., The addition of yellowfin tuna (Thunnus albacares) skin collagen powder as active ingredients candidate in the production of anti-aging cream have a role as moisturizer agent for the skin. This study aimed to determine the anti-aging cream’s characteristics and the best concentration yellowfin tuna (T. albacares) skin collagen as active ingredients candidate for the anti-aging cream. This research phase involved making anti-aging cream preparations and determining the best formulation. Anti-aging cream formulated with 0%, 0,5%, and 1% collagen (w/w). The best anti-aging cream formulation found on cream with pepsin soluble collagen yellowfin tuna skin at concentration of 0,5% (KA). The selected anti-aging cream has followed the existing references. KA cream (0,5% yellowfin tuna skin collagen) had an average sensory value of 7,06, pH value of 7,53, spreadability about 7,05 cm, adhesion of 21,81 seconds, viscosity of 9650 ± 268,51 cP, and ability to moisturize the skin by 26,19%.
Keyword: formula, kolagen larut pepsin, kosmetik, krim, pelembab

Judul: Collagen Extraction of Yellowfin Tuna (Thunnus albacares) Skin Using Pepsin and Papain Enzymes
Abstrak: Kolagen merupakan senyawa protein rantai panjang yang tersusun atas asam amino alanin, arginin, lisin, glisin, prolin, serta hiroksiprolin. Kolagen merupakan protein jaringan ikat yang dapat dihasilkan dari limbah kulit ikan. Tujuan penelitian ini untuk menentukan nilai aktivitas spesifik enzim pepsin yang diekstraksi dari lambung ikan tuna serta menentukan karakteristik kolagen yang diekstraksi dengan metode enzimatis. Metode penelitian terbagi menjadi 2 tahap yaitu tahap ekstraksi enzim pepsin dari lambung ikan tuna sirip kuning dan tahap ekstraksi kolagen kulit tuna dengan metode enzimatis. Enzim pepsin yang diekstraksi dari lambung tuna sirip kuning memiliki nilai aktivitas spesifik 8680 U/mg. Waktu perendaman dengan NaOH terbaik adalah 12 jam. Waktu Hidrolisis kulit dengan asam asetat terbaik adalah 72 jam. Kolagen larut papain memiliki bobot molekul 310 kDa, gugus fungsi amida A, B, I, II, dan III,dengan rendemen 2,13%. Kolagen larut pepsin sebagian memiliki bobot 328 kDa, gugus fungsi amida A, I, II, dan III, dengan rendemen 0,8%. Hidrolisat kolagen larut pepsin memiliki bobot molekul 69 kDa, gugus fungsi amida A, I, dan III, dengan rendemen 32%., Collagen is a long-chain protein compound composed of the amino acids alanine, arginine, lysine, glycine, proline, and hydroxyproline. Collagen is a connective tissue protein that can produce from fish skin waste. The purpose of this study was to determine the specific activity value of the pepsin enzyme extracted from the stomach of tuna and to determine the characteristics of the collagen extracted by the enzymatic method. The research method was divided into 2 stages, namely the extraction stage of the pepsin enzyme from the stomach of yellowfin tuna and the extraction stage of tuna skin collagen using the enzymatic method. The pepsin enzyme extracted from the stomach of yellowfin tuna has a specific activity value of 8680 U / mg. The best soaking time with NaOH is 12 hours. Hydrolysis time of skin with acetic acid is best 72 hours. Papain soluble collagen has a molecular weight of 310 kDa, amide functional groups A, B, I, II, and III, with a yield of 2,13%. Pepsin soluble collagen partly weighed 328 kDa, amide functional groups A, I, II, and III, with a yield of 0,8%. Pepsin soluble collagen hydrolyzate has a molecular weight of 69 kDa, amide functional groups A, I, and III, with a yield of 32%.
Keyword: papain, pepsin, extraction, collagen

Judul: Bifurkasi Hopf pada siklus bisnis IS-LM tanpa dan dengan waktu tunda
Abstrak: One of business cycle models in dynamical economics is the IS-LM business cycle model with time delay, where the time delay lies in stock capital variables. It is a time delay between the existence of stock capital and the time to get ready to invest. In a model without time delay, changing the parameter of investment rate on income could affect the system stability. On the other hand, in a model with time delay, there exists critical time delay changing the system stability. This shows limit cycle, which can be concluded that Hopf bifurcation occurs
Keyword: Bogor Agricultural University (IPB), time delay, Hopf bifurcation, business cycle model