Judul: The Role of The Tripsin Enzyme of Big Eye Tuna Improving The Quality of Red Tilapia Surimi
Abstrak: Pemanfaatan limbah jeroan ikan dapat didgunakan sebagai sumber potensial enzim pencernaan, salah satunya enzim tripsin yang diekstrak dari usus ikan tuna mata besar. Pemanfaatan enzim protease pada produk perikanan sudah banyak, contohnya pada surimi. Surimi merupakan produk perikanan yang memiliki tekstur unik dan gizi yang tinggi. Bahan baku surimi lebih sering menggunakan ikan berdaging putih banyak terdapat di spesies ikan air tawar, salah satunya ikan nila. Ikan nila sangat cocok untuk pembuatan surimi karena dagingnya yang tebal dan berwarna putih. Tujuan penelitian ini adalah ekstraksi dan karakterisasi tripsin dari usus ikan tuna mata besar serta menentukan kosentrasi tripsin terbaik dalam meningkatan mutu surimi ikan nila merah. Penelitian terbagi menjadi dua tahap, yang pertama yaitu ekstaksi dan karakterisasi enzim tripsin. Tahap kedua yaitu aplikasi enzim tripsin pada pembuatan surimi. Analisis yang digunakan pada penelitian meliputi penentuan aktivitas, konsentrasi protein, suhu dan pH optimum enzim. Konsentrasi tripsin 0%, 1%, 2%, 3%, 4% (v/b) ditambahkan dalam pembuatan surimi dan kemudian dilihat pengaruhnya terhadap kualitas surimi yang dihasilkan. Analisis data dilakukan menggunakan metode Rancangan Acak Lengkap (RAL) dengan tiga ulangan. Ekstrak kasar tripsin memiliki aktivitas 0,121 U/mL. sedangkan untuk konsentrasi protein yang didapatkan yaitu 0,158 mg/mL dengan suhu optimum 50 ºC dan pH 7. Surimi dengan penambahan tripsin 2% menunjukkan hasil terbaik yaitu kadar air 81,54%, kadar protein 13,99%, kadar abu 0,23%, kadar lemak 0,48%, pH 7, protein larut garam (PLG) 0,9 mg/mL, WHC 18%, derajat putih 62%, ukuran partikel 1054 μm, kenampakan 8, uji lipat 2,7 dan uji gigit 6,5., Utilization of fish offal waste can be used as a potential source of digestive enzymes, one of which is the trypsin enzyme extracted from the intestines of bigeye tuna. There are many uses of protease enzymes in fisheries product, for example in surimi. Surimi is a fishery product that has a unique texture and high nutrition. The raw material for surimi more often uses white-fleshed fish, which is found in many freshwater fish species, one of which is tilapia. Tilapia is very suitable for making surimi because of its thick and white flesh. The purpose of this study was to extract and characterize trypsin from the intestines of bigeye tuna and to determine the best trypsin concentration in improving the quality of red tilapia surimi. The research was divided into two stages, the first was extraction and characterization of the trypsin enzyme. The second stage is the application of the trypsin enzyme in the manufacture of surimi. The analysis used in this study included determining the activity, protein concentration, temperature and optimum pH of the enzyme. Trypsin concentrations of 0%, 1%, 2%, 3%, 4% (v/w) were added in the manufacture of surimi and then seen their effect on the quality of the surimi produced. Data analysis was performed using a completely randomized design (CRD) method with three replications. The crude trypsin extract has an activity of 0.121 U/mL. while the protein concentration obtained was 0.158 mg/mL with an optimum temperature of 50 C and pH 7. Surimi with the addition of 2% trypsin showed the best results, namely 81.54% water content, 13.99% protein content, 0.23%
Keyword: pH, proximate, protease

Judul: Characteristics and Stability of Trypsin Enzyme in NaCl Isolated from Intestine, Liver, and Spleen of Tuna
Abstrak: Kebutuhan enzim di Indonesia sangat tinggi dan masih diimpor dari negara lain. Tripsin komersial biasanya diekstraksi dari pankreas babi dan sapi, sehingga diperlukan sumber alternatif lainnya yang bersumber dari ikan, yaitu usus, hati, dan limpa ikan tuna. Penelitian ini bertujuan menentukan karakteristik dan stabilitas enzim tripsin dalam NaCl, serta hubungan usus, hati, dan limpa ikan tuna terhadap aktivitas tripsin menggunakan Principal Component Analysis (PCA). Aktivitas tripsin berada pada kondisi optimum pada suhu 60 ̊C dan pH 8 dengan nilai aktivitas spesifik pada usus sebesar 0,948±0,114 U/mg; hati sebesar 0,610±0,029 U/mg; dan limpa sebesar 0,605±0,159 U/mg. Kecepatan reaksi maksimum (Vmaks) menunjukkan nilai usus yang paling besar sebesar 0,248 mmol/s, diikuti oleh hati 0,138 mmol/s, dan limpa 0,096 mmol/s, sedangkan nilai konstanta (Km) yang diperoleh usus sebesar 2,342 mM; hati sebesar 2,268 mM, dan limpa sebesar 1,276 mM. Bobot molekul pada tripsin berkisar antara 20-30 kDa. Konsentrasi NaCl yang tinggi akan menyebabkan aktivitas semakin menurun. Bagian usus, hati, dan limpa memiliki korelasi positif., The need for enzymes in Indonesia is very high and they are still imported from other countries. Commercial trypsin is usually extracted from the pancreas of pigs and cattle, so that other alternative sources are needed from fish, namely the intestines, liver and spleen of tuna. The relationship between intestine, liver and spleen of tuna trypsin activity using Principal Component Analysys (PCA) was used to determine characterisics and stability of the trypsin enzyme in NaCl as the study aims. Trypsin activity was at its optimum at a temperature of 60 ̊C and pH 8 with a specific activity value in the intestine of 0,948 ± 0,114 U/mg; liver of 0,610 ± 0,029 U/mg; and spleen of 0,605 ± 0,159 U/mg. The maximum reaction speed (Vmax) showed the largest intestinal value of 0,248 mmol/s, followed by the liver 0,138 mmol/s, and the spleen 0,096 mmol/s, while the constant value (Km) obtained by the intestine was 2,342 mM; liver of 2,268 mM, and spleen of 1,276 mM. The molecular weight of trypsin ranges from 20-30 kDa. The high concentration of NaCl decreased the activity. Sections of intestine, liver, and spleen had a positive correlation.
Keyword: karakteristik enzim tripsin, stabilitas NaCl, jeroan tuna

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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