Judul: Eksplorasi Potensi Kolagen pada ikan laut yaitu pada kulit ikan bawal putih (Pampus argenteus), ikan bandeng (Chanos chanos), dan ikan sebelah (Psettodes erumei) dengan menggunakan Metode Asam
Abstrak: This study aims to determine the potential of fish skin collagen through product white pomfret (Pampus argenteus), milkfish (Chanos Chanos), and flatfish (Psettodes erumei) based on the characteristics of the skin and studying the physical and chemical properties of collagen produced. Collagen obtained through acid extraction process on a sample of fish skin, collagen extracts were then tested HPLC to obtain the amino acid composition, Brookfield viscometer to obtain the value of viscosity, and FTIR to obtain functional groups. Besides testing the chemical composition such as levels of protein, water, ash, fat and skin of fish is also performed. The analysis showed the value of using a collagen yield a concentration of 0.1 M acetic acid produced the highest of fish skin Next by 7,57%, followed by White Bawal fish skin is 6.93%, and the lowest milkfish fish skin is 5.43%. Value collagen yield using acetic acid produced the highest concentration of 0.2 M Next to skin fish of 2.90%, followed by White Bawal fish skin is 2.81%, and the lowest milkfish fish skin is 1.44%. Value collagen yield using acetic acid produced the highest concentration of 0.3 M Next to skin fish of 1.38%, followed by White Bawal fish skin is 1.25%, and the lowest milkfish fish skin is 0.86%. The analysis showed the highest viscosity values resulting from fish skin collagen White Bawal is 2.52 cP, followed by Next to the fish skin collagen of 2.41 cP, and the lowest milkfish fish skin collagen which is 2.37 cP. Collagen that has the best potential value of the quantity produced from fish skin collagen Next to collagen because it produces the highest yield value. Collagen that has the potential value of the best quality based on the quality parameters for the development of gelatin in the food industry resulting from fish skin collagen Bawal White because it has the highest viscosity.
Keyword: Bogor Agricultural University (IPB), White pomfret (Pampus argenteus) skin, quantity, Flatfish (Psettodes erumei) skin, Milkfish (Chanos chanos) skin, Collagen

Judul: Ekstraksi dan Karakterisasi Kolagen dari Kulit Ikan Tongkol (Euthynnus affinis)
Abstrak: Collagen is the most abundant protein in the living body and comprising approximately 30% of the total protein content. Utilization of waste from the skin of eastern little tuna to produce collagen is one alternative to increase the economic value of its waste. Pretreatment process in extracting collagen affects the quality of collagen that obtained. The different concentration of NaOH (0.05; 0.1; and 0.2 M) and soaking time (2, 4, 6, 8, 10, and 12 hours) were used as the pretreatment step. The best result of pretreatment was obtained from soaking the skin in a solution of 0.05 M NaOH for 12 hours with the lowest of soluble non-collagen protein concentration was 0.140 mg/mL. The yield and pH of the best collagen were 7.459% and 5.29, respectively. The highest solubility of collagen was 90.80% at pH 3. Amino acid analysis showed that the collagen has a glycine, proline, arginine, and alanine were dominant. FTIR analysis showed the major absorption bands of amide A, B, I, II, and III were at wavenumber 3395 cm-1, 2929 cm-1, 1652 cm-1, 1543 cm-1, and 1237 cm-1, respectively.
Keyword: amino acid, collagen, eastern little tuna, FTIR, yield

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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