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: Ekstraksi dan Karakterisasi Kolagen dari Kulit Ikan Cobia (Rachycentron canadum)
Abstrak: Cobia fish (Ranchycentron canadum) was used for a culinary purpose, but their skin was waste part. Convert in a value added product like collagen was a good practice of post harvest management. Isolation of collagen from the skin of cobia fish (Rachycentron canadum) has been successfully conducted with three stages: first soaked in 0,05 M NaOH with a sample/solution ratio of 1:10 (w/v) for 6 hour, second soaked in 0,1 M acetic acid with a sample/solution ratio of 1:6 (w/v) for 2 hour, and third extraction with destilated water at temperature 40 ºC for 3 hour. The yield of collagen was 10,508%. The pH of collagen was 7,08; protein content 86,46%; moisture 11,08%; fat 0,26%; and ash contents 0,19%. Amino acid analysis of collagen revealed the high proline and glycine. FTIR spectra analysis revealed that collagen molecules had the compact triple helical structure stabilized mainly by the hydrogen bond. Fourier transform infrared (FTIR) spectroscopic study showed major absorption bands of amide A, B, I, II and III at 3310, 2932, 1651, 1543 and 1242 cm-1 respectively.
Keyword: FTIR, water ekstraction, cobia (Rachycentron canadum), collagen

Judul: Analysis of M/G/1 Queue Model with Two Phases of Service and Bernoulli Feedback System
Abstrak: Model antrean M/G/1 dengan sistem feedback Bernoulli adalah model antrean dengan proses kedatangan mengikuti proses Poisson. Pada karya ilmiah ini dibahas sistem antrean M/G/1 dengan dua fase layanan. Setelah layanan pertama selesai, pelanggan dapat memilih untuk meninggalkan sistem dengan peluang ... dst, The M/G/1 queueing model with the Bernoulli feedback system is a queueing model with the arrival process following the Poisson process. In this manuscript M/G/1 queueing system with two phases of service is discussed. After the first service is completed, the customer can choose to leave the system with probability ... dst
Keyword: queue, Bernoulli, probability generating function, expected value