Judul: Pengaruh Antioksidan dan Lama Perendaman Terhadap Kualitas Tepung Kentang
Abstrak: Kentang merupakan salah satu tanaman yang banyak ditanam di Indonesia. Berbagai macam olahan dapat dihasilkan dari kentang salah satunyan adalah tepung kentang. Tepung kentang merupakan produk setengah jadi yang dapat bertahan lama. Permasalahan yang sering terjadi dalam pengolahan kentang adalah terjadinya browning. Penelitian ini bertujuan untuk mengetahui pengaruh penambahan jenis antioksidan dan lama perendaman terhadap sifat fisik,kimia dan organoleptik mutu tepung kentang. Jenis antioksidan yang digunakan yaitu Natrium Metabisulfit (N2S2O5) dan Asam Sitrat (C₆H₈O₇). Metode penelitian adalah merendam kentang dengan antioksidan dengan waktu perendaman 20 menit, 40 menit, dan 60 menit. Hasil penelitian menunjukkan bahwa perlakuan terbaik yaitu menggunakan Natrium Metabisulfit dengan perendaman 60 menit dengan kadar air terendah 10%, rendemen yang tinggi sebesar 12,84% dan kadar abu yang rendah sebesar 0,48%. Uji organoleptik yang dihasilkan disukai dari segi warna, aroma dan tekstur., Potato is one the most widely grown crops in Indonesia. Various kinds of preparations can be produced from potatoes, one of which isi potato starch. Potato flour is a semi.finished product that can last a long time . The problem that often occurs in potato processing is the occurrence of browning. This study aims to determine the effect of adding types of antioxidants and soaking time on the physical, chemical and organoleptic properties of potato flour quality. The types of antioxsidants used are sodium metabisulfite (N2S2O5) and citric acid (C6H8O7). Thr research method was soaking potatoes with antioxsidants with soaking times of 20 minute, 40 minutes, and 60 minutes. The result showed that the best treatment was using sodium metabisulfite with 60 minutes of immersion with the lowest water content 10% , high yield of 12,84% and low ash content of 0,48%. The organoleptic test produced was both in terms of color, aroma and texture.
Keyword: antioxsidants, browning, potato, immersion

Judul: Perubahan Warna Tepung Kentang Atlantik Selama Penyimpanan Dan Pendugaan Umur Simpannya
Abstrak: The effect of packaging and temperature storage on color quality attribute of potato fluor was investigated. Color quality is measured by the value of brightness (L*) using Chromameter Minolta CR-200, browning index, whiteness index, enzyme polyphenol oxidase activity, water content of starch during storage and organoleptic quality. Estimation of shelf life was measured using the method ASLT (Accelerated Storage Studies) semi-empirical Arrhenius equation in the varied storage temperatures (20oC, 30oC, and 40oC) and two types of packaging (polypropylene and low density polyethylene). It was found that shelf life of potato flour in lower temperature storage resulted in better color retention. Potato flour shelf life based on the parameters of brightness and browning index is at a temperature of 30oC storage box that is 4 month 24 days. Packaging and storage methods had obvious effect on the product quality.
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Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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