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: Penghambatan Reaksi Pencoklatan Enzimatis dan Nonenzimatis pada Pembuatan Tepung Kentang
Abstrak: Potatoes are a good source of carbohydrate that can improve the nutrient status. In the fresh condition, the potatoes will easily damaged and require further processing. During the milling process, potatoes can undergo browning process, either through enzymatis or non-enzymatis reaction. The aim of this research are (1) determine variety and thickness of potatoes slices and natrium metabisulphite concentrations to prevent browning process and (2) determine the physicochemical caracteristic of selected potatoes flour. Potatoes were used in this research was the Atlantic and Granola potatoes. This research used three treatments i.e. : (1) thickness slices (2, 3, and 4 mm); (2) natrium metabisulphite concentrations (0, 750, 1500, 2250, and 3000 ppm); and (3) blansir process. Potatoes flour from potatoes without blansir and submersion in natrium metabisulphite was used as control. Based on lightness value, index browning, sulfite residue, and organoleptic analysis the potatoes flour selected was originate from Atlantic potatoes with blansir treatment, thickness slices 2 mm, and submersion in natrium metabisulphite 750 ppm. The chemical caracteristics consist of the water, protein, starch, carbohydrate, fat, ash, fyber content and index browning of potatoes flour selected were respectively : 6.86%, 9.91%, 81.34%, 88.07%, 0.79%, 1.22%, 0.67% (dry base/db) and 0.046. The phisycal caracteristics of the potatoes flour such as bulky density and water absorpsion capacity were 725.36g/L and 3.53 g water/g flour, whereas the colour caracteristics value such as lightness (L), greenness (a), and yellowness (b) were respectively : 96.90, -3.24, and 13.37. In addition, the initial temperature gelatinitation and viscocity of the potatoes flour at 930C were 630C and 240 brabender unit (BU) and that viscocity at 930C and 500C after 20 minutes were 330 and 460 BU.
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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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