Judul: Karakteristik Sate Padang dalam kemasan dengan Suhu dan Lama Waktu Penyimpanan Berbeda
Abstrak: Penelitian ini bertujuan untuk mengevaluasi kemampuan kemasan retort pouch dalam menjaga kualitas produk sate Padang dengan menganalisis sifat fisik, kimia, dan mikrobiologi sate Padang yang dikemas dalam kemasan retort pouch kemudian disimpan selama 21 hari. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) dengan 2 faktor dan 4 ulangan. Nilai pH dan Total Plate Count (TPC) dipengaruhi secara signifikan oleh interaksi suhu dan waktu penyimpanan, namun variabel lainnya tidak. Nilai pH menurun secara signifikan (p<0,05) setelah 14 hari penyimpanan pada suhu ruang dan suhu dingin. Nilai TPC produk masih berada di bawah nilai maksimal yang ditentukan SNI hingga penyimpanan 21 hari. Aktivitas air mengalami penurunan pada hari ke 7 dan 14 penyimpanan namun meningkat kembali ke nilai awal setelah 21 hari penyimpanan. Nilai MDA meningkat signifikan setelah penyimpanan 21 hari (p<0,05). Aktivitas antioksidan menurun secara signifikan (p<0,05) hingga penyimpanan 14 hari, namun meningkat kembali setelah 21 hari penyimpanan. Kesimpulan penelitian ini yaitu pengemasan sate Padang dalam kemasan retort pouch mampu mempertahankan kualitas mikrobiologi dan aktivitas antioksidan hingga 21 hari penyimpanan pada suhu ruang dan suhu dingin, namun belum mampu menghambat pembentukan MDA.
Keyword: Padang satay, retort pouch, storage, temperature

Judul: Pengaruh Jenis Kemasan Dan Suhu Penyimpanan Terhadap Kesegaran Dan Kualitas Buah Salak Padangsidimpuan (Salacca sumatrana)
Abstrak: This study aims to obtain the storage temperature and type of packaging which suitable for salak Padangsidimpuan. The research was conducted in two stages, i.e. preliminary research and primary research. Preliminary research carried out by measuring the initial quality (total weight lose, perishable fruit, water content, total titrated acid, total soluble solids, vitamin C and organoleptic). The results and than are used as initial data to conduct primary research. Primary research was conducted by coated 1 kg of salak and then packed with cartons, bamboo basket, plastic PE with cartons and plastic PE with bamboo basket. All samples were storaged in at 15oC and room temperature. Salak without treatment was also stored at room temperature as a control. Samples were analyzed the qualities every three days. Based on this research, physico-chemical characteristic of salak Padangsidimpuan showed that the water content was 78.12%, total titrated acid was 6.34%, total soluble solids was 15oBrix, vitamin C was 1.87 mg/100 g fruit, the preference score for color was 4, aroma was 4, flavor was 3, texture was 3 and general acceptance was 3. Based on the ANOVA analysis, Duncan test and “t” test, can be concluded that salak Padangsidimpuan were stored at a temperature of 15oC hold maximum of 30 days, with cartons, bamboo basket, plastic PE with cartons and plastic PE with bamboo basket. However the best condition of packaging resulted from this research was bamboo basket in 15oC.
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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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