Judul: Pengaruh Waktu Penyimpanan Ekstrak Rennet Abomasum Domba Lokal terhadap Kualitas Keju
Abstrak: The study was aimed to examine the storage effect of rennet extracted from abomasum of local sheep on the texture and organoleptic qualities of cheese including color, flavor, salty taste, and bitter taste. Each five samples of crude rennet extract was stored for 2 weeks and 24 weeks respectively. The rennet extract was then used as milk clotting agent in cheese making process. Streptococcus thermophilus and Lactobacillus bulgaricus were used as starter in those process. The fresh cheese was coated with beeswax and ripened for 20 days in refrigerator. The ripened cheese was analyzed for the quality. The texture was analyzed by using warner blatzer shear (INSTRON®) and the data were evaluated with completely randomized design (CRD). The result showed that both time storage of rennet extract were not significantly influence on cheese texture (P<0.05). The organoleptic tests of color, flavor, salty taste, and bitter taste were rated by 25 panelists and then the data were analyzed with Friedman test. The time storage of rennet extract resulted variation on organoleptic quality of cheese. Descriptive statistical analyses provided information that each panelist has varied preferences on cheese samples. It can be concluded that the storage of rennet extract had no significantly influence on the texture of cheese and provided variation on organoleptic test.
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Judul: Pengaruh Penyimpanan Beku terhadap Kualitas Rennet yang Diekstrak dari Abomasum Domba Lokal
Abstrak: Penelitian ini bertujuan untuk mengetahui pengaruh penyimpanan beku terhadap kualitas protein rennet hasil ekstraksi mukosa fundus abomasum domba lokal umur dewasa muda (5-12 bulan). Sampel yang digunakan adalah delapan ekstrak abomasum domba lokal yang dibagi kedalam dua kelompok yaitu kelompok yang tidak disimpan (N = 4) dan kelompok yang disimpan selama sepuluh bulan (N = 4). Ekstraksi dilakukan menggunakan modifikasi dari metode Qadri et al. (1962). Analisa kualitas rennet dilakukan berdasarkan uji koagulasi susu (Scott 1981) dan sodium dodecyl sulphate polyacrilamide gel electrophoresis (SDS-PAGE). Parameter yang diamati adalah bentuk koagulan dan waktu yang dibutuhkan untuk mengkoagulasi susu, serta gambaran pita protein. Hasil uji koagulasi susu menunjukkan bahwa kedua perlakuan mampu mengkoagulasi susu dengan bentuk koagulan (curd) yang padat dan waktu koagulasi dari kedua perlakuan tersebut tidak berbeda nyata (P > 0,05). Hasil SDS-PAGE menunjukkan bahwa pada rennet yang disimpan selama sepuluh bulan terlihat pita-pita yang lebih tebal dan gelap dibandingkan dengan rennet yang tidak disimpan. Kata kunci: rennet, penyimpanan beku, koagulasi susu, SDS-PAGE.
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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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