Judul: Pengaruh Penambahan Jenis Susu terhadap Karakteristik Yogurt Kacang Kedelai (Soygurt)
Abstrak: Soygurt is fermented soy milk products are made by using lactic acid bacteria, that are Streptococcus thermophilus and Lactobacillus bulgaricus. The aim of this research were to determine the effect of adding kind of milk on characteristics, physichochemical, and organoleptic of soygurt. This research were divided into three stages, which are 1) Soy milk production, 2) Soygurt production, and 3) physicochemical analysis and sensory evaluation. The obtained data were treated by analysis of variance followed by Duncan’s test. The results of this research indicate that addition of kind of milks as much as 2%, 4%, 6%, and 8% give significant effect on pH value, total lactic acid, viscosity, texture, aroma, taste, and acceptability (overall). However, the addition of kind of milk did not give significant effect on appearance of soygurt. Best formula of this research is soygurt with the addition of skim and full cream milk as much as 6%.
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Judul: Pengaruh Penambahan Susu Full cream terhadap Mutu Soygurt
Abstrak: Soygurt is the fermented product of lactic acid bacteria on soybean extract. Soygurt are generally has an unpleasant odor typically preferred as soy beans. Soygurt has a high nutrient content which is proximately same as yogurt. One attempt of the addition of full cream milk is to improve taste. This research was conducted to see the effect of full cream milk addition to the acceptance rate of set soygurt. Soygurt on the research is using the bacteria Streptococcus thermophilus and Lactobacillus bulgaricus. The addition of full cream milk is done by four different concentrations (0%, 3%, 5%, and 7%). The making of soybean extract is using modified Illinois method. Soybean extract added sugars as much as 6% and then pasteurized. After that, the extract of soy is cooled down to temperatures of 450C and innoculated starter culture as much as 5%. Incubation is done for 16 to 18 hours at a temperature of 370C. The results can be concluded that the addition of full cream milk on soygurt’s characteristics against influential include pH, total of lactic acid, viscosity, and organoleptic (appearance, texture, aroma, flavor, and overalls. The treatment with the addition of full cream milk by as much as 5% and 7% did not different. Product with the addition of full cream milk as much as 7% was chosen as the best because it has the highest organoleptic score compared to the three.
Keyword: full cream milk., lactic acid fermentation, soygurt

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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