Judul: Karakteristik Fisik, Organoleptik, dan Fungsional Gel Cincau Hijau Manis (Premna oblongifolia Merr.) Terpasteurisasi.
Abstrak: Green grass jelly (Premna oblongifolia Merr.) can be processed into pasteurized green grass jelly product. The purpose of this study was to determine the type and concentration of sweeteners that could increase physical, organoleptic, and functional characteristics of pasteurized green grass jelly so the product would be more acceptable and have better characteristics. In this study, sucrose, sorbitol, and aspartame were used as sweeteners. The addition of sucrose with concentration of 12% showed the best physical characteristics and organoleptic results. Then, sucrose was replaced by aspartame and sorbitol in order to have low calorie sweetened green grass jelly. Sweetener equivalence organoleptic test was used to determine the sweetness level of the sweeteners that equaled 12% sucrose concentration. Aspartame and sorbitol concentrations that had sweetness level equaled 12% sucrose concentration were 0.05% and 13% respectively. Furthermore, the addition of sorbitol and aspartame did not have any significant impact on the physical and the organoleptic characteristics of the product. However, the functional characteristic analysis showed that sample with 0.05% aspartame concentration had the highest antioxidant capacity of 1.13 mgAEAC/100g and sample with 13% sorbitol concentration had the highest fenol of 156.90 mg GAE/100g. In conclusion the addition of sweeteners to green grass jelly can increase the physical, sensory, and functional characteristics of the product significantly.
Keyword: sensory properties, physical properties sweeteners, green grass jelly, Functional properties

Judul: Gel Cincau Hijau (Premna oblongifolia Merr.) Manis yang Diperkaya dengan Flavor dan Antioksidan Ekstrak Mint, Pala, dan Suji
Abstrak: Green grass jelly is a low-calorie food that contains many bioactive components. In the previous research, green grass jelly with addition of hydrocolloid and NaHCO3 had been made to maintain its physical characteristic after heat treatment. Addition of natural flavor can provide a variety of phytochemicals active components as source of antioxidant. The natural flavor that used in this study were nutmeg and mint. Sucrose (12%) & Suji (5%) were also added as sweetener & to maintain the color of green grass jelly. The purpose of this study was to obtain the best formulation of pasteurized green grass jelly with the addition of nutmeg, mint, and suji extracts. The selected formulation were 10% for mint and 7.5% for nutmeg based on physical analysis at texture, color, pH, and syneresis rate parameter as well as hedonic rating sensory evaluation. Characterization of functional properties showed total chlorophyll content, total phenol, and antioxidant capacity respectively were 0.0284 mg/g w.b, 25.8425 mg GAE/g w.b, and 0.3088 mg AEAC/g w.b for green grass jelly with mint flavor; 0.0311 mg/g w.b, 28.1736 mg GAE/g w.b, and 0.2912 mg AEAC/g w.b for green grass jelly with nutmeg flavor; and 0.0205 mg/g w.b, 17.9144 mg GAE/g w.b, and 0.1306 mg AEAC/g w.b for control (sweet green grass jelly without flavor). In comparison with control, addition natural flavor increased functional properties of green grass jelly in general. Total Plate Count result showed Total Plate Count was <2.5x102 CFU/g, this value in compliance with the requirement of SNI that is <1.0x104 CFU/g.
Keyword: suji, nutmeg, mint, green grass jelly, antioxidant

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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