Judul: Antioxidant Activity, Characterization,  and Organoleptic Test of Goat's Milk Yogurt with Addition of Purslane Extract
Abstrak: Yogurt susu kambing merupakan salah satu produk pangan fungsional yang memiliki potensi sebagai sumber antioksidan yang diperlukan oleh tubuh. Pada penelitian ini yogurt susu kambing dimaksimalkan potensinya dengan penambahan ekstrak krokot (Portulaca oleracea) yang berasal dari Banyumas, Jawa Tengah. Penelitian ini bertujuan menentukan formula yogurt susu kambing dan ekstrak krokot yang optimum berdasarkan nilai aktivitas antioksidan tertinggi serta karakteristik yang sesuai dengan SNI. Metode penelitian meliputi ekstraksi, formulasi yogurt, karakterisasi fisik dan kimia, uji organoleptik, dan uji proksimat. Perlakuan terdiri atas F1 (susu kambing tanpa ekstrak krokot), F2 (susu kambing + 2.5% ekstrak krokot), F3 (susu kambing + 5% ekstrak krokot), F4 (susu kambing + 7.5% ekstrak krokot), dan F5 (susu kambing + 10% ekstrak krokot). Hasil penelitian menunjukkan bahwa yogurt formula F2 sebagai yogurt yang paling optimum dengan karakteristik fisik, organoleptik, dan proksimat yang sesuai dengan SNI serta aktivitas antioksidan yang tinggi. Simpulan penelitian ini yaitu F2 merupakan yogurt hasil formulasi dengan karakteristik terbaik., Goat milk yogurt is one of the functional food product that have the potential as a source of antioxidants needed by the body. In this study, the potency of goat's milk yogurt was maximized by the addition of purslane extract (Portulaca oleracea) from Banyumas, Central Java. The aim of this study was to determine the optimum formula for goat's milk yogurt and purslane extract based on the highest antioxidant activity value and characteristics according to SNI. The research steps consisted of extraction, yogurt formulation, physical and chemical characterization, organoleptic test, and proximate test. The treatments consisted of F1 (goat's milk without purslane extract), F2 (goat's milk + 2.5% purslane extract), F3 (goat's milk + 5% purslane extract), F4 (goat's milk + 7.5% purslane extract), and F5 (goat's milk + 10% purslane extract). The results showed that the yogurt formula F2 was the most optimum yogurt with physical, organoleptic, and proximate characteristics in accordance to SNI and the high antioxidant activity. It was concluded that F2 was yogurt with the best characteristics.
Keyword: Antioxidant, DPPH, Formulation, Goat's Milk Yogurt, Portulaca  oleracea

Judul: Physical and Organoleptical Properties of Goat Milk Probiotic Yogurt with Addition of Red Fruit (Pandanus conoideus)
Abstrak: Yogurt susu kambing merupakan jenis minuman yang berasal dari susu kambing etawah yang memiliki ciri rasa asam, dan segar dari proses fermentasi. Buah merah merupakan tumbuhan endemik Papua. Buah merah membantu penyembuhan penyakit, termasuk kanker dan HIV/AIDS. Penelitian ini bertujuan menganalisis sifat fisik dan organoleptik yogurt susu kambing dengan penambahan ekstrak buah merah. Taraf pemberian ekstrak buah merah tersebut adalah 0% (P0), 2,5% (P1) dan 5% (P3). Penelitian ini menggunakan rancangan acak lengkap (RAL) dengan tiga kali pengulangan. Pengujian sifat fisik adalah nilai pH, nilai aw, viskositas dan total asam tertitrasi (TAT). Pengujian sifat organoleptik yang dianalisis adalah flavour, warna, aroma, dan tekstur. Data sifat fisik dianalisis dengan ANOVA satu faktor dan diuji lanjut dengan uji Duncan, hasil menunjukkan bahwa perbedaan penambahan ekstrak buah merah pada yogurt berpengaruh nyata (P<0,05) pada pH. Data sifat organoleptik dianalisis dengan uji non parametrik Kriskal-wallis dan diuji lanjut dengan Mann Whitney hasil hedonik menunjukkan berpengaruh nyata (P<0,05) pada parameter warna, sedangkan pada mutu hedonik berpengaruh sangat nyata (P<0,01) pada warna, aroma, flavor, dan kekentalan., Goat milk yogurt is a type of drink derived from goat's milk etawah which has a sour taste, and fresh from the fermentation process. Red fruit is a plant endemic Papua. Red fruit helps cure diseases, including cancer and HIV / AIDS. The research was aimed to analyze the physical and organoleptical properties of goat's milk yogurt with the addition of red fruit extract. Those levels consisted the control 0% (P0), 2,5%(P1), and 5%(P2) of red fruit extract. The research used completely randomized design (CRD) with three replications. The observed variables of physical properties were pH, aw, viscosity and total acid titrated (TAT). The observed organoleptic properties were flavor, color, aroma, and texture. Physical data were analyzed by one-factor ANOVA and further tested by Duncan test, the results showed that the difference in the addition of red fruit extract to yogurt had a significant effect (P <0,05) on pH. Organoleptic properties data were analyzed by non-parametric Kruskal-wallis test and further tested with Mann Whitney, the hedonic results showed a significant effect (P<0,05) on color parameters, while the hedonic quality had a very significant effect (P<0,01) on color, aroma, flavor and viscosity.
Keyword: buah merah, fisik, organoleptik, yogurt susu kambing

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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