Judul: Physicochemical Properties and Organoleptic Test of Yogurt with The Addition of Red Dragon Fruit Juice (Hylocereus polyrhizus) as an Antioxidant
Abstrak: Yogurt merupakan produk susu dan memiliki rasa asam untuk meningkatkan rasa asam ditambahkan perisa alami yaitu sari buah naga merah . Buah naga merah merupakan buah yabg mengandung antioksidan. Penelitian ini bertujuan untuk memanfaatkan yogurt dengan penambahan sari buah naga merah sebagai antioksidan alami dan mengetahui sifat fisikokimia yogurt yang dihasilkan dari penambahan berbagai kadar sari buah naga merah meliputi ph, aw, viskositas dan titrasi total asam. Hasil yang diperoleh diharapkan dapat dijadikan acuan dalam pembuatan yogurt buah naga merah yang memiliki sifat fisikokimia sesuai dengan yang diharapkan. Rancangan yang digunakan dalam analisis data penelitian ini adalah Rancangan Acak Lengkap (RAL) yang kemudian juga dilakukan pengujian Tukey Test. DataOrganoleptik diuji menggunakan uji statistik non parametrik Kruskal-Wallis. Hasil yang diperoleh diharapkan dapat dijadikan acuan dalam pembuatan yogurt buah naga merah yang memiliki sifat fisikokimia sesuai dengan yang diharapkan., Yogurt is a dairy product and has a sour taste to increase the sour taste, natural flavor is added, namely red dragon fruit juice. Red dragon fruit (Hylocereus polyrhizus) is a fruit that contains antioxidants. This study aims to utilize yogurt with the addition of red dragon fruit juice as a natural antioxidant and determine the physicochemical properties of yogurt produced from the addition of various levels of red dragon fruit juice including ph, aw, viscosity and total acid titration. The results obtained are expected to be used as a reference in making red dragon fruit yogurt that has physicochemical properties as expected. The design used in the analysis of this research data is a completely randomized design (CRD) which is then also tested by Tukey Test. Organoleptic data was tested using the Kruskal-Wallis non-parametric statistical test. The results obtained are expected to be used as a reference in making red dragon fruit yogurt that has physicochemical properties as expected.
Keyword: antioxidant, hylocereus polyrhizus, milk, yogurt

Judul: Physical and Organoleptic Properties of Probiotic Yogurt With The Addition of Red Fruit (Pandanus conoideous L.).
Abstrak: Yogurt can be made from homogenized milk, low-fat milk or skimmed milk with the addition of powdered milk. Starter culture commonly used in yogurt is Lactobacillus bulgaricus and Streptococcus thermophillus can not survive in environments with high acidity, so probiotics needed. One of the fruits that can be used in the process of making yogurt is red fruit (Pandanus Conoideus L). The observed physical characteristics consist of pH, viscosity, total acid concentration and water activity (aw) and organoleptic arachnids observed consisting of color, flavour, aroma and consistency. This research using a complete randomized design (RAL. The results showed that the addition of red fruit has a real effect (P<0.05) on pH, viscosity and total acid titrated and organoleptic test shows the addition of red fruit has a noticeable effect on color, flavour, aroma and viscosity in hedonic quality tests, then in hedonic tests affect aroma and flavour. Based on the results of yogurt testing with the addition of 2.5% this is the closest to control and acceptable to indonesian national standards (SNI)., Yogurt dapat dibuat dari susu yang telah dihomogenisasi, susu berkadar lemak rendah atau susu skim dengan penambahan susu bubuk. Kultur starter yang biasa digunakan dalam yogurt yaitu Lactobacillus bulgaricus dan Streptococcus thermophillus tidak dapat bertahan pada lingkungan dengan keasaman yang tinggi, sehingga diperlukan probiotik. Salah satu buah yang dapat ditambahkan adalah buah merah (Pandanus Conoideus L). Karakteristik fisik yang diamati terdiri atas pH, viskositas, total asam tertitrasi dan aktivitas air (aw) serta karakteristik organoleptik yang diamati terdiri atas warna, flavour, aroma dan kekentalan. Penelitian dilakukan dengan menggunakan rancangan acak lengkap (RAL). Hasil penelitian menunjukan bahwa penambahan buah merah berpengaruh nyata (P<0,05) terhadap pH, viskositas dan total asam tertitrasi. Uji organoleptik memperlihatkan penambahan buah merah berpengaruh nyata terhadap warna, flavour, aroma dan kekentalan pada uji mutu hedonik, lalu pada uji hedonik berpengaruh pada aroma dan flavour. Berdasarkan hasil pengujian yogurt dengan penambahan 2,5% ini yang paling mendekati dengan kontrol dan memenuhi standar nasional Indonesia (SNI).
Keyword: yogurt, red fruit, probiotic, characteristic physic, characteristic organoleptic

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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