Judul: Physicochemical Characteristics, Nutritional Value And Organoleptic Of Synbiotic Yoghurt Gembili Flour (Dioscorea esculenta L.)
Abstrak: Yoghurt merupakan pangan fungsional dari susu yang memiliki variasi jenis, tekstur, dan rasa. Salah satunya adalah yoghurt sinbiotik yaitu susu hasil fermentasi mikroba probiotik dan ditambah prebiotik. Prebiotik terdapat diberbagai bahan pangan, salah satunya umbi gembili (Dioscorea esculenta L.) dengan kandungan inulin sebesar 14,77%. Penelitian bertujuan menganalisis karakteristik fisikokimia, nilai gizi dan organoleptik yoghurt sinbiotik tepung gembili. Penelitian menggunakan Rancangan Acak Lengkap (RAL) untuk mengamati karakteristik fisikokimia (pH, Aw, viskositas, dan total asam titrasi (TAT)), nilai gizi (protein, lemak, air, abu, karbohidrat, gula, dan serat pangan (dietary fiber) serta uji organoleptik. Penambahan tepung gembili berpengaruh nyata (P<0,05) terhadap pH, viskositas, kadar lemak, air, abu, karbohidrat dan serat pangan. Uji hedonik dan mutu hedonik berpengaruh nyata (P<0,05) terhadap warna, rasa, dan tekstur. Formulasi terbaik yaitu penambahan tepung gembili 6% dengan kandungan serat pangan sebesar 4,22% serta telah memenuhi SNI 2981:2009 tentang yoghurt., Yoghurt is a functional food made from milk that comes in various types, textures, and flavors. One is synbiotic yoghurt, which is milk fermented by probiotic microorganisms and supplemented with prebiotics. Prebiotics can be found in various food ingredients, and one of them is the gembili tuber (Dioscorea esculenta L.) tuber, with an inulin content of 14,77%. The research aims to analyze the physicochemical characteristics, nutritional value, and organoleptic of synbiotic yoghurt by adding gembili flour. The research employs a completely randomized design (RAL) to observe the physicochemical characteristics (pH, Aw, viscosity, and total titratable acid (TAT)), nutritional value (protein, fat, moisture, ash, carbohydrates, sugar, and dietary fiber), and organoleptic test. Adding gembili flour significantly affects (P<0.05) the pH, viscosity, fat content, moisture, ash, carbohydrates, and dietary fiber. The hedonic test and hedonic quality significantly affect (P<0,05) the color, taste, and texture. The best formulation is the addition of 6% gembili flour with a dietary fiber content of 4,22%, which meets the Indonesian National Standard (SNI 2981:2009) for yoghurt.
Keyword: gembili flour, nutritional value, physicochemistry, organoleptic, yoghurt

Judul: Formulasi Yoghurt Sinbiotik dengan Penambahan Puree Pisang dan Inulin
Abstrak: Recently, one of functional food which has become popular in the market is probiotic, prebiotic and or synbiotic yoghurt. Synbiotic yoghurt is fermented milk containing both probiotic and prebiotic. Many inovations in yoghurt production by food scientists were developed by adding local ingredients. Banana is abundant local comodity in West Java. Besides having high nutrient, banana also contains 0.5-1.4 g/100g inulin which is a good source of prebiotic. The purpose of this research was to make synbiotic yoghurt containing banana puree and inulin as a functional food using local comodity. In this research, the synbiotic yoghurt was made from banana puree added with Lactobacillus casei as probotic and commercial inulin as prebiotic. This research was divided into three steps, first step was to obtain an optimum ratio between skim milk and banana puree to produce an acceptable yoghurt by sensory evaluation (hedonic ranking test), second step was to obtain an optimum one by addition of commercial inulin to the previous formula based on sensory evaluation (hedonic rating test), and the third step was to determine chemical and microbiology quality of the synbiotic yoghurt. Result of the first step of the research, suggested that skim milk : banana puree ratio = 1:1 was the most preferred product by panelists. Addition of 2% inulin yoghurt resulted in the highest rank yoghurt likened by the panelists. Based on the chemical and microbiological analysis, the resulted synbiotic yoghurt complied standard requirement yoghurt in Indonesia (SNI 01.2981-2009). The synbiotic yoghurt contained BAL 3.6 x 109 cfu/ml probiotic lactic acid bacteria and approximately about 3.88 g/100g prebiotic. Based on proximate analysis, the fat content of this synbiotic yoghurt is less than 5% thus it can be classified as non fat yoghurt.
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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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