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: Optimation Formula Yoghurt of Goat Milk and Mushroom with Mixture Design and Potential Functional Properties
Abstrak: Etawah Breed goat milk has not been widely consumed in Indonesia because it has distinctive characteristic of prengus smell so that it is not appreciated by the public, and the lack of public knowledge concerning the benefits of goat’s milk. Milk fermentation process causes the formation of distinctive flavor as the result of activities from lactic acid bacteria, such as acetaldehyde and diacetyl compounds that can reduce or even eliminate the prengus smell. Conventionally, the bacteria commonly used in the formulation of yoghurt were Lactobacillus bulgaricus and Streptococcus thermophilus. However, it was later discovered that the bacteria are not sufficient to maintain the health of digestive tract. To increase the functional value of the yoghurt product, probiotic bacteria should be added. Lactobacillus acidophilus is one of probiotic bacteria that can be added in the making of yoghurt. White oyster mushrooms and shiitake mushrooms are two types of mushrooms well known by the people of Indonesia with affordable prices and potential prebiotic. The fiber and polysaccharides content in these two mushrooms, makes the mushrooms as potential prebiotic. Probiotic yoghurt enriched with the addition of prebiotics produces the product known as synbiotic yoghurt. The formulation of yoghurt can be performed by adding full cream and skim milk. Mixture design is a collection of mathematical and statistical techniques that are useful on modeling and analysis of the problem of the response that is influenced by several variables. The method serves to determine the optimum formula. Indonesia has a huge wealth of biodiversity, including medicinal plants and spices. The spices that have been known for a long time in Indonesia are ginger, cloves, anise and cinnamon. The addition taste in the form of spices syrup into yoghurt, will create a new taste variations. This research aims to assess the formulation of goat milk yoghurt to get the optimum formula using mixture design and determining the functional characteristics of yoghurt optimum formula based on resistance to gastric pH, antimicrobial activity based on E. coli, and amino acid content. This research also aims to examine the effects of spices syrup addition on the preference of the yoghurt. The result showed that the optimum formula was a mixture of 0.5% white oyster mushroom, 3% skim milk, 96% goat skim milk. The optimum formula has pH of 4.30, viscosity of 6200 cP, total titrated acid 1.08%, lactic acid bacteria 1.1 x 1010 cfu/ml. For a functional food criteria of 9.5 x 105 cfu/ml the yoghurt resists based on gastrointestinal tract pH, has 10.9 mm antimicrobial activity based on E.coli and content amino acid. The result of hedonic test that the addition of spices syrup as a topping that the highest score of the taste properties were 4.37 for 4 ml addition of ginger syrup; 4.13 for 6 ml addition of mixture of cloves-cardamom-anise syrup, and 4.23 for 6 ml addition of mixture of cloves-cardamom-cinnamon syrup. Based on these results, the consumer preference was still at the level of netral.
Keyword: goat milk, lactic acid bacteria, mixture design, mushrooms, yoghurt

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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