Judul: Physical, Chemical. Microbiological Quality of Buffalo Milk Curd from Bukittinggi and Isolation of Lactic Acid Bacteria
Abstrak: Dadih adalah produk fermentasi susu kerbau tradisional dalam tabung bambu dari Sumatera Barat. Proses fermentasi dilakukan oleh Bakteri Asam Laktat (BAL) yang secara alami terdapat pada susu kerbau. Penelitian ini bertujuan untuk mengevaluasi kualitas fisik, kimia dadih dan mikrobiologi serta mengisolasi bakteri asam laktat dari dadih susu kerbau asal Bukittinggi Sumatera Barat. Dari penelitian yang telah dilakukan didapatkan hasil pada uji nilai pH, aktivitas air (aw), kadar air, dan kadar protein menunjukkan bahwa dadih susu kerbau asal Bukittinggi tidak berpengaruh nyata (P>0,05). Data penelitian menunjukkan bahwa dadih susu kerbau berpengaruh nyata (P<0,05) terhadap peubah kadar lemak, kadar abu, total BAL, total E.coli, dan total mikroba yang dihasilkan. Hasil identifikasi menunjukkan bahwa dadih susu kerbau asal Bukittinggi yang di dapat berupa Gram positif berbentuk basil dan kokus, homofermentatif, dan katalase negatif., Dadih is a traditional fermented product of buffalo milk in a bamboo tube from West Sumatra. The fermentation process is carried out by lactic acid bacteria (LAB) naturally present in buffalo milk. This study aims to evaluate the physicochemical quality and microbiology and isolate LAB from dadih. From the research that has been done, the results on the pH, water activity test (aw), water content, and protein content show that the curd from Bukittinggi buffalo milk has no significant effect (P> 0.05). The research data showed that the curd of buffalo milk had a significant effect (P<0.05) on the variables of fat content, ash content, total LAB, total E.coli, and total microbes. The results of the identification showed that the curd from buffalo milk from Bukittinggi which was obtained was gram-positive in the form of bacilli and cocci, homofermentative, and catalase negative.
Keyword: bacteria, buffalo, curd, lactic, milk

Judul: Pembuatan Starter Kering Bakteri Asam Laktat dan Pengaruhnya terhadap Karakteristik Dadih Susu Sapi yang Dihasilkan.
Abstrak: Dadih is a traditional food from West Sumatera resulted from natural fermentation of buffalo milk. This natural fermentation process involves a number of microorganisms, including gram-positive and gram-negative bacteria. The presence of gram negative bacteria that are pathogenic can become an obstacle to get safe and healthy food product to consume and easy in the marketing of products, due to the security aspect is less reliable. The processing through a more controlled fermentation process using lactic acid bacteria starter without involving the bacterial pathogens are expected to improve the quality of the resulting dadih. The provision of culture with the preservation in the dry form will facilitate the handling of starter cultures, so that the fermentation is more controlled and the product quality is more assured. Besides that, the availability of dry starter cultures will facilitate the distribution and transportation of starter cultures because dry starter cultures can be sent for long distances without losing the activity of Lactic acid bacteria and have a long storage. Raw materials used in the manufacture of dadih in West Sumatera derived from buffalo milk. The availability of buffalo milk is very limited, that, the alternative used is cow modified with skim milk and jelly therefore it is expected produce Dadih which has the characteristic similar with dadih from buffalo’s milk. This study aimed to verify the making of dry starter of lactic acid bacteria (the combination Streptococcus thermophilus and Lactobacillus casei also Lactobacillus bulgaricus and Lactobacillus casei) and its effect towards the characteristic of resulting cow’s milk dadih. Various analytical results indicate that the interaction of combinations of lactic acid bacteria starter and concentration of dried starter powder of lactic acid bacteria significantly affect to the pH value and moisture content of dadih. interaction of a combination of lactic acid bacteria starter and dried starter powder concentration of lactic acid bacteria did not influence significantly to the value of titrable acid total, viscosity, ash content, and the total amount of lactic acid bacteria in dadih. Friedman test results showed that the assessment of panelists for color, aroma, taste, texture, and general acceptance of dadih was not significantly different. Based on weighting method for the determination of the best dadih products, showed that dadih fermented by a combination of starter S. thermophilus: L. casei (1 : 2) as much as three grams of powder has the highest weight value. Thus, the recommendation of the best dadih product is dadih product fermented by a combination of starter S. thermophilus : L. casei (1: 2) as much as three grams of dried starter powder. Microbiological test results showed that the lowest total lactic acid bacteria contained in dadih products, that is 8.4 x 109 CFU/ml. Thus, the dadih is eligible as fermented milk for the minimum amount of total lactic acid bacteria ranged 106-109 CFU/ml (Sari, 2007).
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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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