Judul: Pengaruh Jenis Bakteri Asam Laktat Terhadap Kualitas Dadih Sapi Probiotik Selama Penyimpanan dalam Suhu Ruang dan Suhu Rendah
Abstrak: Dadih merupakan salah satu produk susu fermentasi asli dari Sumatra Barat Indonesia. Dadih dibuat dengan memfermentasi susu kerbau secara alamiah di dalam bambu selama 48 jam. Fermentasi dadih melibatkan berbagai jenis mikroorganisme, sehingga hasil yang didapat tidak seragam dengan mutu yang tidak stabil. Komersialisasi dadih cukup potensial untuk dikembangkan menjadi makanan fungsional (functional food) sebagai produk probiotik. Penggunaan susu kerbau sebagai bahan baku dadih perlu dipertimbangkan, mengingat jumlah susu kerbau di Indonesia yang semakin hari semakin sedikit. Penelitian ini menggunakan aternatif bahan baku susu sapi yang memiliki ketersedian bahan lebih banyak. Selain itu susu sapi difermentasi menggunakan starter bakteri asam laktat (BAL) Lactobacillus acidophilus, Lactobacillus casei, dan Bifidobacterium longum yang diisolasi dari dadih susu kerbau. Penelitian ini bertujuan untuk mendapatkan starter bakteri asam laktat (BAL) terbaik untuk menghasilkan dadih sapi probiotik dalam penyimpanan selama satu minggu di suhu ruang (27oC) dan selama 21 hari di suhu rendah (4oC). Starter BAL terbaik ditentukan berdasarkan parameter uji yang meliputi uji pH, total asam tertitrasi (TAT), total BAL, ketahanan BAL terhadap garam empedu, ketahanan BAL pada pH rendah dan pengujian organoleptik. Rancangan percobaan menggunakan RAK dengan dua kali ulangan. Perlakuan yang digunakan terdiri atas dua faktor, yaitu formulasi starter BAL yang terdiri atas 12 taraf perlakuan dan lama penyimpanan yang terdiri atas tiga taraf (hari ke-0, 4 dan 7) pada suhu ruang (27oC) dan empat taraf (hari ke-0, 7, 14 dan 21) pada suhu rendah (4oC). Dadih sapi yang disimpan pada suhu ruang menunjukkan bahwa formula starter BAL dan lama penyimpanan mempengaruhi secara nyata (P≤0,05) terhadap pH dan TAT. Formula starter BAL mempengaruhi total BAL secara nyata sedangkan faktor lama penyimpanan mempengaruhi ketahanan BAL terhadap garam empedu secara nyata pada penyimpanan suhu ruang. Pada uji ketahanan BAL pada pH rendah selama penyimpanan suhu ruang, semua faktor tidak mempengarhi secara nyata. Dadih sapi yang disimpan pada suhu rendah menunjukkan bahwa formula starter BAL dan lama penyimpanan mempengaruhi secara nyata (P≤0,05) terhadap pH, TAT dan total BAL. Faktor formula BAL mempengaruhi ketahanan BAL terhadap garam empedu secara nyata (P≤0,05) selama penyimpanan suhu rendah, sedangkan pada ketahanan BAL pada pH rendah tidak dipengaruhi secara nyata oleh semua faktor perlakuan. Ketahanan BAL terhadap garam empedu pada dadih yang disimpan pada suhu ruang berkisar antara 0.003% - 51,333% sedangkan pada suhu rendah berkisar antara 0.106% - 90,253%. Ketahanan BAL pada pH rendah yang disimpan pada suhu ruang berkisar antara 1% - 302% sedangkan pada suhu rendah berkisar antara 0,135% - 302%. Dari hasil penelitian ini dapat disimpulkan bahwa formula starter Lactobacillus casei : Bifidobacterium longum (2:1) memiliki keunggulan pada warna, aroma, rasa, penerimaan umum (uji hedonik) dan tahan terhadap garam empedu maupun pH rendah (uji kelayakan probiotik). Selain itu, penelitian ini menunjukkan bahwa dadih sapi dari semua formula starter BAL merupakan produk probiotik karena mampu mempertahankan viabilitas BAL >106 CFU/ml setelah dilakukan pengujian probiotik ketahanan BAL terhadap garam empedu dan pada pH rendah.
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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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