Judul: Microbial Population and Morphology of Mold, Yeast, and Lactic Acid Bacteria from Red Oncom and Black Oncom Bogor
Abstrak: Oncom merupakan pangan fermentasi kapang yang terdiri dari dua jenis, yaitu oncom merah dan oncom hitam, yang dibuat dengan menggunakan kapang dan bahan baku yang berbeda. Umumnya, oncom merah terbuat dari ampas tahu dengan kapang Neurospora sitophila, sedangkan oncom hitam terbuat dari bungkil kacang tanah dengan kapang Rhizopus oligosporus dan/atau Mucor. Penelitian ini bertujuan mengetahui populasi mikroba dan karakteristik morfologi dari isolat kapang, khamir, serta bakteri asam laktat yang berasal dari oncom yang diperoleh dari industri yang berbeda. Evaluasi juga dilakukan terhadap tekstur dan pH sampel oncom. Sampel yang dianalisis berasal dari tiga industri oncom merah dan dua industri oncom hitam di Bogor. Kelima industri oncom ini memiliki metode produksi yang berbeda-beda. Hasil analisis menunjukkan bahwa populasi mikroba oncom hitam lebih tinggi dibandingkan oncom merah. Oncom merah mengandung total mikroba 7,5–9,2 log CFU/g; total kapang dan khamir 6,0–7,2 log CFU/g; bakteri asam laktat (BAL) 7,2–8,4 log CFU/g; Enterobacteriaceae 7,0–8,7 log CFU/g; dan spora bakteri 2,8–6,1 log CFU/g. Sementara pada oncom hitam terdapat total mikroba sebesar 9,6–10,1 log CFU/g; total kapang dan khamir 8,0–8,8 log CFU/g; BAL 9,2–10,0 log CFU/g; Enterobacteriaceae 7,0–8,8 log CFU/g; dan spora bakteri 2,2–2,6 log CFU/g. Berdasarkan morfologi kapang, pada oncom merah terdapat Neurospora sp., Mucor sp., Acremonium sp., dan Cladosporium sp., sedangkan pada oncom hitam terdapat Rhizopus sp., Neurospora sp., Geotrichum sp. dan Penicillium sp.. Kapang Neurospora sp. terdapat pada kedua jenis oncom. Oncom merah menunjukkan tekstur yang lebih lunak dari pada oncom hitam, dengan nilai tingkat kekerasan berada pada kisaran 14,93–22,42 mm/5 detik, sedangkan nilai tingkat kekerasan pada oncom hitam sebesar 7,78–13,85 mm/5 detik. Ketiga sampel oncom merah memiliki nilai pH pada kisaran 5,41–5,84. Sementara nilai pH sampel oncom hitam S4 dan S5 sebesar 6,18 dan 4,71., Oncom is a mold fermented food consisting of two types, i.e., red oncom and black oncom, which are made using different molds and raw materials. Generally, red oncom is made from solid waste of tofu with Neurospora sitophila, while black oncom is made from peanut press cake with Rhizopus oligosporus and/or Mucor. The research objectives were to determine the microbial population and morphological characteristics of the isolates of mold, yeast, and lactic acid bacteria obtained from oncom samples and evaluate the texture and pH value of oncom samples. The samples are analyzed from three red oncom industries and two black oncom industries in Bogor. These five oncom industries have different production methods. The results of the analysis showed that total microbial count of black oncom was higher than red oncom. Red oncom contains total microbes, mold and yeast, lactic acid bacteria (LAB), Enterobacteriaceae, and bacterial spores were in the range of 7.5–9.2 log CFU/g, 6.0–7.2 log CFU/g, 7.2–8.4 log CFU/g, 7.0–8.7 log CFU/g, and 2.8–6.1 log CFU/g, respectively. Meanwhile, black oncom contains total microbes, mold and yeast, LAB, Enterobacteriaceae, and bacterial spores were in the range of 9.6–10.1 log CFU/g, 8.0–8.8 log CFU/g, 9.2–10.0 log CFU/g, 7.0–8.8 log CFU/g, and 2.2–2.6 log CFU/g. Based on mold morphology, red oncom contained Neurospora sp., Mucor sp., Acremonium sp., and Cladosporium sp., while black oncom contained Rhizopus sp., Neurospora sp., Geotrichum sp., and
Keyword: oncom hitam, oncom merah, pH, profil mikroba, tekstur

Judul: Variety of Rhizopus on Black Oncom Base Material
Abstrak: Oncom adalah makanan tradisional masyarakat di Jawa Barat. Oncom merupakan salah satu produk fermentasi campuran bungkil kacang tanah, ampas kelapa dan ampas tahu atau onggok oleh Rhizopus (Mucorales). Beragam spesies Rhizopus asal oncom hitam segar telah dilaporkan. Namun ragam Rhizopus asal bahan dasar oncom hitam belum pernah dilaporkan. Oleh sebab itu, penelitian ini bertujuan untuk menginventarisasi Rhizopus yang berasosiasi dengan bahan dasar oncom hitam dan membandingkannya dengan Rhizopus asal oncom segar. Bahan dasar oncom diambil dari satu pasar tradisional dan oncom segar diambil dari pengrajin oncom di kota Bogor, Jawa Barat. Kultur spora tunggal dari sporangium tunggal Rhizopus diidentifikasi berdasarkan suhu maksimum pertumbuhan koloni pada Agar Kentang Sukrosa setelah dua hari inkubasi dan ciri morfologinya. Suhu maksimum pertumbuhan semua kultur adalah antara 33 − < 42°C sehingga semuanya tergolong dalam kompleks spesies R. arrhizus/oryzae. Hasil identifikasi menunjukkan bahwa ciri strain yang diperoleh bervariasi. Pada semua bahan dasar oncom hitam terdapat R. arrhizus var. tonkinensis dan pada oncom hitam segar terdapat var. arrhizus. R. arrhizus var. arrhizus diduga merupakan hasil domestikasi dari R. arrhizus var. tonkinensis asal bahan dasarnya yang berubah ciri sporangiofor dan ciri kolumelanya. Perubahan ini diduga terjadi akibat penggunaan sedikit bahan fermentasi sebelumnya secara terus-menerus sebagai sumber inokulum., Oncom is a traditional food from West Java. Oncom is a fermented product of a mixture peanut meal, coconut pulp and tofu waste or onggok by Rhizopus (Mucorales). Various species of Rhizopus from fresh black oncom have been reported but variety of Rhizopus from black oncom has never been reported. This study aims to make inventory of Rhizopus associated with the basic ingredients and compare with fresh oncom. The basic ingredients are taken from traditional market and fresh oncom are taken from oncom craftsmen in Bogor, West Java. Single spore culture of single sporangium Rhizopus was identified based on the maximum temperature growth on Sucrose Potato Agar after two days of incubation and morphological characteristics. The maximum temperature for growth of all cultures was between 33 − < 42°C belonged to the species complex R.arrhizus/oryzae. The identification results showed that the characteristics of thestrains obtained varied. In all the basic ingredients there is R. arrhizus var.tonkinensis and in fresh black oncom there is var. arrhizus. R. arrhizus var.arrhizus is thought to be domestication of R. arrhizus var. tonkinensis originating from its basic material which changed its sporangiophore and columellar characteristics. This change thought to have occurred due to continuous use of a small amount of previously fermented material as a source of inoculum.
Keyword: Coconut meal, domestication, identification, onggok

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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