Judul: Validasi Sekunder Metode Uji Staphylococcus Aureus Pada Produk Susu Cair
Abstrak: Staphylococcus aureus adalah sekumpulan bakteri penghasil enterotoksin yang berbentuk bulat seperti anggur, non motil, pembentuk spora dan bersifat Gram positif. Bakteri ini biasa digunakan untuk mengidentifikasi tingkat sanitasi dalam berbagai produk makanan dan minuman. Tujuan dari penelitian ini adalah untuk memverifikasi metode uji analisis Staphylococcus aureus secara kuantitatif pada susu cair. Metode uji pada penelitian ini mengacu pada SNI 2332.9:2011. Karakteristik kinerja yang dilakukan meliputi parameter akurasi (derajat keterulangan kembali) dan presisi (RSD). Hasil menunjukkan nilai derajat keterulangan kembali dari metode ini sebesar 106.23 - 124.30 % (inokulum 101) dan 84.55 - 115.57 % (inokulum 102), serta nilai RSD sebesar 0.00173 % (inokulum 101) dan 0.0422 % (inokulum 102). Dapat disimpulkan bahwa hasil metode pengujian bakteri Staphylococcus aureus pada susu cair memiliki karakteristik kinerja yang baik. Serangkaian uji tambahan seperti uji koagulase menggunakan plasma kelinci dan staphylase test kit juga dilakukan, dan hasil menunjukkan bakteri yang tumbuh setelah dilakukan spiking pada susu cair adalah bakteri Staphylococcus aureus.
Keyword: Staphylococcus aureus, validasi, karakteristik kinerja, susu cair

Judul: Validasi dan verifikasi metode analisis bakteri asam laktat pada produk susu
Abstrak: Lactic acid bacteria (LAB) is a group of bacteria that capable converting carbohydrates (glucose) into lactic acid and mostly grow at facultatif anaerobic condition. At present, the most widely method used to enumerate LAB in some laboratory in Indonesia is incubation in aerob condition. In order to ensure that the method has a good performance, there is a need of method validation. Validation is the confirmation by examination and provision of objective evidence that particular requirements for specified intended use are fulfilled. The purpose of this study is to validate the quantitative method for enumeration of lactic acid bacteria. Two methods of enumeration of LAB in yoghurt were studied, i.e. ISO 7889-2003(E) as a reference method and SNI 2981-2009 as an alternative method. The principle of this method is to grow the facultative anaerobic bacteria in aerobic and anaerobic condition incubated for 3 days at 37 oC on MRSA media. The anaerobic condition was made using Anaxomat jar whose enrich with 10% CO2. The result obtained by these two method were compared. Therefore several parameters such as precision (RSD), relative accuracy, linearity, limit of detection, and limit of quantification were evaluated. The results showed that RSD of these methods between 0.44% and 3.03%, percent recovery of these methods between 97% and 101%, and limit of detection are 3 cfu/mL. It can be concluded that these two methods have good performance characteristics.
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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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