Judul: Physicochemical Properties and Antioxidant Activity of Grilled Beef with Addition of Torch Ginger and 12 or 24 Hours Marinating Time
Abstrak: Marinasi daging sapi dengan bahan tinggi antioksidan umum digunakan untuk menghambat terjadinya oksidasi yang dapat menghasilkan senyawa toksik, seperti malondialdehida (MDA). Penelitian bertujuan menganalisis pengaruh penambahan kecombrang pada bumbu dengan lama marinasi 12 atau 24 jam terhadap sifat fisikokimia, aktivitas antioksidan dan MDA daging sapi panggang. Rancangan yang digunakan adalah rancangan acak kelompok (RAK) 2 faktor, dengan faktor pertama, yaitu penambahan bumbu marinasi (tanpa bumbu marinasi (kontrol), 0%, dan 10% bunga kecombrang) dan faktor kedua waktu marinasi (12 atau 24 jam). Hasil penelitian menunjukkan bahwa penambahan bumbu marinasi berpengaruh secara nyata terhadap pH, aktivitas antioksidan dan kapasitas antioksidan (p<0,05). Penggunaan bumbu marinasi dengan ataupun tanpa bunga kecombrang menghasilkan penurunan pH dan peningkatan aktivitas antioksidan dibanding kontrol (p<0,05). Lama waktu marinasi nyata meningkatkan pH daging sapi panggang (p<0,05). Kadar air, aktivitas air (aw) dan kadar MDA tidak menunjukkan perbedaan nyata akibat perlakuan yang diberikan. Kesimpulannya, lama marinasi baik dengan atau tanpa bunga kecombrang lebih efisien dilakukan selama 12 jam., Marinating beef using high antioxidant ingredients is commonly used to inhibit oxidation which can lead to forming toxic compunds, such as malondialdehyde (MDA). This study aims to determine the effect of adding marinade and torch ginger flower with marinating time of 12 or 24 hours on physicochemical properties, antioxidant activity and MDA value of grilled beef. This study used two factor completely randomized designs (CRD) with three treatments marinade formulas (without marinade, 0%, and 10% torch ginger flower) and marinating times (12 or 24 hours). The result showed that the addition of marinade significantly effected pH value, antioxidant activity and antioxidant capacity (p<0,05). The addition of marinade with or without torch ginger flower decreased the pH value and increased the antioxidant activity than the control (p<0,05). Marinating time significantly increased pH value of grilled beef. Water content, water activity (aw) and MDA value did not show any significant differences due to the treatment given. So, 12 hours marination with or without torch ginger flower showed the best result.
Keyword: antoxidant activity, grilled beef, torch ginger flower, marination, physicochemical properties

Judul: Physicochemical Properties and Antioxidant Activity of Grilled Beef with the Additional of Kecombrang and Different Marination Duration
Abstrak: Penelitian ini bertujuan menganalisis pengaruh penambahan bunga kecombrang pada bumbu dan waktu marinasi yang berbeda terhadap sifat fisikokimia (kadar air, aw, pH) dan aktivitas antioksidan daging sapi panggang. Penelitian ini menggunakan daging sapi bagian shortplate yang diiris dengan ketebalan 3,5 cm. Daging sapi panggang sebelumnya dimarinasi dengan bumbu tanpa kecombrang, atau bumbu yang ditambah kecombrang selama 30 atau 60 menit. Sebagai kontrol digunakan daging yang tanpa marinasi. Hasil penelitian menunjukkan bahwa penggunaan bumbu marinasi, baik dengan ataupun tanpa penambahan bunga kecombrang nyata menurunkan pH (p<0,05) dan meningkatkan aktivitas penghambatan terhadap DPPH serta kapasitas antioksidan (p<0,05) dibanding kontrol. Tidak ada perbedaan pH dan aktivitas antioksidan pada daging sapi yang dimarinasi dengan bumbu tanpa ataupun dengan penambahan bunga kecombrang. Tidak ada perbedaan antara lama marinasi 30 ataupun 60 menit pada semua peubah. Kesimpulannya adalah bahwa untuk efisiensi waktu, marinasi selama 30 menit menggunakan bumbu, baik tanpa maupun dengan penambahan bunga kecombrang merupakan lama marinasi terbaik untuk diaplikasikan., The aim of this study was to analyze the effect of kecombrang flowers addition to seasonings and different marination duration on physicochemical properties (moisture content, aw, pH) and antioxidant activity of grilled beef. This study used beef shortplate sliced with a thickness of 3.5 cm. The grilled beef is previously marinated using seasoning without or with kecombrang flowers for 30 or 60 mins. As a control, unmarinated meat was used. The results showed that the use of marinade, either with or without the addition of kecombrang flowers significantly reduced the pH (p<0.05) and increased the DPPH scavenging activity and antioxidant capacity (p<0.05) compared to the control. There was no difference in pH and antioxidant activity in marinated beef using seasonings with or without kecombrang flower addition. There was no difference between 30 or 60 mins marinations duration on all variables. The conclusion is that for time efficiency, marinating for 30 mins using seasoning, with or without kecombrang flower addition is the best marination duration to apply.
Keyword: antioxidant activity, grilled beef, marinade, marination duration, physicochemical properties

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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