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 and Antioxidant Activity of Grilled Beef with Different Seasoning Formulations and Marinated Time
Abstrak: Marinasi dengan bumbu kaya antioksidan dapat menghambat pembentukan senyawa berbahaya, seperti malonaldehida dan zat karsinogenik pada pembuatan daging panggang. Penelitian ini bertujuan menganalisis pengaruh penambahan kecombrang pada bumbu marinasi dan lama waktu marinasi terhadap sifat fisikokimia (kadar air, aw, pH), aktivitas antioksidan dan kadar malonaldehida daging panggang (grilled beef). Daging sapi dimarinasi menggunakan formula bumbu tanpa kecombrang dan formula bumbu dengan kecombrang selama 1 jam dan 12 jam sebelum dipanggang. Penambahan formula bumbu pada daging panggang berpengaruh nyata (P<0,05) terhadap nilai pH dan aktivitas antioksidan, namun tidak mempengaruhi kadar air, nilai aw, dan kadar MDA (malondialdehida). Penambahan formula bumbu mempengaruhi penampakan visual daging. Perbedaan waktu marinasi 1 jam dan 12 jam tidak memberikan pengaruh pada sifat fisikokimia dan aktivitas antioksidan daging sapi panggang sehingga waktu marinasi 1 jam sudah cukup untuk efisiensi waktu. Secara keseluruhan, penggunaan bumbu pada daging sapi panggang menunjukkan sifat fisikokimia dan aktivitas antioksidan yang lebih baik dibandingkan dengan daging panggang tanpa marinasi (kontrol)., Marinating with antioxidant-rich spices can inhibit the formation of harmful compounds, such as malondialdehyde and carcinogenic substances, during the preparation of grilled meat. This study aims to analyze the influence of adding kecombrang to the marinade and the duration of marination on the physicochemical properties (water content, water activity, pH), antioxidant activity, and malondialdehyde content of grilled beef. Beef is marinated using a spice formulation without kecombrang and with kecombrang for 1 hour and 12 hours before grilling. The addition of the spice formulation to the grilled beef, whether with or without kecombrang, significantly affects (P<0,05) the pH value and antioxidant activity, while it does not impact the moisture content, water activity, MDA (malondialdehyde) content. The addition of the spice formulation alters the visual appearance of the meat. The difference in marination duration of 1 hour and 12 hours does not influence the physicochemical properties and antioxidant activity of the grilled beef, making a 1 hour marination sufficient for time efficiency. Overall, the use of the spice formulation on the grilled beef demonstrates better physicochemical properties and antioxidant activity compared to non-marinated grilled meat (control).
Keyword: antioxidant, grilled beef, marinade formulation, marination

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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