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: 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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