Judul: Characteristics of Beef Rendang with Addition of (Zingiber officinale var. Rubrum) During Storage at Room Temperature
Abstrak: Rendang adalah makanan khas Minangkabau yang dibuat selama 4-6 jam dan disimpan untuk waktu yang lama. Selama penyimpanan rendang dapat mengalami ketengikan sehingga penambahan jahe merah selama pembuatan rendang diharapkan mampu meningkatkan antioksidan untuk mencegah ketengikan serta meningkatkan umur simpan rendang. Penelitian ini bertujuan untuk menganalisis karakteristik fisikokimia, mikrobiologi, organoleptik dan aktivitas antioksidan rendang daging dengan penambahan jahe merah sebanyak 0%, 15%, dan 30%. Rendang yang diuji disimpan di dalam stoples penyimpanan yang tertutup rapat dan dibiarkan pada suhu ruangan. Hasil penelitian menunjukkan bahwa penambahan jahe merah berpengaruh nyata (p<0,05) terhadap nilai pH, aktivitas air, kadar air, kadar protein, nilai TBARS, total plate count (TPC), aktivitas antioksidan dan kapasitas antioksidan, namun tidak berpengaruh terhadap kadar abu, kadar lemak, dan keempukan. Penambahan jahe merah pada pembuatan rendang daging nyata meningkatkan (p<0,05) nilai pH, kadar air, nilai aw, kadar protein, dan aktivitas antioksidan serta mampu menurunkan peningkatan nilai TBARS dan menghambat pertumbuhan mikrobiologi selama penyimpanan. Karakteristik kadar abu, kadar lemak dan keempukan tidak menunjukkan perbedaan nyata dengan rendang daging tanpa penambahan jahe merah secara statistika. Dari semua sampel yang telah diuji, pemberian jahe merah sebanyak 30% memberikan hasil terbaik. Secara organoleptik, penambahan jahe merah tidak memberi pengaruh terhadap kesukaan panelis terhadap rendang yang dihasilkan. Dapat disimpulkan penambahan jahe merah pada pembuatan rendang daging memberikan efek positif terhadap karakteristik fisikokimia, meningkatkan aktivitas antioksidan, serta menghambat pertumbuhan mikrobiologi.
Keyword: antioxidant, microbiology, organoleptic, red ginger, rendang

Judul: Characteristics of Beef Dendeng Added by Fresh Red Ginger (Zingiber officinale var. Rubrum) as A Seasoning
Abstrak: Dendeng merupakan produk olahan daging yang dapat mengalami ketengikan akibat adanya reaksi oksidasi lipida. Penambahan jahe merah segar sebagai bumbu dapat menghambat pertumbuhan bakteri, meningkatkan aktivitas antioksidan dan berpotensi meningkatkan keempukan. Penelitian ini bertujuan menguji karakteristik dendeng sapi yang diberi penambahan jahe merah segar sebagai bumbu. Penelitian ini menggunakan perlakuan penambahan jahe merah segar dengan konsentrasi sebesar 0%, 12,5% dan 25% dari berat daging. Daging sapi diiris dengan ketebalan 5 mm dan dimarinasi dengan bumbu selama 12 jam. Daging yang telah dimarinasi, dikeringkan dalam oven pada suhu 60 °C selama 3 jam dan dilanjutkan dengan menggunakan suhu 70 °C selama 5 jam. Hasil penelitian menunjukkan bahwa penambahan jahe merah segar pada dendeng mampu meningkatka pH, aw, kadar air, aktivitas penghambatan DPPH, dan kapasitas antioksidan, serta menurunkan tingkat kekerasan, kadar MDA dan TPC. Bakteri Salmonella sp., Escherichia coli dan Staphylococcus aureus tidak terdeteksi keberadaanya pada semua perlakuan dan lama penyimpanan. Berdasarkan keempukan yang dihasilkan, penambahandan jahe merah segar sebesar 12,5% dan 25% pada dendeng sapi matang lebih disukai panelis. Dendeng sapi dengan penambahan jahe merah segar sebesar 25% menunjukkan hasil terbaik untuk pengujian sifat fisikokimia, organoleptik, mikrobiologi, dan aktivitas antioksidan., Dendeng is a processed meat product that can have rancidity due to lipid oxidation and microbiology activity. Adding fresh red ginger as a spices can influencing taste, inhibit the growth of bacteria, increasing antioxidant activity, and potentially increasing tenderness. This study aims to examine the characteristics of beef jerky added by fresh red ginger (Zingiber officinale var. Rubrum) as a seasoning in marination step. This study used the addition of fresh red ginger with proportion 0%, 12,5% and 25% from meet weight. Beef was sliced with a thickness of 5 mm then was marinated with spices for 12 hours. Marinated beef was dried using oven at 60 °C for 3 hours and was continued by using temperature of 70 °C for 5 hours. The results showed that the addition of fresh red ginger to beef jerky was able to increase pH, aw, moisture content, DPPH inhibitory activity, and antioxidant capacity, as well as reduce hardness level, MDA and TPC numbers. Salmonella sp., Escherichia coli and Staphylococcus aureus bacteria were not detected in all treatments and storage time. Based on the tenderness result, the addition of fresh red ginger by 12.5% and 25% in cooked beef jerky was preferred by the panelists. Beef jerky with the addition of 25% fresh red ginger showed the best results for testing the physicochemical, organoleptic, microbiological, and antioxidant activity properties.
Keyword: antioxidant, beef jerky, fresh red ginger, microbiology, sensory

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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