Judul: Sifat Fisikokimia, Organoleptik dan Aktivitas Antioksidan Dendeng Sapi dengan Penambahan Jahe Merah (Zingiber officinale Var. Rubrum) Segar
Abstrak: Dendeng merupakan produk olahan daging yang dapat mengalami ketengikan akibat reaksi peroksidasi lipid. Ketengikan dapat dicegah dengan penggunaan antioksidan, seperti jahe merah. Penelitian ini bertujuan menguji sifat fisikokimia, organoleptik dan aktivitas antioksidan dendeng sapi yang diberi penambahan jahe merah segar dengan konsentrasi sebanyak 0%, 10% dan 20% berdasarkan berat daging. Sampel dendeng yang diuji organoleptik berupa dendeng mentah dan matang. Pengujian sifat fisikokimia dan aktivitas antioksidan menggunakan dendeng yang mentah. Hasil penelitian menunjukkan bahwa penambahan jahe merah segar terhadap dendeng sapi berpengaruh nyata (P<0,05) terhadap nilai pH, aw, kadar air dendeng sapi, dan karakteristik organoleptik pada atribut rasa, aroma dan kelenturan dendeng sapi mentah dan matang. Penambahan jahe merah segar tidak berpengaruh nyata pada nilai TBARS dan aktivitas antioksidan. Secara keseluruhan, dendeng sapi dengan penambahan jahe merah segar sebesar 10% menunjukkan hasil terbaik untuk pengujian sifat fisikokimia, organoleptik dan aktivitas antioksidan., Jerky or dendeng is a processed meat product that can have rancidity due to lipid peroxidation reactions. Rancidity can be prevented by using antioxidants such as red ginger. This study aims to examine the physicochemical, sensory properties and antioxidant activity of beef jerky with the addition of fresh red ginger with proportion 0%, 10% and 20% based on beef weight. The sample that used for sensory evaluation were raw and cooked dendeng. Physicochemical properties as well as antioxidant activity measurement used raw dendeng. The addition of fresh red ginger to dendeng had a significant effect (P<0,05) on pH value, water activity dan sensory properties of taste, flavor and flexibility attribute. The addition of fresh red ginger to dendeng had no significant effect on TBARS value and antioxidant activity. Overall, beef jerky with the addition of 10% fresh red ginger showed the best results for physicochemical, sensory properties and antioxidant activity measurement.
Keyword: antioxidant, beef jerky, fresh red ginger, organoleptics

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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