Judul: The Effect of Palm Sugar and Tamarind on The Quality of Tempe Orek During Storage
Abstrak: Tempe orek merupakan produk olahan tempe yang umum ditemui di Indonesia. Tempe orek umumnya dibuat dalam jumlah banyak untuk pemakaian berulang yang disimpan pada suhu ruang. Gula merah dan asam jawa yang merupakan bumbu utama dalam pembuatan tempe orek menjadi faktor penting dalam memengaruhi kualitas produk selama penyimpanan. Penelitian ini bertujuan untuk menganalisis pengaruh interaksi perlakuan gula merah, asam jawa, dan lama penyimpanan terhadap mutu tempe orek, serta mengukur profil sensori, tingkat kesukaan, dan komposisi kimia dari tempe orek terbaik. Mutu tempe orek yang diuji, yaitu kadar air, pH, tekstur, angka lempeng total (ALT), dan angka kapang khamir (AKK). Perlakuan terbaik ditentukan dengan metode skoring serta pengujian sensori Rate-all-that-apply (RATA), rating hedonik, dan uji proksimat. Kombinasi perlakuan gula merah, asam jawa, dan lama penyimpanan berpengaruh nyata terhadap parameter kadar air dan pH. Perlakuan terbaik diperoleh pada konsentrasi gula merah 50% dan asam jawa 2,50%. Pada perlakuan tersebut diperoleh nilai kadar air, pH, kekerasan, ALT, dan AKK yang menunjukkan bahwa tidak terjadi penurunan mutu tempe orek yang signifikan selama penyimpanan. Namun, terjadi penurunan intensitas atribut dan tingkat kesukaan terhadap tempe orek dengan perlakuan terbaik selama penyimpanan., Tempe orek is a processed tempe product that is commonly found in Indonesia. Tempe orek is generally made in large quantities for repeated use and stored at room temperature. Palm sugar and tamarind are the main spices and the important factors in influencing the quality of product during storage. This research aims to analyze the interactions of palm sugar, tamarind, and storage time on affecting the quality of tempe orek, and to measure the sensory profile and chemical composition of the best tempe orek. Water content, pH, texture, total plate count (TPC), and the total yeast and mold count (TYMC) were tested as the quality parameters. The best tempe orek was determined using the scoring method, and Rate-all-that-apply (RATA), hedonic rating, and proximate were tested. The interaction of palm sugar, tamarind, and storage time had a significant effect on water content and pH. Sample with concentration of 50% palm sugar and 2,50% tamarind were the best tempe orek. In this sample, the value of water content, pH, hardness, TPC, and TYMC showed that there was no significant decrease in the quality of tempe orek during storage. However, there was a decrease in the attribute intensity and the preference of the best tempe orek during storage.
Keyword: palm sugar, quality, storage, tamarind, tempe orek

Judul: The Effect of Storage Time of Air Blast Freezing  Tempe and Its Thawing Process on the Physical and Sensory Quality
Abstrak: Tempe merupakan produk pangan yang sangat diminati karena mengandung zat gizi yang tinggi. Potensi tersebut membuka peluang ekspor tempe menuju negara lain, salah satunya Jepang. Namun, tempe memiliki masa simpan yang tidak tahan lama sehingga dilakukan pembekuan dengan Air Blast Freezer (ABF) dan penyimpanan pada suhu rendah (-19 oC). Proses thawing pun perlu dilakukan sebelum tempe beku diolah. Oleh karena itu, penelitian mengenai mutu fisik dan sensori tempe beku hasil ABF berdasarkan lama penyimpanan dan proses thawing perlu dilakukan. Analisis mutu fisik tempe ABF selama 12 minggu menunjukkan peningkatan nilai aw serta penurunan nilai daya iris, kekerasan, dan WHC. Warna tempe berubah menjadi kuning kecokelatan. Berdasarkan analisis mutu fisik, proses thawing dengan cara direndam pada air ±20 ⁰C selama 25 menit merupakan proses thawing terbaik. Hasil uji hedonik menunjukkan konsumen lebih menyukai tempe segar dibandingkan dengan tempe ABF 0 dan 12 minggu. Hasil uji CATA menunjukkan bahwa tempe ABF 12 minggu memiliki atribut dominan berupa aroma alkohol, serta tekstur yang soft dan mudah hancur. Tempe ABF 12 minggu yang digoreng pun memiliki atribut dominan yang sama ditambah rasa pahit. Atribut dominan pada tempe ABF 12 minggu jauh berbeda dari tempe ideal dimana menandakan adanya penurunan mutu selama masa penyimpanan., Tempe is a food product with great demand because it contains high nutrients. This potential opens opportunities for tempe exports to other countries, one of which is Japan. However, tempe has a short shelf life, so it should be frozen in Air Blast Freezer and stored at low temperature (-19 oC). The thawing process needs to be done before the frozen tempe is processed. Therefore, research on the physical and sensory quality of frozen tempe from ABF based on storage time and thawing process needs to be carried out. Analysis of the physical quality of ABF tempe for 12 weeks showed an increase in the aw and a decrease in the slicing power, hardness, and WHC. Tempe color changes to yellow-brown. Based on the analysis of physical quality, the thawing process by soaking it in ±20 ⁰C water for 25 minutes is the best thawing process. The results of the hedonic test showed that consumers preferred fresh tempe compared to 0 and 12 week ABF tempe. The results of the CATA test showed that the 12 week ABF tempe had dominant attributes in the form of an alcoholic aroma with a soft and easily crushed texture. Tempe ABF 12 weeks which is fried also has the same dominant attribute plus a bitter taste. The dominant attribute of 12 week ABF tempe is far different from ideal tempe which indicates a decrease in quality during the storage period.
Keyword: Air blast freezer, Physical quality, Sensory quality, Tempe

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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