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: Physicochemical and Microbiology Changes of Beverage Powder Based on Tempe Protein Concentrate at Various Storage Temperature
Abstrak: Tempe merupakan makanan khas Indonesia yang dihasilkan melalui proses fermentasi kacang kedelai oleh kapang Rhizopus spp. Adapun upaya pengembangan produk dan diversifikasi pangan yaitu memanfaatkan tempe sebagai bahan utama dalam pembuatan serbuk minuman berbasis konsentrat protein tempe. Pengolahan tempe menjadi serbuk minuman diharapkan dapat meningkatkan konsumsi tempe dan memenuhi kebutuhan protein masyarakat. Sebuah produk pangan akan mengalami penurunan mutu seiring dengan lama waktu penyimpanan. Oleh karenanya penting untuk diketahui perubahan karakteristik fisikokimia dan mikrobiologi agar produk tetap layak dikonsumsi. Penelitian ini bertujuan untuk mengetahui perubahan mutu karakteristik fisikokimia dan mikrobiologi produk SMBKPT selama penyimpanan pada berbagai suhu. Karakteristik fisikokimia yang diuji yaitu nilai proksimat, aw, pH, aktivitas antioksidan dan derajat putih. Karakteristik mikrobiologi yang diuji yaitu total kapang dan angka lempeng total. Nilai kadar air mengalami peningkatan pada suhu penyimpanan 35⁰C dan 45⁰C, sedangkan pada suhu penyimpanan 55⁰C nilai kadar air cenderung menurun. Kandungan protein dan lemak cenderung stabil selama penyimpanan. Aktivitas antioksidan mengalami peningkatan pada suhu penyimpanan 25, 35 dan 45⁰C dan mengalami penurunan pada suhu penyimpanan 55⁰C. Nilai total kapang mengalami peningkatan pada suhu penyimpanan 25 dan 35⁰C. Selanjutnya pada parameter kadar abu, aw, pH, derajat putih, angka lempeng total mengalami penurunan pada setiap suhu penyimpanan. Kata kunci: fisikokimia, mikrobiologi, mutu pangan, serbuk minuman, tempe, Tempe is a typical Indonesian food produced through the fermentation process of soybeans by the fungus Rhizopus spp. As for product development efforts and food diversification, namely utilizing tempe as the main ingredient in the manufacture of beverage powders based on tempeh protein concentrate. Processing tempeh into beverage powder is expected to increase the consumption of tempeh and meet the protein needs of the community. A food product will experience a decrease in quality along with the length of storage time. Therefore, it is important to know the changes in physicochemical and microbiological characteristics so that the product remains fit for consumption. This study aims to determine changes in the quality of the physicochemical and microbiological characteristics of SMBKPT products during storage at various temperatures. The physicochemical characteristics tested were proximate value, aw, pH, antioxidant activity and whiteness degree. The microbiological characteristics tested were total mold and total plate count. The value of water content increased at a storage temperature of 35 and 45⁰C, while at a storage temperature of 55⁰C the value of the water content tended to decrease. Protein and fat content tends to be stable during storage. Antioxidant activity increased at storage temperatures of 25, 35 and 45⁰C and decreased at storage temperature of 55⁰C. The value of molds increased at storage temperatures of 25 and 35⁰C. Furthermore, the parameters of ash content, aw, pH, degree of whiteness, total plate number decreased at each storage temperature. Keywords: beverage powder, food quality, microbiology, physicochemical, tempe
Keyword: beverage powder, food quality, microbiology, physicochemical, 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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