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: The Impact of Blanching and Vacuum Packaging to The Shelf Life of Fresh Seasoned Tempe
Abstrak: Tempe is an indigenous fermented food from Indonesia, prepared by the action of molds, Rhizopus sp., on cooked soybeans. In 2012, up to 60% of soybean production went to tempe industry with consumption of tempe reaching 8.5 kg per person per year in Indonesia. However, the export of tempe seems still impossible due to its perishable characteristic whose shelf life is very short. Preblanching and vacuum packaging were expected to extend the shelf life of tempe. This research was aimed to study the application of blanching and vacuum packaging on the shelf life of fresh-seasoned tempe. Steam blanching of 80 oC for three minutes was selected from pre-investigation for pre-treatment of the tempe without inducing cooked-tempe characteristic. The result of main research revealed that steam blanching and vacuum packaging were able to extend the shelf life of fresh-seasoned tempe for two days in room temperature (23-24 oC), 32 days in refrigeration temperature (4-6 oC), and 49 days in chilling temperature (0-4 oC). The pH of tempe was found increasing during storage with texture getting overstuffed or tender during storage.
Keyword: Bogor Agricultural University, vacuum packaging, storage temperature, shelf life, Fresh-seasoned 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.
Keyword: