Judul: Pendugaan Umur Simpan Opak Singkong
Abstrak: Untuk mengetahui ketahanan produk opak singkong dari mulai produk opak diproduksi hingga rusak maka diperlukan pendugaan umur simpan. Tujuan dari penelitian ini adalah mengetahui perubahan mutu opak singkong selama penyimpanan meliputi kadar air dan kadar asam lemak bebas, menentukan pengaruh penambahan perasa makanan terhadap umur simpan opak singkong, serta menentukan umur simpan produk opak singkong dalam kemasan menggunakan metode Arrhenius. Opak singkong dengan rasa original dan barbeque dikemas menggunakan plastik PP dan disimpan pada suhu 30oC, 40oC, dan 50oC kemudian diamati perubahan kadar air dan kadar FFA pada 12 titik pengamatan juga organoleptik sebelum dan sesudah penyimpanan. Umur simpan opak singkong original dan barbeque berdasarkan uji kadar air berturut-turut adalah 93 dan 110 hari, sedangkan umur simpan opak singkong original dan barbeque berdasarkan uji kadar FFA berturut-turut adalah 43 dan 81 hari.
Keyword: shelf life, cassava, cassava chips

Judul: Estimation of Shelf Life Banana Chips “Barong Chips” with the Accelerated Shelf-Life Testing (ASLT) Method
Abstrak: Keripik pisang “Barong Chips” merupakan salah satu produk olahan pisang dari Desa Klirong, Kecamatan Klirong, Kabupaten Kebumen, Jawa Tengah. Keripik pisang dapat mengalami penurunan mutu selama penyimpanan akibat pengaruh kondisi lingkungan seperti RH, oksigen, kemasan, dan suhu penyimpanan, sehingga perlu dilakukan pencantuman informasi umur simpan. Penelitian ini bertujuan mengetahui karakteristik awal, mengidentifikasi penurunan mutu selama penyimpanan, dan melakukan pendugaan umur simpan. Pengamatan dilakukan terhadap produk yang dikemas menggunakan plastik polypropylene dengan tebal 0,05 dan 0,08 mm, pada tiga suhu yaitu 25 , 35 , dan 45ºC selama 8 minggu. Parameter yang diamati yaitu kadar air, asam lemak bebas (FFA), kekerasan, dan kecerahan warna setiap 7 hari sekali. Karakteristik awal keripik pisang yang digunakan memenuhi SNI 01-4315-1996, kecuali kadar lemak. Hasil penelitian menunjukan perubahan mutu berupa peningkatan kadar air dan FFA, serta penerimaan panelis. Pendugaan umur simpan dilakukan berdasarkan parameter yang menyebabkan produk cepat rusak yaitu laju peningkatan kadar air. Umur simpan keripik pisang “Barong Chips” pada suhu ruang (30ºC) yaitu 84 hari., “Barong Chips” is one of banana chips produced by a small scale enterprise Klirong Village, Kebumen, Central Java. Banana chips quality will decrease during storage time due to the influence of environmental conditions such as RH, oxygen, packaging, and storage temperature, so it is necessary to include information on shelf life. The study objective are determining the initial characteristics of “Barong chips”, identifying its quality changes during storage time, and estimating its shelf life. The research was conducted by storing the product that packed in 0,05 and 0,08 thickness polyprophylene film, at three level of temperatures, i.e. 25 , 35 , and 45ºC for 8 weeks. The parameters observed were moisture content, free fatty acid (FFA), hardness, and color brightness every 7 days. The initial characteristics are appropriate to quality standards, except for fat. The result showed changes in the form of an increase in water content and FFA, as well as panelist acceptance. Estimation of shelf life is carried out based on the parameters that cause the product to spoil quickly, the rate of increase air content. The shelf life of “Barong Chips” banana chips at room temperature (30ºC) is 84 days.
Keyword: ASLT, “Barong Chips”, packaging, shelf life

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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