Judul: The Study of Frying Process on the Characteristics of Purple Sweet Potato (Ipomoea batatas L.) Simulated Chips
Abstrak: Umbi ubi jalar berukuran kecil sering kali tidak memenuhi spesifikasi industri dan tidak laku dijual, sehingga pemanfaatannya rendah dan menimbulkan masalah kehilangan hasil panen. Teknologi pengolahan keripik simulasi menawarkan solusi pemanfaatan umbi berukuran kecil melalui proses pengadonan, pembentukan lembaran, dan pencetakan. Keripik simulasi dimasak melalui penggorengan, satuan operasi kompleks yang memengaruhi karakteristik keripik yang dihasilkan. Penelitian ini bertujuan mendapatkan proses penggorengan yang menghasilkan keripik simulasi ubi jalar ungu yang paling disukai oleh panelis. Percobaan dilakukan menggunakan rancangan acak lengkap (RAL) dengan perlakuan kombinasi kadar air sebelum penggorengan (basah; kering) dan kondisi penggorengan (160 oC, 1 menit; 175 oC, 25 detik; 190 oC, 10 detik). Karakter produk yang dianalisis adalah kadar air, warna, tekstur, dan skor kesukaan konsumen pada uji organoleptik. Keripik terbaik ditentukan berdasarkan skor kesukaan atribut overall tertinggi. Keripik terbaik memperoleh skor kesukaan overall 5,00 dan memperoleh skor atribut aroma 5,02; warna 4,21; rasa 4,84; dan tekstur 5,14 dari skala hedonik 7-poin yang menunjukkan panelis netral hingga agak suka terhadap keripik. Keripik terbaik adalah keripik yang sebelumnya dikeringkan selama 1,5 jam menghasilkan adonan basah dengan kadar air 15%, kemudian digoreng pada suhu 175 oC selama 25 detik. Keripik simulasi ubi jalar ungu memiliki kandungan proksimat protein 1,24%; air 1,63%; abu 2,81%; lemak 22,36%; dan karbohidrat 71,97% dengan nilai kalori 493,16 kkal per 100 g produk. Keripik simulasi ubi jalar ungu memiliki aktivitas antioksidan dinyatakan sebagai IC50 sebesar 5688,61 ppm. Antosianin dan senyawa fenolik lain dalam ubi jalar ungu segar terdegradasi selama pengolahan, sehingga aktivitasnya sebagai antioksidan di dalam produk keripik simulasi lebih rendah apabila dibandingkan dengan ubi jalar ungu segar., Small sweet potato tubers often do not meet industrial specifications and cannot be sold, resulting in low utilization and causing crop loss problems. Simulated chips processing technology offers a solution for utilizing small tubers through kneading, sheet forming, and shaping processes. Simulated chips were cooked through frying, a complex unit operation that affects the characteristics of the products. This study aimed to obtain the frying process which produced the most liked sweet potato chips according to panelists. The experiment was conducted based on a completely randomized design (CRD) with water content before frying (wet; dry) and frying conditions (160 oC 1 minute; 175 oC 25 seconds; 190 oC 10 seconds) as treatments. The observed responses were water content, color, texture, and consumer preference scores on organoleptic tests. The best chips were determined based on the highest overall attribute preference score. The best chips obtained an aroma attribute score of 5,02; color 4,21; taste 4,84; and texture 5,14 from a 7-point hedonic scale, indicating panelists felt neutral to moderately liked the chips. The best chips were first dried for 1,5 hours to produce a wet dough with a moisture content of 15%, then fried at a temperature of 175 oC for 25 seconds. Purple sweet potato simulated chips had a proximate protein content of 1,24%; water 1,63%; ash 2,81%; fat 22,36%; and carbohydrates 71,97% with a caloric value of 493,16 kcal per 100 g of product. The chips had antioxidant activity expressed as IC50 of 5688,61 ppm. Anthocyanins and other phenolic compounds
Keyword: characteristics, frying, purple sweet potato, simulated chips, karakteristik, keripik simulasi, penggorengan, ubi jalar ungu

Judul: Optimasi Formula dan Kondisi Pemasakan Keripik Simulasi Berbasis Komposit Ubi jalar (Ipomoea bat at as L.) dan Beras (Oryza sativa L.)
Abstrak: This research was aimed to obtain the best formula, baking and frying condition based on the physical, chemical and sensorial characteristics of simulated sweet potato based chips: rice, with enrichment of skimed milk, carrot, celery and temurui powders with thickness ± 0.1 mm as the functional ingredients. A completely randomized factorial design of 2 factors (formulation and cooking process) with 2 replication was used. The observed parameters include color, texture, proximate, and hedonic ratings of sensory analysis. The result showed that formula and cooking process of the baked simulated chips significantly affected (p<0.05) the brightness, hardness, and protein content. Whereas formula and cooking process of the fried simulated chips significantly affected (p<0.05) the brightness, hardness, fat content, and protein content. The best simulated chips obtained from a combination of cooking process and formula sweet potato: rice 80: 20, baked at 180 °C for 8 minutes and, sweet potato simulated chips: rice 60: 40, fried at 160 °C for 1 minute. The best baked simulated chips had characteristic of bright color (± 69.32), not hard texture (± 382.97 gf), protein content (± 4.09%), and low fat (± 1.67%). The best fried simulated chips had characteristic of bright color (± 46.77), not hard texture (± 827.77 gf), high protein (± 3.07%), and low fat (± 28.01%). Besides, the best simulated chips produced had fine micro structure and massive.
Keyword: Bogor Agricultural University (IPB), rice, sweet potato, composite, simulated chips

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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