Judul: The Effect of Ethephon and Beeswax Concentrations on Degreening and Shelf Life of Medan Honey Siamese Mandarin (Citrus nobilis L.)
Abstrak: Jeruk Siam Madu Medan (Citrus nobilis L.) merupakan jeruk yang berpotensi tinggi karena manis, segar, dan mengandung vitamin C yang tinggi. Umumnya jeruk ini memiliki warna hijau dan kuning yang tidak merata meskipun sudah matang dibandingkan dengan jeruk impor yang jingga penuh sehingga menyebabkan tingginya volume impor. Degreening adalah proses menghasilkan pigmen karotenoid dan menurunkan pigmen klorofil yang dapat memperbaiki kualitas warna kulit buah jeruk. Penelitian ini bertujuan mengetahui pengaruh konsentrasi ethephon terhadap perubahan sifat fisik dan konsentrasi lilin lebah dalam memperpanjang umur simpan buah jeruk. Degreening dilakukan menggunakan konsentrasi ethephon 0, 500, dan 1000 ppm. Pelilinan dilakukan menggunakan konsentrasi lilin lebah 0% dan 4%. Hasil analisis penelitian menunjukkan selama penyimpanan 27 hari pada suhu ruangan 26.5-28.0 oC dan RH 52.7-61.0% tidak terdapat interaksi antara ethephon dan lilin lebah. Perlakuan ethephon berpengaruh nyata terhadap degreening dengan konsentrasi ethephon 500 ppm menghasilkan warna jingga tertinggi dengan nilai CCI 7.51 dan ohue 70.12 pada 14 HSP. Pelapisan lilin lebah konsentrasi 4% efektif mencegah pengurangan ukuran diameter buah sebesar 0.60 cm dari 6 hingga 14 HSP, namun hanya berpengaruh nyata dalam menekan susut bobot pada 2 HSP. Degreening hanya mempengaruhi kualitas eksternal, namun tidak dengan internal buah jeruk Siam Madu Medan., Medan Honey Siamese mandarin (Citrus nobilis L.) is high potential fruits because its sweet, fresh, and high of vitamin C. Visually, these mandarins have uneven green and yellow color even though already ripe compared to the imported mandarins with fully orange color that causing Indonesia has high import volume. Degreening is a process of producing carotenoid and degrading the chlorophyll chemically to improve the quality of citrus peel color. The study aims to observe the effects of ethephon and beeswax concentrations on changes the physical properties and extending the shelf life of citrus fruits. Degreening was conducted using ethephon at concentrations of 0, 500, and 1000 ppm and beeswax coating at concentrations of 0% and 4%. The analysis showed that during 27 days of storage at room temperature of 26.5-28.0 oC and RH 52.7-61.0%, degreening with 500 ppm ethephon produced the highest orange colour with Citrus Color Index (CCI) value of 7.51 and ohue 70.12. The treatment of 4% beeswax effectively suppressed the diameter shrinkage by 0.6 cm at day 6 to 14, but only effected on reducing weight loss at second day after treatment. Postharvest degreening treatment only affected the external quality but not the internal quality of Medan Honey Siamese mandarins.
Keyword: carotenoid, coating, exogenous, peel color, rutaceae

Judul: egreening of siam tangerine on different ethylene exposure time and temperature. Supervised by Y ARIS PURWANTO and ROEDHY POERWANTO.
Abstrak: Jeruk siam pada umumnya berwarna hijau. Teknologi degreening yang tepat dapat memperbaiki warna kulit jeruk tropika menjadi jingga secara merata. Degreening merupakan proses perombakan pigmen hijau (klorofil) pada kulit jeruk secara kimiawi dan membentuk warna kuning atau jingga (karotenoid) tanpa mempengaruhi kualitas internal buah. Tujuan dari penelitian ini adalah untuk mengkaji pengaruh durasi pemaparan etilen dan suhu degreening untuk memunculkan warna jingga pada jeruk siam. Etilen 200 ppm diinjeksikan ke dalam box degreening yang berisi jeruk sebanyak 2.8 kg dan dipaparkan pada cooling chamber dengan suhu 15, 20 dan 25 oC selama 0, 24, 48 dan 72 jam.Pemaparan etilen dilakukan dengan metode single shot dan multiple shot. Setelah pemaparan, jeruk kemudian disimpan pada suhu ruang. Pengamatan dilakukan setiap dua hari: (a) pengamatan non-destruktif dilakukan dengan menggunakan color reader dan metode citrus color chart (CCC)untuk mengetahui perubahan warna; (b) pengamatan destruktif dilakukandengan mengukur kandungan klorofil dan karotenoid serta mengukur kekerasan,TPT, TAT dan vitamin C untuk mengetahui perubahan fisikokimia jeruk. Hasil penelitian menunjukkan durasi pemaparan terbaik pada jeruk siam Jember dan Banyuwangi adalah selama 48 jam pada suhu 20 oC. Durasi pemaparan dan suhu terbaik dapat mengubah nilai CCI dari -0.60 menjadi 6.55 pada jeruk siam Jember dan pada jeruk siam Banyuwangi -0.33 menjadi 9.41. Pada jeruk siam Jember warna optimum yang dihasilkan adalah kuning sedangkan jeruk siam Banyuwangi adalah jingga cerah. Degreening dapat mengubah warna jeruk menjadi jingga cerah dan tidak memberikan pengaruh negatif terhadap kualitas internal buah., Siam Tangerine peel is green. Degreening technology can improve the citrus peel color becomes uniformly orange. Degreening is a process to break down green pigment (chlorophyll) on citrus peel chemically and form the orange color (carotene) without affecting internal quality of fruit. The purpose of this study was to determine the effect of ethylene exposure duration and temperature to bring out the color on siam tangerine. Ethylene 200 ppm was injected into the box containing 2.8 kg citrus and was exposed to the cooling chamber with a temperature of 15, 20 or 25 °C for 0, 24, 48 or 72 hours. Ethylene exposure was conducted using multiple shots method. After exposure, tangerine were put at room temperature condition. Observations were conducted every two days: (a) non-destructive observation conducted using color reader and CCC method to determine the color changes; (b) destructive observations for measuring chlorophyll and carotenoids content and physico-chemical changes i.e. firmness, soluble solid content, titratable acidity and vitamin C. The results showed that the best combination was 48 hours ethylene exposure duration at 20 oC both for siam Jember, as well as siam BanyuwangiThis degreening technique alter the CCI value from -0.60 to be 6.55 in siam Jember, and from -0.33 to be 9.41 in siam Banyuwangi, that was changed the tangerines into a yellow of siam Jember and bright orange of siam Banyuwangi. Degreening has not negative impact for internal quality.
Keyword: Carotenoid, Chlorophyll, Citrus color chart, Citrus color index, Cooling chamber, Tropical citrus, Degreening technology, Green pigment, Fruit quality, Ethylene exposure, Siam Jember, Siam Banyuwangi, Internal quality

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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