Judul: Deteksi Gejala Chilling Injury Buah Jambu Kristal Selama Penyimpanan pada Suhu Rendah dengan NIR Spectroscopy
Abstrak: Salah satu cara efektif untuk mempertahankan mutu buah jambu kristal adalah dengan metoda penyimpanan suhu rendah. Namun penyimpanan pada suhu rendah yang tidak tepat atau produk yang sensitif terhadap suhu rendah dapat menyebabkan kerusakan dingin (Chilling Injury/CI). Gejala CI dapat diamati dari kenaikan jumlah ion yang dikeluarkan dari membran sel (ion leakage). Perubahan pH juga dapat dijadikan petunjuk terjadinya CI. Penelitian ini bertujuan mengembangkan model kalibrasi near infrared (NIR) untuk memprediksi pH buah jambu kristal selama penyimpanan pada suhu 5 oC dan memprediksi gejala CI buah jambu kristal berdasarkan perubahan slope ion leakage selama penyimpanan menggunakan reflektan NIR. Penelitian dilakukan di Labolatorium Teknik Pengolahan Pangan dan Hasil Pertanian, Departemen Teknik Mesin Biosistem, Institut Pertanian Bogor pada bulan Maret sampai April 2019. Penyimpanan buah pada penelitian ini dilakukan pada suhu 5 oC selama 19 hari dengan setiap pengukuran dilakukan 3 kali ulangan. Hasil kalibrasi dan validasi PLS dengan praperlakuan data berupa normalisasi menghasilkan model regresi kalibrasi yang terbaik (r = 0.8343, CV = 2.69%, dan konsistensi = 87.76%) pada pendugaan pH. Slope ion leakage berkolerasi dengan pH berupa pola linear dan dapat ditentukan dengan persamaan sebagai berikut : y= 0.2584x -0.8002. Berdasarkan persamaan tersebut nilai slope ion leakage mengalami peningkatan pada hari ke-7 penyimpanan maka diprediksi telah mencapai puncak kebocoran membran dan CI.
Keyword: CI, ion leakage, jambu kristal, NIR, pH

Judul: Deteksi Gejala Chilling Injury Buah Belimbing (Averrhoa carambola L.) Yang Disimpan Pada Suhu Rendah Dengan NIR Spectroscopy
Abstrak: Cold storage or low temperature storage is an effective method to extend the self life and assuring quality product of horticulture such as star fruit. However, stored in low temperature may cause chilling injury which decreases the quality of star fruit. Chilling injury of star fruit has correlation with the change of pH content during storage. The change of pH content during storage my be determined nondestructively using near infrared (NIR) Spectroscopy. The objectives of this study were to determine quality of star fruit during storage, to build calibration model of NIR reflectance spectra to predict the pH content during storage at 5 oC temperature, and to determine chilling injury symptoms based on change of ion leakage slope during storage using NIR reflectance. Calibration were built using partial least squares (PLS). Result of analysis showed that the change of pH content could be predicted well by NIR reflectance using the calibration model of PLS for star fruit stored at 5 oC. The change of ion leakage slope based on change of pH content also could be determined using NIR reflectance for star fruits stored at 5 oC.
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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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