Judul: Rekayasa Proses Pengikatan Limonin dan Naringin oleh Siklodekstrin pada Sari Jeruk Siam
Abstrak: Siam juice contain limonin and naringin that produce a bitter taste although these compounds useful as an antioxidant and anticancer. Bitter taste in juice is unfavor for consumer. The purpose of this research was to find the best conditions in reducing bitter taste in Siam juice by using cyclodextrin and cellulose acetate. These research performed at variation of mixing temperature (27; 60 and 80ºC), cyclodextrin concentration (0.1; 0.3 and 0.5% (w/v)) and cellulose acetate ( 0.2; 0.4 and 0.6% (w / v)). The results showed that the use of cyclodextrin and cellulose acetate were able to trap limonin and naringin. The higher reducing limonin juice was 91.57% by addition cyclodextrin 0.1% at 60ºC, whereas for naringin obtain by addition cellulose acetate 0.5% at 79.69% . At this temperature, the juice quality (vitamin C) can be maintained.
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Judul: Model Perpindahan Massa pada Mikrofiltrasi untuk Penghilangan Limonin dan Naringin dari Jus Jeruk Siam (Citrus nobilis L. var microcarpa)
Abstrak: Bitterness in citrus juice primarily due to the presence of limonin and naringin. Using membrane technology is expected to remove the bitterness. The decreasing of flux is a general membrane problem. Understanding of mass transfer mechanisms, the decreasing of membrane performance could be controlled. The research aimed to remove limonin and naringin from Siam citrus juice by microfiltration, to get the best condition of operation of microfiltration i.e. higher permeate flux and rejection, and to predict mass transfer mechanisms on the microfiltration for removing limonin and naringin from Siam citrus juice. Raw material of the study was Siam citrus. The steps of the study were citrus juice characteristics, effect of transmembrane pressure and cross flow velocity on the permeate flux, rejection, quality of citrus juice, and mass transfer mechanism on the microfiltration of citrus juice according to the total recycle operation mode. Mass transfer mechanism was analyzed by comparing the experimental data with calculation data using thin film models of non-Newtonian fluids based on non-dimensional analysis with Brownian diffusion and shearinduced diffusion approach, Zidney-Colton model, and Davis-Sherwood model. The results showed the fresh citrus juice is a non-Newtonian fluid and a character of dilatant. The limiting flux reached at the transmembrane pressure of 1.84 bar. Optimum condition for microfiltration citrus juice at the transmembrane pressure of 1.74 bar and flow rate of 0.08 ms-1 for 30 minutes, with the permeate flux about 63.16 L m-2h-1. In these conditions, the microfiltration of citrus juice could remove limonin and naringin, respectively by 92.54 % and 71.34 %. The limonin rejection was higher than naringin because limonin is more hydrophobic so that adsorbed onto membrane surface easier. High transmembrane pressure application caused decreasing vitamin C and total soluble solids content in the permeate, respectively by 44.48 % and 38.18 %. Mass transfer mechanisms on the microfiltration of citrus juice strongly depend on citrus juice properties. Presence of particles in citrus juice caused increasing of shear rate on membrane wall, so that increase particle deposition rates from membrane surface. Mass transfer mechanisms on the microfiltration of citrus juice were affected by particle size, particle concentration, and shear rate as showed by close value of experimental data with Zidney-Colton model. Finally, the mass transfer mechanism on the microfiltration Siam citrus juice for removing limonin and naringin could be decribed as mass transfer mechanism by shear-induce diffusion and fresh citrus juice is a dilute suspension.
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Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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