Judul: Model Perpindahan Massa pada Pemekatan Jus Jeruk Siam dengan Reverse Osmosis
Abstrak: Reverse Osmosis (RO) telah menjadi teknik yang efektif untuk pemisahan dan pengkonsentrasian komponen ionik dari air sehingga penerapan aplikasi ini dewasa ini masih didominasi untuk proses desalinasi air laut. Semakin berkembangnya teknologi memperluas penerapan RO untuk pemisahan komponen dalam industri makanan dan farmasi. Salah satu penerapan RO dalam industri makanan yang memiliki prospek menjanjikan adalah pemisahan air untuk pemekatan jus jeruk. Penelitian ini bertujuan untuk memperoleh kondisi operasi RO (tekanan transmembran dan laju alir umpan) yang terbaik, mendapatkan tingkat pemekatan tertinggi dari proses RO dengan tekanan rendah (LPRO) dan memperoleh faktor-faktor yang berpengaruh untuk pemisahan jus jeruk dari model perpindahan massa pada pemekatan jus jeruk dengan RO. Bahan baku yang digunakan dalam penelitian adalah jus jeruk siam Pontianak (Citrus nobillis L var microcarpa) hasil filtrasi membran mikrofiltrasi ukuran pori 0,1 μm dengan komposisi kandungan total padatan terlarut 6.82 oBrix, asam sitrat 0.56 % dan vitamin C sebesar 11.65 mg per 100 mg. Penelitian menggunakan membran RO berbentuk lilitan spiral (spiral wound) berbahan poliamida (PA) dengan luas permukaan 0.59 m2 dan rejeksi NaCl 93%. Aplikasi membran Low Pressure Reverse Osmosis pada penelitian dilihat sebagai proses pra-pemekatan dengan RO.
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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: Distribution and Diversity of Ectoparasite Mites on Geckos in Indonesia
Abstrak: Data on the diversity and dispersal of parasitic mites on house geckos in Indonesia are very scarce. In this work, the distribution and diversity of mites living on three species of house geckos, namely Cosymbotus platyurus, Hemidactylus frenatus, and H. garnotii collected throughout Indonesia, has been elaborated. Geckos and mites were captured and immediately preserved in 70% ethanol. Whole mount of the mites was prepared by clearing in lactophenol followed by mounting on polyvinyl lactophenol solutions. The SEM preparation was conducted to examine the detail morphological characters of the mites. The results showed that among 448 individuals of geckos, 221 geckos were infected by Geckobia mites. Prevalences of C. platyurus, H. frenatus, and H. garnotii infested by mites were 14.8%, 50.69%, and 79.6%, respectively. Three different spesies of Geckobia (G1, G2, and G3) could be differentiated; and based on similarities of their morphological characters to ones described in published literatures, Geckobia G2 is Geckobia glebosum and Geckobia G3 is Geckobia bataviensis while G1 could not be identified to the species level. The highest mean intensity of Geckobia G1 infestation was found on H. garnotii (I=7.0), G. glebosum infestation on H. frenatus (I=3.5), and G. bataviensis infestation on H. garnotii (I=11.8). In general, C. platyurus was infested by the least number of mites. Geckobia G1 were found living on the skin folds on the claws, G. glebosum were found mainly on the body and thigh, and G. bataviensis were found on almost all parts of the host’s body. Geckobia mites are distributed randomly throughout Indonesian Archipelago, following the pattern of distribution of their hosts. So it is concluded that Geckobia G1, G. glebosum, and G. bataviensis are sympatric.
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