ABSTRAKUmbi porang (Amorphophallus oncophyllus) mengandung kadar glukomanan yang cukup tinggi dan sangat berguna bagi industri pangan, nonpangan maupun kesehatan. Masalah utama dalam pengembangan tepung porang yaitu adanya kalsium oksalat yang menyebabkan rasa gatal, iritasi dan gangguan kesehatan. Optimasi penurunan kalsium oksalat pada proses penepungan untuk memproduksi tepung porang secara mekanis menggunakan stamp mill dan fraksinasi blower. Optimasi dilakukan dengan metode permukaan respons (RSM), Rancangan Komposit Pusat pada tiga variabel yaitu berat chip, waktu/lama dan kecepatan penumbukan dengan respons kadar kalsium oksalat. Model respons adalah kuadratik dengan kondisi optimum berat chip porang 1,3 kg, 17,4'8'', dan kecepatan penumbukan 19,23. Respons kadar kalsium oksalat pada kondisi optimum ini diprediksi sebesar 0,2978% dan aktual 0,3%, menurun 95,12%.Kata kunci: kalsium oksalat, tepung porang, optimasi, mekanis ABSTRACT Porang Tuber (Amorphophallus oncophyllus) has high Glucomanan content which is very useful in food and non food industry as well as in medical industry. The only main problem in development of porang flour is its Calcium Oxalate content that stipulates irritation (itchiness) and health disorder. Optimization study of diminution (reduction) content of CalciumOxalate during mechanical grinding process using stamp mill and blowing fractionation. Optimization was performed by applying Response Surface Model (RSM), central composite model. Three variables i.e. weight of porang chip, grinding time and grinding speed were studied in order to study the Calcium Oxalate content as a response. Response model obtained was quadratic which was acquired at 1.3 kg porang optimum weight; grinding time 17.4'8"; and grinding speed at 19,23 rpm. Optimum Calcium content has been predicted at 0.2978% which was 0.3% in actual, decrease 92,12%

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A moderately thermophilic bacterium, strain A-471, capable of degrading chitin was isolated from a composting system of chitin-containing waste. Analysis of the 16S rDNA sequence revealed that the bacterium belongs to the genus Ralstonia. A thermostable chitinase A ( Ra-ChiA) was purified from culture fluid of the bacterium grown in colloidal chitin medium. Purification of the enzyme was achieved mainly by exploiting its binding to the colloidal chitin. The molecular mass of the enzyme was estimated to be 70 kDa and the isoelectric point approximately 4.7. N-terminal amino acid sequencing revealed a sequence of ADPYLKVAYYP, which had high homology (66% identity) with that of chitinase A1 from Bacillus circulans WL-12. The pH and temperature optima were determined to be 5.0 and 70 degrees C, respectively. The enzyme was classified as a retaining glycosyl hydrolase and was most active against partially N-acetylated chitosans. Its activities towards the partially N-acetylated chitosans, i.e. chitosan 7B, chitosan 8B, and chitosan 9B, were about 11-fold, 9-fold, and 5-fold higher than towards colloidal chitin, respectively. Ra-ChiA cleaved (GlcNAc)6 almost exclusively into (GlcNAc)2. Activation of Ra-ChiA was observed by the addition of 1 mM Cu2+, Mn2+, Ca2+, or Mg2+. Degradation of the partially N-acetylated chitosan produced oligosaccharides with a degree of polymerization ranging from 1-8; these are products that offer potential application for functional oligosaccharide production.

In this study, we cloned the gene encoding goose-type (G-type) lysozyme with chitinase (Ra-ChiC) activity from Ralstonia sp. A-471 genomic DNA library. This is the first report of another type of chitinase after the previously reported chitinases ChiA (Ra-ChiA) and ChiB (Ra-ChiB) in the chitinase system of the moderately thermophilic bacterium, Ralstonia sp. A-471 and also the first such data in Ralstonia sp. G-type lysozyme gene. It consisted of 753 bp nucleotides, which encodes 251 amino acids including a putative signal peptide. This ORF was modular enzyme composed of a signal sequence, chitin-binding domain, linker, and catalytic domain. The catalytic domain of Ra-ChiC showed homologies to those of G-type lysozyme (glycoside hydrolases (GH) family 23, 16.8%) and lysozyme-like enzyme from Clostridium beijerincki (76.1%). Ra-ChiC had activities against ethylene glycol chitin, carboxyl methyl chitin, and soluble chitin but not against the cell wall of Micrococcus lysodeikticus. The enzyme produced alpha-anomer by hydrolyzing beta-1,4-glycosidic linkage of the substrate, indicating that the enzyme catalyzes the hydrolysis through an inverting mechanism. When N-acetylglucosamine hexasaccharide [(GlcNAc)6] was hydrolyzed by the enzyme, the second and third glycosidic linkage from the non-reducing end were split producing (GlcNAc)2 + (GlcNAc)4 and (GlcNAc)3 + (GlcNAc)3 of almost the same concentration in the early stage of the reaction. The G-type lysozyme hydrolyzed (GlcNAc)6 in an endo-splitting manner, which produced (GlcNAc)3 + (GlcNAc)3 predominating over that to (GlcNAc)2 + (GlcNAc)4. Thus, Ra-ChiC was found to be a novel enzyme in its structural and functional properties.

Rice is the main food for approximately 3.5 billion people worldwide, especially in Asians, who have consumed more than 90% of the total rice produced. Restructured rice is another designation of artificial rice is an effort to diversify staple foods processed from carbohydrate-based raw materials with the addition of certain substances to improve the quality of staple foods. Restructured rice can be done with several techniques, such as using extrusion. This study aimed to investigate the effect water content (35%, 37.5%, 40%, 42.5%, and 45%) and temperature (100oC and 26oC) on the surface and characteristics of restructured rice using a pasta extruder. Results of this study showed the treatment with water content 40% and temperature 100oC to be the best, more precisely seen from the results of laser microscope, color, WAI, WSI, WAR, Cooking losses, and cooking time. Pores and surfaces of restructured rice are almost the same as milled rice. Water absorption index (WAI) value = 2.273±0.10 g/g, WSI = 2.114±0.11%, WAR = 150.99±0.77%, CL = 1.92±0.10% and cooking time 4 mins. Suggestions for this research are further studies such as fortification with other ingredients using a pasta extruder technology and are expected to be implemented and commercialized.

:The use of antibiotics in animal husbandry cannot be avoided either as an act of therapy, supportive or prevention. This study was aimed to determine the existence of antibiotic residues in broiler chicken products which were produced by poultry farm and to determine the safety level of residues in the product which was associated with a drug application and harvesting time. Thigh meat and liver samples of broiler were taken when thinning and harvesting time in poultry farm at Pamijahan-Bogor using purposive sampling method. Residue testing was conducted through bioassay screening test. Positive results were followed by a confirmatory test using HPLC. Total positive samples were detected residues reached 27.08% which included the macrolide group reached 22.92% and tetracycline group reached 4.17%. These residues were found in the liver, reaching 50% of the total sample of the liver. In addition, 53.85% of the positive samples came from broiler chicken samples taken during thinning period. Macrolide antibiotics in liver samples were detected in the form of erythromycin with the level compounds between 0085 -0702 ppm. Moreover, 90.9% of the samples had levels exceeding MRL defined in SNI 01-6366-2000 and CAC/MRL-2-2012. Tetracycline antibiotic was detected in the form of doxycycline with the level compounds between 0-0067 ppm on thigh meat and 0-0085 ppm in the liver although these levels were still below the MRL. The residues existence was closely related to the drug dose and farmer's knowledge about withdrawal time.

This study aims to find out the optimum treatment of the feed moisture in porang glucomannan (PGM), and Ca(OH) 2 in the production of the restructured rice using a pasta extruder. Feed moisture (35-45%), PGM (3-7%), and Ca(OH) 2 (0.04-0.10%) were the independent variables, while the water absorption index (WAI), the water soluble index (WSI), whiteness, and hardness were responses using a response surface methodology (RSM). Data were analyzed for the chemical components, the 3D surface, the microstructure, the cooking characteristics, and the estimated glycemic index (eGI). The results reported that the WAI and WSI ranged from 2.904 to 3.99 g/g and 2.018 to 3.302%, respectively, whereas whiteness and hardness ranged from 72.83 to 85.02 and 4.921 to 7.537 kgf. The chemical components, the cooking characteristics, and the eGI of the optimum restructured rice PGM reported a significant difference when they were compared to milled rice. The result of the 3D surface of the optimum restructured rice with PGM is similar to milled rice which is seen to be like a convex shape.

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