Judul: Degradation Of Calcium Oxcalate In Porang Flour Employing Microbubble Cavitation
Abstrak: Porang flour contains a fairly high calcium oxalate (CO) in which consuming it directly can cause kidney stone disease in humans. The aim of this study was to obtain the optimal operating parameters of the CO degradation process in porang flour using a swirling-flow nozzle hydrodynamic cavitation technique. This study consists of 3 stages; stage 1 determining the particle size, concentration of NaCl solution and ratio (porang flour: NaCl solution: isopropyl alcohol) to the level of viscosity for the cavitation process; the 2 nd stage, determining the limit values on the air flow rate, fluid, and cavitation time to optimize the CO degradation; 3 rd stage, CO degradation process with variable operation on hydrodynamic cavitation technique by swirling-flow nozzle type. The hydrodynamic cavitation tool used in this study had a 7 mm nozzle orifice in a vertical position. The nozzle used is made of Plexiglas with an outer diameter of 80 mm and a height of 160 mm which consists of a vortex chamber and air holes. The fluid flow in this tool is regulated by a centrifugal pump type. The optimization process was carried out using the response surface method of the box-behnken model in design expert 13.0 software with 17 formulations and 3 verification processes for optimal operating parameters. The finest solution formulation could pass through the nozzle and formed microbubbles with a viscosity level of >10 cP on 40 mesh particles, 5% NaCl concentration, and ratio (porang flour: NaCl: isopropyl alcohol) 1:20:20 (w/v). The limit values for the optimization process were in the range Qg = 0.5-1.5 lpm, Ql = 8-12 lpm, and cavitation time of 15-25 minutes. The preeminent CO degradation process was obtained at Ql/Qg = 10/1 lpm ratio with a cavitation time of 20 minutes. This process produced 29.7 mg/100g CO content with a degradation percentage of 85.53%. The produced calcium oxalate indicates that it meets the required standard tolerance limit for the human body which is 71 mg/100g, and below SNI 7938:2020 which is a maximum of 30 mg/100g. In other words, porang flour produced from this process is safe for consumption.
Keyword: Porang Flour, Calcium Oxcalate, Microbubble, Optimization, Response Surface Method

Judul: Optimization of Oxalate Content Decrease in Kathak Porang Bulbil (Amorphophallus sp.) Flour Through Immersion in Warm NaHCO3 Solution
Abstrak: Umbi porang (Amorphophallus sp.) merupakan komoditas yang diminati karena memiliki kandungan serat pangan yang tinggi. Porang dapat berkembang biak dari bulbil yang disebut kathak. Bulbil kathak porang dapat dipanen dalam jumlah yang produktif. Akan tetapi, terdapat keterbatasan lahan untuk mengembangbiakkannya. Maka dari itu, muncul kekhawatiran akan berlebihnya stok bulbil kathak porang di masa yang akan datang sehingga potensi penggunaannya sebagai bahan pangan perlu diteliti. Salah satu bahan pangan yang dapat diolah dari umbi-umbian adalah tepung, tetapi bulbil kathak mengandung oksalat yang kadarnya perlu diturunkan terlebih dahulu. Optimasi proses perendaman dalam larutan NaHCO3 hangat dapat menurunkan kadar oksalat pada umbi-umbian. Tepung yang telah melalui proses optimum akan dikarakterisasi proksimat, kadar glukomanan, warna, densitas kamba, dan profil gelatinisasi. Tepung dengan penurunan kadar oksalat optimum (62,70%) diperoleh dengan perlakuan perendaman dalam larutan NaHCO3 hangat konsentrasi 6% dengan durasi perendaman 60 menit. Tepung yang telah melewati proses optimum masih mengandung kadar air, abu, dan oksalat yang cukup tinggi serta derajat putih yang kurang baik sehingga diperlukan optimasi lebih lanjut. Berdasarkan profil gelatinisasinya, tepung bulbil kathak porang memiliki setback viscosity yang rendah sehingga cocok diaplikasikan sebagai pengental atau penstabil pada produk pangan., Porang tubers (Amorphophallus sp.) is a commodity with great demand due to its high content of dietary fiber. Porang can be cultivated from bulbil called kathak. Bulbil kathak porang can be harvested in productive quantity. However, the land to cultivate them is limited. Therefore, there’s a concern of excessive kathak porang bulbil stock in near future, so the study for its potential use as food is necessary. One of the foodstuffs that can be processed from tubers is flour, but kathak porang bulbil has oxalate content which needs to be decreased first. Optimization of the immersion process in warm NaHCO3 solution can decrease oxalate content in tubers. Flour that has gone through the optimum process will be characterized by proximate, glucomannan content, color, kamba density, and gelatinization profile. The flour with optimum decrease of oxalate content (62,70%) was obtained by immersion in warm 6% NaHCO3 solution for 60 minutes. The flour that has gone through the optimum process had high water, ash, and oxalate content, and also a less preferred whiteness degree, therefore it still needs further optimization. Based on the gelatinization profile, kathak porang bulbil flour had low setback viscosity thus suitable to be thickener or stabilizer in foodstuffs.
Keyword: bulbil kathak porang, NaHCO3, oksalat, tepung

Judul: igenvalues and Eigenvectors of Tridiagonal Matrix with Non Constant and Recurrent Diagonal Entries.
Abstrak: Matriks tridiagonal adalah suatu matriks yang mempunyai entri-entri bernilai nol kecuali pada diagonal utama, di bawah diagonal utama (subdiagonal) dan di atas diagonal utama (superdiagonal). Entri pada diagonal utama tidak konstan dan berulang. Setiap entri pada matriks tridiagonal ini adalah bilangan kompleks. Dalam karya ilmiah ini, akan dibuktikan 3 teorema untuk menentukan nilai eigen dengan 2 kasus dan 1 teorema untuk menentukan vektor eigen. Teorema pertama menentukan polinomial karakteristik dari matriks tridiagonal. Polinomial karakteristik dari matriks tridiagonal tersebut digunakan untuk menentukan nilai eigen pada teorema kedua dan ketiga serta menentukan vektor eigen pada teorema keempat
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