Judul: Effect of acetic acid and table salt solution on reduction of calcium oxalate in porang banten flour (Amorphophallus muelleri)
Abstrak: Menurunnya harga umbi porang memberikan dampak perekonomian bagi petani. Petani pada umumnya hanya mengolah umbi porang menjadi chips porang maupun tepung porang dengan kadar kalsium oksalat tinggi. Konsumsi kalsium oksalat dalam jumlah tinggi mengakibatkan gatal di tenggorokan, rasa panas di mulut, serta menyebabkan batu ginjal. Penurunan kadar kalsium oksalat dapat dilakukan dengan perendaman larutan garam dapur maupun asam asetat. Penelitian ini bertujuan mempelajari pengaruh jenis larutan, teknik perendaman, serta lama perendaman terhadap kadar kalsium oksalat dan karakteristik tepung porang. Perlakuan yang diberikan pada chips porang basah berupa perendaman dalam CH3COOH 20% dan NaCl 15%. Teknik selama perendaman adalah pengadukan dan tanpa pengadukan, masing-masing selama 60, 90, dan 120 menit. Penelitian dilakukan dalam dua tahap yaitu pembuatan tepung porang serta karakterisasi fisikokimia yang terdiri dari analisis kadar air, kadar abu, kadar glukomanan, kadar kalsium oksalat, dan nilai derajat putih. Hasil penelitian menunjukkan bahwa perlakuan pengadukan dan semakin lama perendaman mampu menurunkan kadar kalsium oksalat. Hasil penelitian terbaik diperoleh dari perendaman NaCl dengan pengadukan selama 120 menit. Perlakuan tersebut menghasilkan kadar kalsium oksalat 69,59 mg/100 g dengan persentase penurunannya sebesar 92,24% dibandingkan kontrol. Hasil karakteristik lain yang diperoleh yaitu kadar air 9,88%, kadar abu 9,23%, kadar glukomanan 43,11%, dan derajat putih 50,65%., The decline in the price of porang tubers has an economic impact on farmers. Farmers generally only process porang tubers into porang chips and porang flour with high levels of calcium oxalate. Consumption of high amounts of calcium oxalate causes itching in the throat, burning sensation in the mouth, and causes kidney stones. The decrease in calcium oxalate levels can be done by soaking in a solution of table salt or acetic acid. This study aims to study the effect of the type of solution, immersion technique, and duration of immersion on calcium oxalate levels and characteristics of porang flour. The treatment given to wet porang chips was immersion in 20% CH3COOH and 15% NaCl. The technique during immersion was stirring and without stirring, for 60, 90, and 120 minutes, respectively. The research was conducted in two stages, namely the manufacture of porang flour and physicochemical characterization consisting of analysis of moisture content, ash content, glucomannan content, calcium oxalate content, and whiteness value. The results showed that the stirring treatment and the longer soaking were able to reduce calcium oxalate levels. The best research results were obtained from soaking NaCl with stirring for 120 minutes. This treatment resulted in calcium oxalate levels of 69.59 mg/100 g with a percentage decrease of 92.24% compared to controls. Other characteristic results obtained are 9.88% moisture content, 9.23% ash content, 43.11% glucomannan content, and 50.65% whiteness.
Keyword: acetic acid, calcium oxalate, glucomannan, porang flour, salt

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: 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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