Judul: Adsorption Process in Stevia Extract Purification (Stevia rebaudiana) with Ca-Bentonite Adsorbent.
Abstrak: Peningkatan industri makanan dan minuman berbanding lurus terhadap kenaikan permintaan gula sebagai pemanis. Tanaman stevia (Stevia rebaudiana) merupakan pemanis alami substitusi gula tebu, memiliki tingkat kemanisan 200-300 kali yang disebabkan oleh kandungan steviosida. Proses pemurnian ekstrak kasar stevia menggunakan metode adsorpsi untuk mereduksi kadar pengotor tanin dan klorofil, komponen rasa pahit dalam ekstrak. Adsorben bentonit kalsium teraktivasi asam dapat menjerap lebih banyak komponen pengotor. Variabel yang digunakan dalam penelitian ini adalah konsentrasi adsorben dalam ekstrak kasar gula stevia (1, 5, dan 10% b/v), suhu pemurnian (30 dan 50 °C), dan waktu pemurnian (15, 30, 45, dan 60 menit). Hasil penelitian menunjukkan pada perlakuan konsentrasi adsorben 5% (b/v), suhu 30 °C, dan waktu 15 menit menghasilkan penurunan kadar steviosida sebesar 22% (b/v), penurunan kadar pengotor tanin dan klorofil sebesar 30% dan 31% (b/v), serta meningkatkan kejernihan ekstrak mencapai 33% dari ekstrak sebelumnya., The growth of food and beverages industry directly increased the sugar need for additional food. The stevia plants (Stevia rebaudiana) are known as a natural sweetener for the common table sugar substitute of more than 200-300 sweetness from stevioside. Purification of stevia crude extract used adsorption method, to reduced tannins and chlorophyll, a bitter taste component from the extract. Activated calcium bentonite showed good performance to adsorb impurities. Variable process used in this research was activated calcium adsorbent in stevia crude extract (1, 5, and 10% w/v), temperature (30 and 50 °C), and time (15, 30, 45, and 60 minutes). The results shown that the adsorbent concentration of 5% (w/v), temperature 30 °C, and time process of 15 minutes, would decreased tannins and chorophyll by 30% and 31% (w/v), and increased clarity extract up to 33%. The losses of stevioside were 22% (w/v) to achieve more clear solution.
Keyword: adsorpsi, kejernihan, klorofil, steviosida, tanin

Judul: Aplikasi Proses Adsorpsi untuk Pemurnian Ekstrak Cair Stevia (Stevia rebaudiana)
Abstrak: Pemanis stevia merupakan alternatif pemanis alami rendah kalori yang dihasilkan dari proses ekstraksi daun kering tanaman stevia menggunakan air. Ekstraksi daun stevia menghasilkan larutan yang berwarna kecoklatan dan sedikit rasa pahit atau getir. Proses pemurnian diperlukan untuk memperoleh ekstrak dengan kualitas yang sesuai untuk kegiatan komersil. Proses pemurnian ekstrak cair stevia bertujuan untuk mengurangi konsentrasi pengotor dalam ekstrak, yaitu klorofil dan tanin. Metode pemurnian yang digunakan adalah adsorpsi menggunakan bentonit Na teraktivasi asam. Variabel yang digunakan dalam penelitian adalah rasio adsorben bentonit Na dan ekstrak cair stevia (1%, 5%, dan 10% b/v), waktu pemurnian (15, 30, 45, dan 60 menit), dan suhu pemurnian (30 dan 50°C). Hasil penelitian menunjukkan perlakuan pemurnian pada rasio adsorben – ekstrak 10% (b/v), suhu pemurnian 30°C, dan waktu pemurnian 15 menit. Kondisi perlakuan ini menghasilkan peningkatan kejernihan sebesar 69,74%, penurunan konsentrasi tanin sebesar 51,79%, penurunan konsentrasi klorofil sebesar 45,58%, dan penurunan konsentrasi steviosida sebesar 46,54%. Bentonit Na dapat digunakan sebagai adsorben dalam pemurnian stevia namun tidak selektif terhadap komponen tertentu dalam ekstrak stevia., Stevia can be used as one of low-calories natural sweetener by extract dried-leaf stevia plant using water as a solvent. Crude extract of stevia is sweet with bitter testing and dark brown color. Purification is essential process needed by crude extract stevia before use in commercial industry. Purification aimed to remove all impurities in stevia extract, such as tannin and chlorophyll. The process variable used in this research is ratio bentonite Na and crude extract (1%, 5%, and 10% b/v), time (15, 30, 45, and 60 minutes), and temperature (30 and 50 °C). The final result in this research was purification using temperature at 30°C for 15 minutes in ratio bentonite Na and crude extract 10% (b/v) could increase clarity 69.74%. This result followed by decreasing 51.79% tannin, 45.58% chlorophyll, and also decreasing 46.54% steviosides. Na-bentonite could be used as adsorbent but didn’t selective in certain component of stevia extract.
Keyword: adsorption, Na-Bentonite, stevia extract

Judul: Construction of Strongly Optimal Binary Linear Code with Minimum Distance 9 and 11
Abstrak: A binary linear code of length n over q F is a subspace of n q F . A code has three parameters that attached to it, namely length, dimension, and minimum distance. A code with length n, dimension k and minimum distance d is often called [n, k, d ]-code. Usually, when two parameters are given, then we want to find a code that has the best value for the last parameter. Based on Gilbert- Varshamov bound, if a [n, k, d ]-code exists and can not be expanded, we call it a strongly optimal code. In this paper, we construct strongly optimal code with minimum distance 9 and 11. In constructing the code, we created a theorem and algorithm based on Gilbert-Varshamov bound before we implement the algorithm to MAPLE programming language. Because of computational limitations, the program can only construct up to k = 10 for d = 9 and k = 12 for d = 11.
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