Judul: Immersion Treatment by Lime Solution in Making Mango (Mangifera indica L. var. Ariumanis) Peel Extract which was Added to Mango Puree
Abstrak: The arumanis mango (Mangifera indica L var. Arumanis) puree product with mango peel extract addition had the highest antioxidant activity compared to puree from flesh only or unpeeled mango. However, the addition of extracts to mango puree produced dark color, bitter taste and astringent flavor which was suspected to be caused by high tannin content in the skin, about 15%. The objective of this research was to study the improvement of sensory quality and antioxidant ability of arumanis mango peel extract by removing tannin using peel immersion in lime solution treatment before extraction. In addition, in this research also studied the optimum sensory results and antioxidant activity of the arumanis mango puree that had been added with the extract obtained. The making of the puree mango added to the extract was implemented using the method of previous studies by modifying part of sample preparation because there was a soaking treatment in lime solution before extraction. Formula optimization was performed using Response Surface Methodology (RSM) with the Design Expert 11 program. The immersion treatment of mango peel by lime solution before extraction could reduce tannin levels in mango peel extract significantly by 39%. The result of formula optimization of mango puree with peel extract addition 0.7% could reduce tannin levels significantly by 28% without decreasing their antioxidant activity. However, immersion treatment by lime solution was unable to improve sensory acceptance on either the color attribute, aroma, taste, or overall.
Keyword: Puree, Ekstrak Kulit Mangga, Tanin, Larutan Kapur, Response Surface Methodology

Judul: Total Phenolic and Flavonoids Content, and Antioxidant Activity of Mango Peel Extract of Cengkir Variety based on Simplisia’s Particle Size
Abstrak: Kulit mangga diketahui memiliki senyawa polifenol sehingga berpotensi sebagai antioksidan. Aktivitas antioksidan pada kulit mangga dapat ditingkatkan dengan memperkecil ukuran partikel simplisia. Penelitian ini bertujuan menentukan pengaruh ukuran partikel simplisia terhadap kadar total fenolik dan flavonoid, serta aktivitas antioksidan ekstrak kulit mangga varietas cengkir. Penelitian ini menggunakan dua ukuran partikel simplisia yang berbeda. Kulit mangga diekstraksi dengan cara maserasi menggunakan pelarut air. Kadar total fenolik dan flavonoid, serta aktivitas antioksidan dari masing-masing ekstrak diukur secara kolorimetri. Hasil penelitian menunjukkan kadar total fenolik ekstrak 40 mesh (≤420 x 103 nm) dan ekstrak nanopartikel (597 nm) kulit mangga varietas cengkir berturut-turut sebesar 156,61 ± 2,32 mg GAE/g bobot kering dan 170,42 ± 2,84 mg GAE/g bobot kering. Kadar total flavonoid ekstrak 40 mesh dan ekstrak nanopartikel kulit mangga varietas cengkir berturut-turut sebesar 115,76 ± 0,96 mg QE/g bobot kering dan 132,15 ± 1,05 QE/g bobot kering. Ekstrak 40 mesh kulit mangga varietas cengkir termasuk antioksidan sedang, sedangkan ekstrak nanopartikel kulit mangga varietas cengkir termasuk antioksidan kuat. Ukuran partikel simplisia secara positif memengaruhi kadar total fenolik dan flavonoid, serta aktivitas antioksidan kulit mangga varietas cengkir., Mango peel is known to contain polyphenol compounds so its potential as antioxidant. The antioxidant activity of mango peel can be increase by reducing the simplisia’s particle size. This research was aimed to determine the effects of simplisia’s particle size on total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity of cengkir mango peels. This research used two differents simplisia’s particle size. Mango peel was extracted by maceration using water as a solvent. TPC, TFC, and antioxidant activity of each extract were measured in colorimetric way. The result showed that TPC of 40 mesh (≤420 x 103 nm) extract and nanoparticle (597 nm) extract of cengkir mango peels were 156,61 ± 2,32 mg GAE/g dry weight and 170,42 ± 2,84 mg GAE/g dry weight, respectively. The TFC of 40 mesh extract and nanoparticle extract of cengkir mango peels were 115,76 ± 0,96 mg QE/g dry weight and 132,15 ± 1,05 mg QE/g dry weight, respectively. The 40 mesh extract of cengkir mango peels were moderate antioxidant, while the nanoparticle extract of cengkir mango peels were strong antioxidant. Simplisia’s particle size positively affects the TPC, TFC, and antioxidant activity.
Keyword: antioxidant, cengkir mango peels, flavonoid, nanoparticle, phenolic

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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