Judul: Pengaruh Ph Larutan Penyeduh Dan Lama Penyeduhan Terhadap Kapasitas Antioksidan Ekstrak Teh Daun Sirsak (Annona Muricata Linn)
Abstrak: Daun sirsak memiliki kandungan fitokimia antioksidan yang tinggi. Di Indonesia air rebusan daun sirsak telah digunakan sebagai obat tradisional. Pada penelitian ini, daun sirsak diolah menjadi bentuk teh untuk meningkatkan kestabilannya selama penyimpanan. Penelitian ini bertujuan unuk mengkaji pengaruh pH larutan penyeduh (6, 4 dan 3) dan lama penyeduhan (5, 7.5, 10 dan 12.5 menit) terhadap kapasitas antioksidan, total fenolik dan total flavonoid dari ekstrak teh daun sirsak. Hasilnya menunjukkan bahwa kapasitas antioksidan dan total flavonoid pada larutan peyeduh pH 6 lebih besar daripada pH 3 dan 4 (p<0.05), sedangkan total fenolik tidak dipengaruhi pH larutan penyeduh (p>0.05). Lama penyeduhan (5, 7.5, 10 dan 12.5 menit) tidak berpengaruh nyata (p>0.05) terhadap kapasitas antioksidan, total fenolik dan total flavonoid yang diduga karena penurunan suhu selama penyeduhan mengakibatkan proses ekstraksi kurang efektif.
Keyword: antioksidan, lama penyeduhan, pH ekstraksi, teh daun sirsak

Judul: Pengaruh Lama Penyimpanan dan Perebusan Daun Sirsak Segar (Annona muricata Linn) terhadap Aktivitas Antioksidan Sari Daun Sirsak.
Abstrak: Soursop (Annona muricata Linn) leaves have been used as traditional medicine. Antioxidant compounds contained in the soursop leaves are steroids or terpenoids, flavonoids, coumarins, alkaloids, saponins and tannins. The objectives of this research was to assess effect of storage time (0, 3, 7 and 14 days) at low temperature (4-8oC) and boiling time (5, 7 and 10 minutes) of fresh soursop leaves with boiling water (98oC) on antioxidant activity of soursop leaves extract. Analysis performed to the extracts were water content, pH, antioxidant activity (DPPH method), total phenolics and total flavonoids. The results analysis of variance showed that soursop leaves storage and boiling time gave significant (α<0.05) impact to antioxidant activity, total phenolics, total flavonoids and pH values. Fresh soursop leaves that stored in low temperature (4-8oC) longer have lower average value of antioxidant activity, total phenolics and total flavonoids of soursop leaves extract, but higher average value of pH. Moreover, longer boiling time resulted to higher average value of antioxidant activity, total phenolics and total flavonoids extract of soursop leaves, but lower average value of pH. The best treatment is based on the highest value of antioxidant activity, obtained from soursop leaves storage time treatment of day-zero with boiling time 10 minutes.
Keyword: Annona muricata Linn, antioxidant, boiling time, storage time

Judul: Analysis of Unequal Income Distribution with Cobb-Douglas Production Function
Abstrak: This paper studies the economic growth model by Moav (2002). Moav model shows the existence of unequal income distribution between low-income with high-income community. That kind of unequal income distribution is caused by uneven distribution of income. On this Moav model, there is one area called the threshold. Threshold becomes a benchmark to determining whether a society is categorized into low- or high- income community. The production function used in this paper is the Cobb-Douglas function. The dynamics of this model is described as difference equation of low-income, threshold, and high-income community. Simulation study on the model is carried out using Maple 13 and Mathematica 7.0 software. Overall, from the observed case, high-income community will reach a stable condition earlier, followed by the threshold, and then the low-income community.
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