Judul: Characteristics of Spirulina Yoghurt by starter Lactobacillus plantarum SK(5) in Different Biomass Concentration and Incubate Term
Abstrak: Lactobacillus plantarum SK(5) merupakan bakteri probiotik asal bekasam dan dapat digunakan sebagai starter dalam pembuatan yoghurt. Spirulina platensis termasuk kedalam cyanobacteria yang memiliki banyak manfaat bagi tubuh. Penambahan spirulina dalam fermentasi yoghurt dengan starter L. plantarum SK(5) bertujuan menentukan suhu dan lama fermentasi yoghurt spirulina berdasarkan perubahan pH menentukan pengaruh perbedaan konsentrasi spirulina basah dan waktu inkubasi terhadap nilai pH, kadar asam tertitrasi, dan total BAL yoghurt spirulina; serta menentukan karakteristik yoghurt terpilih setelah fermentasi 24 jam. Penelitian terdiri dari empat tahap yaitu 1) penyegaran dan kultivasi spirulina; 2) penyiapan kultur starter L. plantarum SK(5); 3) penentuan waktu dan suhu inkubasi yoghurt spirulina; 4) Pembuatan yoghurt spirulina dengan waktu dan suhu inkubasi terpilih menggunakan starter L. plantarum SK(5). Suhu dan lama fermentasi terbaik pada yoghurt spirulina terpilih yaitu 37oC dan 24 jam. Penambahan spirulina dan waktu inkubasi mempengaruhi secara nyata terhadap nilai pH, kadar TAT, dan total BAL yoghurt spirulina. Penambahan spirulina 1.5% dengan lama fermentasi 24 jam merupakan perlakuan terpilih berdasarkan nilai pH dan kadar TAT. Karakteristik dari yoghurt spirulina terpilih memiliki nilai pH 3.9, kadar TAT 1.195%, Total BAL 9.11 log cfu/mL, viskositas 85.25 cPs, kadar protein 38.43%, kadar lemak 26.93%, dan nilai IC50 297.06 mg/L., Lactobacillus plantarum SK(5) is a probiotic bacteria which isolated from bekasam and that can be used as starter in yoghurt process. Spirulina platensis belong to cyanobacteria which hold many function for healthy. The addition spirulina in yoghurt with starter L. plantarum SK(5) expected to determined effect of temperature and time of fermentation yoghurt spirulina by based on pH, determined effect of spirulina wet biomass concentration and incubation time to pH, total acid content, with total L. plantarum SK(5), and the characteristics of selected product after fermentation for 24 hours. This research consist to four stage namely 1) refreshing and cultivation of spirulina; 2) the preparation culture starter L. plantaurm SK(5); 3) the determination time and temperature of incubation yoghurt spirulina; 4) the production yoghurt spirulina with the selected time and temperature using L. plantarum SK(5) as starter. The temperature and incubation time selected for spirulina yoghurt were 37oC and 24 hour. The addition spirulina and incubation time had a significant effect on the pH alue, the levels of TAT, and total LAB yoghurt spirulina.The best treatments in this research was the addition of 1.5% spirulina with incubation times of 24 hours. Characteristics of yoghurt spirulina 1.5% include pH 3.9, total acids contents 1.195%, total LAB 9.11 log cfu/mL, viscosity 85.25 cPs, protein contents 3.00%, fat contents 3.14%, and IC50 287.06 mg/L
Keyword: lactic acids, Lactobacillus plantarum SK(5), probiotic, spirulina, spirulina yoghurt

Judul: Characteristic of Powdered Spirulina Yoghurt with Lactobacillus plantarum SK (5) Starter During Storage
Abstrak: Pembuatan yoghurt spirulina bubuk dengan metode spray drying dapat dilakukan untuk meningkatkan masa simpan produk yoghurt spirulina. Tujuan penelitian ini membandingkan karakteristik yoghurt spirulina cair dan bubuk dan menentukan pengaruh penyimpanan terhadap nilai aw, viabilitas bakteri asam laktat, dan aktivitas antioksidan yoghurt spirulina bubuk selama 28 hari di suhu ruang. Yoghurt spirulina dibuat melalui fermentasi susu dengan 15% starter L. plantarum SK (5) dan 1.5% biomassa basah S. platensis hasil kultivasi. Yoghurt spirulina bubuk disimpan dalam kemasan PET/ALU/LLDPE pada suhu ruang (27-29 oC), lalu dilakukan pengamatan setiap 7 hari. Yoghurt spirulina bubuk memiliki kadar air, kadar protein, kadar lemak, nilai pH, kadar TAT, total BAL, dan aktivitas antioksidan yang berbeda nyata dengan yoghurt spirulina cair. Yoghurt spirulina bubuk memiliki rendemen 6.42%, nilai aw 0.32, kelarutan 72.75%, dan ukuran partikel 5.818 µm. Perlakuan lama penyimpanan tidak berpengaruh secara nyata terhadap total BAL yoghurt spirulina bubuk (P<0,05), namun nilai aw dan aktivitas antioksidan yoghurt spirulina bubuk mengalami perubahan yang signifikan setelah penyimpanan 28 hari., Spirulina yoghurt shelf life could be improved by making a powdered yoghurt with spray drying method. The aim of this study was to compare the characteristics of liquid and powdered spirulina yoghurt and the changes in water activity (aw), lactic acid bacteria (LAB) viability, and antioxidant activity of powdered spirulina yoghurt during 28 days of storage. Spirulina yoghurt was made by fermentation process of milk with 15% starter of L. plantarum SK (5) dan 1.5% wet biomass of cultivated S. platensis. Spirulina yoghurt powder was kept in PET/ALU/LLDPE pouches at room temperature (27-29 oC), and observed per 7 days. The moisture content, protein content, fat content, pH values, TAT levels, total LAB, and antioxidant activity of spirulina yoghurt powder has a significant difference with spirulina liquid yoghurt. Spirulina yoghurt powder has 6.42% of yield, 0.32 of aw level, 72.75% of solubility, and 5.818 µm of particle size. The storage time treatment did not affect the total LAB of spirulina yoghurt powder significantly (P<0,05), but the aw levels and antioxidant activity was changed significantly after 28 days storage.
Keyword: antioksidan, fermentasi, Lactobacillus plantarum SK (5), probiotik, spray drying, yoghurt

Judul: Penentuan Harga Opsi Put Amerika dengan Simulasi Monte Carlo
Abstrak: An American option is an option that can be exercised at the strike price anytime before or on the date of expiration. In this thesis, Monte Carlo simulation for valuation of American option is presented. Monte Carlo simulation is one of the numerical methods used to determine the price of American options. The simulation provides several examples of initial stock price , rate of interest , exercise time , volatility , and strike price K. The simulation study shows the cost of the option c decreases when S increases, c decreases when r increases, c increases when T increases, c increases when  increases, and c increases when K increases.
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