Judul: Process Design and Physicochemical  Characterics of Arabica Coffee (Coffea arabica) Skin Extract
Abstrak: Kulit kopi memiliki kandungan yang sangat bermanfaat bagi tubuh. Kulit kopi dihasilkan dari pengolahan kopi yang menghasilkan sekitar 50% kulit kopi dari hasil panen cherry kopi. Salah satu kandungan kulit kopi yang sangat bermanfaat adalah asam klorogenat yang dapat berguna sebagai antioksidan. Tujuan penelitian ini adalah merancang desain proses ekstraksi komponen bahan aktif kulit kopi dan mengkarakteristik komposisi fisikokimia ekstrak kulit kopi. Penelitian ini dilakukan dengan tahapan desain keteknikan yang terdiri dari tahap eksplorasi, pendefinisian masalah, ideasi, pengembangan prototipe, dan validasi. Uji proksimat menunjukkan kandungan tertinggi dalam kulit kopi adalah karbohidrat sebesar 25,637% dan serat kasar 39,894%. Kulit kopi kemudian dimaserasi dengan 3 iterasi yakni iterasi 0 tanpa perlakuan, iterasi 1 dengan penggunaan selulase serta iterasi 2 dengan kombinasi penggunaan selulase dan pektinase. Iterasi 2 memberikan hasil ekstrak dengan kadar antioksidan paling baik yakni 1,21µg/ml. Desain proses ekstraksi yang dihasilkan adalah pengecilan kulit kopi, pelarutan menggunakan air, penambahan enzim pektinase dan selulase, maserasi selama 24 jam pada suhu kamar, filtrasi, dan mendapatkan ekstrak kulit kopi., Coffee skin has very beneficial content for the body. Coffee skin was produced from coffee processing which produced about 50-60%% of coffee skin from the coffee cherry harvest. One of the most beneficial contents of coffee skin was chlorogenic acid which could be useful as an antioxidant. The purpose of this research was to design the process of extracting the active ingredient components of coffee skin and characterizing the physicochemical composition of coffee skin extract. This research was conducted with engineering design stages consisting of exploration, problem definition, ideation, prototype development, and validation. Proximate test showed that the highest content in coffee skin was carbohydrate at 25.637% and crude fiber at 39.894%. The coffee skin was then macerated with 3 iterations, iteration 0 without treatment, iteration 1 with the use of cellulase and iteration 2 with a combination of cellulase and pectinase. Iteration 2 gave the extract with the best antioxidant content of 1.21µg/ml. The design of the resulting extraction process was the reduction of coffee skin, dissolving using water, adding pectinase and cellulase enzymes, maceration for 24 hours at room temperature, filtration, and obtaining coffee skin extract.
Keyword: Coffee skin, extraction, enzyme, antioxidant, design engineering

Judul: Proses Pembuatan Functional Drink dari Ekstrak Kulit Kopi
Abstrak: Kulit kopi memiliki potensi sebagai bahan baku berbagai produk dikarenakan adanya kandungan senyawa aktif seperti tanin, pektin, kafein, asam klorogenat, dan antosianin. Salah satu potensi kulit kopi adalah diolah menjadi minuman fungsional yang bermanfaat untuk kesehatan. Tujuan dari penelitian ini adalah mengembangkan minuman fungsional ekstrak kulit kopi dengan mengetahui kadar proksimat kulit kopi, menentukan proses ekstraksi terbaik dengan rendemen dan aktivitas antioksidan tinggi serta membandingkan minuman fungsional ekstrak kulit kopi tanpa dan dengan lemon. Penelitian dilakukan dengan analisis proksimat, ekstraksi kulit kopi, pembuatan functional drink, dan uji organoleptik. Analisis proksimat kulit kopi menunjukkan kadar air sebesar 2,237%, kadar lemak 7,033%, kadar abu 4,033%, kadar protein 11,196%, kadar karbohidrat 25,637%, dan kadar serat kasar 39,894%. Ekstrak kulit kopi terbaik diperoleh dengan bantuan enzim selulase dan pektinase dengan rendemen sebesar 23,50% dan aktivitas antioksidan sebesar 1,21 µg/ml. Hasil uji organoleptik menunjukkan minuman fungsional ekstrak kulit kopi dengan penambahan ekstrak lemon adalah produk terbaik dari penelitian ini., Coffee cherry skin has the potential to be used as a raw material for various products due to the content of active compounds such as tannins, pectin, caffeine, chlorogenic acid and anthocyanins. One of the potentials of coffee cherry skin is to be processed into a functional drink that is beneficial for health. The purpose of this research is to develop a functional drink from coffee skin extract by determining the proximate content of coffee skin, identifying the best extraction process with high yield and antioxidant activity, and comparing the functional drink made from coffee skin extract with and without lemon. The research was conducted through proximate analysis, coffee skin extraction, functional drink formulation, and sensory evaluation. Proximate analysis of coffee skin revealed a moisture content of 2,237%, fat content of 7,033%, ash content of 4,033%, protein content of 11,196%, carbohydrate content of 25,637%, and crude fiber content of 39,894%. The best coffee skin extract was obtained using cellulase and pectinase enzymes, with a yield of 23,50% and antioxidant activity of 1,21 µg/ml. Results from the sensory evaluation indicated that the functional drink made from coffee skin extract with added lemon extract was the best product from this research.
Keyword: functional drink, coffee skin, extraction, enzyme

Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model