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: Processed Product Design Based on Coffee Fruit Peel at KTH Cibulao
Abstrak: Petani yang masuk ke dalam Kelompok Tani Hutan (KTH) Cibulao rata-rata menghasilkan 4 kwintal kopi per 3 bulan, pengolahan biji kopi menjadi satu- satunya keluaran dari pengolahan buah kopi, sehingga dengan presentase 40% terdapat hasil samping berupa kulit buah kopi yang kaya akan antioksidan, serat tinggi dan keunggulan lainnya yang dapat dimanfaatkan menjadi produk olahan pangan sebagai nilai tambah dari kulit buah kopi. Penelitian ini bertujuan mengembangkan produk olahan pangan dengan memanfaatkan hasil samping kulit buah kopi Cibulao dengan menetapkan alternatif solusi berdasarkan kriteria keberhasilan desain produk yaitu enak, mudah dikonsumsi, segar, dan menyehatkan dengan memperhatikan ketersediaan bahan baku dan alat sederhana. Rancangan desain produk berbasis kulit buah kopi pada penelitian ini sudah diuji pada produk dan menghasilkan antioksidan pada nilai IC50 produk kombucha cascara sebesar 26.049 mg/l ppm yang merupakan kategori antioksidan sangat kuat karena nilainya kurang dari 50 ppm, serta telah melewati tahap uji konsumen melalui metode hedonik skala 1-4 dengan kriteria (1) Sangat Tidak Suka ; (2) Tidak Suka ; (3) Suka ; (4) Sangat Suka. dengan hasil perhitungan rata-rata pada setiap parameter masuk ke dalam katergori suka dan sangat suka., Farmers who are part of the Cibulao Forest Farmer Group (KTH) produce an average of 4 quintals of coffee per 3 months, coffee bean processing is the only output from coffee cherries processing, so that with a percentage of 40% there is a by-product in the form of rich coffee berry skin. of antioxidants, high fiber and other advantages that can be utilized into processed food products as added value from coffee pod skins. This research aims to develop processed food products by utilizing the by-products of Cibulao coffee pod skin by determining alternative solutions based on product design success criteria, namely delicious, easy to consume, fresh, and healthy by taking into account the availability of raw materials and simple tools. The product design based on coffee pods in this study has been tested on products and produces antioxidants at the IC50 value of kombucha cascara products of 26,049 mg/l ppm which is a very strong antioxidant category because the value is less than 50 ppm, and has passed the consumer test stage through the method hedonic scale 1-4 with criteria (1) Very Dislike; (2) Dislike ; (3) Likes ; (4) Really Like. with the results of the average calculation on each parameter into the like and really like category.
Keyword: cascara, cherry coffee peel, Cibulao, kombucha, jam slices

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