Judul: Proses pengolahan kopi bubuk (campuran arabika dan robusta) serta perubahan mutunya selama penyimpanan
Abstrak: Kopi merupakan bahan minuman yang tidak saja terkenal di Indonesia tapi juga terkenal di seluruh dunia. Hal ini disebabkan karena kopi, baik dalam bentuk bubuk maupun seduhannya memiliki aroma yang khas yang tidak dimiliki oleh bahan minuman lainnya. Di Indonesia, sebagian kopi bubuk yang dihasilkan adalah berasal dari biji kopi jenis robusta karena biji kopi jenis ini mendominasi perkebunan kopi di Indonesia hingga saat ini karena mempunyai sifat yang lebih unggul dan sangat cepat berkembang. Akan tetapi, kualitas buah dari kopi robusta lebih rendah daripada kopi arabika dengan rendemen kira-kira 22% serta memiliki kandungan kafein yang lebih tinggi dibandingkan dengan kopi arabika dengan rendemen kira-kira 18%. Kandungan kafein kopi robusta yang tinggi yang menyebabkan seduhan kopinya terasa lebih pahit, karena semakin kecil kandungan kafein dalam biji kopi maka akan semakin enak rasa kopi yang dihasilkan. Namun, kopi arabika memiliki rata-rata produksi sedang dengan harga yang relatif lebih tinggi dibandingkan dengan kopi robusta. Selain itu, perubahan sifat fisik dan kimia pada biji kopi juga terjadi pada saat penyangraian. Penggunaan media penyangraian yang berbeda seperti wajan stainless steel dan wajan tanah liat juga dapat mempengaruhi cita rasa dari kopi bubuk yang dihasilkan karena suhu pada saat penyangraian akan mempengaruhi keasaman dari seduhan kopi. Tujuan Penelitian ini adalah mendapatkan perbandingan blending kopi arabika dan robusta serta media penyangraian yang terbaik agar memperoleh aroma dan rasa yang maksimal yang disukai konsumen, mengetahui karakteristik kopi bubuk yang dihasilkan, serta mengetahui pengaruh kemasan yang digunakan, yaitu kertas kraft dan plastik Polypropilen (PP) selama penyimpanan kopi bubuk terbaik yang dihasilkan sebelumnya pada suhu 30oC, 35oC, dan 45oC terhadap perubahan mutunya serta melakukan pendugaan umur simpan dengan metode Arrhenius…
Keyword: Blending, Ground coffee, Stored, Shelf life, Bogor Agricultural University, Institut Pertanian Bogor, IPB

Judul: Pengaruh Penambahan Bahan Aditif Dalam Proses Pengolahan Kopi Bubuk dan Perubahan Mutunya Selama Penyimpanan
Abstrak: The ground coffee is the coffee beans which are roasted and then ground, with or without the addition of other materials in certain amount that is not harmful to health. The addition of additives in the roasting process such as butter, margarine, and oil is expected to be able to improve the flavor of ground coffee because of the flavors contained in each of these additives. The roasting process used different media like a clay or stainless steel pan that was believed to be able to increase the flavor of ground coffee due to its level of heat delivery that might affect the acidity of coffee brew. The objective of this study was to find out the effects of additives in the roasting process on the ground coffee produced and to learn the quality changes during storage and shelf life prediction. The research was preceded by determining the test characteristics of coffee beans (Arabica and Robusta). The test results showed that water content of robusta and arabica coffee beans was respectively 10.25% (wb) and 14.71% (wb). The ash content was 4.57% (db) and 3.90% (db). The protein content was at 13.47 % (db) and 11.08% (db). The fat content was 1.17 (db) and 2.15% (db). The fiber content was 68.31(db) and 67.20% (db). Finally, the carbohydrate by difference was 2.23% and 0.96%. The research proceeded with the making of ground coffee with a treatment, namely with the addition of additives and the difference in roasting media in the coffee roasting process. The comparison blending of arabica and robusta coffee used was 60:40. Meanwhile, the concentration of an additive used was 3%. The ground coffee obtained underwent a test to find out the water content, VRS (Reducing Volatile Substance), pH, levels of pollen, and organoleptic. Based on the test, it was found out that the best ground coffee was the ground coffee without the addition of additives and the use of a clay pan in its roasting process. The conclusion was that the addition of additives had no significant effect on the ground coffee produced. The best ground coffee was kept to determine the quality changes during storage. The ground coffee packed with PP plastic and kraft paper was stored at temperatures of 30 0C, 35 0C and 45 0C. Based on linear regression, the quality of ground coffee during storage tends to decline characterized by the increase in water content, VRS, and increase in the pH. The estimation of shelf life is conducted to find out the age of the product. In the prediction of shelf life, a critical parameter used is the water content. This is because the product water content is the most rapid element that causes the decrease in the quality of ground coffee and even damage to ground coffee. Based on the Arrhenius method, product shelf life of ground coffee that was packed with kraft paper was 71 days at 30 0C, 53 days at 35 0C, and 40 days at 45 0C. Meanwhile, the coffee products that were packed with plastic PP, the shelf life was 325
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Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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