Judul: Application of Honey Process for  “Coastal Arabica” Coffee at Yuam Roasted Coffee Kebumen Jawa Tengah
Abstrak: Kopi memiliki peran yang cukup penting dalam kegiatan perekonomian Indonesia. Yuam Roasted Coffee menjual kopi yang area tanamnya tergolong dataran rendah baik kopi jenis robusta maupun arabika. Produktivitas kopi arabika pesisir di kawasan ini tergolong rendah sehingga perlu dilakukan variasi pengolahan baru, seperti honey process. Tujuan penelitan ini adalah mengetahui perbedaan kandungan kopi, penerimaan konsumen, serta mengnalisis nilai finansialnya jika diolah menggunakan honey process dan dibandingkan dengan fullwashed process yang lebih umum digunakan. Pengujian kandungan yang dilakukan meliputi kadar air, kadar abu, kadar lemak, kadar sari yang menggunakan analisis proksimat gravimetri, serta pengujian kadar kafein yang menggunakan alat spektrofotometer. Pengujian penerimaan dilakukan menggunakan uji organoleptik hedonik. Analisa finansial menggunakan parameter net present value dan benefit/cost ratio. Hasil penelitian menunjukkan penerapan honey process pada kopi arabika pesisir mengubah secara nyata kadar air, kadar sari, kadar gula dan kadar kafein. Cita rasa secara keseluruhan dari honey process memiliki penerimaan lebih baik (nilai penerimaan rata-rata 3,77). Analisa finansial honey process memiliki nilai lebih tinggi (awalnya memiliki nilai NPV sebesar Rp 243.081.500 dan b/c ratio 1,42 untuk fullwashed process. Kemudian nilai proyeksinya bertambah menjadi sebesar Rp 326.245.222 dan 1,64 untuk honey process), Coffee has an important role in Indonesia's economic activities. Yuam Roasted Coffee sell coffee where planted in lowlands both robusta and arabica coffee. Arabica coffee productivity here is relatively low so it is necessay to carry out a new processing such as honey processing. The purpose of this research is to find out the differences in coffee content, consumer preferences, and to see the financial analysis when coffee is processed using the honey processing, compared with the fullwashed processing which is more commonly used. The method tests that carried out includes water content, ash content, fat content, extract content using the gravimetric proximate analysis, as well as caffeine content test using a spectrophotometer. Preferred testing is done using hedonic organoleptic tests. While the financial analysis uses by net present value and benefit/cost ratio parametric. The research showed that application of honey process for “coastal arabica” coffee changes moisture content, extract content, sugar content and caffein content significanly. The overall taste of honey process have higher value (average preference is 3,77) and the finance analysis is higher (NPV and b/c ratio were Rp135.048.284 and 1,24 for fullwashed process and then increase to Rp 326.245.222 and 1,64 for honey process).
Keyword: Kopi Arabika Pesisir, honey process, kandungan kopi, preferensi, analisis finansial

Judul: Effect of Initial Temperature and Degree of Roasting on Physicochemical Properties and Taste of Solok Arabica Coffee
Abstrak: Kopi merupakan salah satu komoditas ekspor unggulan dari Indonesia. Pengolahan biji kopi menjadi minuman siap saji terbagi menjadi dua yaitu pengolahan primer dan pengolahan sekunder. Proses penyangraian adalah salah satu proses pada pengolahan sekunder. Variabel yang digunakan pada saat proses penyangraian beragam diantaranya adalah suhu awal dan derajat penyangraian. Penelitian ini bertujuan untuk menganalisis sifat fisikomia dan melakukan uji citarasa terhadap kopi Arabika Solok dengan perlakuan suhu awal dan derajat penyangraian yang berbeda. Penelitian diawali dengan melakukan analisis sebelum sangrai, melakukan penyangraian dengan suhu awal 180C, 200C dan 220C pada setiap derajat sangrai ringan (light), sedang (medium) dan gelap (dark) serta melakukan pengujian terhadap sifat fisikomia dan citarasa kopi Arabika Solok. Analisis data yang dihasilkan menggunakan Analisis of Variance (ANOVA) dua arah dan jika menghasilkan pengaruh yang signifikan dilanjutkan dengan uji Duncan’ Multiple Range Test (DMRT). Hasil penelitian menunjukkan bahwa suhu awal penyangraian hanya mempengaruhi sifat rendemen, atribut flavour dan aftertaste, sedangkan derajat penyangraian berpengaruh signifikan terhadap beberapa sifat fisikomia diantaranya rendemen, densitas kamba, kadar air, warna, keasaman (pH) dan beberapa atribut citarasa diantaranya fragrance, flavour, acidity, body, aftertaste, sweetness dan overall dan tidak ada interaksi antara kedua variabel terhadap semua sifat yang diuji. Sifat fisikomia dan citarasa yang tidak terpengaruh suhu awal dan derajat penyangraian adalah kadar abu, aktivitas antioksidan, balance, uniformity, dan clean cup. Kopi dengan perlakuan derajat sangrai medium mendapatkan skor akhir tertinggi yaitu 82,3 (specialty)., Coffee is one of the leading export commodities from Indonesia. Processing of coffee beans into ready-to-drink drinks is divided into two, namely primary processing and secondary processing. Roasting process is one of the processes in secondary processing. Variables used during the roasting process include the initial temperature and the degree of roasting. This study aims to analyze the physicochemical properties and perform taste tests on Arabica Solok coffee with different initial temperatures and roasting degrees. The study begins with the analysis before roasting, then roasting with the initial temperature of 180οC to 200οC and 220οC at any degree of roasting light, medium and dark and for the last, testing of the physicochemical and taste properties of Solok Arabica coffee. Analysis of the resulting data using two-way Analysis of Variance (ANOVA) and if it gives a significant effect, then continued with the Duncan' Multiple Range Test (DMRT). The results showed that the initial roasting temperature only affected the yield, flavor and aftertaste attributes . While the degree of roasting has a significant effect on several physicochemical properties including yield, density of kamba, water content, color, acidity (pH) and several taste attributes including fragrance, flavor, acidity, body, aftertaste, sweetness and overall and there is no interaction between two variables on all tested properties. The physicochemical properties and taste attributes that were not affected by the initial temperature and roasting degree were ash content and antioxidant activity, balance, uniformity, and clean cup. Coffee with medium roasting degree treatment got the highest final score of 82,3 (specialty).
Keyword: Arabic, physicochemistry, roasting, taste, specialty

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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