Judul: Effect of Drying Method on Organoleptic Properties of Arabica Coffee Beans
Abstrak: Sektor pertanian menjadi aspek penting dalam kehidupan manusia dan menjadi penunjang kehidupan seluruh masyarakat Indonesia, salah satunya adalah kopi. Kopi tidak hanya berperan sebagai sumber devisa melainkan juga merupakan sumber penghasilan bagi kurang lebih dari satu setengah juta jiwa petani kopi di Indonesia. Salah satu yang menjadi daya tarik terhadap kopi adalah dari segi citarasa kopi. Salah satu tahapan yang menentukan mutu dan kualitas kopi adalah pengeringan, dimana kadar air maksimal pada biji kopi kering menurut SNI yaitu 12.5% dan kualitas kopi akan menentukan citarasa kopi itu sendiri. Tujuan dilakukan penelitian ini adalah untuk mengetahui pengaruh metode pengeringan terhadap citarasa biji kopi arabika. Penelitian ini dilakukan pada bulan Juni hingga Oktober 2020 di Laboratorium Teknik Pengolahan Pangan dan Hasil Pertanian (TPPHP), Laboratorium Leuwikopo, Greenhouse Seafast, dan Balai Penelitian Tanaman Industri dan Penyegar (BALITTRI) Sukabumi. Sampel yang digunakan adalah buah kopi arabika varietas sigarar utang petik merah yang diolah dengan proses basah (full washed). Metode pengeringan yang digunakan adalah metode pengeringan Sun Drying, Efek Rumah Kaca (ERK), Mechanical Drying, dan pengeringan dengan angin (kering angin). Hasil penelitian menunjukkan perbedaan metode pengeringan tidak memberikan perbedaan yang signifikan terhadap citarasa biji kopi arabika. Metode pengeringan Mechanical Drying menunjukkan waktu pengeringan dengan efektifitas waktu tertinggi selama 18 jam dengan besar drying rate 2,324 %/jam untuk mengeringkan biji kopi dari kadar air 54% sampai 11% dengan hasil cupping skor didapat sebesar 76,1 dan masuk kedalam kategori fine commercial menurut SCAA (Specialty Coffee Association of America)., The agricultural sector is an important aspect of human life and supports the lives of all Indonesians, one of which is coffee. Coffee not only acts as a source of foreign exchange but is also a source of income for approximately one and a half million coffee farmers in Indonesia. One of the main attractions of coffee is the taste of coffee. One of the step that determines the quality of coffee is drying, where the maximum moisture content in drying coffee beans according to SNI is 12.5% and the quality of the coffee will determine the taste of the coffee itself. The purpose of this research was to investigate the effect of the different drying methods to the organoleptics of arabica coffee beans. This research was conducted from June to October 2020 at the Food and Agricultural Products Processing Engineering Laboratory (TPPHP), Leuwikopo Laboratory, Greenhouse Seafast, and Research Institute of Industrial Plant and Refreshments (BALITTRI). The samples used were arabica coffee cherries, varieties of sigarar utang that were processed using a wet process (full washed). The drying method used were Sun Drying, Greenhouse Effect (ERK), Mechanical Drying, and wind Drying. The results of research showed that the different drying methods did not give a significant difference to the taste of Arabica coffee beans. Mechanical Drying methode was found as a methode which have a highest time efficiency compared with another methods with drying time of 18 hours with amount of drying rate 2,324 %/hour to drying a cofffee beans moisture content from 54% to 11% with a cupping score 76,1 and it is categorized fine commercial according to SCAA (Specialty Coffee
Keyword: Cupping, Arabica coffee, Drying method, Organoleptic

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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