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: Processing Ground Coffee (Blending of Arabica and Robusta) and The Quality Changes During Storage
Abstrak: Coffee is beverage ingredient that not only popular in Indonesia but also around the world. Because either ground coffee or liquid coffee has a unique flavor which is not contained in other beverage ingredients. Some of ground coffee is derived from seed of Robusta coffee which is dominated plant in Indonesia. Seed of Robusta coffee has superior characteristic and very fast growing. However, seed quality of Robusta Coffee is poor compare with Arabica coffee that contain about 22% of yield and higher caffeine content with approximately 18% of yield. Caffeine content of Robusta Coffee causes taste of Robusta coffee is bitter, otherwise less content of caffeine will make the taste of coffee more delicious. However, the Arabica coffee has higher price due to the production capacity. In addition, changes of physical and chemical content of coffee seed also occur during roasting process. The use of different media such as stainless steel pan and clay pan also influence the taste of ground coffee because temperature during roasting period will affect acidity of steeping coffee. The purpose of this research were finding the best blending ratio between Arabica and Robusta coffee and also finding the media to obtain the maximum taste and flavor which is preferred by consumers, analyzing the characteristic and the quality change during storage temperature in level of 30°C, 35°C, and 45°C in different media packaging that are kraft paper and polypropilen (PP). This research also estimated shelf life of ground coffee through Arrhenius method. Based on organoleptic test, there were significant differences among each treatment. Analysis of moist content, VRS, coffee extract content, and pH also showed significant differences for each treatment. In the other hand, yield of ground coffee showed that there is no significant difference for every treatment. Based on result of hedonic test which is supported by result of moist content, yield, and VRS, there was selected blending ratio between 10% of Arabica coffee and 90% of Robusta coffee using clay roasting media. The best ground coffee was stored during one and a half month through observation in 10 points using kraft paper and polypropilen (PP) at several temperature levels, those are 30°C, 35°C, and 40°C. Some parameters which were measured such as: the change of moist content, (Volatile Reducing Substances), and the degree of acidity (pH). The quality of ground coffee decline during storage period. The result of the research showed that the moist content and pH vale were increasing, whereas VRS content was reducing. The packaging media that decrease quality of ground coffee was PP plastic at 30°C of temperature. Shelf life of ground coffee using PP were 13 months 27 days at 30°C of temperature, 10 months 27 days at 35°C of temperature, and 8 months 15 days at 45°C at temperature. Meanwhile, the shelf life of ground coffee using kraft paper were 3 months 27 days at 30°C of temperature, 2 months 6 days at 35°c of temperature, and 1 month 9 days at 45°C of temperature. Experiment by all parameters which are measured, it is concluded that the best ratio to blend
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Judul: Invers Drazin dari Matriks Toeplitz Singular
Abstrak: Matriks Toeplitz adalah matriks yang setiap unsur pada diagonal utama bernilai sama dan setiap unsur pada subdiagonal yang bersesuaian dengan diagonal utama juga bernilai sama. Matriks singular adalah matriks yang tidak bisa ditentukan inversnya. Akan tetapi, dapat diupayakan untuk ditentukan inversnya menggunakan invers matriks yang diperumum. Invers Drazin merupakan salah satu jenis invers matriks yang diperumum. Pada karya ilmiah ini ditentukan invers Drazin dari matriks Toeplitz singular dengan menggunakan metode Leverrier Faddeev. Kemudian, ditentukan invers Drazin dari matriks Toeplitz singular yang direpresentasikan sebagai penjumlahan segitiga bawah dan segitiga atas matriks Toeplitz berdasar pada teorema Gohberg dan Semencul., Toeplitz matrix is a matrix in with element on the main diagonal has the same value and on the subdiagonal corresponding to the main diagonal also has the same value. Singular matrix is a matrix that has no inverse. However, it can be attempted to determine the inverse using a generalized inverse matrix. Inverse Drazin is a type of generalized matrix inverse. This paper discussed the inverse Drazin for a singular Toeplitz matrix using the Leverrier Faddeev method. Then, the Drazin inverse of the singular Toeplitz matrix which is represented as a sum of products of lower and upper triangular Toeplitz matrix based on Gohberg and Semencul theorem.
Keyword: inverse Drazine, singular Toeplitz matrix