Skip to main content

Pengaruh Kadar Air dan Kerapatan Biji Kopi Terhadap Proses Roasting Kopi



How Green Coffee Quality Affects Roasting

MOISTURE CONTENT
In roasting, the moisture content of the green bean plays an important role. Under normal conditions, green coffee beans have a moisture content of 10–12 percent. The moisture content will fluctuate freely with the relative humidity content of the ambient air. In cities like Amsterdam and San Francisco, relative humidity levels throughout the year are nearly perfect for storing green beans over a length of time, and for slowing down the aging process of green coffee. This also reduces the likelihood that the roaster operator has to change roast profi les to compensate for possible variances in green coffee moisture.

The moisture inside the green beans is partially free or is present as bound moisture and contained in the carbohydrate molecules. bWe can summarize the roasting process as a three-stage cycle:

The drying phase is when the moisture content of the coffee is reduced to about two percent. During this phase, the “free” moisture—the residue of the process from cherry to green bean—evaporates. Free moisture also plays a role in the heat transfer during roasting. As soon as the beans are energized with heat, the bean’s moisture conducts this heat through out the bean. When the internal bean temperature approaches 212 degrees F or 100 degrees C., the free moisture starts evaporating. In the second phase, from the first crack to the second crack, coffee beans develop their specific aromas and flavors, which, as coffee tasters know, can produce a very complex taste profile. At the end of the second phase, all free moisture has evaporated. The length of the second phase depends on the roasting degree, which can vary from region to region and from product to product. With very dark roasts, there is also a third phase which starts when the second crack is almost completed. During this phase, carbonization takes place and the bound moisture is destroyed.

Beans with a moisture content of less than 10 percent have a sharply reduced free moisture level and will tend to roast much faster, especially in the first phase. In this case, the roaster operator needs to change the roasting profi le by initiating the roasting process at a lower heat level and by maintaining a lower amount of energy supply (less BTUs) during the first roasting phase.
Beans with a high moisture content (fresh crop coffees can have a moisture content in excess of 14 percent) often require that the roaster operator includes a pre-drying phase before starting the first phase of the process. During pre-drying, it is recommended that the roaster maintains a drum temperature of 300 degrees F or 148 degrees C. with the objective to slowly remove the excess free moisture. The actual phase one of the roasting process can begin as soon as the beans start losing their deep green color.

CELL STRUCTURE DENSITY

Lower grown beans generally have a less solid bean structure than higher grown beans. The density of the bean structure is revealed by the shape and the position of the center cut. Bean from Kenya, which was grown at an altitude of at least 5,500 feet or 1650 meters. The center cut is tightly closed and almost seems to be floating in the upper layer of the bean. In sharp contrast, Robusta bean, grown at almost sea level. In this case, the center cut is widely opened and draws like a deep crevasse through the coffee bean.

What is the relationship between bean density and roasting? High-density beans have a denser cell structure and more cells per cubic millimeter than low-density beans. As a result, high-density beans are more resistance to heat, which will be especially noticeable during the first phase of roasting. After the evaporation of free moisture, the color of the coffee beans starts changing from (light) green to yellow to light brown. During this color change, the bean starts expanding. With lowerdensity beans, the centercut will open more quickly, allowing for a faster transfer of heat, which will accelerate the process even further.


Source : ROAST MAGAZINE

JAVA PREANGER COFFEE ADDICT
Fadillah Satria

Comments

Post a Comment

Popular posts from this blog

Perbedaan Biji kopi arabika, Liberika, Ekselsa dan robusta secara fisik

Perbedaan Biji kopi arabika, Liberika, ekselsa dan robusta secara fisik Salam sahabat kopi.. Saya akan berbagi ilmu yang saya ketahui tentang perbedaan fisik antara biji kopi arabika, liberika, Ekselsa dan robusta diantaranya: Biji arabika secara fisik dapat dilihat dari ukuran, bentuk dan warnanya. Rata-Rata ukuranny kecil, lonjong, Aroma khas ada bau bunga, bau kecut dan warnanya hijau tidak bisa kuning, bijinya berat, lapisan biji tipis, menyerap air banyak Biji Liberika secara fisik besar ukurannya, lonjong lancip, lapisan bijinya tebal dan warna kuning. Biji Ekselsa secara Fisik dapat dilihat dari Ukurannya besar lebih besar dari jenis kopi lainnya. Bentuknya bulat besar mirip dengan Robusta, lapisan bijinya tebal dan warnanya kuning pucat dan tidak berat Biji Robusts secara fisik dapat dilihat dari bentuknya Bulat, ukuran berfareasi ada kecil ada yg besar,lapisan bijinya tebal, tapi biji asli dr pohon asli robusta yang pohonny bukan sambungan rata- rata bijinya besar tidak besar ...
Post a Comment
Read more

sera serbi kopi

Jual Kopi Bubuk Lebih Untung LIWA, KOMPAS.com - Sebagian petani kopi di Kabupaten Lampung Barat mulai memproduksi kopi bubuk karena lebih menguntungkan daripada menjual kopi bijian.      "Saya mulai membuat kopi bubuk, walaupun tidak terlalu banyak, tetapi hasil penjualannya lebih menguntungkan," kata petani kopi, Nasir, di Pekon Pagar Dewa, Kecamatan Sukau Kabupaten Lampung Barat, sekitar 282 km sebelah barat Bandarlampung, Senin (16/8/2010).Dia menjelaskan, harga kopi kering kian merosot sehingga mendorong petani mengolahnya menjadi kopi bubuk. "Alasan harga yang membuat petani membuat kopi bubuk, karena lebih menguntungkan daripada menjual kopi bijian," kata dia lagi.      Ia mengatakan separuh hasil panennya diolah menjadi kopi bubuk, yang dijual ke sejumlah pasar di Lampung. "Bila saya menjual kopi biji, jelas pendapatan saya akan berkurang,"katanya. Menurut dia, hasil penjualan kopi bubuk itu mampu membiayai perawatan tanaman kopi dan ...
Post a Comment
Read more

es kopi susu

Bangun pagi, lalu apa yang biasanya kamu lakukan setelah mengucek mata? Pasti ada yang melanjutkan tidur, ada yang buang air, ada juga yang langsung olahraga. Berbeda dengan saya, kebiasaan bangun pagi saya adalah menyiapkan segelas kopi panas yang benar-benar panas. Karena kopi sendiri paling nikmat disajikan saat masih panas. Tapi ada juga lho kpi yang disajikan dalam keadaan dingin.  Kopi dingin paling nikmat adalah diminum saat siang hari dan cuaca yang begitu panas. Bagi anda yang ingin merasakan kopi dingin yang nikmat, begini saya beberkan sedikit cara membuat es kopi susu nikmat . es kopi susu Pertama tama yang harus kamu lakukan adalah menyiapkan Kopi favorit yang biasa kamu minum Gula Cetakan untuk membuat es Lalu cara membuatnya Sedih kopi favorit kamu Tuangkan dalam cetakan es yang sudah disediakan tadi Setelah es jadi, tuangkan beberapa kotak es kopi kedalam gelas Tuangkan susu favorit kamu Diamkan selama beberapa menit dan es kopi susu super enak ini siap untuk dinikm...
Post a Comment
Read more