When I roast a few beans to the same color or same roasting degree on some bean I see oil spots and on others no oil spot. Ok, that is normal. Now, when I roasted a bean to one color in one temperature profile, I saw no oil spot, whereas another temperature profile gave oil spots on every other bean after cooling (I'm talking about the same bean). Ok, that is probably normal. Then, I degassed the bean without oil spot for two days. Now I see lots of big oil spots!! Do people see this? Is this a good thing or a bad thing? P.S. I thought degassing would have to accelerate if I drop the external pressure. I put roasted bean in a washed and dried wine bottle, and used a vacuum pump to drop the pressure. It didn't help. Perhaps the gas is not there, but is being created... if that's the case late appearance of oil spots makes sense... I'm curious how often that happens... -- Ryuji Suzuki "I can't believe I'm here. People always say that I'm a long way from normal." (Bob Dylan, Normal, Illinois, 13 February 1999) homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
Suzuki-san, That is also normal (seeing oil appear on the surface of the beans two or three days after roasting). As far as I know, there is no consensus regarding whether it is good or bad to have oil showing on the beans. Oily beans are usually darkly roasted beans, and that is another area of debate altogether. Some people prefer lighter roasts, other darker. It is all a matter of personal preference and taste. Regards, Rafael |
Clarification: I roasted the same bean to the same degree, but using different temp profile. One exhibited oil spots just after cooling and another after a few days... The bean which gave oil spots days after made such a sweet cup but I'm not 100% confident about this difference yet. Too few samples. Also, I should also control for the temperature of water during extraction. (Now I'm controlling using my finger as a sensor) My photo darkroom thermometers don't go higher than 40C (100F) so I am getting a cheap accurate digital thermometer (about $30). I'll report how it goes... -- Ryuji Suzuki Q. What is your real message? A. Keep a good head and always carry a light bulb. (Bob Dylan 1965) homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
At 01:44 PM 3/30/01 -0500, Ryuji wrote: <Snip> Chaney Instrument Instant Read Meat Thermometer I bought this thermometer at my local Walmart and in boiling water it was dead on 212' and is a little more accurate than my finger! ;0)http://www.walmart.com/catalog/product.gsp?cat&dept&product_idˆ2199&path=0:4044:4057:46342:41845:45235 Note: the above URL most likely wrapped the line. Make sure you get the whole thing into the browser. If that seems impossible, just goto:http://www.walmart.comand enter "thermometer" in the search box on the top of the page. Monty homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
Ryuji, If I had to guess, the oil is generated in flesh of the bean during the roasting process, diffuses to the surface during the "resting" period, and droplets condense there. I've recently roasted the Sulawesi Rantepao (Monsooned) to 4 minutes (Full City) and 4.5 minutes in my FreshRoast. The longer roasting did not significantly darken the beans more, but after a three day rest, the 4 minute beans had oil spots here an there, but the 4.5 minute beans were positively covered with oil and stuck together and to the glass walls of the jar like peanut brittle (peanut brickle to some). I liked the shorter roated beans better, but the longer roast wasn't a bad taste. Slight char and a mild bittersweet aftertaste. In the shorter roast case, not all the beans in the batch had oil spots, either. If I had to guess, therefore, why your two batches were so different, I'd guess there was an inadvertant difference in the time/temperature relationship in the roast. I haven't deliberately tried yet to reproduce a set of values yet; still hunting, so maybe I'll find a similar effect. Cheers, CThomas homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |