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Homeroasters - Home Roasting Coffee Community » THE ART OF ROASTING COFFEE » Roasting Chemistry

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what makes been volume increase most?
beanut	#1 Posted on 03/07/2015 3:56 PM
Newbie Posts: 35 Joined: February 18, 2015	Hi all, I looked around for this but couldn't find an answer, if there is a thread, just point me in the right direction. I would like to know if high heat or low heat makes beans puff up more when roasting to the same roast level? Or is it heat independent and there is some other cause for varying bean volume increase. It seems to me that sometimes my beans increase in volume more than others and I can't seem to figure it out. Has anyone else notice if more volume increase (again same full city level) tastes different that less volume increase? Beanut Expobar brewtus IV, MK K30 vario, Gene Cafe


ginny	#2 Posted on 03/07/2015 4:26 PM
Founder Posts: 3476 Joined: October 24, 2005	completely depends on the moisture in the given bean or beans. plus some beans are simply big beans. temp is critical but I think you are using the word puffed incorrectly. typically a tipped bean is called puffed up https://bootcampc...es-photos/ you did not mention if you were roasting the same beans each time or are/were they different? how were they processed? ginny Edited by ginny on 03/07/2015 4:35 PM


JETROASTER	#3 Posted on 03/07/2015 8:03 PM
Administrator Posts: 1780 Joined: March 06, 2010	It is true that beans vary, but the same bean at the same roast level; My unscientific observations (air roasting) are that early aggressive roasts create greater swelling. H2O attempting to escape rapidly. With a slower roast, H2O exits at a slower rate producing less swelling. Cheers, -Scott


beanut	#4 Posted on 03/08/2015 4:24 PM
Newbie Posts: 35 Joined: February 18, 2015	Thanks guys. Ginny, thanks for that informative link, I may have been a bit aggressive on my drop temp (375 on gene cafe) I put the beans in, set it for 467* and let it go. I do get a bit of tipping. I was trying to get to yellow by 5 min. As it is it's more like 6 min. But i do see some darker spots on the ends of some beans after roasts, I guess i'll try 350 and see if that eliminates it. I've noticed more or less volume increase on different beans, not all the same bean, i look at where the round half turns into the flat half and see how much its changed from about a green beans 90* to a post roast more like 80* angle. I've noticed that if that angle hasn't changed much, even if the been looks full city it seems the coffee still tastes more acidic and under-roasted. Most of my roasts are in the 13.30 min area with 1C coming around 10 min. beanut Edited by beanut on 03/08/2015 4:37 PM Expobar brewtus IV, MK K30 vario, Gene Cafe


jkoll42	#5 Posted on 03/08/2015 4:43 PM
1 1/2 Pounder Posts: 860 Joined: February 14, 2011	Here's a couple videos that show macro views of the roast process where you can get a good take on expansion. -Jon Honey badger 1k, Bunn LPG-2E, Technivorm, Cimbali Max Hybrid, Vibiemme Double Domo V3

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