I did a bunch of reading yesterday on roasting and the affect to sweetness and flavor and such.
Sweet Maria's has the best library of info on such topics I have found online so far.
She did some experimenting with "stretching" the roast of coffee beans and how it affected a few factors such as body, sweetness, acidity, etc.
It was very interesting and full of detailed info on her results and some info on her approach. It is a 3 part'er you can read all about it here:
Part 1 -
https://legacy.sweetmarias.com/library/node/2934
Part 2 -
https://legacy.sweetmarias.com/library/content/stretchin-out-roast-pt-2
Part 3 -
https://legacy.sweetmarias.com/library/node/4726
She didn't summarize her findings but from what I read and can remember it seems that sweetness can be affected in a few different ways by targeting a sweetness type (malt, candy, fruit, etc.), acidity, and body/mouth feel to present the kind of flavors you want the drinker to have.
For example in her first stretching of the time between the end of the 1st crack and beginning of the 2nd crack she discovered that how the Acidity is perceived (front, middle, or back of the palate) affects body perception of the coffee as well as the type of sweetness (malt, candy, fruit, chocolate, etc.). So stretching the roast in this way a Roaster can affect the flavor profile by messing with the sweetness flavor and where the acidity is felt in the palate.
In the 2nd stretching she mentions that stretching out the 1st crack (time between beginning 1st crack sound to ending of the 1st crack sounds) didn't affect sweetness flavor but the body/mouth feel affected the delivery of the sweetness so it is expressed in a better manner. She basically states that more body and syrupy texture makes for the sweetness hitting the tongue and mouth differently so you perceive it differently.
In the 3rd stretching of the drying phase she identifies that the toning down of the acidity while not killing the sweetness gives longer finishes to the sweetness. This may greatly affect how a taster perceives the sweetnes.
It is all very interesting stuff.
When I look back on my last attempt I had a stretched all of her same phases inadvertently because of how my burner is working for me hahahaha. I roasted my beans for a good 20+ minutes to hit my 428F mark.
It looks like I basically hit many if not all of her sweetness points which is funny because as the coffee was being drank there as a definite mention about the sweetness of it that was written off to maybe be a byproduct of the creamer hahaha
Anyhow enough of me rambling I just wanted to share all this super interesting info since we are all kind of discussing the same kind of points that Maria seems to be honing in on when roasting :)