Maximizing sugars with rate of change and amount of heat

by **Arpi** on Sat Apr 09, 2011 10:49 am

Hi.

There has been some talks about humidity but there has been little or no talks about sugars.

Different beans have different amounts of sugars and they could be roasted with different rates of change and amount of heat applied (time-length*BT-temperature). Small amounts of heat applied could make the sugar content smaller (it would not develop to its maximum potential). And if the amount of heat is too much, it could revert the developed sugars in to something else. Sugars would peak at a specific amount of heat based on the potential of the bean (different bean-different potential).

What is your opinion about using different rates of change, and amount of heat, for low sugar content beans and high sugar content beans? Should they be treated different (assuming different beans have a different potential for sweetness)?

Since the rate of change affects the amount of heat applied, should the rate of change seek a "best" amount of heat for beans with different sugar content?

Thanks

by **another_jim** on Sat Apr 09, 2011 3:52 pm

Sugar are never created in a roast. Bad roasting, i.e. too fast or too slow destroys them to no avail.

In the context of competent roasts, you have a choice how to change the sugars into other flavors. If you roast slow to the first crack, and finish fast (aka Diedrich's profile), the sugars will combine with amino acids to form Maillard reaction compounds - malt, toast, new oak, and broth-like (savory/umami) flavors. If you take it to the first crack fast, using upo fewer sugars, the remaining ones will caramelize into candy like tastes.

Roast too slowly, and the Maillard and caramel compounds polymerize into long chain, inert compounds; too fast, and you get the scorched flavors. One of these sequences has the ominous name of Strecker Degradation, but I'm not sure which one.

Cupping roasts, as fast and light as possible, retain the most straight sugars and sweetness, but also the most acids and some of the chlorogenic (grassy tasting) compounds. So their overall taste balance is rarely as sweet as darker or more leisurely roasts.

The sweetest possible taste, as opposed to the most sugar, is a balancing act. I tend to get it at medium fast roasts (11 to 13 minutes) stopped just ahead of the second crack. But I'm guessing that is equipment dependent. It also depends on how tolerant you are to unsweetened acidic and bitter tastes. For instance, to an acid lover, a given light roast may taste sweet, while to less of an acid head, it would tastes sour.

How these reactions are affected by the instantaneous heat flux, i.e. proportional to ET-BT, versus the total heat transfer, i.e proportional to the integral of the ET-BT over roast time, I have no clue.

by **Arpi** on Sat Apr 09, 2011 8:31 pm

Thanks Jim. I guess I was mixing the term sugar and caramelization. But I see now that they mean different things.

I was thinking that maybe caramelization has a peak that is dependent on 'cook' time. And then it would help to find out at what range of temperature it happens, and also the time limits upon which it starts to go up and down.

Cheers

by **Martin** on Sat Apr 09, 2011 9:12 pm

another_jim wrote: . . . The sweetest possible taste, as opposed to the most sugar, is a balancing act. I tend to get it at medium fast roasts (11 to 13 minutes) stopped just ahead of the second crack. But I'm guessing that is equipment dependent. It also depends on how tolerant you are to unsweetened acidic and bitter tastes. For instance, to an acid lover, a given light roast may taste sweet, while to less of an acid head, it would tastes sour. . . .

This is good point that's missing from lots of cupping and roasting discussions. Recalling my own and other newbies' quest for "chocolaty," I suspect that an acid preference or tolerance (less than full-city espresso roasts) is partly learned----a work in progress. And it may explain much else. For example, why a signature blend at a respected cafe might not be as interesting as a home roast SO.

Curious about your referring to an 11 to 13-minute roast as "medium fast." So here's a possibly unrelated question: What are some examples of coffees that benefit from a roast that is longer than, say, 15 minutes? I've always thought that while going beyond that time might be necessary as a function of the equipment and batch size, it's not something the roaster pursued as a matter of profile preference.

by **another_jim** on Sat Apr 09, 2011 9:38 pm

Martin wrote:So here's a possibly unrelated question: What are some examples of coffees that benefit from a roast that is longer than, say, 15 minutes?

Glad you asked. Turns out I've been perfecting the roasting of dessert coffees all my life.


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