Grassy flavours, whats the reason?

[Bradleysteenkamp]

Hi everyone,

I'm roasting on a 15kg ozturk and with a couple of recent roasts I've noticed some grassy, straw like flavours that I don't particularly enjoy. Most noticeable when the coffee is prepared as a filter using a v60. Isn't an issue when made as espresso and not that noticeable when cupping the coffee

the coffee is a natural process Costa Rica from las lajas, it's very high quality. I'm thinking its most likely due to a slightly underdeveloped roast although this batch was dropped out as 1st crack was almost finished at a total roast time of about 15 minutes.

We are constantly under pressure to roast really light as some many of the good roasters over in the UK seem to be doing this. However, i find these grassy flavours aren't all that nice at all!

has anyone else found this happens with their light roasts, any advice or tips? Next time I roast this coffee I'm planning to let it clear 1st crack and hope that cures the issue. Trouble is, I don't want to be accused of roasting too dark!

 

[JumpinJakJava]

Very interesting to me,That across the ocean "that many of the good roasters" "roast really light".
To me, "really light" tends to be sour or bitter, and yes grassy.
May be my taste buds! I have no desire to cause controversy in the forum, but in New England, is is mostly medium roasted coffees.

I was wondering on the average what size batches are you roasting? What is your charge temp per batch size? What is your finish temps?

Time is very important, but temp is just as important. I hardly ever drop coffee under 422degres. I always like to touch 2nd crack, or be sure 1st crack
is finished. I use an Ambex 10K, average batch sizes 6-12lbs.,9lb. would be my true average batch size. So my charge temps would be between
385deg. to 420deg. Most of my coffee is roasted Full City to Full City+. I find good development at this roast stage(426-432degress).
IMHO 370 degrees at about 12 minutes is where I like to be. Getting ready for 1st crack in a minute or so.
I know many other roasters will chime in. That is great about this forum. Give and take, learn and share.

 

[CoffeeJunky]

The Grassy taste comes from under roasting of the beans.
How long do you roast each batch.
I would roast at lower temp and longer time. Because you can get to first crack fast and it will under roast your beans.

But I will ask Eldub on this since he can give you step by step advise.

 

[peterjschmidt]

You didn't mention your batch size. Are you perhaps roasting at the limits of your Ozturk, so that it's not as responsive to profiling changes? The reason I ask is that 15min. to get into 1C is a long time. Dropping before 1C is finished is not the answer on how to do a very light roast properly, even though the boss or the customers are asking for that.

My guess at the reason for the grassiness is too high a drop temp, which will take you through the drying phase too quickly. I would go slower up to around 280-300* and then pour on the heat after that, lowering the heat 20* or so before 1C, and then watching the temp rise through 1C, both so that you don't stall the roast and so that you can finish the roast right at the end of 1C. It's part of my 'zen' roasting philosophy (for lack of a better term) that beans like to be dumped/roast ended when the beans have had a chance to settle into their final temperature; this allows for the heat to penetrate to the center of the bean. IOW, if 420* is going to be your dump temp, don't run the beans up to 420 with so much energy and momentum that they could easily hit 440*. Those beans will be 420* on the outside, but not through and through, and so the flavor development will be stifled. If 420* is to be my dump temp, I'll let 'em sneak up on it; it'll be an actual/honest 420* and the beans will be happier.

 

[eldub]

That's what you get when roasting to first crack, imo. I have yet to find a single bean that I like roasted to that level. I used to take our Costa Rican beans to 435* but prefer the results at 438-440* now.

My light roasts are a bit darker than some on the cutting edge and my dark roasts a bit lighter than many out there.

To me those folks pushing very light, underdeveloped roasts have palates that aren't very discerning and are more interested in being in on the latest fad than serving a good product.

But that's just me……

 

[Bradleysteenkamp]

Hi guys,

Thanks so much for the replies and the info. Firstly, although the Ozturk is a 15kg I find it to be fairly underpowered. The biggest batch I tend to go for is 10kg and if I want that to hit 2nd crack In 20 minutes I seem to need to drop in at 428f on the roaster drum probe which is usually about 500f on my thermocouple probe that is connect to the computer. High temps I know but, if I look back at some of the graphs a recent 10kg roast was dropped from the drum at 17min 30sec having cleared 1st crack with a short amount of development time and a thermocouple temp of 420f (the probe is in the bean mass in the bottom area of the drum). I liked this roast however the customer said it was good but he'd prefer it lighter with less 'roast' character (this was for espresso)

The Ozturk is very much a slow roasters, batch sizes of 8kg or less can be completed quite quickly but it just doesn't seem to have the flame power to offer much control with bigger batches. If I'm roasting 10kg (usually an espresso blend) I will need to have the heat at max the whole way through the roast to get it completed in around 18 minutes (that would be about half way between 1st and 2nd crack).

Over here in the UK certain roasters have made the light roasts extremely popular, many of them are dropping coffee towards the end of 1st crack with hardly any development past that point. Some people love it and some hate it but there is often a lot of pressure to conform!

 

[eldub]

if I look back at some of the graphs a recent 10kg roast was dropped from the drum at 17min 30sec having cleared 1st crack with a short amount of development time and a thermocouple temp of 420f (the probe is in the bean mass in the bottom area of the drum). I liked this roast however the customer said it was good but he'd prefer it lighter with less 'roast' character (this was for espresso)

Over here in the UK certain roasters have made the light roasts extremely popular, many of them are dropping coffee towards the end of 1st crack with hardly any development past that point. Some people love it and some hate it but there is often a lot of pressure to conform!

Are you saying that you completed a roast at 420* bean temp and the client said it was too "roasty?" I can't imagine an espresso blend being developed sufficiently at that point. Imo, there is absolutely no "roast" characteristic with beans taken to 420*.

Imo, you are maybe baking the beans more than roasting them if your batches are taking 20 minutes to get to second crack.

I had a client who brought in a sack of light roast Panamanian beans from Peets awhile back. The packaging was beautiful. There was even a card attached giving details of the beans provenience as well as flavor profile. I brewed up a cup and it was grassy as hell. Then I brewed a cup of our lightest roast. (A yirgacheffe) At that point, the customer told me that our offering tasted like coffee and that he then found the Peets was pretty much undrinkable. There was nothing but grass in the cup. The yirg was light and bright with a lemon/spice/floral character. However, he needed to sample them side by side understand the difference.

 

[Bardo]

I just ordered some Yirga Cheffe beans last week. Can't wait for them to arrive!

 

[Bradleysteenkamp]

Thanks Eldub,

A while ago I roasted two batches of the same blend, one reached 420f and dropped at 22minutes and the other 14 minutes. I sent both marked just as A and B to the importer (a speciality coffee importer in the UK) and asked them to cup and taste test both and to provide me with feedback. Sample A, the slow one they though didn't show the same brightness that same B showed but they didn't suggest that the slow roast had a baked flavour! It was cupped by 3 people, one a Q grader who's worked in the industry for quite some time. An interesting experiment!

Still, having said this, I do find it frustrating that the Ozturk roasts so slowly. Not a problem with batches up to 8kg but an bigger and it really does get slow. I've booked someone to come and take a look at our propane setup to make sure that isn't causing an issue.

 

[Bradleysteenkamp]

One of our suppliers was telling us once that he has an allergy to an enzyme found in green coffee beans but this isn't a problem once it's been roasted. However, he mentioned one roaster that roasts their coffee so light that it's given him an allergic reaction in the past! Something that he said has only started happening in the recent trend towards the super light roasts.

 

[JumpinJakJava]

Bradleysteenkamp, I am assuming(cautiously), the Ozturk has a manual gas throttle like the Ambex. I know that I could do a 15lb. batch in 15min.
and reach well over 450deg. in my 10K. if I chose to. So I was wondering if you need to check if you air flow has some blockage and
needs some deep cleaning. Also do you sufficiently warm up the machine for the first roast? Are you getting enough blue flame charge?
The reason I am asking these questions is because I seem to have the opposite problem, especially with small batches.
turning my gas way down(almost yellow top flame) to stretch the roast and then coast to my desired roast end.
From what I understand (Ozturk, Toper, Ambex) are very similar animals.
May I also ask if your machine is propane fired, what size tank or tanks are you using?
Sound like a strange question, but I knew someone who was trying to run a 10K on a 20lb. LP tank,
it was not big enough. 100lb LP recommended. If you are using natural gas, questions ommitted.

 

[Bradleysteenkamp]

I am indeed using propane. Interesting about the tank size. We've been using 40lb tanks, so not that big. In fact the user manual does suggest running a bank of tanks if using smaller ones. I'm having a propane guy come take a look soon. The airflow system is clear as I checked it over recently. It does have a manual gas control which is very useful. I find that even with the gas at the max the flame is blue but with about 1/3 orange.

pressure too is showing a bit low on the inlet gauge, only 22mbar when the manual suggest 30 is needed.

 

[JumpinJakJava]

Propane guy. Good idea.

 

[JumpinJakJava]

By the way, I run 2(100lb. tanks side by side). No problems so far.