Coffee Data Science

120g Batch vs 60g Batch for Coffee Roasting

Small batch size testing

Robert McKeon Aloe
3 min readJun 7, 2024

--

Let’s do a simple test on batch size. I switched to 120g batches because some had claimed 100g doesn’t work well in the Roest. In this same discussion, 50g batches also work well. So I tried 60g.

I used a thermal pulsing profile for both, but the 60g roasted so fast that I suspect I need to make an adjustment for smaller or larger batches.

While they had a similar Rate of Rise (RoR), this doesn’t tell much because of the short length of development.

The difference in roast was particularly seen in the number of cracks.

The weight loss for 120g was 86.5% and 86.1% for 60g, so they were close in that metric. I didn’t collect other data because the 60g was too small for the Syncfo 4in1, but I could have collected color information.

Tasting Equipment/Technique

Espresso Machine: Decent Espresso Machine, Thermal Pre-infusion

Coffee Grinder: Zerno

Coffee: Home Roasted Coffee, medium (First Crack + 1 Minute)

Pre-infusion: Long, ~25 seconds, 30 second ramp bloom, 0.5 ml/s flow during infusion

Filter Basket: 20 Wafo Spirit

Other Equipment: Acaia Pyxis Scale, DiFluid R2 TDS Meter

Metrics of Performance

I used two sets of metrics for evaluating the differences between techniques: Final Score and Coffee Extraction.

Final score is the average of a scorecard of 7 metrics (Sharp, Rich, Syrup, Sweet, Sour, Bitter, and Aftertaste). These scores were subjective, of course, but they were calibrated to my tastes and helped me improve my shots. There is some variation in the scores. My aim was to be consistent for each metric, but some times the granularity was difficult.

Total Dissolved Solids (TDS) is measured using a refractometer, and this number combined with the output weight of the shot and the input weight of the coffee is used to determine the percentage of coffee extracted into the cup, called Extraction Yield (EY).

Shots

I ended up pulling 5 shots total, so these should all be taken with a grain of salt. They tasted similarly with one outlier in the 60g batch.

The same was true for EY.

I was hopefully some big taste difference would be noticeable, but there wasn’t. I might come back to batch size testing in the future, particularly for larger batches. My focus on espresso shot taste means that it is possible these roasts would have a different presentation under different brewing conditions.

If you like, follow me on Twitter, YouTube, and Instagram where I post videos of espresso shots on different machines and espresso related stuff. You can also find me on LinkedIn. You can also follow me on Medium and Subscribe.

Further readings of mine:

My Second Book: Advanced Espresso

My First Book: Engineering Better Espresso

My Links

Collection of Espresso Articles

A Collection of Work and School Stories

--

--

Robert McKeon Aloe

I’m in love with my Wife, my Kids, Espresso, Data Science, tomatoes, cooking, engineering, talking, family, Paris, and Italy, not necessarily in that order.