Weight Losses during Coffee Roasting/コーヒー焙煎時の重量減

Japanese Coffee Japanese Food

Since I got the commercial coffee grinder, I’ve been making coffee brewing experiments on a daily basis, spending 20 or 40 g of coffee beans per experiment, which means that my coffee bean consumption has increased significantly.
Today, I have roasted another batch, with a different approach this time. At first, I decided on the desired amount of roasted coffee beans and the desired roast level, 500 g and 15.0%, respectively. This translates into 500/(1 – 0.15) = 588 g of green beans. I decided to measure the weight while roasting. Here are some of the results.
0:00: 588
6:00: 577 (down 1.8%)
9:00, heat turned to high: 566 (down 3.7%)
12:00, 1st crack: 540 (down 8.2%)
15:30, end of roasting: 500 (down 15.0%)

I though I successfully roasted by carefully measuring the weight of the coffee beans, but when I weighed them after cooling, I found they were 491 g, thus 16.5% weight loss.

I will continue to do the same for my subsequent roasting sessions so I can roast coffee at my desired levels accurately.
業務用のコーヒーミルを買ってから、毎日、コーヒー抽出の実験をしています。一回当たり、コーヒー豆を20 gか40 g使っています。というわけで、コーヒー豆の消費量がかなり増えてしまいました。
今日は、また焙煎をしたのですが、今回は別のアプローチで焙煎しました。まず、希望する仕上がりのコーヒー豆の量と希望する焙煎具合を決めます。それぞれ500 g、15%。ということは生豆が500/(1 – 0.15) = 588 g必要です。また、焙煎中に重さを測ることにしました。その結果です。
0:00: 588
6:00: 577 (1.8%減)
9:00, 火を強火に: 566 (3.7%減)
12:00, 1ハゼ: 540 (8.2%減)
15:30, 焙煎終了: 500 (15.0%減)

コーヒー豆の重さを慎重に測ることで、うまく焙煎できたと思ったのですが、冷やした後に測ると、491 gで、重量減は16.5%でした。


Edited to add some photos:
Beans that I used:

Indonesia Mandheling G-1 Honey Elegant

Roasted beans:

Medium roast.

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