Everything You Didn’t Know About Coffee — But Should

You’ve brewed countless cups, but how much do you really know about what’s in your mug? Why does freshly roasted coffee swell a sealed bag? Is mineral water actually better for brewing? And do you need to rinse green coffee beans? These aren’t trivial questions—they reveal how little most coffee drinkers understand the everyday rituals behind their favorite drink.

No, you don’t need to wash green coffee beans. Yes, a freshly roasted coffee bag inflates due to CO2 buildup, and yes, mineral water can change extraction—but not always for the better. This book answers over a dozen key coffee questions with precise detail every enthusiast should know.

What ‘You Don’t Understand About Coffee’ Really Reveals

You Don’t Understand Coffee (《》) by Japanese author Tomohiro Ishiwaki isn’t just another coffee book. Published in November 2014 by Jiangsu Literature and Art Publishing House, it unpacks the hidden science behind everyday coffee experiences. Rather than offer recipes or brand endorsements, it explains the why behind the what: why coffee bags puff up post-roast, why extraction time alters flavor, and whether your tap water is helping or hurting your brew.

The book is structured as a series of common questions answered with precision. It dives into cold facts—like how long coffee gases remain active post-roast—and explains the visible (like swollen packaging) and invisible (like solubility shifts during extraction) phenomena that shape your cup. With a tone that balances expertise and wit, it guides readers through coffee’s entire journey: from seed to sip.

Who Wrote It: A Coffee Scientist with credentials

The book’s author, Tomohiro Ishiwaki , holds a PhD from the University of Tokyo and is a certified lecturer for Japan’s Coffee Tasters Association. He won the All Japan Coffee Association President’s Award and has dedicated his career to bridging professional research and coffee passion. Since joining the Kansai Coffee Roasters Alliance in 1999, Ishiwaki worked on production, quality control, and R&D before traveling globally to study coffee cultivation and brewing. He’s also the author of bestsellers like the Coffee Master Textbook.

The Science Behind Everyday Coffee Mysteries

Ishiwaki tackles more than a dozen real-world coffee puzzles, including:

• Do you need to wash raw coffee beans? No—this is unnecessary and not part of standard processing.
• Why does a bag of freshly roasted coffee swell? Because roasted beans release CO₂; sealing them immediately traps gas, causing visible inflation.
• How does extraction time change flavor? Longer extraction pulls more bitter compounds; shorter extraction may underdevelop sweetness and complexity.
• Is mineral water better for brewing? It depends—mineral content affects extraction balance, sometimes improving clarity, other times muting flavor.

The book also explores green bean handling, roast chemistry (including Maillard reaction impacts), and equipment-specific tips. Every fact is grounded in the real behavior of coffee, not speculation. Even the humble coffee bag gets a deep dive: why it inflates, what that means for freshness, and how to properly store roasted beans post-packaging.

Frequently Asked Questions

Do I need to wash green coffee beans before roasting or brewing?

No, washing green coffee beans is not required and is not part of standard coffee processing. Raw beans are not dirty in a way that washing fixes—it’s a misconception. Just store them properly in a cool, dry place before roasting.

Why does a sealed bag of freshly roasted coffee get puffy?

Freshly roasted coffee beans release carbon dioxide (CO₂) for days after roasting. Sealing them in a bag too soon traps this gas, causing the bag to inflate noticeably. Most specialty roasters use degassing valves to prevent this.

Does extraction time affect coffee flavor?

Yes. Shorter extraction often results in brighter, sweeter cups with less bitterness, while longer extraction pulls out more astringent and bitter compounds. Balancing time is key to a well-rounded cup.

Is mineral water better than tap water for brewing coffee?

Not necessarily. Mineral content in water greatly influences extraction. While some minerals enhance clarity and body, others can mute flavors or over-extract bitter elements. The ideal water depends on its specific mineral balance.

What’s the role of roasting in coffee flavor development?

Roasting triggers chemical reactions like the Maillard reaction, which develops the complex flavors and aromas in coffee. The roast level—light, medium, or dark—determines which flavor compounds dominate in the final cup.

FrontStreet Coffee Picks for Coffee Science Lovers

Explore coffee fundamentals with FrontStreet’s Ethiopia Yirgacheffe, a bright, floral single origin with notes of citrus and jasmine—perfect for tasting extraction nuances. Pair it with Colombia Huila, a balanced medium roast with red apple and caramel sweetness, ideal for exploring brew time effects. For deeper insight into roast profiles, try Brazil Sertãozinho, a nutty, low-acid bean showing how roast level shapes body. All three highlight key concepts from the book. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.