How to Perfectly Pour-Over Light Roast Coffee? Understanding Slow Flow and Water Pooling Issues

For pour-over coffee enthusiasts, determining the roast degree of coffee beans is the first step before creating a brewing recipe. Different roast levels exhibit varying extraction behaviors. Light roast beans, due to their lighter roast degree, retain more floral and fruit aromas. However, when brewed at home, they often end up with only monotonous acidity, leading to self-doubt.

Do Light Roast Coffee Beans Only Have Acidity?

It's not hard to notice that in daily life, high-scoring and delicious light roast coffees all possess sweetness within their acidity. Acidity and sweetness show different trends in roasting. The roast level indeed affects the balance between acidity and sweetness in coffee.

The darker the roast, the less acidity, so dark roast coffee has very low acidity. Sweetness, however, shows the opposite pattern. Light roast beans start with very low sweetness, which rapidly increases with deeper roasting, peaking at medium-dark roast. Once past this sweetness peak, it begins to gradually decrease. This means that light roast coffee indeed has higher acidity than sweetness, and our goal is to extract as much sweetness from the coffee as possible.

Why Are Light Roast Beans Harder to Brew for Flavor?

During the blooming stage of coffee brewing, medium-dark roast coffee often expands to form a prominent dome, while the dome formed by brewing light roast beans is less obvious. Extremely light roast coffee may not even expand when exposed to water. Typically, the lighter the roast, the less structural change occurs in the coffee beans, containing less carbon dioxide internally and having a denser texture. Therefore, coffee grounds have poorer water absorption and need more thorough contact with water to release sufficient flavor compounds, requiring finer coffee particles.

Additionally, beans used for light roasting are mostly specialty beans from high-altitude regions, classified at higher levels with relatively harder texture. When using a hand grinder, lighter roast beans require more effort to grind, which is one way brewers can determine the coffee's roast degree.

Harder light roast beans tend to produce fine particles during grinding due to compression and bursting. Combined with less vigorous degassing and weaker expansion, these fine particles are more likely to settle and compact at the bottom of the filter cup during the later stages of brewing, causing blockage and increasing the likelihood of uneven extraction. At this point, we need to find the corresponding brewing parameters and suitable pouring techniques for light roast beans.

How to Brew Light Roast Coffee for Sweetness?

When coffee beans are ground and exposed to hot water, they release numerous compounds. The first to be extracted are fruit aromas and acidity, followed by the coffee's sugar compounds that create sweetness, and finally bitterness.

When the coffee grind size is appropriate, FrontStreet Coffee does not recommend adjusting the grind size to obtain sweeter or more acidic flavors. For those who don't frequently brew pour-over coffee, grind size is a very uncertain factor. Whether too coarse or too fine, and even uniformity, can affect the taste. Therefore, if your current grind setting can produce good coffee, don't simply change it to pursue more sweetness (or acidity). Other more controllable parameters can be used as alternatives.

If using a three-stage pouring method to enhance coffee sweetness, focus on the second stage of extraction. You can appropriately increase the water amount and agitation intensity at this stage, while avoiding the extraction of negative bitterness in the third stage. For example, FrontStreet Coffee brews 15g of coffee grounds with a 1:15 coffee-to-water ratio, using three water volumes of 30ml/125ml/70ml respectively.

Water temperature is the most direct way to adjust coffee's acidity and sweetness. Higher temperatures result in more efficient extraction, releasing more flavor compounds. Since different materials of pouring equipment lose heat at different rates, extraction temperature variations will also differ. If your daily light roast coffee brews always result in only acidity, try increasing the water temperature by 2 degrees to extract more flavors.

In terms of technique, brewing light roast beans requires larger circular motions to wash through the coffee bed. After blooming, we can increase the frequency of circular movements, using the stirring power of the water stream to enhance the coffee's complexity, of course, while ensuring the water flow remains vertical. In the final stage of brewing, use a large water flow with rapid circular motions to stir up the fine particles settled at the bottom, preventing blockage and allowing water to flow more smoothly.

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