The Secret of Coffee Sweetness: "Hard Water" and "High-altitude Spring Water"

JC咖啡小學堂

2024-04-26

「硬水」和「高海拔山泉水」讓咖啡回甘的秘密

Contents:

1. Definition of Coffee Sweetness
2. What is Hard Water?
3. Is Hard Water Ideal for Pour-Over Coffee?
4. Is Spring Water Suitable for Pour-Over Coffee?
5. The Impact of Hard Water on Extraction Rate
7. Higher Extraction Rate Leads to Noticeable Sweetness
8. Spring Water Pour-Over Testing
9. Creating Pleasant Taste Impressions

Definition of Coffee Sweetness

In the lexicon of coffee tasting, sweetness refers to the enduring sensation of sweetness left in the mouth after drinking coffee. This sweetness is not derived from added sugar but rather from natural compounds present in the coffee beans themselves. Sweetness is an essential quality characteristic of coffee and is often regarded as one of the indicators of high-quality coffee.

What is Hard Water?

The total hardness of water mainly reflects the total concentration of calcium ions and magnesium ions. According to the standards set by the WHO (World Health Organization), water hardness is classified into four categories:

1. Soft water: Total hardness 0~60 mg/L

2. Moderately soft water: Total hardness 60~120 mg/L

3. Hard water: Total hardness 120~180 mg/L

4. Very hard water: Total hardness above 180 mg/L

1 mg/L = 1 ppm (parts per million)

Hard water refers to water with a hardness of 120~180 mg/L (ppm).

Is Hard Water Ideal for Pour-Over Coffee?

The Specialty Coffee Association (SCA) provides recommendations for water quality suitable for brewing coffee, suggesting that Total Dissolved Solids (TDS) should fall within the range of 75~250 ppm, with an ideal value of 150 ppm.

When comparing the recommended range of total TDS with water hardness levels, it can be observed that it roughly falls within the range between moderately soft water and hard water. The SCA's recommended ideal value of 150 ppm is equivalent to the WHO-defined hard water range of 120~180 mg/L (ppm).

TDS建議範圍與水的硬度等級對照

│Further reading:Change the Water for A Better Coffee

Is Spring Water Suitable for Pour-Over Coffee?

Spring water originates from natural water sources in rainfall mountainous areas, undergoes natural purification through soil and rock layers, and is bottled without storage. Unlike mineral water, spring water is less stable and undergoes changes due to climate conditions, with its composition varying, especially during heavy rain or typhoon days. It is generally considered clear, pure, and uncontaminated, often containing subtle mineral components that may impart unique mouthfeel and flavor. Lu Yu, the Sage of Tea, once said, "Water from the mountain is best, followed by river water, and the worst is underground water."

Spring water typically contains some minerals but not in large quantities. It is neither soft water nor very hard water. Theoretically, pristine spring water is suitable for pour-over coffee. However, the main concern with self-sourced spring water is contamination and parasitic issues. It is recommended to filter and disinfect spring water before consumption. Otherwise, it is preferable to opt for commercially bottled spring water that has undergone standard testing during production.

The Impact of Hard Water on Extraction Rate

The hardness of water affects the extraction rate of coffee. Hard water, which contains more minerals such as calcium and magnesium, can facilitate the dissolution of coffee flavor compounds, thereby increasing the extraction rate. Conversely, soft water, which contains fewer minerals, may result in suboptimal extraction. For example, calcium ions in water can bring out the creamy richness in coffee flavor, while magnesium ions can enhance the fruity acidity, such as lemon and apple acids. Different mineral ions affect the extraction capacity of coffee, thereby adjusting the coffee flavor.

Higher Extraction Rate Leads to Noticeable Sweetness

Coffee with a higher extraction rate typically exhibits pronounced sweetness. This is because a higher extraction rate means more dissolved substances in the coffee, including sweetness and flavor components inherent in the coffee beans, including those with sweet aromatic compounds. With a foundation of rich flavor and high sweetness in the coffee beans themselves, a slightly higher extraction rate results in a more pronounced sweetness and aftertaste. However, higher extraction rate does not always equate to better quality. For dark roasted coffee, exceeding the optimal extraction range can lead to over-extraction, resulting in unpleasant bitterness.

Spring Water Pour-Over Testing

Testing Bean Selection: Ecuador Loja Vilcabamba Mejorado Fermented Washed

Cupping Flavor: Floral, lemongrass, honey, berry, grapefruit, orange, caramel, honey grapefruit aftertaste, bright acidity, mellow and pleasant mouthfeel

▶ 0 ppm Commercial Distilled Water

Prominent bright acidity, lemon, berry, with a lemon peel acidity in the aftertaste.

▶ 130 ppm Commercial French Volcanic Water

Fruit acidity with fruit sweetness, honey, orange, with a pleasant honey grapefruit aftertaste.

▶ 220 ppm Commercial Mineral Water

Rich and full-bodied, caramel, grapefruit, with a caramel bitterness in the aftertaste.

From this test, it is evident that using extremely soft water at 0 ppm results in coffee with pronounced acidity. Using SCA-recommended hard water at 130 ppm for pour-over coffee results in a balanced acidity, relatively rich flavor, pleasant aftertaste, and good sweetness perception. Using very hard water at 220 ppm for pour-over coffee results in a slightly bitter flavor and aftertaste, with less pronounced sweetness compared to 130 ppm.

山泉水手沖測試

Creating Pleasant Taste Impressions

Sweetness is often described as a sweet, lingering aftertaste that plays an important role in the coffee tasting experience. Coffee with the appropriate increase in extraction rate can more fully release this sweetness, making the coffee drinking experience richer and more balanced. Find the water quality that best suits your preferences and brew coffee that creates a pleasant taste impression for yourself.