Why are green coffee beans sour?

Why do green coffee beans become sour?

Coffee is one of the most popular drinks in the world, and the taste of coffee mainly depends on the quality of coffee beans and the degree of roasting. Among these factors, acidity is a very important characteristic. So why do raw coffee beans have a sour taste? This article will explain this question from multiple angles.

1. The characteristics of the coffee plant

First, we need to understand the characteristics of the coffee plant itself. The coffee plant belongs to the Rubiaceae family, and its berries can be picked when they are ripe to get the so-called "coffee beans". However, when the berries are picked before they are ripe, they are raw coffee beans.

Different types and varieties of coffee plants have different levels and types of acidic compounds. The most common and influential ones are organic acids such as citric acid, malic acid and gluconic acid. Those are responsible for the noticeable pungent feeling in green beans. These acidic compounds play a protective role in the fruit of the coffee plant, helping the fruit resist attack by pathogens and insects.

2. Green Bean Processing

In addition to the characteristics of the coffee plant itself, the green bean processing process also affects the acidity. After picking, the coffee cherries need to go through a series of processing steps to get clean coffee beans.

The first step is to peel and pulp the fruit. This process is usually done by soaking or mechanical methods. However, fermentation reactions may occur at this stage, resulting in the production of more organic acids and increasing the overall acidity.

The next step is water washing or natural fermentation. Water washing can effectively remove impurities such as pectin remaining on the surface of the beans, but it may also lead to the loss of some organic acIDs.

3. Storage conditions

Another factor that affects the acidity of green beans is storage conditions. If the green beans are not properly stored and preserved, the moisture and other chemical components inside them may continue to develop and change.

Under improper storage conditions, green beans may become contaminated with mold or bacteria, leading to further fermentation reactions. These reactions produce more organic acids and increase the overall acidity.

4. Baking process

The last factor is the roasting process. Roasting is one of the key steps in transforming green beans into edible coffee beans. During the roasting process, temperature and time have an important impact on the internal structure and chemical composition of coffee beans.

Lighter roasts usually retain more organic acids and have a noticeable sour taste, while darker roasts convert these organic acids into other substances, reducing the overall acidity.

Summarize

To summarize, the sour taste of green coffee beans is mainly due to the following reasons: the characteristics of the coffee plant itself, fermentation reactions that may occur during processing, improper storage and preservation, and the effects of temperature and time during roasting on the internal structure and chemical composition.

Understanding these factors is very important for coffee lovers because they determine the taste and flavor of the final coffee. At the same time, it also provides some ideas for studying and improving the coffee production process.