Can Decaf Coffee Beans Be Eaten? The Story and Characteristics of Decaf Coffee Beans, and Why They Have More Defective Beans

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Possible Hypotheses About Defective Decaffeinated Coffee Beans

Processed decaffeinated coffee beans often show defects. When compared with unprocessed beans of the same grade, this phenomenon is clearly abnormal. After discussion, we proposed several possible hypotheses:

1. Improper Storage Conditions

Decaffeinated coffee beans may not have been properly stored. After undergoing water treatment, the bean structure itself is not very tight, and flavors are more easily lost compared to normal beans. Under improper storage conditions, the raw beans themselves may undergo some undesirable changes.

2. Activated Carbon Treatment Process

The article mentioned earlier described the commonly used processing method: the Swiss Water Process, which includes an activated carbon treatment step. As we know, activated carbon is a very aggressive substance. Therefore, we can hypothesize that during the activated carbon treatment process, not only caffeine is removed, but other substances are also filtered away together. Even some structural components might be partially removed, which can easily cause defects and loss of content in the coffee beans.

3. High-Temperature High-Pressure Processing

Coffee beans are, after all, a type of bean, similar to mung beans or soybeans. When we make mung bean soup or soy milk, we soak the beans overnight to soften the dense beans, making them easier to cook or blend. The caffeine removal process always occurs in solution and requires high temperature and high pressure environments, which increases the porosity of the raw beans. After activated carbon filtration and heating for drying, it's difficult for the coffee bean contents not to be lost.

Regardless of which hypothesis is correct, or perhaps all three are valid, the result is obvious: processed raw beans have loose structure, reduced volume, low gloss, many defects, and unpleasant odor. Due to improper storage, they may even have developed oily flavors and other off-season notes, suggesting severe flavor loss.

Second Roasting Experiment Results

Judging from the characteristics and aroma of roasted decaffeinated coffee beans, our hypothesis and approach regarding second roasting were correct. After increasing the initial temperature and shortening the roasting time, we were pleasantly surprised to find that some defect flavors in the beans, such as off-season notes, were eliminated. The previously thin aroma developed some complexity and became richer and more mellow.

Different development processes create different flavor changes. Although we may not yet understand exactly which substances changed and how, this experiment provided us with an excellent research direction, which is what excites us most.

Second Roasting Temperature and Time Control

Through experimentation, we found that the difficulty of second roasting lies mainly in setting the initial temperature. We planned to use the endpoint temperature from the previous roasting, or rather the drying phase, as the starting temperature for this roasting. Although there isn't much literature available for reference, based on the condition of the roasted beans from several roasting sessions, we ultimately set the initial temperature at 200°C. Combined with the loose bean structure, we completed this roasting in just 6 minutes, with a development time of 1 minute and 20 seconds when the beans came out of the roaster.

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