Is the caffeine content of cold coffee better than hot coffee?

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The emergence of cold coffee is to improve the flavor, not to solve health problems.

The process of "brewing" coffee is the process of extracting soluble substances from coffee powder into water. The purpose of grinding coffee beans into powder is to reduce the particle size and increase the contact area between water and coffee powder, thus speeding up the extraction process.

There are two key factors in the extraction process. One is "how much can be extracted into water". Professionally, it is a thermodynamic concept, indicating the maximum amount that can be extracted, and the other is "how fast is the extraction speed." professionally, it is a kinetic concept, indicating how much it can be extracted within a given period of time. In practical operation, the time used for extraction is always fixed, so the extraction speed is also very important.

The flavor of coffee is made up of extracted substances. There are at least hundreds of flavor substances in coffee beans, each of which has different thermodynamic and kinetic characteristics of extraction. Temperature, the ratio of coffee powder to water and extraction time determine the amount of these substances extracted into water.

Most importantly, different substances react differently to these conditions. Some substances are extracted more under this condition, and some substances are extracted more under that condition, so the same coffee will get different flavor if different extraction conditions are used.

Temperature has a great influence on the thermodynamics and kinetics of extraction. At low temperature, the extraction speed of all kinds of substances will be greatly reduced, but the extent of reduction of different substances is different. The idea of cold-extracted coffee is that at low temperatures, the extraction rate of astringent substances decreases more, and the content in the final coffee is relatively low, so the flavor of the coffee is better. Of course, because the extraction speed of all substances has slowed down greatly, so the cold extraction takes more than ten hours to complete.

There are no obvious "unhealthy" ingredients in coffee, so cold coffee or hot coffee, it doesn't matter which is "healthier". Of course, if the hot coffee temperature is too high (for example, higher than 65 °C), it will be unhealthy. However, this "disadvantage" is only the effect of high temperature and has nothing to do with coffee.