Sub critical water extraction is an emerging area of interest to the applications where chemicals need to be extracted from their plant materials or any other source. When water is subjected to sub critical state under high pressures and high temperature, hydrogen bonds between water molecules breaks out making every molecule of water behave like an organic compound making it non polar in nature. This technique is widely accepted where organic solvent traces can be completely eliminated. The proposed invention is a cost effective and a more viable innovation where aroma, taste, quality of the compounds will be retained compared to the existing technologies.
Background of invention
Coffee extraction is the process of dissolving soluble flavours from coffee grounds in water. Proper brewing of coffee requires using the quantity of coffee, ground precisely, extracted to the correct degree, controlled by the correct time and correct temperature.
Extraction yields depend primarily on temperature, brew time, and grind size, and in a complex way on method. Yield is inverse to grind size (smaller grinds have more surface area, so extract faster) and increases roughly linear with time, as the extraction proceeds. Thus for a given temperature and grind size, there is an ideal brew time, with larger grinds requiring longer brewing. French press features the largest grinds of conventional methods, hence the longest brewing, on the order of 3- 4 minutes, while filter coffee has smaller grinds and shorter brewing, and espresso has yet smaller grinds and shorter brewing, on the order of 20- 30 seconds.
Water temperature is crucial to the proper extraction of flavour from the ground coffee, as it affects the proportions in which solubles are extracted -one wishes to extract the desired flavours as much as possible, and the undesirable flavours as little as possible. If cooler, some of the solubles that make up the flavour will not be extracted. If the water is too hot, some undesirable, bitter, elements will be extracted, adversely affecting the taste. Another consideration is the difference between the temperature of the water and the temperature of the coffee slurry: for example, certain brewing methods (e.g., manual pour over) can result in losing a significant amount of heat to the atmosphere during the brewing process.
Extraction using superheated water tends to be fast because diffusion rates increase with temperature. Organic materials tend to increase in solubility with temperature. Therefore, extraction with sub critical water can be both selective and rapid, and has been used to extract coffee, tea, herbal or seeds.