Your Extraction Yield Changes how Much Liquid is Retained
When preparing coffee, regardless of what brew method you use, you are constantly reducing the mass of undissolved coffee throughout the extraction process. If we apply this reasoning to LRR, then we can expect an inverse relationship between extraction yield and LRR — e.g., if you operate from the basis which Earl E Lockhart did, which expected the LRR to be around 2ml per 1g of coffee, you would expect to lose 30ml of brew water if you had a 15g dose of coffee. But what if you achieve a 20% extraction yield? This means your coffee grinds are now 20% smaller. If they are smaller, they can’t retain as much liquid!
Or can they? The cellulose matrix is insoluble under ordinary brewing conditions, so it could be that after effectively hollowing out these cells throughout the process of extraction, we are possibly making room for more water. We might then expect liquid retained ratios to increase as bean porosity increases as roasting progresses. In order to put these theories to the test, we have set you some more homework.
Click on the image to participate in the homework exercises
This exercise will be dual-purpose. Firstly it will help you get a better idea of where your LRR ratios sit for your coffee so you can more accurately calculate extraction yields. Secondly, your contribution to this research will help us see some wider trends with LRR and changes in extraction yield and degree of roast which will benefit all ACM students. Here’s a link to the form.