These was actually a sort of fun and popular research paper about this, https://www.cell.com/matter/fulltext/S2590-2385(19)30410-2 https://www.cell.com/matter/

These was actually a sort of fun and popular research paper about this, https://www.cell.com/matter/fulltext/S2590-2385(19)30410-2 https://www.cell.com/matter/fulltext/S2590-2385(19)30410-2 They suggest a courser size and less pressure to avoid channeling. I’ve been using this technique for a while, I think the results are better (but of course there’s a strong bias when people think they are doing the cleverer thing in food preparation). For light roasts I hold the pressure at around 1 bar for ~30 seconds before increasing to 7 or so.