extractor of juices, vegetable
榨 centers on pressing or squeezing something to extract its contents, especially juices from vegetables or other plant matter. The meaning extends naturally to the tool or person that does the extracting.
榨 is a phono-semantic compound: 木 (tree, wood) suggests a wooden press, and 窄 likely contributes the sound. The character is associated with pressing or squeezing, especially in the context of extracting liquids.
A wooden (木) press (窄) is used to squeeze vegetables until their juice comes out. Picture a heavy wooden frame crushing fresh produce.
For サ, imagine the sound of juice sizzling as it hits a hot surface after being extracted: 'sa!' The sharp hiss cues サ while the juice comes from the press.