There are a few differences between the two. First is their base and acidity; lemon extract has an alcohol base and is less acidic than lemon juice, which is squeezed directly from the lemon fruit. Lemon extract won’t cause your dairies to curdle. Next is the flavor and texture. Lemon extract has a strong lemon flavor with little to no tartness and bitterness, while lemon juice has a less concentrated lemon flavor with a prominent tartness and bitterness.