Table 2.

Effect of extraction condition on lignin yield and composition of extracts.

Extraction Conditions	Lignin Yield a (g kg−1 Flax Shives)	Lignin Extraction Efficiency b (%)	Carbohydrate Content c (g kg−1 Flax Shives)	Free Phenolic Content d (g kg−1 Flax Shives)
Method 1—Alkali hydrolysis: 1.25 M NaOH, 80 °C, 5 h	92 ± 20	33.7	N/M	N/M
Method 2—PLPW: 0.47 M NaOH: 100 °C, 82 min	33 ± 2	12.1	177 ± 2	1.0 ± 0.1
Method 2—PLPW: 0.47 M NaOH: 140 °C, 82 min	72 ± 1	26.4	213 ± 2	3.0 ± 0.3
Method 2—PLPW: 0.47 M NaOH: 180 °C, 82 min	241 ± 32	88.3	302 ± 6	4.7 ± 0.3
Method 2—PLPW: Water: 180 °C, 82 min	27 ± 5	9.9	311 ± 2	3.9 ± 0.1

Values are means ± standard deviations.

^aLignins were obtained by precipitation at pH 1.5 by addition of 6 N HCl after isolation of the solubilized hemicelluloses;

^bcalculated as g lignin extracted per g lignin present in flax shives;

^cDetermined by phenol-sulfuric acid reaction method, expressed as glucose equivalent;

^dTotal soluble phenolic compounds in extract after removal of hemicelluloses and lignin, expressed as vanillin equivalent. N/M = Not measured.