Influence of water presoak on enzyme-retting of flax

Abstract

Enzyme-retting offers an alternative to the current method of dew-retting to extract fibers from flax ( Linum usitatissimum L.). Additional steps could improve the efficiency of enzyme-retting and modify the properties of the resulting fibers. Samples of ‘Ariane’ flax, which were grown in South Carolina during the winter and harvested early for quality fiber or late for both fiber and seed, were presoaked with distilled water before enzyme-retting. Soaked, enzyme-retted, and air-dried fibers were compared with unsoaked, control samples for yield and properties, and the water extract (or a freeze-dried portion) was tested in various methods for its influence on enzyme-retting. Presoaking increased fine fiber yield in some cases, but fiber strength at times was reduced. Analyses of the freeze-dried residue from soaking showed a mixture of sugars (128.6 and 101 mg g −1 for early and late harvest, respectively) and aromatic components including p-coumaric and ferulic acids and guaiacyl and syringyl units (3.51 and 3.05 mg g −1 total aromatics for early and late harvest, respectively). Water extracts from presoaking treatments at 1.0–2.0% (w/v) were not inhibitory to the retting fungus Rhizopus oryzae sb or to Viscozyme used for enzyme-retting, based on the Fried test and enzyme activities. Turbidity tests showed slight growth inhibition for Eschericia coli and Streptococcus sp. in the presence of water extracts from early versus late harvest flax at 0.5% (w/v), with those from late harvest flax more inhibitory. Benefits on the efficiency of water presoaking prior to enzyme-retting were moderate and not uniform in this study, and modifications may depend upon particular flax harvests.