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United States Department of Agriculture

Agricultural Research Service

Title: Latex Yield and Quality During Storage of Guayule (Parthenium Argentatum Gray) Homogenates

Authors
item Cornish, Katrina
item Van Fleet, Jennifer
item Brichta, Jenny
item Knuckles, Benny

Submitted to: Association for the Advancement of Industrial Crops Conference
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 2003
Publication Date: October 12, 2003
Citation: Cornish, K., Van Fleet, J.E., Brichta, J.L., Knuckles, B.E. 2003. Latex yield and quality during storage of guayule (parthenium argentatum gray) homogenates. Association for the Advancement of Industrial Crops Conference. p.8.

Technical Abstract: Extraction and purification of latex from guayule (Parthenium argentatum Gray) requires that harvested shrub first be homogenized in an alkaline aqueous buffer. We have extended an earlier invistigation into the stability of the latex in homogenates made in different ways and stored under different conditions. Latex concentration declined at acidic pH, and after one month at 24 oC in one experiment, and after six months in another, when the initial latex concentration in homogenate prepared from defoliated shrub was below 5 mg/ml. This decline was less apparent in homogenates made from leafy shrub, suggesting a protective effect derived from the leaves. Storage at 4 oC prevented latex loss under all treatments. The quality of the rubber polymers in the latex fraction was investigated using size exclusion chromatography/multiangle laser light scattering detection. Polymer molecular weight and molecular radius declined in parallel, but declined faster in the dilute homogenate generated from the second grind of the guayule bagasse than in the more concentrated homogenate from once-ground shrub. Degradation was greatly slowed in all treatments when the homogenates were stored refrigerated. Polydispersity values were low in all treatments, only slightly increasing over time, with the exception of homogenate generated by the second grind of shrub in the presence of leaves and stored at 24C. The relatively rapid polymer degradation of the latex fraction in this homogenate led to an increase in polydispersity followed by a decrease as the latex fraction was degraded to below detection levels. We conclude that guayule homogenate provides a stable environment for latex yield and quality, even at room temperature, for at least 13 - 16 weeks provided that the pH is basic and the concentration of rubber particles is at least 5 mg/ml. This is in contrast to the extractable latex content of harvested branches, which is prone to rapid coagulation and degradation in situ unless the branches are stored hydrated and refrigerated.

Last Modified: 12/18/2014
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