Submitted to: Industrial Crops and Products
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/29/2006
Publication Date: 11/1/2006
Citation: McMahan, C.M., Cornish, K., Coffelt, T.A., Nakayama, F.S., Mccoy, R., Brichta, J.L., Ray, D. 2006. Post-harvest Storage Effects on Guayule Latex Quality from Agronomic Trials. Industrial Crops and Products. 24:321-328. Interpretive Summary: Commercialization of natural rubber latex from Parthenium argentatum, is underway, following years of research supported by the ARS. Success in growing economic value will depend on, among other factors, continuous improvement in agronomic practices. Guayule latex quality is affected by shrub storage. Under severe conditions, for example high temperatures and extended times, field storage has a dramatic effect on latex quantity and quality. Polymer molecular weight reduction of up to 30% has been observed in earlier and the present study. Shrub storage treatment effects are complex and difficult to quantify, especially when measurements are made under field conditions and at multiple locations over an extended period of time. The commercial guayule harvesting and processing practices should take into account-established factors such as time, temperature, variety, form of stored material, and seasonal effects. This study confirms the importance of those variables and recommends additional factors: moisture, plant age, and a consideration of the specific process to be used, to preserve latex quality while providing maximum flexibility in the harvesting process.
Technical Abstract: Current guayule commercialization efforts are based upon the production of hypoallergenic latex. However, little is known about the optimal agronomic conditions for maximum latex production. The objective of our present study was to determine how latex yield and quality are affected by post-harvest plant storage in order to provide flexibility in the harvesting, chipping, and downstream processing steps for guayule latex. The experiments were conducted on two lines (11591 and AZ-2) at the University of Arizona Maricopa Agricultural Center, from March 2001, through the end of 2004. Average value of weight-average molecular weight of guayule latex increased as the plants aged from about 1.7 to 2.7 years. Guayule latex quality was affected by shrub storage conditions, and moist storage effectively extended the storage time for guayule shrub without severely impacting molecular weight. Both varieties (AZ-2 and 11591) were quite resilient with respect to storage treatment effects on latex quality. However under extreme conditions, for example high temperatures and extended dry storage times, polymer molecular weight reduction of up to 30% occurred.