Submitted to: International Conference on Industrial Crops and Rural Development Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/2/2005
Publication Date: 9/17/2005
Citation: Mcmahan, C.M., Cornish, K., Mccoy, R.G., Brichta, J.L., Wilson, S., Coffelt, T.A., Nakayama, F.S., Ray, D.T. 2005. Post-harvest storage conditions on guayule latex quality from agronomic trials. In: M.J. Pascual-Villalobos, F. S. Nakayama, C.A. Bailey, E. Correal and W.W. Schloman, Jr., editors. Proceedings of the Association for Advancement of Industrial Crops (AAIC) Annual Meeting, Murcia, Spain, September 17-21, 2005. pp. 575-596.
Interpretive Summary: Guayule latex quality is affected by shrub storage, and moisture can quite effectively extend the usable storage time for guayule shrub without severely impacting molecular weight. Under severe conditions, for example high temperatures and extended times, field storage has an adverse effect on latex quality. Polymer molecular weight reduction of up to 30% has been observed in earlier and the present study. The average value of weight-average molecular weight of guayule latex increases as the plant ages from about 1.5 to 2.5 years. For the youngest plants, line 11591 is slightly higher in molecular weight than AZ-2. After 2 years there are no Mw differences between lines. Both varieties are quite resilient with respect to storage treatment effects on latex quality. 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. A series of agronomic trials were carried out over four years to investigate latex yield and quality in different lines of guayule planted at different times of year, and at different densities. Sub-samples of plants were harvested several times to determine the effect of shrub age on yield and quality. The effects of storage conditions on the harvested shrubs were also investigated. In this presentation, we report on the effects of the agronomic and post-harvest storage trials on the quality of latex extracted and purified from chipped shrubs from the agronomic trials. The latex quality parameters measured include rubber particle size distribution, rubber molecular weight, latex protein content, and other physical properties.