Rapid evolution of biochemical and physicochemical indicators of ammonia- stabilized Hevea latex during the first twelve days of storage

Abstract

Abstract The impact of NH3-stabilization of latex on its biochemical and physicochemical indicators at various storage times (0–41 days) was investigated. Liquid latex was characterized by pH, dry rubber content, total solid content, surface tension, lipid and protein contents. In addition, lipid and protein profiles were monitored by TLC and SDS-PAGE, respectively. Thin latex films were studied by AFM to unravel their morphology, stiffness and adhesion, whereas infrared and wettability measurements provided information on composition and wetting properties. NH3-stabilization method was shown to rapidly (12 days) and significantly impact lipid and protein contents resulting in drastic changes in the morphology as well as in the mechanical and physicochemical properties of films. The presence of a layer of very high stiffness (GPa) on the rubber surface was noticed which was hypothesized to contain REF1 and SRPP1, the two major latex proteins. This was later confirmed by imaging a film of dry latex extract, known to contain both REF1 and SRPP1 proteins, which revealed stiffness of the order of GPa. As a protein known for its amyloid-forming capacity, REF1 could be the main component responsible for GPa-range stiffness of NH3-stabilized films and might then play a crucial role on the final properties of natural rubber.