Color is an important indicator for evaluating the quality of natural rubber (NR). Light-colored standard rubbers are widely used in high-grade products and have high economic value. This paper first introduces the history and test standards of the standard light-colored rubber. The origin of color deepening in NR processing, color substances, and its biosynthetic pathway are reviewed. Then, the discoloration mechanism of NR is studied from the perspectives of enzymatic browning (caused by polyphenol oxidase and polyphenols) and non-enzymatic browning (including Maillard reaction and lipid oxidation). Finally, the strategies to control the discoloration of NR will be described.

Chitosan microspheres were prepared by ion induction and chemical cross‐linking using water as the medium. Natural rubber/chitosan microsphere blends were then prepared by blending the chitosan microsphere suspension with natural rubber latex. An infrared spectrometer, particle size analyser, scanning electron microscope, surface contact angle analyser, thermogravimetric analyser, and differential scanning calorimeter were employed for structure and property characterisation. The results showed that the average particle diameter and the polydispersity index of chitosan microspheres were 323.8 nm and 0.283, respectively. The thermal stability and mechanical properties of natural rubber/chitosan blends were enhanced by introducing chitosan microspheres into natural rubber latex. The water contact angle was significantly decreased, from 94.64° to 55.47°, indicating improved hydrophilic properties for the natural rubber/chitosan film. The natural rubber/chitosan blends showed excellent antibacterial properties when the chitosan microsphere content was >4.00% w/w.