Effect of acid and microbial growth on green color degradation of blanched broccoli (Brassica oleracea) during storage at 7C was studied. When broccoli was submerged in McIlvaine's buffer at pH 3–8, color degradation accelerated as pH decreased, as expected. High Performance Liquid Chromatography (HPLC) was used to show that the color degradation was due to the conversion of chlorophyll to pheophytin only. Pheophytinization followed a first order reaction. the logarithm of the reaction rate constants were linearly correlated to the environmental pH, up to pH 7. Acids containing a benzene ring caused a faster color change than acids with a simple carbon chain due to their hydrophobicity. Microbial growth accelerated color change by producing acid and produced what appear to be holes in the surface of the broccoli, as shown by Environmental Scanning Electron Microscopy (ESEM).