Abstract: We examined the effects of different pH values on the stability of thylakoid membrane in spinach and oilseed rape after heat treatment in terms of color value, polypeptide composition, soluble protein content, absorption spectrum and inverted fluorescence imaging of chlorophyll. The results showed that the color values (?a*) of spinach and oilseed rape thylakoid membrane solution were significantly decreased at low pH (3.6 and 4.6), the polypeptide components of chlorophyll protein complex were obviously degraded, the soluble protein content was significantly decreased, and the fluorescence distribution was aggregated (P < 0.05). It was confirmed that low pH could destroy the structural and functional stability of thylakoid membrane and chlorophyll protein complex, thus releasing more free chlorophyll and accelerating the degradation of chlorophyll; under the same pH condition, the stability of spinach thylakoid membrane was lower than that of oilseed rape thylakoid membrane. The chlorophyll protein complex of photosystem I was more sensitive to low pH than that of photosystem II.

Key words: pH, thylakoid membrane, chlorophyll protein complex, chlorophyll