Change and correlation analysis of pigment contents and color value during growth of Chlorella vulgaris

Automatic color spectrometer was used based on CIE-L^*a^*b^* color system to monitor the color value change in the growth process of Chlorella vulgaris. The cell density and pigment contents, as well as their correlational relationship were analyzed. The results show that C. vulgaris growth was divided into four phases (seeding, rapidly growing, stable and declining). The general trends of green and yellow pigments were increasing, as well as yellow value (b^*), color difference (ΔE) and chroma (C), but those of lightness value (L^*), red value (a^*) and hue angle (H°) were decreasing. Strong correlation had been observed between color values and cell density, pigment content. The linear regression models had a high fit degree especially in rapid growing phase. The b^* and ΔE values could be used as good indicators. The establishment of non-contact quantity and quality dynamic prediction model can make the prediction quick and accurate, and provide a theoretical basis for improving the precision operation and efficiency in the process of aquaculture.