Detection in situ of carotenoid in microalgae by transmission spectroscopy

• Vis/NIR transmission spectra in situ to determine the CC in Spirulina sp.
• Variable selection method of LW analysis, UVE and SPA were used.
• The prediction performance of x-LW-PLS, UVE-PLS and SPA-PLS were compared.
• A high RPD value of 3.40 and 3.44 were obtained by x-LW-PLS and SPA-PLS models.

Carotenoids, which can be part of the food additives and drug additive, are one of important internal quality indexes for living microalgae. In the present study, visible/near infrared (Vis/NIR) transmission spectra in situ of Spirulina sp. suspension were required using an Ocean Optics USB 4000 Spectrometer in the wavelength range of 346–1038 nm, and the loading weights (LW) analysis, uninformative variables elimination (UVE) and successive projections algorithm (SPA) were used to select important variables related to the carotenoids content (CC) for the Spirulina sp. suspension. Different concentrations of 100 samples of Spirulina sp. suspension were selected. The results showed the correlation coefficient (r), root mean square error (RMSE) and residual predictive deviation (RPD) in the prediction sets were 0.96, 0.23 mg/L, 3.40, 0.89, 0.39 mg/L, 1.59 and 0.96, 0.24 mg/L, 3.44 for x-LW-PLS, UVE-PLS and SPA-PLS model respectively. It indicated that SPA-PLS gave the best result, while x-LW-PLS was better than UVE-PLS. So, Vis/NIR transmission spectra combined with SPA method was feasible to assess CC of Spirulina sp. suspension. And SPA variable selection method can simplify the prediction model and improve the model prediction precision. Furthermore, the method can be used as a good example for the detection in situ of other pigment content in other microalgae.