Hyperspectral imaging for one-step growth simulation of Brochothrix thermosphacta in chilled beef during storage

In this work, one-step growth models using hyperspectral imaging (HSI) (400–1000 nm) were successfully developed in order to estimate the microbial loads, minimum growth temperature (T_min) and maximum specific growth rate (μ_max) of Brochothrix thermosphacta in chilled beef at isothermal temperatures (4–25 ℃). Three different methods were compared for model development, particularly using (Model Ⅰ) the predicted microbial loads from partial least squares regression of the whole spectral variables; (Model Ⅱ) the selected spectral variables related to microbial loads; and (Model Ⅲ) the first principal scores of HSI spectra by principal component analysis. Consequently, Model Ⅰ showed the best ability to predict the microbial loads of B. thermosphacta, with the coefficient of determination (R_v²) and root mean square error in internal validation (RMSEV) of 0.921 and 0.498 (lg (CFU/g)). The T_min (–12.32 ℃) and μ_max can be well estimated with R² and root mean square error (RMSE) of 0.971 and 0.276 (lg (CFU/g)), respectively. The upward trend of μ_max with temperature was similar to that of the plate count method. HSI technique thus can be used as a simple method for one-step growth simulation of B. thermosphacta in chilled beef during storage.