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

Abstract

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 (Tmin) and maximum specific growth rate (μmax) 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 (Rv2) and root mean square error in internal validation (RMSEV) of 0.921 and 0.498 (lg (CFU/g)). The Tmin (–12.32 ℃) and μmax 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 μmax 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.

Keywords

• brochothrix thermosphacta
• beef
• hyperspectral imaging
• growth simulation
• one-step analysis
• predictive microbiology