Mapping the spatiotemporal distribution of acid and moisture in food structures during gastric juice diffusion using hyperspectral imaging

This study investigated the feasibility of using hyperspectral imaging (HSI) to characterize the diffusion of acid and water within food structures during gastric digestion. Two different sweet potatoes (steamed and fried) and egg white gels (pH5 and pH9 EWGs) structures were exposed to in vitro gastric digestion before scanning by HSI. Afterward, the moisture or acid present in the digested sample was analysed for calibration purposes. Calibration models were subsequently built using partial least squares (PLS). The PLS models indicated that the full-wavelength spectral range (550–1700 nm) had a good ability to predict the spatial distribution of acid (Rcal2>0.82) and moisture (Rcal2>0.88). The spatiotemporal distributions of moisture and acid were mapped across the digested food, and they were shown to depend on the food composition and structure. The kinetic data revealed that the acid and moisture uptakes are governed by the Fickian diffusion or both diffusion and erosion-controlled mechanism.