Samples of large residuals of 5.12, 5.46, 6.62, 4.98, and 4.92 mg/100 g, respectively from left to right: (a) Visualized prediction of TVB-N over the surface; (b) Color
images of the samples in (a). The large portion marked in white in the left 4 columns and the steep left side in the most right column induced the discrepancies between the
predictions and their chemical references. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)