Meanwhile, contrary to our previous study on carrots, among the six cooking methods, the greatest loss of total carotenoids and anthocyanins occurred during frying ( Lim et al., 2009). The most dramatic
isomerization of all- trans-b -carotene into 9Z -b -carotene also occurred through this cooking process. In fact, while significant water loss was not observed in the tap root of carrots during frying, a large amount of water loss was associated with the frying processing of sweet potato. This water loss could be related
to the carotenoid and anthocyanin loss. The previous study reported that small amounts of carotenoids were lost during the frying process of sweet potatoes ( Bengtsson et al., 2008). This discrepancy might have resulted from the fact that the sweet potato slice, a quarter of a root (from stem to root end) used in that study, was much bigger than the thin chips in this study. In that experimental condition, water loss would have occurred only on the surface of the sample. Another related research report found
that the preparation of chips with a thickness of 0.2–0.3 cm by drying resulted in a significant reduction of carotenoid content compared to other processing methods ( Kidmose et al., 2007).