Effects of Initial Moisture Content on the Oil Absorption Behavior of Potato Chips During Frying Process

During frying process, whether and how moisture content in materials affects oil absorption remain unclear. Herein, we provided direct evidence suggesting that although the initial moisture content had no significant effect either on the final oil content or oil fraction, the moisture content did greatly affect the rate of oil absorption. We analyzed the total oil (TO), surface oil (SO), structural oil (STO), penetrated surface oil (PSO), and oil distribution during frying process in once-fried and twice-fried potato chips, and found that SO fraction was lowest (about 0.90-1.66 %) among three different fractions of TO, while PSO was the dominant section (about 50 %) for TO. Surprisingly, there were no significant difference among the final TO, SO, STO, and PSO for two kinds potato chips (P > 0.05), a finding suggesting that the initial moisture content itself might have no effect on oil absorption. Compared with once-fried potato chips, twice-fried chips much quicker (around sevenfold) reached equilibrium at 180 °C, which might be attributed to no inner resistance of water evaporation in twice-fried potato chips. More importantly, our confocal laser scanning microscopy (CLSM) inspection established that oil of twice-fried chips entered the core faster than once-fried chips. Oil followed the cell shapes and located in cell walls and inside the intercellular spaces for both samples. Taken together, this study provided compelling new data to clarify the relationship between the initial moisture content and oil absorption during frying process, and laid the groundwork for introducing a pre-drying strategy to frying process in food industry.