De-oiling and Pre-treatments for High-Quality Potato Chips
Kim, Tae Hoon
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A de-oiling step using a centrifuge ensures oil content reduction and improves the quality of fried snacks. A commercial deep-fat fryer with the basket loaded with potatoes and a sample holder was used to fry potato slices, non-pretreated, blanched in hot water (85?C/3.5min) and rinsed in 3 percent NaCl solution (25?C/5min). A de-oiling step (350 1 rpm and 457 1 rpm) for 1 min was conducted after the frying (145?, 165? and 185?C or 165?C) and cooling (0, 15, 30, 45 and 60 s or 0.60 and 120 s) steps. Lower frying temperature, higher centrifuge speed, and shorter cooling time resulted in the lowest oil uptake in potato chips. Pre-treatments (blanching and soaking) decreased (5 percent and by at least 10 percent), respectively, compared to the untreated chips. De-oiling led to increased hardness of the chips fried at 145? and 165?C (0 s cooling time), and the hardness decreased as cooling time. Pre-treatments (blanching and soaking) increased hardness (by 46 percent and 38 percent) and decreased work (by 20 percent and 27 percent), respectively, so that, during rupture, the pre-treated chips resulted in more crunchiness and firmness than the untreated chips. Potato chips showed less lightness and redness when fried at 145?C, and more lightness and redness when fried at 185?C; yellowness increased b* values as temperature increased. As cooling time increased, the lightness of the chips decreased, and the redness and the yellowness of the chips increased. Pre-treated samples resulted in increasing in lightness (L*) and yellowness (b*), whereas the redness (a*) values of the final products fluctuated. Higher frying temperature, centrifuge speed, and higher cooling time usually resulted in increasing shrinkage in thickness of potato chips; the chips fried at 165?C resulted in increasing in thickness. All the fried and de-oiled products resulted in a decrease in thickness, diameter, and volume except for the thickness of the chip soaked in NaCl, compared to raw slices. A consumer test showed that, blanching and de-oiling without cooling enhanced texture and overall quality of the chip, soaking and de-oiling improved the color, flavor, and the overall quality, and the two pre-treatments did not significantly influence the odor of the chip.