Color kinetics and acrylamide formation in NaCl soaked potato chips

摘要

The objective of this work was to study the kinetics of color development in blanched and blanched-NaCl impregnated potato slices during frying by using the dynamic method and also to evaluate the effect of NaCl in reducing acrylamide formation in potato chips. The measurement of color was done by using an inexpensive computer vision technique which allowed quantifying in a more precise and representative way the color in L~*a~*b~* units of complex surfaces such as those of potato slices during frying. The effect of potato slice soaking in NaCl was evaluated not only for color change but also for acrylamide formation. Prior to frying, potato slices (Desiree variety, diameter: 37 mm, width: 2.2 mm) were blanched in hot water at 85℃ for 3.5 min; these slices were considered as the control. Slices of the same dimensions were blanched as in the previous step, and soaked at 25℃ in a NaCl solution of 0.02 g/l 5 min at 200 rpm of agitation. These samples were considered as NaCl soaked potato chips. Blanched and soaked slices were fried at 120, 140, 160 and 180℃ until reaching moisture contents of ～1.8% (total basis) for color evaluation. Acrylamide content was evaluated only in final samples fried from 120℃ to 160℃. Color values in L~*a~*b~* units were recorded at different sampling times during frying at the four mentioned temperatures using the total color change parameter (ΔE). Experimental data of surface temperature, moisture content and color change in potato chips during frying were fitted to empirical relationships, with correlation coefficients greater than 90%. A first-order rate equation was used to model the kinetics of color change. In all cases, the Arrhenius activation energy decreases alongside with decreasing chip moisture content. Soaking in NaCl solution of potato slices before frying reduced dramatically acrylamide formation in potato chips in ～90% (average value) in comparison with control chips.