Comparative study of physical and sensory properties of pre-treated potato slices during vacuum and atmospheric frying

The objective of this research was to study the effect of different processing conditions on physical and sensory properties of potato chips. Potato slices of Desiree and Panda varieties (diameter: 30 mm; thickness: 3 mm) were pre-treated in the following ways: (i) control or unblanched slices without pre-drying; (ii) blanched slices in hot water at 85 degrees C for 3.5 min and air-dried at 60 degrees C until a final moisture content of similar to 0.6 kg water/kg dry solid; (iii) control slices soaked in a 3.5 kg/m(3) sodium metabisulphite solution at 20 degrees C for 3 min and pH adjusted to 3. Pre-treated slices were fried at 120 and 140 degrees C under vacuum conditions (5.37 kPa, absolute pressure) and under atmospheric pressure until they reached a final moisture content of similar to 1.8 kg water/100 kg (wet basis). An experimental design (3 x 2(3)) was used to analyze the effect of pre-treatment, potato variety, type of frying and frying temperature over the following responses: oil content, instrumental color and texture and sensory evaluation. Vacuum frying increased significantly (p < 0.05) oil content and decreased instrumental color and textural parameters. Sensory attributes, flavor quality and overall quality, were significantly improved using vacuum frying. The higher frying temperature (140 degrees C) increased Delta E, maximum breaking force, hardness and crispness and decreased L* and b* values. On the other hand, Panda potato variety improved the color of the product. A great improvement on color parameters was obtained using sulphited potato slices instead of the other pre-treatments. Although, the better flavor was obtained for control potato chips, no significant differences were found for overall quality between control and sulphited potato chips. Significant correlations (p < 0.01) between sensory and instrumental responses were found. (C) 2008 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.