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Pol. J. Food Nutr. Sci. 2007;57(Special issue 2A):175–181
The aim of the work was to estimate the effect of microwave and convective dehydratation parameters of potato strips after blanching on French fries quality. After washing and peeling, potato tubers were cut into strips, which underwent one-stage blanching in water (for 10 min at 75oC). After blanching the potato strips (10x10 mm) were dried with two methods: vacuum-microwave at two levels of magnetrons power (360 W and 480 W) and by changing pressure at the range from 4 kPa to 6 kPa, and convective pre-drying performed at 50oC and 75oC at constant air speed of 2m/s. The control samples were made of blanched, not pre-dried potato strips. After potato strips pre-drying the French fries were prepared with the two-stage frying method in canola oil. French fries were subjected to sensory evaluation. Their fat content, colour and texture were determined with instrumental methods. The texture of French fries was estimated in two tests: cutting and bending. Changes in the structure of potato tissue were determined using a scanning electron microscope. It was stated that the pre-drying time in the vacuum microwave method was about four-times shorter than that in the convective method. French fries made of strips pre-dried with the vacuum microwave method absorbed less fat (by about 9% on average), than those pre-dried with the convective method. Pre-drying of potato strips lowered the fat content in the finished product by 28% compared with the non-pre-dried control samples The smaller cutting force and bending strength were exhibited byFrench fries made of potato strips pre-dried with the convective pre-drying method at 75oC and 50oC compared with the microwave method. Based on the sensory and instrumental results, it was found that French fries pre-dried with the vacuum microwave method were characterised by better quality attributes, as compared with French fries pre-dried with the convective method and control samples without pre-drying.