Study The Effect Of Blanching And Pre-frying On The Quality Of Frozen French Fries

The objectives of this paper were to explore the process of blanching and pre-frying, to get high quality French fries. Firstly, the physical and chemical compositions of raw potato were analyzed. Secondly, in order to optimize processing of frozen potato strips and improve the index of color and texture about chips, Shepody were used as raw materials, the method of variance analysis and correlation analysis were used to estimate the technology of the degree of starch gelatinization, the sugar content of blanching water, blanching and pre-frying effect on the quality of chips. Finally, the feasibility of the instrument way to predict the sensory quality of French fries was studied by the method of regression analysis.1. By study the mode of blanching, it was confirmed that high quality of frozen French fries could be obtained by blanching at short time with high temperature and long time at low temperature. The technology of blanching was studied in a factor experimental and the degree of starch gelatinization of potato chips was made as index. Blanching temperature was found to correlate significantly with potato starch gelatinization degree, while the blanching time had no significant correlation with potato starch gelatinization degree.2. The impact of blanching temperature and time on the sugar degree of blanching water was preliminary explored, and it was found that fresh water should be regularly added in order to regulate the content of sugar in blanching water in industrial. In addition, blanching time should be extended in order to bleach sugar efficiently and achieve a uniform and moderate color of French fries.3. The correlations between the blanching temperature, time and the texture, color of French fries were studied. It was found experimentally that the first blanching stage(85℃,7min) profited a good texture of French fries, and the second blanching stage(75℃,15min) had significant effect on the color of French fries. The texture of powdery was easy to get by high temperature at short time blanching and the step of low temperature of blanching was confirmed to adjust the sugar distribution in chips. High quality of French fries could be produced under the two-step-blanching processing.4. The single factor experiment of pre-frying was carried out with the index of texture and color of French fries. The correlations were found between the brightness, yellow blue value and green value of French fries with the pre-frying technology. It was concluded that the parameters of processing was optimized as180-190℃,0.5-lmin for pre-frying.5. Through the analyzing of the correlation between the measurement of instrument and sensory evaluation on the texture of French fried potatoes it was discovered that the hardness, chewiness, brittleness and floury texture of sensory evaluation correlate significantly with instrument measurement of French Fries. And the overall preference correlates well with instrument measurement indicator. Through multiple linear regression analysis a predicted model of sensory evaluation was established and it could be transformed from sensory evaluation to instrumental measurement on the quality of French fries.