Deep-fat frying of potato strips: Simulation of heat and mass transfer during frying and experimental measurements of frying and texture.

摘要

The potato processing industry needs improvements for their potato flying process for optimizing the quality and cost, especially in relation to the primary variable, which was oil content. Improved modeling is crucial to better understand and study the process. In this study four semi-empirical models were developed to simulate deep fat flying of "French fries" and the effects of drying on oil uptake and the texture of the final products were investigated. Twelve experiments were conducted under different predrying periods. The results of the Simple Transient (heat transfer) and Simple Crank (moisture and oil transfer) models with one variable showed reasonable agreement with experimental results. The Finite Surface Resistance Model showed closer agreement with the experimental results than the Simple Transient and Simple Crank models did, while the Variable Diffusivity models fit the data exactly because of the characteristics of the models.; Refitting the models to the data using values from the parameter correlations showed that the ability of the simple models to make future predictions was better than the more complex models, the finite surface resistance and variable diffusivity models. The complex models displayed a greater effect from factors other than the one tested in this study (initial moisture). Other uncontrollable variables, such as oil physical properties, the bubbling density, and the crust formation reduced the effectiveness of the correlation results with the complex models. It was found that moisture content and crust formation in the potato strips has an effect on the thermal diffusivity, moisture diffusivity, and oil diffusivity, although the finite surface resistance model indicated the effect of resistance to heat and moisture transfer, but not oil uptake, at the surface of the strips was small during much of the process.; A study of the effect of the initial moisture content of the potato strips on the oil uptake during the deep fat frying concluded that the moisture content of the strip surface was the limiting factor. The drying of potato strips during deep fat frying takes place completely in the falling rate period; therefore, it seems to be completely controlled by internal moisture mass transfer. The pre-drying process can control the oil uptake and the crispness of fried potato strips.