Heat and mass transfer modeling and quality changes during deep fat frying: A comprehensive review

Abstract The deep fat frying of food involves simultaneous heat and mass transfer between the food product and surrounding oil and hence the frying operation is complex in nature. Heat is transferred from the frying medium to the product surface by convection and from the surface to the core of the food through conduction. The specific heat, thermal conductivity, thermal diffusivity, and convective heat transfer coefficient are the major factors that greatly affect the rate of heat transfer. The heat transfer study for deep fat frying of food products revealed that the Fourier number was in the range of 0.1–0.5. The fat uptake and moisture loss are the primary modes of mass transfer during this process. For deep fat frying, the mass transfer coefficient for different food materials was found to be in the range of 10 −4 –10 −6 m/s. The moisture diffusivity for various food materials was measured in the range of 10 −6 –10 −10 m 2 /s. This review presents the different models implemented to assess the heat and mass transfer parameters during deep‐fat frying of different food materials. The effects of frying process parameters on color, texture, and different physical properties of fried food were discussed. Overall, this review includes information related to the frying of different food products that will assist the food processing connoisseurs and industries in predicting and optimizing the frying process parameters to obtain the desired quality in the product and make the process energy efficient. Practical Applications Frying involves the convective heat transfer from the frying medium to the surface of the food product and conduction heat transfer within the food. During frying, the moisture and oil transport are controlled by diffusion gradient and capillary flow. Most of the oil penetrates into the food during cooling through the channels and pores of the product. The physicochemical changes in the fried product are regulated by frying process factors such as frying oil temperature, frying time, and thermal characteristics of the food. The intense heat of frying imparts a rich aroma and texture to fried foods. Modeling and optimization of frying is very important in order to produce high‐quality fried food products. Heat transfer parameters such as thermal diffusivity, heat transfer coefficient, Fourier number, and Biot number are important in analyzing and improving the product's frying operation. The food technologists would be able to analyze the mechanism of oil absorption and produce low‐oil fried food products if they had a better understanding of heat and mass transfer.