Multi-compartment model for heat and mass transfer during the frying of frozen pre-fried French fries

Abstract

This paper develops a model for hot-air frying of frozen pre-fried french fries. A dynamic three-compartment model including heat and vapour transfer was developed. The model takes into account four major stages: defrosting, warm-up, convective drying and boiling drying. X-ray microtomographic observations led to the assumption of a compartmental structure: a central compartment (#1) with a high water content, a peripheral compartment (#3) corresponding to the dry crust and an intermediate compartment (#2) filled with vapour which appears during frying. The model was validated against experimental measurements: french fries core temperature, and average water content. Validations were made on three different hot-air frying conditions (combining convection and radiation). Heat transfer coefficient (ranging from 66 to 76 W⋅m−2K−1) and water transfer coefficient (ranging from 0.0035 to 0.0040 m⋅s−1) were identified. This model represented well enough the behaviour of french fries from defrosting to boiling drying to be used as a performant numerical tool to control and optimize hot-air frying.