MASS AND HEAT-TRANSFER DURING DEEP-FAT FRYING OF POTATO SLICES .1. RATE OF DRYING AND OIL UPTAKE

The influence of oil temperature, dry matter content of potato tubers and thickness of slices on drying and oil uptake during deep fat frying of potato chips (British: potato crisps) was investigated. Experiments were carried out on a laboratory scale at strictly isothermal frying conditions, and by using uniform slices cut from potato tubers of known weight (size) and specific gravity (dry matter content). An exponential model and a multiple linear regression model was applied successfully to describe dehydration and oil uptake, respectively. Drying may be accelerated by increasing oil temperature. A higher initial dry matter content abbreviates drying time due to the start of the process at lower moisture content. As oil uptake calculated on the weight of potato chips is controlled primarily by residence time in the frying unit, final fat content is lower at higher oil temperatures and initial dry moisture contents. Oil uptake calculated on the constant basis of wet weight of raw potato slices is correlated positively to the oil temperature, to the initial dry matter content and to the inverse of the slice thickness. This indicates that oil is deposited on the surface and does not penetrate into the centre of slices to a large extent. (C) 1995 Academic Press Limited