Comparison between atmospheric and vacuum frying of apple slices. http://dx.doi.org/10.1016/j.foodchem.2007.09.031

Abstract

Vacuum deep-fat frying is a new technology that can be used to improve quality attributes of fried food because of the low temperatures employed and minimal exposure to oxygen. In this paper atmospheric and vacuumfrying of appleslices were compared, in terms of oil uptake, moisture loss and color development. In addition, some appleslices were pre-dried (up to 64% w.b.) before vacuumfrying to determine the overall effect. To carry out appropriate comparisons between both technologies equivalent thermal driving forces were used in both processes (ΔT = 40, 50, 60 °C), keeping a constant difference between the oil temperature and the boiling point of water at the working pressure. Vacuumfrying was shown to be a promising technique that can be used to reduce oil content in fried appleslices while preserving the color of the product. Particularly, drying prior to vacuumfrying was shown to give the best results. For instance, when using a driving force of ΔT = 60 °C, pre-dried vacuum fried slices absorbed less than 50% of the oil absorbed by atmospheric fried ones. Interestingly, a strong relationship between water loss and oil content was observed in both technologies, allowing the extension of observations that have been made for atmosphericfrying.