The variations in moisture content and oil content of samples of 1.5-mm thick slices of potato (c.v. Record U.K.) were examined after various frying times at frying temperatures of 145, 165 and 185°C. The loss of moisture and the uptake of oil were found to be interrelated and both were linear functions of the square root of frying time. Within the temperature range examined, moisture loss and oil uptake were found to be independent of frying temperature. From the data and visual observations the mechanism of moisture loss and its influence on oil content in the final product were discussed. Suggestions are made for means of reducing the total oil content by modifications in the frying process.

The distribution of oil taken up during frying was investigated in chips, snacks, and fries using red-stained oil. The effect of pre-drying using microwaving and lyophilization was also examined in chips. These studies indicated that some oil uptake occurred during frying which was not exclusively an end of frying effect. The distribution of oil depended upon the structure of the food and the ease of moisture loss. Oil uptake was influenced by slice thickness, the moisture content, its distribution and ease of transfer, the cutting edge, and degree of blistering during frying. Oil was associated with areas of moisture loss.

Microwave, hot air (40 and 105OC) and freeze drying were used to remove varying amounts of moisture from 1.3 mm thick potato slices. The partially dried slices were then fried in oil at 165°C either for a constant 2 minor a variable frying time based on the amount of pre-drying. The microwave and hot air treatments resulted in a reduction in the final oil content, which was related to the degree of pre-fry drying. Freeze drying resulted in an increase in the oil content, again related to the initial moisture reduction. Oil distribution at the microscopic and macroscopic level was determined and found to be related to the initial moisture distribution in the slice. It is suggested that pre-fry drying may be a more successful point of influence than post-fry treatment in the manufacture of a 'lower fat crisp'.

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