Ultrasound as a pretreatment to reduce acrylamide formation in fried potatoes

Abstract

Abstract Acrylamide is a compound that is potentially carcinogenic for human. This means that levels of acrylamide in foods should be reduced to a maximum. The acrylamide molecule is present in foods subjected to processes at temperatures above 120 °C, and it is formed through the reaction that takes place between asparagine and reducing sugars in the Maillard reaction. Fried potatoes are one of the main sources of acrylamide. In order to provide healthier food, this investigation proposes to apply high intensity ultrasound (US) as a frying pretreatment in water for 30 min, in order to reduce the acrylamide content of fried potatoes. Different US treatments were studied at distinct frequencies (35 and 130 kHz), ultrasonic power densities (0, 9.5, 47.6 and 95.2 W/kg), and water temperatures (30 and 42 °C). To evaluate the effects caused by ultrasonic cavitation, the increment of weight and moisture, the decrease in reducing sugars and the electrical conductivity of water in different treatments were evaluated. After frying, colorimetric analyses (L*, a* y b*) were carried out to ascertain the indirect formation of acrylamide in potatoes. At the temperature of 42 °C, the weight gain was greater as the ultrasonic power used in both frequencies was lower. Increments in US power densities decreased the potatoes' moisture gain and increased the electrical conductivity of soaking water. A treatment of 35 kHz and 92.5 W/kg at 42 °C provided an additional extraction of 31% of the reducing sugars over that of control samples. The colorimetric parameters L * and a * decreased and increased, respectively, with the frying time for the treatment at 35 kHz/92.5 W/kg/42 °C, which are a consequence of the reduction of reducing sugars by ultrasound. Thanks to the application of this treatment, 90% acrylamide content reduction was determined compared to potatoes fried directly, and up to 50% reduction with respect to control samples only soaked in water (42 °C/30 min). This investigation has demonstrated that US pretreatments can serve as a valid strategy to reduce the acrylamide content of fried potatoes.