Influence of sunflower oil unsaturation level on French fries characteristics

Deep-fat frying is a quick and easy way of cooking, which produces highly appreciated foods, with a typical dry and crispy crust and a tender inside. In the crust, Maillard reactions provide the characteristic color and flavor that, together with texture and color, are essential attributes in the consumer perception of the French fries quality. These attributes are determined by various factors, including the raw potato characteristics as well as the processing conditions and the properties of the frying medium. In particular, during frying several chemical reactions take place, which modify the oxidative and hydrolytic status of the frying fat, improving heat exchange phenomena and accelerating water evaporation. Thus, heat stability of the fat used for frying might influence the quality characteristics of the fried food. The aim of this work was to investigate the influence of sunflower oil unsaturation level on the quality attributes of French fries. Deep-fat frying experiments (two replicates for each oil) were carried out using cv. Agria potato sticks and two virgin sunflower oils different for oleic and linoleic acid contents. Oleic and linoleic acids were 29% and 60% in the most unsaturated oil, and 87% and 4% in the least unsaturated oil. Each frying session lasted 18 hours, without oil replenishment, cooking a total of 6.5 kg of potatoes, in subsequent 8 min cooking cycles separated by 7 min breaks. Potatoes to oil ratio was maintained constant (25 g: 1 L). At regular intervals during the 18 h of frying, French fries were analyzed for moisture, fat content, texture, color and shape features. No clear influence of oil unsaturation level or frying time was observed on potato characteristics. This could be ascribed to the relatively good heat stability of the oils used, which prevented from reaching an oxidative and hydrolytic degradation levels able to significantly modify the quality of the French fries. The extreme variability of the raw potato sticks might also have influenced the results.