Potato chips frying
Deep-frying is a common multifunctional unit operation for fast dewatering, texturing or cooking foods, which simultaneously involves heat and mass transfer. Deep-frying promotes a series of complex reactions and the development of a large series of compounds, including volatile compounds, which simultaneously influence texture, flavour, and colour of the final product. Products of oil degradation may generate unpleasant flavour and further cause health problems. Aldehydes (e.g. acrolein, hexanal, nonanal and other unsaturated aldehydes) are major products of this degradation, and have high relevance due to their capacity to induce toxicological effects. Determination of the content of polar compounds and hexanal has been suggested as indicators of the oxidation state and oil quality during frying of foods. Potato chips frying also poses the risk of developing acrylamide, a toxic compound produced in starchy foods during cooking. Considerable research has been carried out on the mechanism of formation and its toxicity, and guidelines now exist which food manufacturers within the EU must apply in order to mitigate its formation. Key factors to limit the acrylamide formation during frying are frying time and temperature. The use of low temperature of frying (around or below 160 ºC) reduces the concentration of acrylamide, but also some quality characteristics of the product like colour, texture, water and oil content. Actually frying process should ensure a suitable compromise between the development of the quality attributes, the mitigation of undesired effects (mainly related with oil uptake, no contaminant formation and oil degradation) and the energy consumption. Computer vision systems have been developed for the on-line evaluation of potato chips in industrial plants. Chips are sorted according to defects such as black spots or blisters. Some researchers have been also working on promising devices that are able both to classify chips according to colour and to monitor fat, dry matter and acrylamide levels in potato chips using NIR and imaging technologies.