Quality assessment of frying fats and fried snacks during continuous deep-fat frying at different large-scale producers

Changes in quality characteristics of frying oils and fried snacks were studied by means of two experiments carried out at six large-scale Spanish producers. Analytical parameters recorded in order to monitor oil degradation during continuous frying included viscosity, dielectric constant (DC), C18:2n − 6/C16:0 ratio, iodine value, acid value (AV), lipid UV absorption, p-anisidine value (AnV), and polymer and diacylglycerol contents. Changes in DC, AV, lipid UV absorption, AnV and polymer content were useful to monitor frying oil quality. Only in some oils and frying conditions, the evolution of AV paralleled the changes in the rest of useful parameters. For all tested conditions, parameters that were most closely related to oxidation, such as AnV, lipid UV absorption, polymer content and DC, were the best complement/alternative to AV for routine quality control of frying oils during continuous deep-frying. Lipid extracts from fried snacks were also analyzed and the results were similar to those obtained for their counterpart frying oils. We conclude that continuous deep-fat frying produces commercial fried snacks with a relatively uniform and high quality.