Determination of the Masking Effect of the 'Zapateria' Defect in Flavoured Stuffed Olives Using E-Nose

Spanish-style table olives are one of the most common processed foods in the Mediterranean countries. Lack of control during fermentation can lead to one of the main defects of the olive, called 'Zapateria', caused by the combination of volatile fatty acids reminiscent of rotten leather. In this study, table olives altered with 'Zapateria' defect were stuffed with a hydrocolloid flavoured with the aroma 'Mojo picón' to improve consumer acceptance. Sensory analysis, determination of volatile compounds and electronic nose (E-nose) were used to evaluate the quality of the olives. The control samples had a high concentration of the defect 'Zapateria' and were classified in the second commercial category, while higher 'Mojo picón' flavour concentrations resulted in these olives being classified as 'extra category' (a masking effect). The main volatile compounds in olives with 'Zapateria' defect were cyclohexanecarboxylic acid and pentanoic acid. E-nose allowed discrimination between stuffed olives without added flavouring and olives with 'Mojo picón' flavouring at different concentrations. Finally, PLS regression allowed a predictive linear model to be established between E-nose and sensory analysis values. The RP2 values were 0.74 for perceived defect and 0.86 for perceived aroma. The E-nose was successfully applied for the first time to classify Spanish-style table olives with 'Zapateria' defect intensity and with the addition of the 'Mojo picón' aroma masking the defect.